Boring the stock intake manifold?

[camok5]

I'm currently running a small block tbi thats bored out to 1 15/16'' sitting on top of a edelbrock performer manifold with a tbi adapter plate. I dont really like this set up because for some reason the tbi wont sit flush and keeps getting vacuum leaks. I was thinking of taking my old stock intake and having it bored out but I dont know how much power that will cost me. I know I can use a holley projection manifold or a edelbrock tbi manifold and try and bore it out but was looking for a cheaper solution first. How much power will I lose and does it really hurt the power band for a low end torque built 383?

 

[dyeager535]

I'd suspect in low end you'd probably not notice the loss. Just a guess, but even if there is a loss, probably not so much that you'll be amazed. Again, low end only, should really hurt the thing as RPM's increase.

Have you taken a straight edge to all of your gasket surfaces? It may be as simple as a bad adapter plate. I think I'd do that, make sure your TBI isn't warped while you are at it!

 

[camok5]

Yeah I didnt think it would hurt the low end to much. I think its a combo of both the manifold needing to be surfaced and the adapter plate not being perfectly flat.

 

[ryoken]

mill that chit... flat file is a wonderful tool...

personally I hate adapter plates for a couple reasons.. when I go 383, I'll do the Edelbrock TBI...

 

[camok5]

mill that chit... flat file is a wonderful tool...

personally I hate adapter plates for a couple reasons.. when I go 383, I'll do the Edelbrock TBI...

I was also thinking about using the edelbrock tbi manifold but I have heard that if your not careful when boring it out you can end up cutting into the egr passage. I dont want to spend that much for a manifold just to end up with it ruined. The holley projection already comes with 2'' bores but you have to move your brackets around to make it work, it is a lot cheaper though. I figured that if I was going to have to remove my current manifold I might as well replace it with a real tbi one so as not to have to deal with the stupid adapters anymore. Has anyone used a after market throttle and tv bracket because I know that the stock one wont work with the holley projection manifold?

 

[rcamacho]

If you bore the manifold to match the TBI it should be a non-issue. Might as well port match to the heads while you're at it.

 

[camok5]

Well I think the other problems are runner length and plenum volume. I'm not sure how much different they are from the other manifolds.

 

[4X4HIGH]

On my new engine (yet to be installed) i used a stock TBI intake and had my buddy put it into the CNC mill and bore the manifold for 2" bores since i'm going to be running a 454 TBI unit on it. Once he had the manifold all set up in the mill he bored it for the 2" bore but tapered the bore as it went down so it will help build more velocity and should make it better than stock.