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LT1 Heads Conversion for SBC

Old 09-06-2016, 06:24 PM
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LT1 Heads Conversion for SBC

Alright, I know this has been done before but I wanted to do a small "how to" write-up because like some of you I have spent hours researching this and trying to find ways to build a motor without breaking the bank. Hopefully by me putting this information out there it will help someone else. Shoutout to Robert Philip Frank for all of the help. Couldn't have done it without you.

LT1 Heads conversion for SBC with pics. This is an easy mod if you have access to some metal working equipment and a TiG welder.


So first things first, the LT1 heads as we all know are reverse flow, stock form they will bolt onto a SBC but the 2 extra coolant ports will dump coolant into the lifter valley.


Those ports will need to be filled so plugs are needed. I had access to some machinery, so I precision machined the 4 plugs I would need using 1/4" 6061 Aluminum plate.


All of the coolant ports were slightly different in size, so depending on the port, the plug either had to be tapped in with a hammer or held in place with a rod I tacked onto the plug. I put the plugs so they were maybe .010-.020" above the surface of the rest of the head.
I then tack welded the plugs in 2 places on either side.


Next, using an air DOTCO with a 1/4" Carbide rotary bit I beveled all around the plug to help get penetration when Its welded.
Be sure to cover up the rest of your coolant ports when grinding. Also, dipping your carbide bit in a cutting oil will prevent it from gumming up with aluminum.


Lastly, weld them up!
Be sure to clean the aluminum with alcohol really good before welding, and every time before you weld to get rid of the cutting fluid.

This is where I left off,
Next I will be milling/decking the heads to get them even/machined surface again. I only have about .015" Or so clearance from the valve seat to the rest of the head so I won't be taking off much.


Lastly, I'll be using the head gasket as a template to drill one last coolant hole where I put the plugs. I am using an LT1 intake so I will not be doing the aluminum tube deal or modifying anything else except adding a remote thermostat housing. So really that's it for now.


Take your time, go slow and watch out for the misc. coolant/mounting holes that are near the ports you are welding.


Hope this helps!


Also, if anyone is interested in buying the plugs to do this yourself shoot me a message. If I get enough interest I may start making them to sell. I have a lot more work to do but I will be modifying a LT1 Intake to work with my setup. So far I have only made the 1/4" spacer that's angled for the distributor.

My Current project that I am doing this for is an 87' Camaro originally a 305 TPI 5 speed car. Motor going in is a 350 out of a 3/4 ton Vortec truck.

More to come!


Thanks for reading!
Attached Thumbnails LT1 Heads Conversion for SBC-10.jpg   LT1 Heads Conversion for SBC-3.jpg   LT1 Heads Conversion for SBC-2.jpg   LT1 Heads Conversion for SBC-4.jpg   LT1 Heads Conversion for SBC-5.jpg  

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Old 09-07-2016, 03:31 PM
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Re: LT1 Heads Conversion for SBC

This thread would be so much better if you used the insert picture button to insert pictures in the middle of the text and it'll not be thumbnails.

In the quick reply box below the 7th icon from the left is the icon. Edit your original post and use that button in advanced editing to fix the post.
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Old 09-07-2016, 03:40 PM
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Re: LT1 Heads Conversion for SBC

This only seems beneficial to those who can tig weld themselves. If not this would cost alot to do and start getting into aftermarket head castings that flow better for the money than stock lt1 heads. But they are good castings and can make big power if you know how to port them
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Old 09-07-2016, 03:42 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Orr89RocZ View Post
This only seems beneficial to those who can tig weld themselves. If not this would cost alot to do and start getting into aftermarket head castings that flow better for the money than stock lt1 heads. But they are good castings and can make big power if you know how to port them
You definitely don't need to tig weld. Brazing can be done by an amateur to get the same effect. I've contemplated this many times.
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Old 09-07-2016, 04:10 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Vanilla Ice View Post
This thread would be so much better if you used the insert picture button to insert pictures in the middle of the text and it'll not be thumbnails.

In the quick reply box below the 7th icon from the left is the icon. Edit your original post and use that button in advanced editing to fix the post.
I will definitely do that!
I apologize, I am not much of a forum poster. I will fix it when I get home tonight.
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Old 09-07-2016, 11:59 PM
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Re: LT1 Heads Conversion for SBC

Good to see you on here Jeff. Project will be awesome when finished
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Old 09-08-2016, 06:31 AM
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Re: LT1 Heads Conversion for SBC

tpi_roc, who used to be a moderator on the TPI forum did this back in 2003. He used an LT1 intake as well, drilled the front of both heads for his remote thermostat, etc. Unfortunately his webserver has been down for years so all of the pictures are lost.

