lost 37rwhp with head/cam
Thread Starter
TECH Regular
Joined: Feb 2005
Posts: 472
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From: Davidson, NC
lost 37rwhp with head/cam Hi This is the second time I changed the heads and cam. The first time I hand ported the heads myself and swaped the valve springs with a mild cam and it ran great. This time I had the heads shaved,ported,valve job 2.02int,1.57exh at a shop and the guy ported the exh side the size of the gasket. I did not tell him to do that. My cam is a Thunder racing reverse split 230/224 .575/.563. The only thing I changed was the heads and cam. My other mods are ls6 intake,SLP airlide,nos 80 mm mass air,ceramic coated long tube headrs. I had it dyno tuned and the guy said basically its eating and not sh**ting. Please help 
It sounds like your combo is not working together properly. Unless it is setup custom for a certain set of heads and the rest of the combo, reverse split cams have had less than stellar results on N/A LS1's. Might want to look into that.
Depending on what gasket he used to match the exhaust port to you are real thin on the top and bottom of the port. The water jacket it not too far away. Need to check in towhat gasket was used and post it up here so I can see it. Another thing about matching the port like that is almost every LS1 exhaust gasket is larger than the average 1.75 header so what is happening is the burned gasses are hitting the lip, shoulder of the header flange when it transitions from port to tube and its causing excess reversion.
Thread Starter
TECH Regular
Joined: Feb 2005
Posts: 472
Likes: 0
From: Davidson, NC
On thunder racings site the cam made great power with stock heads, The gaskets used are the paper ones that cam with the headers. Plus he did not port the intake side. I have a stock set of 02 heads but Im thinking about 6.0 instead.
Flow the heads (at an independant of course).
Opening an exhaust port to the gasket is a major no no....I'm assuming you have a complete round exhaust outlet. Basically the the short turn "floor" of the exh. port was just destroyed and your larger exhaust port now flows less air than it did before it was opened up (certainly a good chance of that anyway).
Also, anyone that would take that approach on the exhaust port might have "handicapped" your intake port as well. You probably have larger heads that flow less air.....the complete OPPOSITE of the desired results. Flow and cc the heads....The results of that test should be interesting.
Good luck...
Tony M.
Opening an exhaust port to the gasket is a major no no....I'm assuming you have a complete round exhaust outlet. Basically the the short turn "floor" of the exh. port was just destroyed and your larger exhaust port now flows less air than it did before it was opened up (certainly a good chance of that anyway).
Also, anyone that would take that approach on the exhaust port might have "handicapped" your intake port as well. You probably have larger heads that flow less air.....the complete OPPOSITE of the desired results. Flow and cc the heads....The results of that test should be interesting.
Good luck...
Tony M.
Last edited by Tony Mamo @ AFR; Feb 3, 2005 at 11:16 AM.
Yes, the short turn floor in actual reality is just best left alone other tha blending. The main thing I was concerned with was the actual durability of the cylinder head itself for being so thin. Pm Tony and he might be able to help ya out on finding a dependable place to flow that thing to see what you actually have.
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Originally Posted by Formula-T/A
Thanks guys I was hopping I wouldnt have to change cams again.
One other thought since losing that much power is quite a change. Maybe double check that that the cam timing is right. I have seen big cams off one tooth make about the same or a little less than a stock cam and run okay. Just a though and a simple check. The heads may have been wrecked when ported, but boy would they have to be bad to lose that much power. Definitely possible though. Checking the cam timing would be the easiest at this point and a good place to start, maybe a simple solution. Easy mistake to make also. Hope this helps.
Mike Norris
Mike Norris