TorchRedlt4man

According to Jim Mason (96 Grand Sport fame) this is a mod that is beneficial to a slightly modded LT4.

http://www.hashmarks.com/techtips/in...ke_porting.htm

I need to replace my intake manifold gaskets. A little bit of seepage at the rear.

While I have my intake off, I was thinking of porting the intake manifold to the size of the intake gasket. Time consuming but this would be the ideal time to do this.

Anyone have any thoughts or tips?

Pete K

Typically, gasket matching results in minimal gains. I would not think that paying someone $100+ an hr would make it worth it, but if you are doing it yourself, it is a great deal. You may only get 2-3 hp. Then again, 203 is not a bad deal. You could get a few more if you are lucky. Get grindin

all4c4lt4

Sounds like a perfect time to pull the heads and send both the heads and intake off for a full matching port job!

Otherwise, I doubt you'll see any real gain from only matching the gasket alone. If you do it yourself, good luck, and be careful as the oem lt4 intakes are getting hard to find and are $$$. I would definitely not pay someone to do the intake gasket matching port work alone.

ALLT4

What's being described in that article isn't full gasket matching. He's just matching the top of the ports (intake) to the stock head port's shape.

When I fully matched mine it was with a 12367777 gasket both on the intake and heads. There is a considerable amount of material to take out of both to do this. Originally I was just going to do the port matching but after some reading I discovered it didn't do much without some further bowl cleanup and further porting.

So in the end the end I went a full port job and what is supposed to be a 5 angle cut.

Here's the numbers with JUST a Hot Cam and tune. Everything else is stock from the exhaust manifolds back.

rocco16

Why would one assume that the holes in a gasket are the ideal size/shape/location?

I say, "What's the point?" Do it right....full, professional porting job. Won't give you much, but will help when you add the other stuff like cam/headers/etc.

Larry
code5coupe

LT4BUD

I matched mine to the ....777 intake gaskets.....

Jim Mason knows what he is talking about!!!!!

Also Doug Rippie promoted this mod way back....and others

It just makes sense to correct any mismatch if you after maximum performance.....

Gary04Z06

I don't know how much gain you'll see, but Jim Mason knows what he is talking about, I've seen him go past me to many times on the track to disagree with him.

ALLT4

Here's what it looks like when you fully match the heads to a 12367777 gasket, quite different from the Jim Mason page.

Then look here and find LT4's with just a Hot Cam and see if they're making the same power. Some are but they have headers also. I'm positive this is where my low torque number is coming from. Still it's a substantial gain from a bit of porting.

So I'm anxious to see what happens with a full exhaust. Priorities keep getting in the way though.

I was always under the impression that's why the LT4 intake was different, so that when the time came you could use the extra material to fully match the ports. Frankly I thought it was common knowledge.

rocco16

Went there, but there were no cars with just port matching to compare with the one car that had just a Hot Cam. By the way, that one car had a problem somewhere, since he made the exact same RWHP with the HC as my bone stock LT4 made....so I wouldn't compare that car to anything at this point.

Absolutely no way port matching will give as much power as the Hot Cam can give. None. Nada. Zip.


Larry
code5coupe

d48mclain

I've always considered it's the little details make the whole.

Port matching has been controversial regarding power output for sure but on highly modded cars the intake is a definite restriction. GM never in their wildest dream intended these engines to make 600 hp and the intake is one area that can be improved.

The biggest restriction lies right around where the injectors sit and there is not enough metal just above the injectors to port the intake properly. If that area has additional material welded and the path straightened, then port match (really porting) adds significantly to a cars capablility of producing a lot of airflow.

At what power level this appreciately helps? Not sure, but for sure if your in the 450rwhp or above it adds at least 10 hp.

If you do your own porting make sure you remove the plate underneath the intake and clean it very well before putting the intake back on the car. One intake I had was professionally ported and the car came out way below what we expected. Then all of a sudden the car picked up on it'w own. Turns out there were shavings from the intake that got caught between the pistons and the cylinder wall and the rings were not seating. After this had cleared itself the car ran great but we didn't know why until after the teardown.