He ran a cc306 cam and it went 12s of I remember.

Anyway, not many people have done it because the rewards don't outweigh the work and cost involved. A set of Vortec heads flow essentially the same.

If the thermostat wasn't such a PITA I think it would be more popular.

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Old 09-08-2016, 12:07 PM
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Re: LT1 Heads Conversion for SBC

Granted, for someone who has to pay others to do this, I agree that the cost/work involved would be better suited for vortecs but if you have access to welding/machining equipment then this is definitely the way to go. As we all know. LT heads respond extremely well to porting and the benefit of the weight savings pays for it self.
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Old 09-08-2016, 12:27 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by robertfrank View Post
Granted, for someone who has to pay others to do this, I agree that the cost/work involved would be better suited for vortecs but if you have access to welding/machining equipment then this is definitely the way to go. As we all know. LT heads respond extremely well to porting and the benefit of the weight savings pays for it self.
Perhaps. They are cheap. I think I can get them locally for about $50 per set.

I can weld them and have them milled, but I don't recall what was involved regarding the thermostat if trying to retrofit a SBC intake. Also the bolt pattern is different on the intake so you gotta modify the intake or the heads.

If using an LT1 intake you need to do the remote thermostat, and that could cause packaging issues.

Can LT1 heads outflow L31 heads? I know the flow numbers are almost dead even stock.

-- Joe
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Old 09-08-2016, 12:31 PM
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Re: LT1 Heads Conversion for SBC

Lt1 heads can make about 425whp NA at best.
The remote thermostat along with most is easy. The hardest part of the whole thing is modifying the LT1 intake for the distributer.

There's no point in getting lt1 heads and staying with SBC1 intake unless you're really cheap.
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Old 09-08-2016, 12:36 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Vanilla Ice View Post
There's no point in getting lt1 heads and staying with SBC1 intake unless you're really cheap.
The stock LT1 intake isn't bad for a stock intake, but guys may want to go with a single plane, or perhaps they already have a sheet metal intake.

Then again, if they wern't being cheap they would just buy AFR heads.

The LT1 intake swap was popular 15 years ago when aftermarket EFI intakes were very expensive. Even then, I don't think as many people actually converted LT1 intakes as they talked about it. I knew a few guys that did it, but they didn't keep them very long. Even tpi_roc, whom I mentioned earlier that did the LT1 head and intake swap on an SBC, ended up selling the car about 6 months after it was completed and bought a faster turbo car.

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Old 09-08-2016, 12:40 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Vanilla Ice View Post
Lt1 heads can make about 425whp NA at best.
The remote thermostat along with most is easy. The hardest part of the whole thing is modifying the LT1 intake for the distributer.

There's no point in getting lt1 heads and staying with SBC1 intake unless you're really cheap.
If the heads are heavily worked over they can make alot more than 425. And on that deal, you'll need a different intake anyway, stock lt1 intake will not support it.

But for 1100$ or so in cnc and machine work you can have advanced induction give you a badd **** set of lt1 heads that will rival or outpower aftermarket heads like afr for alot less.
Even stock they can do 360 whp in a manual car cam only. Not bad for budgets. I would have done them too if i could weld aluminum
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Old 09-08-2016, 12:48 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by anesthes View Post
Perhaps. They are cheap. I think I can get them locally for about $50 per set.

I can weld them and have them milled, but I don't recall what was involved regarding the thermostat if trying to retrofit a SBC intake. Also the bolt pattern is different on the intake so you gotta modify the intake or the heads.

If using an LT1 intake you need to do the remote thermostat, and that could cause packaging issues.

Can LT1 heads outflow L31 heads? I know the flow numbers are almost dead even stock.

-- Joe
From what I've seen as far as using an SBC intake with LT heads, you can get away with elongating the 8 corner holes and not even using the center holes. As far as port flow, I believe the LT heads have a an advantage over the Vortecs but it truly depends on the portwork ( I've ported both) .
From all the guys who have run an LT intake on an SBC say that a remote thermostat is no big deal.
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Old 09-08-2016, 12:48 PM
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Re: LT1 Heads Conversion for SBC

I have yet to see any LT1 head car making anything substantial power-wise NA.

The 425 is with the LT1 intake as the OP is planning. Anything over that is being overlygenerous on a dyno.
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Old 09-08-2016, 12:52 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Orr89RocZ View Post
If the heads are heavily worked over they can make alot more than 425. And on that deal, you'll need a different intake anyway, stock lt1 intake will not support it.

