Lt4 carb manifold ?
Thread Starter
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Joined: Oct 2006
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From: POULSBO WA.
Lt4 carb manifold ? Ok here it is guys, i traded my lt1 503 rebuild motor for 1000$ and an 00 ls1. Now heres the catch, i had to seap them. Well the motor has been swapped into the 2000 and i get to the electronics and it really really gets to be a hornets nest. Obviously nothing is compatible.so i figure leave all the electronics in the car so everything works and go to a carb'd setup. BRILLANT RIGHT. so everything works. Now i have a GMPP lt4 manifold can it be modified to work on this lt1??? I dont care if the ports match up but will this manifold seal? Or have it shaved i do know? Thanks. Marc
Check and see if it bolts down. The spot to be concerned with would be above the intake ports interfering with the valvecover rail on the heads.
The LT4 injected manifold had LT1 ports in it, just had more material above the ports and that material would interfere with the valvecover rail on LT1 heads. The heads can be milled a little to clear that extra material, which is better than milling the material off the intake because of you mill it off the intake you loose everything that made it "LT4" and that material could have been used to match it to taller port LT4 heads.
I know the LT4 heads are considered "raised port" but the port is taller, the floor of the port is in about the same place.
Now understand everything I just wrote was specifically insight on the injected manifold, but if GM didn't bother to get the production piece right why would they have done better on the carbed one? At any rate take a close look at things and compare them to what I said and see if it helps you make this work.
Edit, GIZMO has said the carbed intake runners are different and expects to post pics.
The LT4 injected manifold had LT1 ports in it, just had more material above the ports and that material would interfere with the valvecover rail on LT1 heads. The heads can be milled a little to clear that extra material, which is better than milling the material off the intake because of you mill it off the intake you loose everything that made it "LT4" and that material could have been used to match it to taller port LT4 heads.
I know the LT4 heads are considered "raised port" but the port is taller, the floor of the port is in about the same place.
Now understand everything I just wrote was specifically insight on the injected manifold, but if GM didn't bother to get the production piece right why would they have done better on the carbed one? At any rate take a close look at things and compare them to what I said and see if it helps you make this work.
Edit, GIZMO has said the carbed intake runners are different and expects to post pics.
Last edited by 96capricemgr; Nov 3, 2012 at 05:38 PM.
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OMG ya'll are killing me with laughter!!!! Despite all the whiney, little girl drama and smart alec comments that take away from this site.....I can still count on it for a good laugh on a regular basis. THANK YOU!!
OP....cheapest & easiest is to modify an old sbc carb intake's bolt pattern to fit.
Thread Starter
TECH Fanatic
Joined: Oct 2006
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From: POULSBO WA.
Holly "CRAP" my apologies guys, i didnt realize it was my post that got the laughter goin! Yes i meant swap my mistake. I put the lt4 intake on my spare motor and everything seams to line up very well. I cant see down the runners, but i figure i can use maybe the lt4 gasket and silicone both sides and bolt it down. I dont care if the runners line up perfect or not, just want to get the car running well and down the road! I will check tomarrow if there is valve cover problems, and maybe modify them. Thanks
this thread will be known for the laughter by many. 
As I said the LT4 injected intake manifold runners were LT1 runners so my guess would be the runners line up just fine.
Edit, GIZMO has said the carbed intake runners are different.
Edit, GIZMO has said the carbed intake runners are different.
Last edited by 96capricemgr; Nov 3, 2012 at 05:37 PM.
The runners on the LT4 carb intake are nothing like the production intake. I have one around here somewhere and will try to post up photos. From memory, the miss-match will be pretty bad.
Thread Starter
TECH Fanatic
Joined: Oct 2006
Posts: 1,106
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From: POULSBO WA.
From what i can tell from putting it on my spare motor , i dont really see a miss match at all. I think your 1st post Caprice may be correct. Can u tell me where the miss match would be? Thanks
On the top is the LT4 carb intake. In the middle is a typical LT1 head casting. On the bottom is an LT4 production intake. The runner on the LT4 carb intake is clearly wider at all points.
