Anything else i need?

[HottestZ28]

I am purchasing the LT4 intake from summit, is there anything else i need other then gasket, fuel injector o-rings?

[Injuneer]

Hmmmm.... do you already have the LT4 heads that the LT4 intake manifold bolts to?

[HottestZ28]

I want bigger heads then LT4 but i have stock heads right now and was going to port match them for now? OK or not?

[Joe 1320]

Not! the intake is specifically designed for the LT4 heads which have different port dimensions.

[Injuneer]

Well.... sort of.

The reason you can't bolt an LT4 intake on LT1 heads is because there is an interference near the rail that the valve cover sits on. Either the heads of the intake need to be machined to eliminate this interference.

And, surprisingly, while LT4 head intake ports are 0.10" taller than LT1 head intake ports, the LT4 intake manifold ports are pretty much identical those on the LT1 intake..... in fact even the runners are the same. The only difference in this respect on the LT4 intake is that there is more "meat" in the roof of the runner to allow the LT4 intake to be ported to match the LT4 heads. Apparently GM ran out of money (or time) on the LT4 development program, and never "finished" the LT4 intake.

Here is a picture of an LT1 intake gasket held against an LT4 intake:



Here is the LT4 intake before and after porting.

[HottestZ28]

Thanks for all the help!!
But I maybe looking at this stupid but, from what it looks like the LT1 gasket looks to be larger then the ports on the LT4 intake so how can the LT4 intake support more horse then the LT1 with smaller ports

[Injuneer]

Its the LT4 heads that make the difference on a "stock" LT4. The intake has no real advantage. On the stock LT4's, there is a mismatch between the heads and the intake manifold.

If you have a set of well-ported LT4 heads, it takes a lot of work ($350 in my case) to get the LT4 intake to the point where it will support the ported LT4 heads. Even the LT4 intake gaskets are not all that big. You need to get a special oversize gasket to use on ported LT4 intake + ported LT4 heads.

I wish I hadn't "lost" the photos I took of my LT4 intake after CNC Cylinder Heads got done with it.

[HottestZ28]

so basically keep my LT1 intake and get it ported out to the heads i finally decide to go with? or does the LT4 intake better suit larger flowing heads?
Sorry for all the questions just want to understand and not buy something that won't help anything

[Injuneer]

Sort of difficult to understand.... but the LT1 intake will support very high flowing ported LT1 with very little port work on the intake, if any.

I got my LT4 stuff from Pete Incuado at CNC Cylinder Heads in Florida. He claimed to have participated in the LT4 engine design, and is the source for a lot of what I told you above.... in his words, the LT4 intake was "compromised". His LT4 heads were extremely good on the intake side, and when we flow tested the heads + intake on the flow bench, flow increased over the heads alone..... something we could not duplicate with some very expensive, very high flowing LPE CNC LT4 heads and flow matched intake. Unfortunately, Pete's LT4 heads fell flat on their face on the exhaust side, but he sure had the intake nailed.

CNC Cylinder Heads makes the 5-axis CNC machines that outfits like Lingenfelter use to port heads.

[HottestZ28]

So what do you think i should do- i want my car to have like 450 to 500 horse and beable to run high 11.sec quarters but reamain agressive street and not be toally drag. What step should i take to achieve this?