But for 1100$ or so in cnc and machine work you can have advanced induction give you a badd **** set of lt1 heads that will rival or outpower aftermarket heads like afr for alot less.
Even stock they can do 360 whp in a manual car cam only. Not bad for budgets. I would have done them too if i could weld aluminum
AI heads only flow 290/200. They aren't that great.
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Old 09-08-2016, 01:40 PM
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Re: LT1 Heads Conversion for SBC

Its not always about flow lol
The fastest all motor lt1 runs them, atleast at one time. Dont know what the record is now
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Old 09-08-2016, 01:47 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Orr89RocZ View Post
Its not always about flow lol
The fastest all motor lt1 runs them
We are talking about a budget street car. With a 350cc engine, an lt1 intake and unported GM heads.

This is pretty absurd to even discuss Joe O and Abare and the EXTREMELY limited few that have gone beyond the norm.

1 in 100,000 is not an example you should use to validate your point.
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Old 09-08-2016, 01:50 PM
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Re: LT1 Heads Conversion for SBC

Edit, i see the prices went up. 1795$ for the big head, 1400's for the middle head. Ouch
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Old 09-08-2016, 01:52 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Vanilla Ice View Post
We are talking about a budget street car. With a 350cc engine, an lt1 intake and unported GM heads.

This is pretty absurd to even discuss Joe O and Abare and the EXTREMELY limited few that have gone beyond the norm.

1 in 100,000 is not an example you should use to validate your point.
Lol just stating the true facts. The head castings are capable of more than what you suggest. However if using the stock intake i agree 425 is a damn good number.

My point only needed 1 example to validate it btw
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Old 09-08-2016, 02:00 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Orr89RocZ View Post
. The head castings are capable of more than what you suggest.
Not to 99.99% of them. You might as well argue that TPI can do better too. They all can with $40k.

Exceptions to a rule don't change the rule.

Originally Posted by Orr89RocZ View Post
However if using the stock intake i agree 425 is a damn good number.
With any intake.

Originally Posted by Orr89RocZ View Post
My point only needed 1 example to validate it btw
Whatever helps you sleep at night!

I only brought up the hp because they were being compared to L31 heads.
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Old 09-08-2016, 02:22 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Vanilla Ice View Post
I only brought up the hp because they were being compared to L31 heads.
What heads are you running?

The only stock heads I'm running in a car is some old 60s camel humps on my stingray, but that's a slow 350hp turd. I've got some L31 heads in the shop collecting dust, and Don down the street has a bunch of pairs of LT1 heads he was trying to sell for $50 a set. He may have even scrapped them by now. Not many people interested in stock heads anymore, not with all the Procomp and Assault and all that stuff flooding ebay.

I've been using AFR for the past 10 years or so now. They are cheap and make great power. I think I paid $1350 for my AFR 210's, and like $1200 for my AFR 195's

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Old 09-08-2016, 02:57 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Vanilla Ice View Post
Not to 99.99% of them. You might as well argue that TPI can do better too. They all can with $40k.

Exceptions to a rule don't change the rule.


With any intake.


Whatever helps you sleep at night!

I only brought up the hp because they were being compared to L31 heads.
To some it may seem a stretch or an exception...to those who know how to do things i guess not
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Old 09-08-2016, 05:29 PM
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Re: LT1 Heads Conversion for SBC

I am using this site as guide for my conversion. https://www.eecis.udel.edu/~davis/z2...ke_conversion/
As far as the heads go it looks like they will bolt straight onto my block. And ofc the LT1 intake will bolt right onto the heads. As far as the remote thermostat that won't be a huge deal, I will either mount it or fabricate some sort of bracket/weld it near the intake.
I will be porting the heads and intake myself, being a CNC programmer/Operator it is a bit more cost efficient for me to do it myself. I am not trying to build a race car or anything, I just want a fun, street-able daily driver that will be reliable. This is honestly my first engine build, I'm really going along for the ride and having fun with it while learning a lot. Thanks for all of the input guys.

Last edited by Jlp06; 09-08-2016 at 05:29 PM. Reason: Spelling error
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Old 09-08-2016, 09:22 PM
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Re: LT1 Heads Conversion for SBC

How much current are you running to get the penetration needed?
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Old 09-09-2016, 12:56 AM
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Re: LT1 Heads Conversion for SBC

Originally Posted by scooter View Post
How much current are you running to get the penetration needed?
Whenever I weld I usually turn the amperage up pretty high, I like to weld it hot and I like still having pedal to press. I believe I welded it around 150 amps or so. On these heads I tried to not overheat them, just getting them hot enough to weld to minimize warping.
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Old 09-09-2016, 07:01 AM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Jlp06 View Post
Whenever I weld I usually turn the amperage up pretty high, I like to weld it hot and I like still having pedal to press. I believe I welded it around 150 amps or so. On these heads I tried to not overheat them, just getting them hot enough to weld to minimize warping.
A pedal. Man must be nice. My older Miller tig doesn't have a pedal, so I have to constantly stop and adjust the amperage. The gas is also a ****.

