Intake porting...

Bought an LT-4 Intake some years back and used it on the 396 build. Performance on that build was a bit disappointing and while I believe most of it was the result of the totally boned chassis, I was getting the intake ready to put back on top and I noticed this:

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Clearly the intake runners are a lot smaller than the runners on the gasket, which I had trimmed myself to match the previous AFR heads. So THAT tells me that despite the larger heads, the INTAKE was knocking down what the heads could get.

I am thinking that I should send the Intake to Lloyd and have him port it out. Has anyone else had their intake ported? And did you notice any gains?

Lloyd ported my LT4 manifold, but I don't have a before/after because it was never run until it was on the setup I've got now. I will say that he HOGS them out, to the point that your only gasket option is the GM LT4 Race gasket, PN 12347777.

Yeah, I emailed Lloyd on it and he says he removes about 3 lbs, which is a lot of aluminum. SO I am packing it up and sending it to fat camp. Another couple of weeks isn't going to throw this build off 'schedule'... .

Back in "ye olde days" when there was no LE or AI (only LPE and Craig Gallant/GTP), I had a set of LT4 heads and the intake manifold ported by CNC Cylinder Heads in Pinellas Park FL. Talking to Pete Incuado at CNC, he confirmed that the stock LT4 intake was basically the same internally as the LT1 intake, it just had the extra meat at the top of the intake runners to allow the ports to be opened up to match the LT4's raised runners. He claimed he was involved with GM in the development of the LT4 heads and intake, and that GM ran out of money for the project, so they never finished the work on the intake manifold, hence it didn't match the heads.

When I got mine from CNC, it was really opened up on the runners. Pete told me that he always flows with the intake manifold on the heads, to replicate the real world more accurately. He told me to have Second Street install his manifold on the head on the flow bench, and see what happens. When they flowed the heads with the manifold, it picked up 3% more flow at the top end.

NICE!

I had always just assumed it was bigger and better. Until last night I'd never really even considered the intake as a potential point of restriction. From this side, it seems obvious, but since there is only the Lt4 and Lt1 Intakes and I've got the Lt4, I just assumed I was covered.

Thanks for that info. I appreciate it.

Good info Fred. Thanks for sharing that! @Injuneer

I just got back my LT4 intake from Lloyd and DAMN! I wish I would of took before and afters, because I didn't expect to see a difference like that. I'll post pics tomorrow. Lloyd also told me that he takes about 3lbs out the LT4 intake and it weighs about 21 lbs. before he fixes that. It took two weeks for me to ship, have him do his thing, and have him ship it back to me. Not bad at all.

OVA1,

sorry for confusion on the phone, the ported intake is worth about 10 RWHP on a 400 RWHP set up.

When on the phone you asked how much a ported LT1 intake would help and I said "about another 10 HP" then you asked about how much a ported LT4 intake would gain and I said "about another 10 HP" meaning the same 10, not an additional 10 over ported LT1 intake.

I thought I answered the same question twice for you not realizing that you were asking about the difference between LT1/LT4 ported intakes.

As mentioned here, the only difference is a lil extra material at end of port so it can be opened up to the larger to fit the LT4 or LT4 "race gasket" if the heads are that large.

Be sure and send an intake gasket that matches the heads as I mentioned on the phone so I know what size the gasket area on the heads are and I can make the intake the same size.

Lloyd

Thanks Lloyd!

It's on the way and I'll stick a check in the mail tomorrow to cover the porting and shipping. Super jazzed. I spent an entire day trimming the gaskets to fit the old heads, and I cannot BELIEVE that I didn't even THINK about setting it against the intake to check the size of those ports.

LOL!... Rookies.

Hell yes!




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Viva la difference!