ALLT4

I know this. What I'm saying is you'll make a ton more power than with just a Hot Cam. Bryan Herter of PCMforless said he never saw an LT4 make that much power with just a Hot Cam and no headers. Or at least he said it's better than average power anyway from a Hot Cam only.

ALLT4

Beleive me, when I did mine it was already off and then when I was done it went to the car wash and sprayed through several cigs.

MPM IV

I can't see why you wouldn't. It's easy and can be done with a dremel. It isn't going to give incredible gains, but every horsepower helps.

~db~

When I replaced my intakes gaskets, I went with the 777s as well. Thanks Jim Understand that there is a Huge difference btw the standard LT1 app and the 777s gaskets. I also bench sanded the intake ports myself basically just to deburr and smooth a bit, nothing major. Did all the work myself so no money spent except the parts. I WILL tell you that I noticed a SOP difference. No other mods done at the time. I don't have dyno results to post so believe it or not, that's my experience

STL94LT1

If I remember correctly Jim Mason made 342 rwhp with just a Hot Cam, intake porting, shorty headers, and bone stock heads.

LT1GMC

If you take those gaskets and place them up against the stock LT4 INTAKE, you will find the intake needs more than an eighth inch ported on the top side to match the head and gasket, as a matter of fact, the LT1 and LT4 intake PORT HOLES are exactly the same. The LT4 however, has about a quarter inch more material at the top so it can be ported to match. My theory? GM guys ran out of time developing the LT4, and didn't get time to do a new casting for the inside of the manifold, just the outside. How do I know? I bought some of the first
LT4 heads available, and the ORIGINAL LT4 service parts gaskets were made with the ports upside down, the taller part of the port was on the bottom. Calling a friend in engineering, he sent me a blueprint, and it was wrong too. I corrected him, and a few months later, the proper design gaskets, with a new part number, were available.

LT4BUD

My theory is we will never know the true story of the LT4.......but I have become suspicious that the engineers actually built the LT4 as about a 400hp engine, same output as the LT5 to prove pushrod technology, and then had to detune it at the demands of marketing people.....

Things like the mismatched manifold give clues as to this possibility.....if you port match to the ...777gasket, then put in the LT4 hot cam...put in a 52mm throttle body......and what to you have??? 400hp..

But we will never know..

96GS#007

Couple things....The idea behind the ***intake*** port matching on the LT4 has been well documented and discussed at various times by Doug Rippie. As I recall, Lingenfelter also used to do this and you could order a ported intake directly from LPE until a few years ago. All I did was take what those guys did and copied them. One it made sense and two I've done similar types of port matching in the past with success. Yes the gains are very small on these engines. However, at the time I ported mine, I knew that cylinder head work and a cam were in the plans.

Mike mentioned I made 342rwhp with the ported intake, shorty headers, and the HOT Cam. This is correct. With nothing more than mild pocket porting of the cylinder heads and port matching the cylinder head intake runners to the intake manifold I made 363rwhp.

The bottom line....port or don't, it doesn't hurt my feelings. I had a staged plan for the engine and simply tried to document things as I went along for others to use if they found it helpful.

ALLT4

I thought port matching was standard practice for a better breathing motor? This thread has me wondering how many folks actually do it.

Might not make much difference on stock stuff but when you start adding bigger cams and headers I think it's well worth the effort. If you're going to have the intake off, just go a bit further with taking the heads off, clean up the bowls and port match the intakes.

It's only bolts and few more gaskets, plus maybe some extra money to have someone do it if you can't do it yourself.

~db~

a bit further?? I think it may be a wee bit more than that my friend but yes, it would be worth it in the long run. And if you go that far...time for a cam, dual T-chain, WP, wires, plugs, headers. Does it ever stop??