88 GTA

Is it possible to bolt a set of LT1 heads on an L98 motor? Anything special to know about before attempting this?

Drkhrse89

iTrader: (1)

It wont work because the LT1 is reverse coolant flow if I remember rightly.

John Millican

iTrader: (1)

Yes, it's possible but not without modifications. It has to be machined to fit. Here's an article I got from a fellow member.

http://www.lt1intake.com/LT1_retrofit.htm

86 IROC

iTrader: (3)

It can & will work. I found a clean set of 95' LT1 heads for a song. Armed w/ only that article John has posted a link to - I had a local machinist friend do the conversion. It set me back a whopping $125. While some may argue that the ends might not justify the means... these heads went on a mild 357" motor w/ an LT1 intake. I have about $500 total in the heads... where can you get a practically "new" set of aluminum heads for $500?

This is what I invested as follows:
Used LT1 heads - $100
Conversion work - $125
3 angle valve job, mild bowl work, new seals - $303

m23haz

John if you can put LT1 heads on pre-93 blocks then would the intake still have to be modified to fit?

bigals87z28

i would think that they would have to be at least drilled for the dist. ..

86 IROC

iTrader: (3)

You still need a hole for the distributor and outlets for water. Check the article out - they plug off the LT1 speciffic water passages and add a tube to route the water like a Pre-LT1 SBC head.

m23haz

These heads make great power on the LT1 cars when ported. I think if I find a cheap set I might go for this.

86 Iroc: Did the heads increase power for you? Any track times or dyno or anything?

86 IROC

iTrader: (3)

I don't have any results yet - the motor in question is in a state of limbo right now... I am selling the car that it was intended for. The heads & intake I bought came off of a good friend's 95' Z28 A4 car. W/ 245/50-16 Nitto DR's, a cut out, crank pulley, and a few free mods his car ran consistent 13.50's @ 101+. The motor I have has a bigger cam, roller rockers, 52mm TB, adj. FPR, & no doubt will blow through LT headers and true duals vs. LT1 manifolds & a stock exhaust. I chose these heads because I was able to do it on a budget, $100 here, another $125 there... you get the picture. It was either use the LT1's... or dump money into some iron L98 heads I have. The stock LT1's had an adequate valve spring for the cam I'm running, and to my fortune - they all tested out good when checked by the machine shop.

89Formula350WS6

John - do you have a machinist over near you that could modify a set of LT1 heads for me for about the same thing it cost 86 Iroc??

I just might be able to get a set from a friend off his blown motor for a song. (I just sold him a running LT1 for $700.00 so he owes me a deal.) I'd always heard this could be done, but figured it would cost a fortune, or that my local machinist either couldn't or wouldn't tackle it.

mystikkal_69

iTrader: (2)

LT1 Heads + LT1 Intake on a Gen 1 SBC = intresting.....


keep the ideas rolling.:hail:

86 IROC

iTrader: (3)

89Formula350WS6 - If you want, I will talk to Dan, the machinist. If he is interested in doing another set, I will privately email you his home # and the best times to reach him. Dan is the inventor of the C4 to flathead adapter, he created it while working for Challenger Equipment in California. As long as I've known Dan through my father - he's always had something off the wall being built in his shop. The guy is a whiz.

88 GTA

Thanks for all the good info. What are the casting numbers on LT1 heads?

Drkhrse89

iTrader: (1)

Well looks like I shot myself in the foot. This is great I am looking into a set of heads for my new motor and I think that I just found what I am going to be doing if I can find someone around here to do the conversion.

m23haz

Are all of the LT1 heads aluminum? I thought that some of them were iron.

Was that $125 price for the head conversion a "favor" to you or is that what others should expect as far as amount of time and work needed to do the conversion.
Thanks

88 GTA

LT1 heads came in both aluminum and iron. I believe the Impala's, caprice's, etc came with the iron version.

86 IROC

iTrader: (3)

That $125 price wasn't a favor - but I'm sure it helps that I have known him for almost 20 years. You are correct about the heads - B body's got cast LT1 heads, and Y & F cars got aluminum LT1's. I was told by a few LT1 guys that I should avoid 92' & 93 castings.

Drkhrse89

iTrader: (1)

So would this work with a TPI intake or are you limited to running just a LT1 intake?

m23haz

Well since the LT1 intake ports line up to l98 heads I assume that you could use the TPI on LT1 heads that have been modified to the early style.