At least the high frequency is a button

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Old 09-09-2016, 09:24 AM
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Re: LT1 Heads Conversion for SBC

Originally Posted by anesthes View Post
A pedal. Man must be nice. My older Miller tig doesn't have a pedal, so I have to constantly stop and adjust the amperage. The gas is also a ****.

At least the high frequency is a button

-- Joe
Damn, that really sucks. I guess you have to start out low and constantly adjust until you get it just where you want it. I had to certify 6G on TiG to be able to weld aircraft parts, I couldn't imagine having to do it on an older TiG welder like that. What an even bigger pain that would have been.
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Old 09-09-2016, 09:43 AM
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Re: LT1 Heads Conversion for SBC

Yup. It's a 200+amp machine though, so as a stick welder it's great. I often fix my 10,000lb trailers, etc with it. As a Tig it's hard to use. I can and have done aluminum with it but a modern machine would be better.

My new might 180 I think can do alum and I saw some .030 aluminum wire just the other day.

If there is a market for converted lt1 heads maybe I'll weld some up and sell them haha.

One thing to mention, she. Tpi_roc did it back in 2003 he warned that the valve to deck clearance was very tight and his machinest cautioned milling too much. Id be concerned about how much head has to go into the head to weld it, and what the resulting warpage would be my experience with cast aluminum is that you have to boil the crap out of it to get a good weld. I've done some some cast stuff and the head made the part almost turn a corner.

I welded a slot maf flange to a cast procharger elbow last month and it took like 150 amps to get a puddle.


-- Joe
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Old 09-09-2016, 10:07 AM
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Re: LT1 Heads Conversion for SBC

Originally Posted by anesthes View Post
Yup. It's a 200+amp machine though, so as a stick welder it's great. I often fix my 10,000lb trailers, etc with it. As a Tig it's hard to use. I can and have done aluminum with it but a modern machine would be better.

My new might 180 I think can do alum and I saw some .030 aluminum wire just the other day.

If there is a market for converted lt1 heads maybe I'll weld some up and sell them haha.

One thing to mention, she. Tpi_roc did it back in 2003 he warned that the valve to deck clearance was very tight and his machinest cautioned milling too much. Id be concerned about how much head has to go into the head to weld it, and what the resulting warpage would be my experience with cast aluminum is that you have to boil the crap out of it to get a good weld. I've done some some cast stuff and the head made the part almost turn a corner.

I welded a slot maf flange to a cast procharger elbow last month and it took like 150 amps to get a puddle.


-- Joe
Cast aluminum as long as it's pretty clean and doesn't have a lot of contaminants welds pretty good. And yes, there is about 0.015" clearance from
Head surface to valve seat. I will be milling my own heads so I will probably only take off about 0.005" or so. Sometimes a small pre heat on cast aluminum is needed, if your having trouble welding it. Overall though I am not too worried. I will have to make a fixture to properly hold the heads, and then after I will be doing some porting work. As I progress more I'll post more updates.
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Old 09-15-2016, 03:23 AM
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Re: LT1 Heads Conversion for SBC

The best reason I can come up with to do it is if you want to put decent aluminum heads on a 305 bottom end, try to find anything nice that doesn't have 2.02/1.60 valves.

This is my SBE 305, custom 4/7 swap cam with heavily worked aluminum LT1 heads (ports opened up to 1206, chambers and bowls reshaped... ended up having some porosity problems and had to weld up some of the port rooves and reshape them...), very old, heavily ported Vic Jr that I added injector bungs to years ago (before they could be bought that way), LSx style TB and fabbed elbow, etc, etc...


Aluminum LT1 heads on a stock bottom end 305

Will comment more when I have time...
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Old 09-15-2016, 07:37 AM
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Re: LT1 Heads Conversion for SBC

Any numbers on that setup
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Old 09-15-2016, 10:01 AM
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Re: LT1 Heads Conversion for SBC

There is an alternative for those who don't have access to a tig welder. It is old school, but it works. Place the SBC engine on a rotating engine stand, bolt the LT1 heads to the earlier block using MLS head gaskets machined for SBC heads, preferably a used set. Rotate the engine so that the coolant port on the LT1 heads leading to the lifter valley is facing upward. Heat up some aluminum in a steel pan with a torch, and once melted, using a steel funnel, pour the aluminum into the cylinder head then wait for it to dry. I did this process to block off my EGR ports in the 416 heads I am running, Turbo Buick guys do the same for the EGR ports. The LT1 coolant port should be a breeze to do this way...

