Porting LT1 Heads to LT4 Gaskets
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Joined: Jul 2006
Posts: 127
From: Louisville, KY
[QUOTE=96capricemgr;6283730]IF there is enough material what do you think you will accomplish?
I accomplished .50 sec. off my e.t. in the 1/8 mile just port matching and porting my heads and intake. Why does all performance heads have bigger ports than stock then. I would guess for better flow.
I accomplished .50 sec. off my e.t. in the 1/8 mile just port matching and porting my heads and intake. Why does all performance heads have bigger ports than stock then. I would guess for better flow.
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Joined: Feb 2004
Posts: 4,800
Well since you wont listen to me maybe you will listen to someone you think is good.
This is also in reference to port matching to an LT1 gasket as opposed to the LT4, so what you are looking to do is worse yet.
Post number 2 and 14 in particular.
http://www.ls1tech.com/forums/lt1-lt...-question.html
This is also in reference to port matching to an LT1 gasket as opposed to the LT4, so what you are looking to do is worse yet.
Post number 2 and 14 in particular.
http://www.ls1tech.com/forums/lt1-lt...-question.html
Thread Starter
Registered User
Joined: Jul 2006
Posts: 127
From: Louisville, KY
Well after reading that I would agree that it would be wrong to try to gasket match to the LT4 gaskets on LT1 heads. That was defineltly some good information about shapeing the ports. I am glad I did not get to crazy when I was porting mine. The guy at the machine shop said it look liked a good port job. Though I know they are nothing close to LE heads.
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Joined: Aug 2007
Posts: 746
From: Bennett N.C.
DO NOT gasket match the intake. The floor and roof are fine at the gasket area. Just remove material from the divider wall between ports at gasket area and the outer walls just need to be straitened up if you have the intake that tapers smaller at the top. If your intake is pretty much strait on all walls, just leave it alone at the gasket area.
You wanna raise the roof of the intake just behind the inj and remove as much of that ski slope as you can.
You wanna have the port steadily get wider as it goes back to plenum area and have it end up about .100-.120 wider at the plenum area.
Lower the floor (NOT at gasket area) all the way to plenum and correct the angle that the ports on the intake and head match up. It is more of an L shape now and you need to straiten this out.
Open the TB holes up to 58 MM and grind down the IAC bump and make the TB holes go strait back by removing a lot of this hump. Then taper the bump smaller and round the bump off on the back side like an air plane wing. Remove a lot of material from the sides of the intake behind the TB holes and make it slowly taper to the rest of the intake. Make sure and look/feel on the outside of the intake and see where the thin spots are that will limit what you can do.
You wanna raise the roof of the intake just behind the inj and remove as much of that ski slope as you can.
You wanna have the port steadily get wider as it goes back to plenum area and have it end up about .100-.120 wider at the plenum area.
Lower the floor (NOT at gasket area) all the way to plenum and correct the angle that the ports on the intake and head match up. It is more of an L shape now and you need to straiten this out.
Open the TB holes up to 58 MM and grind down the IAC bump and make the TB holes go strait back by removing a lot of this hump. Then taper the bump smaller and round the bump off on the back side like an air plane wing. Remove a lot of material from the sides of the intake behind the TB holes and make it slowly taper to the rest of the intake. Make sure and look/feel on the outside of the intake and see where the thin spots are that will limit what you can do.
The intake port of the heads should not be gasket matched either. You can match the roof, floor and center divider wall but the outer walls just need to be squared up and NOT layed back to the gasket.
Once you open up the push rod pich as far as you can, you want the outer wall to come strait back and keep the cross section as consistant as possible.
Laying the outer wall back to the gasket will do a 2 things . . . .
1 - Make the cross sectionsal areas at the PR pinch and gasket area have more of a variance causing more of a velocity change (faster at PR pinch and slower at gasket area) and hurting flow.
2 - Make the air have to see even more of a turn to go past PR pinch and hurt flow.
You want the gasket areas on the intake manifold and head to match but they do NOT need to match a gasket on the outer wall. If someone ported the heads and gasket matched them and they are all jacked up, I guess the damage is done and gasket matching the intake will not hurt any but if the heads were done correctly and NOT gasket matched, the intake doesn't need to be either.
When you measure in the intake, you will see the gasket area is pretty much the largest area and the last place to grind when trying to help flow. Measure every 1/2 inch or so up through the runner and you will see it gets smallest at the ski slope for the inj. THIS is the one area you want to grind on if you are only gonna grind on one area. Try and get the cross section at this point to match the cross section at the PR pinch and even bigger if possible. Once you have this measurement, try and keep the port the same cross section from there to the gasket area on the intake and from the gasket area to the PR pinch of the head. Once you understand this is what needs to be done, you realize opening the gasket area on the intake and head will make these areas bigger than the 2 restriction areas, you understand why it is wrong.
The gasket areas are NOT the restrictions and the PR pinch and ski slope of intake are.
Once you open up the push rod pich as far as you can, you want the outer wall to come strait back and keep the cross section as consistant as possible.
Laying the outer wall back to the gasket will do a 2 things . . . .
1 - Make the cross sectionsal areas at the PR pinch and gasket area have more of a variance causing more of a velocity change (faster at PR pinch and slower at gasket area) and hurting flow.
2 - Make the air have to see even more of a turn to go past PR pinch and hurt flow.
You want the gasket areas on the intake manifold and head to match but they do NOT need to match a gasket on the outer wall. If someone ported the heads and gasket matched them and they are all jacked up, I guess the damage is done and gasket matching the intake will not hurt any but if the heads were done correctly and NOT gasket matched, the intake doesn't need to be either.
When you measure in the intake, you will see the gasket area is pretty much the largest area and the last place to grind when trying to help flow. Measure every 1/2 inch or so up through the runner and you will see it gets smallest at the ski slope for the inj. THIS is the one area you want to grind on if you are only gonna grind on one area. Try and get the cross section at this point to match the cross section at the PR pinch and even bigger if possible. Once you have this measurement, try and keep the port the same cross section from there to the gasket area on the intake and from the gasket area to the PR pinch of the head. Once you understand this is what needs to be done, you realize opening the gasket area on the intake and head will make these areas bigger than the 2 restriction areas, you understand why it is wrong.
The gasket areas are NOT the restrictions and the PR pinch and ski slope of intake are.
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