John Millican

iTrader: (1)

Sorry, I don't know any machinest's around here where I am.

Omega

iTrader: (1)

Would someone like to post some flow numbers for the LT1 heads?

89Formula350WS6

Thanks for the reply John.

86 Iroc, I'd be interested in the conversion if you can get me some more info on the cost involved if I have a set of good used heads.

Omega, You can find those flow numbers at Chevy High Performance's web site under the "Flow To Go" article.
Maybe one of the most useful series of articles ever written. You've gotta love that they put the specs online for the world to see even if you aren't a subscriber.

86 IROC

iTrader: (3)

89Formula350WS6 - I've got a call in to dan for m23haz. Dan said he'd have to get back to me in a few weeks because he is super busy w/ x-mas and his family. I don't want to push him or he won't want to do them. So, I'm going to let him take his time getting back to me about it and see what he says. I'm pretty sure he'll do them... but it's going to be on his terms and most likely not until next year when the holidays are over.

89gta383

iTrader: (5)

Head flow for LT1:

http://www.malcams.com/legacy/misc/headflow.htm

89Formula350WS6

Thanks Iroc. I'm in no hurry at all.

89gta383: Thanks for posting those flow numbers. For the LT1 heads that's much more complete than the CHP listing.

Vader

Not to confuse the issue even more, but the iron heads actually flow better in stock form (as cast) than the aluminum heads on the intake side, and are fairly close on the exhaust side. Iron heads are easier to work with (IMO) and can probably be acquired for less cash outlay than their aluminum counterparts.

I did some bowl, runner, and radius work on my '94 iron heads when the 2.02/1.60 valves were installed, and noticed an immediate increase in pull to a much higher RPM. The intake runners were increased from an average of 174cc to 196cc, and the exhust runners were opened from 68cc to 76cc. Compression was bumped to 10.6 from the larger valves being installed deeper by 0.010" (1.770" installed height). With a few little associated changes to enhance the package (cam, springs, exhaust, intake porting, etc.), the RW HP/TQ went from 256/328 to 378/455. Not bad for a little home porting and some "lame" iron heads, huh? Of course, the aluminum heads probably would have been a LOT better, or at least that's the standard assumption.

quickL98

iTrader: (2)

i've got a set of ported '96 vette heads with gmpp springs guide plates and all sitting in a box in the dining room, i been sayung i'm going to put them on my '94Z but i still cant locate the motor when i pop the hood

picked them up for under 600 bones.... ot bad for a set of clean worked up heads.

jmd

iTrader: (4)

No they don't. Close, but mismatched. Go for the LT1 intake if you go with LT1 heads.

Jekyll & Hyde

That would mean that the LT1 intake would not match up with the head ports then right? Anyone absolutly sure that they will not line up? Maybe some work on the base manifold.

jmd

iTrader: (4)

They kinda line up and all, it's just that there is port mismatch. There's just not much point of a TPI intake on LT1 heads.

Swapmaster

I think I read that there is a problem with the accessory holes in
the ends of the heads. Like one of the holes is missing or in a
different location or something. Is there any truth to that?

jmd

iTrader: (4)

Who wants to post 86-down & 87-92 heads?

Swapmaster

This is an 88 vette head.

Swapmaster

Are those water outlets in the front of those heads and are they
threaded?

jmd

iTrader: (4)

outlets no, not used as outlets if that's what you meant. threaded plugs to the water jackets yes.

Swapmaster

Here is a shot of the 1989 head. The water passages at the ends
of the head appear to be about the same as the passages on the
LT1 heads that the guy in the article blocked off.

If this is the case then I would not worry about them.

Swapmaster

One thing I notice missing from the LT1 heads are the oil return
holes. How do they get the oil drained from the top of the head?

On the picture above they are the holes just below the water
passages on either end of the head.

Swapmaster

jmd, could you put up a pic of the bottom of your head so we can
see the water passages?

SATURN5

courtsey of Ebay..




It looks like the passage on the LT1 at the corners will need a sleeve to pass water to the intake, but other than that, it looks the same.

Swapmaster

This is an LT1 gasket on an L98 block. Notice the overlap of the
water passages into the lifter valley.