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Old 09-15-2016, 12:18 PM
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Re: LT1 Heads Conversion for SBC

I keep saying it, why not braze the ports?!
WAY easier than all that.
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Old 09-15-2016, 01:12 PM
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Re: LT1 Heads Conversion for SBC

That would work, and be way easier to do. I only hesitate brazing because the rod used to braze the aluminum is mostly made of zinc, and the melting temperature for zinc is about 800 degrees in comparison to 1200 degrees for aluminum. With the location so close to the combustion chamber I would cringe at wide open throttle, but that is just me. Figure just melt aluminum stock and not have to worry, but yes, brazing would work...
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Old 09-15-2016, 01:13 PM
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Re: LT1 Heads Conversion for SBC

But with coolant behind it it should be fine.
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Old 09-15-2016, 01:20 PM
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Re: LT1 Heads Conversion for SBC

I agree, i doubt it would ever get that hot to melt zinc
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Old 09-15-2016, 01:30 PM
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Re: LT1 Heads Conversion for SBC

I hear you guys, but again that is just me trying not to get too close to the edge. When I brazed my cast exhaust manifolds for that twin turbo setup years back, the braze consisted mainly of brass, with a melting point of about 1700 degrees. I convinced myself that despite EGT's reaching that much in some cases (too lean, etc), the material itself was always a couple of hundred degrees cooler that the EGT's, especially when coated. It would have worked, and was way easier as opposed to heating the manifolds and using my mig to weld them with steel rod, but I opted not to, and rewelded them with steel. Again, it's just a preference of mine. The braze would work fine...
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Old 09-15-2016, 01:39 PM
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Re: LT1 Heads Conversion for SBC

How long did you run brazed exhaust manifolds or did you never run it? I thought about this myself, but I am more afraid of that than the heads in the water ports.
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Old 09-15-2016, 04:04 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Orr89RocZ View Post
I agree, i doubt it would ever get that hot to melt zinc
I doubt it too, but brazing is for plumbers.

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Old 09-15-2016, 05:02 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Vanilla Ice
How long did you run brazed exhaust manifolds or did you never run it? I thought about this myself, but I am more afraid of that than the heads in the water ports.
Sadly I never did, I cut one of a set and flipped it to run a twin turbo setup I was planning. The first pic shows right after the cut, second pic just shows a mock up prior to brazing it. I did a lot of smoothing down of the primaries after these pics so that the braze had a good bond. Third pic was a few hours after I brazed them. The side that was brazed was the only side that has air fitting threads in the primaries, those were eventually welded shut...

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Old 09-15-2016, 06:01 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Orr89RocZ View Post
Any numbers on that setup
Justin, no track numbers yet, I've been dealing with other things this year and haven't made it out. I guess you don't remember it but I posted quite a few pics of doing this and other supporting things on MM, as well as flowbench numbers on a 4" and 3.75" bore.

This thing has brutal low end (I have a VE peak at 1800rpm that you wouldn't believe) and it pulls to >7K (I haven't dared to spin the SBE up higher than that). It really is a fun combination but I built it for a turbo setup and the VE peak down low has me freaked out that I won't be able to control detonation down there. I need to try some cooler plugs.

Honestly I've mostly stopped posting here, I don't even know how I ran across this thread...

Originally Posted by Street Lethal View Post
There is an alternative for those who don't have access to a tig welder. It is old school, but it works. Place the SBC engine on a rotating engine stand, bolt the LT1 heads to the earlier block using MLS head gaskets machined for SBC heads, preferably a used set. Rotate the engine so that the coolant port on the LT1 heads leading to the lifter valley is facing upward. Heat up some aluminum in a steel pan with a torch, and once melted, using a steel funnel, pour the aluminum into the cylinder head then wait for it to dry. I did this process to block off my EGR ports in the 416 heads I am running, Turbo Buick guys do the same for the EGR ports. The LT1 coolant port should be a breeze to do this way...
1- you don't want to fill the whole port, the passage behind it has to stay open and you need to otherwise get flow through it or you'll get a hot spot.
2- that won't seal. When you do that with EGR ports it just pores in and you get a plug in the shape of the hole, it is not sealed but a little bit of leaking EGR doesn't matter. If you did manage to pour it in the coolant port and not fill the port too much it will still weep coolant and that will dump into the lifter valley, a VERY bad thing.

