will these bolt up together? are the bolt holes the same? IF so why haven't I seen anyone runnung this combo??

 

If you are asking why no one uses LT1 intakes and Vortec heads on our L98s, Its because the LT1 is a PAIN IN THE A** to convert to a normal distributor/cooling system/head bolt design. If you are talking about why people don't run LT1's with Vortec heads, It is because (1) Vortec heads will not bolt up to LT1s (2) Vortec heads would be downgrading, and (3) You are on the wrong site for LT1s.

------------------
1990 Pontiac Formula 350
Rebuilt 355
COMPCAMS 212/212 .440/.440 cam
Flowmasters 80 series.

 

"Its because the LT1 is a PAIN IN THE A** to convert to a normal distributor/cooling system/head bolt design."

thats all i wanted to know

 

Do a search there are a couple different discussions on this. You need to check out the tech article on converting the LT1. As for the vortecs, they won't bolt up with out some modification, the bolt pattern and port heigth is different. Some say an Lt1 can be modified to work, some say it can't. (Im in the latter group) The vortec heads are an upgrade from any stock third gen head, I don't know how they compare to the stock LT1 heads.

 

I'm one of the brave ones preparing to attempt the buildup. It may be an odd one or not, I dunno...if it is, it'll be a internally balanced 335 stroker with a ZZ4 cam and Vortec heads with a stock TB and an LT1 intake, or the same with a stock late model 350 shortblock. Considering I have everything to build a seperate 350 from my main project motor using new GM parts, I'll probably just do that...stock cast piston late 350...

Either way, the recipient of this motor will be a '91 Sonoma converted to a SBC although the motor may temporarily reside in my '86 IROC.

I did take a look at the '96 Vette LT1 longblock I have...the four outer bolt holes in each head are in the same location at the same angle as Vortec heads...the only concern should be port alignment from what I've seen. The middle 2 bolt holes in the LT1 Vette heads are different but the Vortec heads do not have them anyway...no EGR to have to worry about them. If I do it will be very soon, I will document the findings of the engine's performance. Everything looks posible to me...

Looks to me like a damn good low-buck combo, but the only downside is the modifications it takes...some people can do it, some can't. We'll see...if not, no loss...the intake will end up on the LT1 engine and the Vortec heads and 350 didn't cost me anything anyway!

 

dhirocz,
millican stated " the four outer bolts are in
the same location (same as gen1 heads) and
the last eight had to be filled and redrilled"
on a vortec the bolts that hold the heads to intake
are all at perpendicular angles to the intake.
youll have to build the outter four postitions
upwards and drill 90* to the plane of the intake.
now if you are using dual patterned drill heads
then you will be ok, but im thinking the roof
of the intake will be very short. lt1 or gen1
intake...
airdeano

 

I am looking in to using an lt4 intake on my car I have the fast burn heads on it now with a home made vortec base. I went to the chev garage and ordered a set of lt4 intake gaskets to do some comparing with I will also pic up a set of lt1 as well when I pic them up I’m going to compare them both to the vortec heads and decide witch will be the best to work with I couldn’t find the port size on the net of the lt4 but looking at a pic of it next to the lt1 the lt4 has a lot of meat on the outer edge of the port that can be removed to match the vortec heads if needed the lt1 head ports may even be the same size I wont know until I get the Lt1 and LT4 gaskets. The problem I had when I used the stock tpi base was that the vortec ports went an 1/8 past the edge of the tpi base so I had to build it up with a welder resurface it and then port it to mach the vortec heads not hard work just a lot of time to get the ports shaped right. As far as the bolt pattern goes fast burn heads have the center holes drilled already probably not the correct angle but will see for the stock vortec heads if you decide you have to have the center holes I would have the machine shop drill the heads at the correct angle for the lt1 or lt4 intake witch ever you decide to use. I havent made up my mind yet if I’m going to do this or not I just started the group purchase for the SDPC base and I’m obligated to it know and am not positive if I want to spend a possible 500 to try the lt4 manifold even if I do get it to work I will have to justify the gains to spend an additional 500 dollars for parts plus 150 worth of dyno runs. My car has the hot cam in it so I would probably get a good gain from the lt4 intake moving my peak power up in the rpms . The last thing is I don’t know If I like the way they look I kind of like the look of the TPI better. I don’t know some of you are more familiar with the lt1 intakes then I am what do you think. The car I will be using has a 355 9to1 comp with fast burn heads crain 1.6 rollers and the lt4 hot cam with slp headers the intake now is a stock tpi base modified to use with vortec heads then extrude honed with slp runners and all the free port work 52mm tb and 24lb injectors.

 

airdeano, didn't make a point to look at that, my bad, but either way, it isn't too difficult for me to do that Anybody gonna do this with an LT4 intake? I would but the only thing that keeps me from pulling out my wallet is port alignment. Would the ports on the LT1 fit the LT4, I have heard that the ports are slightly off. Thanks

 