Swapmaster

Here is a closer shot. The opening above the water passage is
the oil drainback hole. This is the only mismatch I see. You could
either have the passages in the heads welded shut or have
material welded to the block in those corners to seal it up.

Swapmaster

As far as getting coolant back out of the engine, I am thinking
instead of having coolant outlets put into the LT1 intake and
drilling and putting sleeves into the heads to match, why not
put our outlets in the back of the heads where they have the
plugs going into the water jackets. Just run your hoses from the
back of the heads to the remote thermostat housing. Then all
you would have to do is have the LT1 intake modified for the
distributor.

Swapmaster

I know the LT1 pulls coolant out through the water pump but
where does the coolant enter the engine at?

jmd

iTrader: (4)

The thermostat controls the incoming of water. The lower radiator hose goes from the PS tank in the radiator and flows water to the water pump in a normal position.

The upper radiator hose goes from the water pump to the DS tank in the radiator.

To answer your question, water goes into the engine at the block, and turns 90 degrees to go directly to the heads.

Matthew

jmd

iTrader: (4)

If you're talking about Gen II LT1 heads on a Gen I block, that would work. Accessories would have to be clear of it, which is obstacle numero uno. You'd have to thermostat control the water coming out of the heads, which is obstacle numero dos; not a big deal though.

m23haz

So in addition to doing what the article says I would also have to fill those holes that overlap in the picture? What if those holes werent filled in, what would happen?

SATURN5

The modifications in the article take care of the holes. The plugs that are pressed into the face of the head will cover the holes. The 3/16th hole thats drilled into the plug is the water passage. To use a standard intake the intake port side of the head will need modifed per the article. Using a LT1 intake may provide a different option.

Swapmaster

The idea I have is to use the LT1 heads and intake together.
Weld the coolant passages in the heads and drill the new 3/16th
hole as the article states. Only do the distributor modification to
the intake manifold. This will bolt the heads and intake to the
L98 block and mount the distributor.

The next issue is creating a way to get the coolant out of the
engine and to a remote thermostat housing as with a standard
LT1 intake swap. I think the most logical way to do this is to use
the hole that is already provided in the end of the head which
has the plug in it. Drill and tap it for a 3/4" NPT nipple and screw
nipples into them to route 3/4" heater hoses to the remote
thermostat housing with the outles in the head at the back of the
engine of course.

Presto, you now have Gen II LT1 heads and intake on your L98
engine.

The cast iron version heads from a Caprice that Vader taked
about flow 230fm on the intake and 147cfm on the exhaust
at .500" lift. I don't know if these numbers are actual but are the
only numbers I could find on this head. The aluminum version from
a Camaro flow 213cfm on the intake and 142cfm on the exhaust.

So as Vader states, the cast version outflows the aluminum heads
quite a bit. The cast heads have a cast# of 10125320 and were
used on 94-96 Caprice, Roadmaster and Fleetwood cars.
I checked availability and found them all over the country in
salvage yards. I ordered a cast iron pair today from a yard in
Missouri for $150 to speculate with. I figure that if this works, it
will be a low cost head and intake setup that most anyone can
afford to do.

Does anyone see any problems with this idea?

m23haz

So when you do the swap you use L98 head gaskets not the LT1 right?

Swapmaster: Why not just modify the heads for that coolant sleeve like in the article and then get the Lt1 intake modified for the coolant passages like John does to save you the trouble of figuring out how to run stuff without the modifications? It would then match up perfectly and you dont have to worry about running the lines out of the back of the heads.

Swapmaster

Yes, you would use the L98 head gaskets. I am looking for the
easiest way of doing this. The heads already have holes tapped
into the water jackets in the ends so why not use them. They may
already be big enough to screw a 90 degree nipple into them but
if not they can easily be drilled bigger for a 3/4" nipple. You could
even screw 90 degree 3/4" AN fittings onto them to use braided
lines so you would never have to worry about them.

Here is a pic of an LT1 intake gasket sitting on top of a Felpro
1205 gasket. The LT1 gasket will not support the use of a coolant
passage. The gasket is not wide enough to cover a coolant port if
one were added. So the outlets in the back of the heads are the
easiest way to go. Another note is the runner ports on the LT1
gasket match the Felpro 1205/Victor 95070 gasket perfectly.