Originally Posted by Vanilla Ice View Post
I keep saying it, why not braze the ports?!
WAY easier than all that.
Aluminum brazing rod is a zinc alloy, most of which melts at a very low temp. I would be surprised if it held, and I wouldn't trust the potential catastrophe that a failure here would cause.

Originally Posted by Jlp06 View Post
Cast aluminum as long as it's pretty clean and doesn't have a lot of contaminants welds pretty good. And yes, there is about 0.015" clearance from
Head surface to valve seat. I will be milling my own heads so I will probably only take off about 0.005" or so. Sometimes a small pre heat on cast aluminum is needed, if your having trouble welding it. Overall though I am not too worried. I will have to make a fixture to properly hold the heads, and then after I will be doing some porting work. As I progress more I'll post more updates.
Yes, if it's a clean casting it's pretty easy to weld. The decks welded OK, but I cut back all the corroded metal, then cut a 45* chamfer and made plugs that pressed into the decks. They would have stayed in without welding, but the weld sealed them up. Where I ran into problems was with some of the bolt holes and ports. Mine had enough porosity in the exhaust ports that they wouldn't pass a pressure test (leaked around the valve guides) and I already had enough work in them that it made sense for me to cut out as much as 1/3 of the top of he port and re-weld it. I tried welding a few of them without cutting them out and the porosity was just too bad to make it work. I ran into the same thing with some of the bolt holes.

Pics exist but I'll need to spend more time searching since I know that it was before 2012 when I welded mine and that's how far back I can easily find stuff.

I had Cometic make me some custom gaskets, that had the LT1 valve/chamber pattern and an SBC coolant pattern, then I unshrouded the valves in the chambers (I ended up trimming back the gaskets a little with a carbide burr to match the chamber shape I ended up with), reshaped them and then cut chamfered the tops of the 305 bores to match where the chamber hung over the bore.






Originally Posted by robertfrank View Post
From what I've seen as far as using an SBC intake with LT heads, you can get away with elongating the 8 corner holes and not even using the center holes. As far as port flow, I believe the LT heads have a an advantage over the Vortecs but it truly depends on the portwork ( I've ported both) .
From all the guys who have run an LT intake on an SBC say that a remote thermostat is no big deal.
Not really, they're in a different location and angle. It works for putting an LT1 intake on SBC heads but not vice versa. You need to weld them shut or at least do a good job plugging and drilling new ones because the location runs into the factory LT1 "burp holes" (used for the rear coolant crossover, which I kept functional to prevent any hot spots)

Originally Posted by anesthes View Post
Perhaps. They are cheap. I think I can get them locally for about $50 per set.

I can weld them and have them milled, but I don't recall what was involved regarding the thermostat if trying to retrofit a SBC intake. Also the bolt pattern is different on the intake so you gotta modify the intake or the heads.

If using an LT1 intake you need to do the remote thermostat, and that could cause packaging issues.

Can LT1 heads outflow L31 heads? I know the flow numbers are almost dead even stock.

-- Joe
I've had good enough results that I have another set that I'm going to do, and at this point between this, converting LT1 intakes to work on SBC's, SBC intakes to work on LT1's... I can pretty much just do them on a bench, I don't need an engine to figure stuff out on.

Out of the box the vortecs are slightly better down low, the LT1's flow better up top and make more power. LT1 Iron heads are sort of a hybrid and they are actually better than the aluminum ones, similar on the intake side, better on the exhaust.

There is a rather weird relationship between vortec, LT1 Iron, LT1 aluminum, LT4 and fastburn heads... there isn't really a clear line of evolution, it sort of jumps around, like the vortec port location is like the LT4, and the LT1 is most like a fast burn, and well the chambers are all different and all over the place. They are even different when comparing exhaust and intake ports.

Originally Posted by anesthes View Post
The stock LT1 intake isn't bad for a stock intake, but guys may want to go with a single plane, or perhaps they already have a sheet metal intake.

Then again, if they wern't being cheap they would just buy AFR heads.

The LT1 intake swap was popular 15 years ago when aftermarket EFI intakes were very expensive. Even then, I don't think as many people actually converted LT1 intakes as they talked about it. I knew a few guys that did it, but they didn't keep them very long. Even tpi_roc, whom I mentioned earlier that did the LT1 head and intake swap on an SBC, ended up selling the car about 6 months after it was completed and bought a faster turbo car.