The outer intake bolts are fine you will not have to redrill these and I dont see why we should redrill the center bolts the vortev heads do not use them any way so why not just fill them in and not use them. I have ben looking in on this all week and this is what I have found the lt4 intake ports are .200 taller then the lt1 the lt1 ports are the same as the l98 heads I have not found the exact port size for the vortec heads so I am going to guy a caliper to check my heads with and compair size to a lt1 and l98 port I have tried to get a set of lt4 gaskets but no one has these in stock and you have to get them from the dealer at 50 a set so Im going to serch the net tonight in hopes of finding the port size of both sets of heads and compair them if they are close I will break down and spend the cash for the gaskets I have talked with a few lt1 guys that did the swap and they have ben useing the lt1 fuel rails and injectors the new lt4 intake is 180 so this is going to cost around 400 to do the swap not bad compaired to a MR and same price as the tpi vortec base and you dont have to get funners I bought a complete lt1 intake to day to use for the fuel rails and injectors if I decide to do this swap we could mod the lt1 buy bulding up 1/2 around the ports and then porting them out to the vortev heads but Im hoping that the lt4 will mach up I was looking at one of the other lt1 posts and saw the site that was making the lt4 a direct bolt on to the lt1 I dont see what they had to grind off but I gess I will if I buy the lt4 intake if some one knows ware I can get a lt4 intake cheap or if they can find some one who needs an lt1 intake for a part trade on one send them my way I will probly break down and order a set of lt4 gaskets tomorrow. I'll keep you guys posted on what I find I tried to get SDPC to comapir a set of vortec gaskets and lt4 gaskets for me they had a set in stock I even told them that if they mach I would buy a set and buy the lt4 intake and they still would not do it they just said it would be a waist of time that it would not work and when I said their was an l98 using a lt1 intake they said their was no way but we no diffrent.

 

Do you realize there's only one period and no commas in the post. Makes for very hard reading.

 

Quote (with punctuation)
The outer intake bolts are fine. You will not have to redrill these. And, I dont see why we should redrill the center bolts. The vortec heads do not use them any way, so why not just fill them in and not use them.

I have been looking in on this all week and this is what I have found. The lt4 intake ports are .200 taller than the lt1. The lt1 ports are the same as the l98 heads. I have not found the exact port size for the vortec heads so I am going to buy a caliper to check my heads and compare it to the size of the lt1 and l98 ports. I have tried to get a set of lt4 gaskets but no one has them in stock. You have to get them from the dealer at $50 a set. So, I'm going to search the net tonight in hopes of finding the port size of both sets of heads. If they are close I will break down and spend the cash for the gaskets. I have talked with a few lt1 guys that did the swap and they have ben useing the lt1 fuel rails and injectors. The new lt4 intake is $180 so this is going to cost around $400 to do the swap. Not bad compared to a MR and the same price as the tpi vortec base. And you dont have to get funners(?). I bought a complete lt1 intake today to use for the fuel rails and injectors if I decide to do this swap. We could mod the lt1, try building up 1/2" around the ports and then porting them out to the vortec heads, but I'm hoping that the lt4 will match up.

I was looking at one of the other lt1 posts and saw the site that was making the lt4 as a direct bolt on to the lt1. I dont see what they had to grind off, but I guess I will if I buy the lt4 intake. If someone knows where I can get an lt4 intake cheap, or if they can find someone who needs an lt1 intake for a part trade, send them my way. I will probably break down and order a set of lt4 gaskets tomorrow. I'll keep you guys posted on what I find.

I tried to get SDPC to compare a set of vortec gaskets and lt4 gaskets for me. They had a set in stock and I even told them that if they match I would buy a set and the lt4 intake. Yet they still would not do it. They just said it would be a waist of time and that it would not work. When I said there was an l98 using a lt1 intake, they said their was no way. But, we know different.

No harm intended, just making a good post easier to read...



[This message has been edited by RCR (edited October 24, 2001).]

 

So you guys were thinking about this to! Anybody got any news?

 

I have already done just what you guys are talking about. To clarify something, the LT1/4 intake will NOT blot up to the Vortec bolt pattern. The bolt holes are just too high on the head. The only way to do this would be to either drill the standard bolt pattern in the Vortec heads or build up some material on the intake manifold so you can drill the bolt holes. Lucky for us though, the Fast Burn heads already come drilled with both bolt patterns.

As for the swap, it is very straight forward and exactly like the LT1 intake swap to standard heads except for one thing. The port alignment is slightly off. Actually, the bottoms of the ports match perfectly. The ports on the Fast Burn heads are slightly larger (taller) than the LT4 intake ports. What I did was buy a set of FelPro 1255 gaskets. These gaskets are perfect for this swap because they have the Vortec ports (they match the Fast Burns perfectly) but they also have both bolt patterns on them. I took these gaskets and taped them to the mounting surface of the LT4 intake. I taped them so the bottom of the port lined up with the bottom of the port on the gasket. Then, I marked all the bolt holes and took a Sharpie and colored in the small areas where the ports on the intake manifold were smaller than the gasket. This was maybe a tenth of an inch at most. I removed the gaskets and took a die grinder and matched the ports on the intake to what I had marked. With that done, the rest of the swap was exactly like the LT1 intake swap. You can do a search for my earlier posts about the swap. I haven't been able to really drive the car that hard yet due to the fact that I put this together on top of a brand new ZZ4 shortblock with an LT4 hotcam. Aside from breaking the motor in (i'm pretty much done with that now), the car hasn't been running well due to the stock chip. I will be trying the 30 lb SVO injectors and new prom that I'm burning on Monday or Tuesday and let everyone know how it goes. I can tell you this though.....even with the stock prom and injectors (bumped up fuel pressure to compensate for lean upper rpms), the motor will kind of slowly walk to 4500 rpms and then it just takes off. The first time I did a pull like that it scared the hell ut of me. It kept pulling hard up to 6000 rpms until I finally let off out of fear of running too lean. I'm confident this setup will be able to scream well up to 6300-6500 rpms. As soon as I get the car running right with the custom prom, I'll try to get some dyno numbers and I'll definitely take it to the track. If anyone has any questions, feel free to ask.

Thanks,
Stephen

 

Wow I just realized this post was almost 6 months old!!!! Oh well maybe I've helped someone out.