-- Joe
I'm not sure why people are as excited about the LT1 intake as they are. It is sort of like a cheap miniram, but it has longer and smaller cross section runners which don't have enough taper. It's OK, but to make big power with it you need to fill the tops of the runners where the injector bungs are, cut that back and then relocate the bungs. At that point a good converted single plane is cheaper and less work.
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Old 09-15-2016, 06:44 PM
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Re: LT1 Heads Conversion for SBC

Originally Posted by 83 Crossfire TA
1- you don't want to fill the whole port, the passage behind it has to stay open and you need to otherwise get flow through it or you'll get a hot spot...
Correct, but this is why I stated to use a funnel, the aluminum must be metered to that of what the OP had originally embellished in his picture, which isn't much, but just enough to seal. Nobody is implying to pour enough to make an additional cylinder head...

Originally Posted by 83 Crossfire TA
2- that won't seal. When you do that with EGR ports it just pores in and you get a plug in the shape of the hole, it is not sealed but a little bit of leaking EGR doesn't matter. If you did manage to pour it in the coolant port and not fill the port too much it will still weep coolant and that will dump into the lifter valley, a VERY bad thing...
Here is where I will disagree though. For starters, my EGR ports do not leak, even when I had the turbo at 12-psi, not to mention thousands of Turbo Buicks who inevitably went the same route prior to Champion cylinder heads being released that are cast with the EGR already blocked off, they too do not leak. Aluminum has a much higher expansion rate than cast iron, and it seals quite well when when the engine reaches operating temperature. This method is crude, but it works, and of course was mentioned by myself as a viable alternative for someone who does not have access to a tig welder. Welding also may distort the aluminum if one is not careful, which will then require resurfacing of the whole entire head, at a minimum. Pouring aluminum stock in like a foundry orientation only requires sanding down that general area on the combustion chamber side once the aluminum cools, not to mention heating the aluminum beyond it's melting point allows it to bond to the cylinder head surface once it's poured in. You may not agree with what I am saying, but the EGR aluminum fill worked well for me, and many others, and it should work even better filling/sealing aluminum.

As for the 305 you're running, do you have any datalogs of that off idle hit?
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Old 09-16-2016, 01:34 AM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Street Lethal View Post
Correct, but this is why I stated to use a funnel, the aluminum must be metered to that of what the OP had originally embellished in his picture, which isn't much, but just enough to seal. Nobody is implying to pour enough to make an additional cylinder head...
Street, have you looked at these heads? The decks are probably a 1/4" thick in that area and there is nothing behind those holes but coolant passage. To even begin to do this you'd have to figure out some way to block that off so you can pour aluminum in there to only be about 1/4" thick. I ACTUALLY considered doing exactly that (I think I even saw the video you linked, i didn't click on it here but i'm pretty sure it was the same one). I couldn't figure out how to keep the aluminum where I needed it.

If you have an idea I'd like to hear it.

Here is where I will disagree though. For starters, my EGR ports do not leak, even when I had the turbo at 12-psi, not to mention thousands of Turbo Buicks who inevitably went the same route prior to Champion cylinder heads being released that are cast with the EGR already blocked off, they too do not leak. Aluminum has a much higher expansion rate than cast iron, and it seals quite well when when the engine reaches operating temperature. This method is crude, but it works, and of course was mentioned by myself as a viable alternative for someone who does not have access to a tig welder. Welding also may distort the aluminum if one is not careful, which will then require resurfacing of the whole entire head, at a minimum. Pouring aluminum stock in like a foundry orientation only requires sanding down that general area on the combustion chamber side once the aluminum cools, not to mention heating the aluminum beyond it's melting point allows it to bond to the cylinder head surface once it's poured in. You may not agree with what I am saying, but the EGR aluminum fill worked well for me, and many others, and it should work even better filling/sealing aluminum.
1- how do you know that they don't leak a little bit? Would a little leak have any affect on the engine? A few drips getting through here in this case would have a significant effect on the engine, it would drip coolant into the lifter valley and then mix with the oil likely killing it pretty quickly
2- Unless you preheat the head and the area significantly a bit of aluminum the size of 2-3 quarters is not going to have enough heat in it to melt the surrounding aluminum. If you put enough heat into it to melt it into the surrounding base metal you're just about guaranteed that you're going to distort the head some. Honestly if you think you're going to seal those up without surfacing the head afterwards you're kidding yourself. Heck, I haven't run across an LT1 or 'vette aluminum head that was used that didn't need surfacing if you checked it for flatness before you did anything.
3- In the end you hit on exactly why this works well in an iron head- the aluminum expands faster than the iron so as it gets warm it seals up (assuming that you had a successful pour that didn't contract too much). On those iron heads you also had much more contact area to work with.

I did mine with a TIG, but after my experience replacing parts of the ports I doubt that I'd do that again. I got tired of futzing around with the TIG there, needed to feed a lot of filler and ended up working something out with a spool gun on a MIG that worked out really well. After the machine shop that did the pressure testing saw the work they were so impressed with how it came out and how fast I did it that they sent 3 heads home with me to do and I did them in exchange for some work from them (though I surfaced my heads on my bridgeport).

I'm pretty sure that I could weld all 4 holes as well as the bolt holes that need to be filled in 10-15min this way (probably an hour or so including setup and pre-heat). I doubt you could run those 4 beads and fill he bolt holes in 30min with a TIG (I know that I can't) and I'd be surprised if you could even get your aluminum casting setup in that time period.
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Old 09-16-2016, 01:51 AM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Street Lethal View Post
As for the 305 you're running, do you have any datalogs of that off idle hit?
I have tons of logs from tuning the MegaSquirt, what are you looking for? Honestly I was going to post a "anyone ever see a VE table like this" thread in the appropriate forum here, so that might be more appropriate, but here is a 3D shot of my fuel table (it's mostly untuned from 3600-7000rpm as you can tell that it's mostly flat in there):



I had to add an 1800rpm column (1600 before and 2000 are after) just to deal with the amount of fuel that it wants there. And before you say that it's something like not enough AE or something I've been all over this on a couple of MS forums/groups. That is a real VE table, the required fuel is set correctly and that's really what it wants (I think I have a log from last night showing the WBO2 going up a little bit in that range), I probably have a little too much AE right now. I also have the timing down to 10* up there >2000rpm just to keep the knock retard reasonable. I'm going to try some colder plugs this weekend, but I already have the stock LT1 heat range plugs in it (TR55's) and 305's typically want a heat range or 2 higher than a 350. I'll likely try some TR6's or autolite 103's in it if I can find them tomorrow.

And yes I'm a bit defensive about it... I've had quite a few tuners freak out seeing that swearing it can't be right...
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Old 09-16-2016, 02:00 AM
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Re: LT1 Heads Conversion for SBC

Originally Posted by Street Lethal View Post
Sadly I never did, I cut one of a set and flipped it to run a twin turbo setup I was planning. The first pic shows right after the cut, second pic just shows a mock up prior to brazing it. I did a lot of smoothing down of the primaries after these pics so that the braze had a good bond. Third pic was a few hours after I brazed them. The side that was brazed was the only side that has air fitting threads in the primaries, those were eventually welded shut...
Brazing works well on cast manifolds. I've never done them to that extent, but I've done quite a few welded ones (to stick a weird engine in a weird chassis, like a 500cid cadillac in a 67 Lemans), and the more than once I ran into a spot where there is just trash in the casting and when you try to weld that spot it just burns away. Rather than cut it out and chase it for half the day you can usually just braze that spot and leave it. Works fine even with a completely crappy casting. That Lemans has been on the road for 10-12 years with half welded and half brazed together manifolds made out of parts of some original El Dorado and Coupe Deville manifolds, some cast plumbing elbows, some 1/4" thick mild steel and outlet flanges cut out of 3/8" mild steel (they look MUCH better than they sound and the owner wanted refused to have headers on that car).

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Old 09-16-2016, 02:24 AM
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Re: LT1 Heads Conversion for SBC

I don't think brazing manifolds in general is bad at all.

What I'm wondering is how it holds up with a turbos exhaust heat.
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Old 09-16-2016, 09:37 AM
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Re: LT1 Heads Conversion for SBC

Especially if you are using an antilag system or dumping fuel/dropping timing etc to get a turbo to spool. Lots of heat in the manifold
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Re: LT1 Heads Conversion for SBC

Originally Posted by Orr89RocZ View Post
Especially if you are using an antilag system or dumping fuel/dropping timing etc to get a turbo to spool. Lots of heat in the manifold
My turbo manifolds were glowing red when initially setting up my motor when I had the T76. Even the 5 minutes it took me to get timing and fuel dialed in properly. And I know that doesn't happen to everyone, but it can happen.

Brazing to me is for plumbing. If you don't have a TIG, pay someone the $100 to do it properly is my position.

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Old 09-16-2016, 10:25 AM
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Re: LT1 Heads Conversion for SBC

My first code $59 turbo car my downpipes were glowing lol i know how hot things can get
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Old 09-16-2016, 01:27 PM
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Re: LT1 Heads Conversion for SBC

I think that pretty much everyone that has done this kind of thing has ended up with a glowing exhaust at one point and everything around them melted, or at least all the plastics nice and shiny from getting heated to that point.

Any glowing should be enough to weaken a braze, I would trust it to patch a crack or something but not to hold together something like in that pic above.
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