Valve Job Question, what to get with my new heads.
10-25-2004, 08:52 AM
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Valve Job Question, what to get with my new heads. I am currently in the process of porting a set of 5.3 heads and installing some Manley 2.02/1.60 valves in them. I will be having machine work done soon and need to know what kind of valve job to look for. I have been looking at some books by David Vizard and he states what works for SBC heads. I take it this is way different for ls1 heads.
Should I go with a three angle or five angle job? What are the angles and what length should each be? I will be running a cam with more overlap then the TREX so low lift flow should not be as important as it would with a cam with less overlap. Thanks?
Also, I know that the valve seats can just be re-cut for the valves in a 5.7 liter 242 casting but can this apply to the 5.3 also? Are they the same seats?
I would think the exhaust is because they are both 1.55 but the intake is only 1.89 compared to the 2.00 of the ls1. Thanks.
Should I go with a three angle or five angle job? What are the angles and what length should each be? I will be running a cam with more overlap then the TREX so low lift flow should not be as important as it would with a cam with less overlap. Thanks?
Also, I know that the valve seats can just be re-cut for the valves in a 5.7 liter 242 casting but can this apply to the 5.3 also? Are they the same seats?
I would think the exhaust is because they are both 1.55 but the intake is only 1.89 compared to the 2.00 of the ls1. Thanks.
10-25-2004, 04:47 PM
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You must open the factory 5.3 intake seat slighly for proper 2.00 valve function. Also I just geta 3 angle cut on the seat and a 30 deg. back cut on the valve. I use David Vizards books also and they are more along the SBC lines of port work.
10-25-2004, 07:43 PM
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I would highly recommend a 5 angle valve job. I have some inside information that says the LS1 heads love a 5 angle valve job and you can see as much as a 20cfm increase from doing this. This information is from a reputable porter that is on these boards.
-Sly
-Sly
10-26-2004, 07:12 AM
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Originally Posted by Bo White
You must open the factory 5.3 intake seat slighly for proper 2.00 valve function. Also I just geta 3 angle cut on the seat and a 30 deg. back cut on the valve. I use David Vizards books also and they are more along the SBC lines of port work.
Thanks Bo, I have been following some of your posts and you seem to have ported a couple of heads. If you have any additional pics and you don't mind sending them to nfulford@hcea.com I would appreciate it.
10-26-2004, 07:13 AM
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Originally Posted by slyws6
I would highly recommend a 5 angle valve job. I have some inside information that says the LS1 heads love a 5 angle valve job and you can see as much as a 20cfm increase from doing this. This information is from a reputable porter that is on these boards.
-Sly
-Sly
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10-26-2004, 11:41 AM
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Originally Posted by Bo White
Sending ya some pix. I also do not like 5 angle on the street, the narrow margin will eventually become wider and the 5 angle cut will no longer be there.
10-26-2004, 06:40 PM
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make sure you open up the throat on the intake side to accomadate the 2.02 valve,, i hear its usually .200 less than valve diameter is a good rule. the 5 angle valve job has nothing to do with the seat width, only that there are two bottom and two top angles, not one in a three angle. just make sure the seat width is atleast .050 wide or so on the intake and .065 or so on the exhaust, then you could put 20 angles on it if you wanted to. i wouldnt get a 5 angle on an ls-1, it usually causes them to back up past .550 lift, though id probably go with a 65 degree bottom with a high lift cam i.e .610 or so. also im told that a 30 degree back cut on a valve isnt the trick, its 33 degree, using a 45 degree seat.
dave
dave
Last edited by IrocLs1; 10-26-2004 at 06:43 PM. Reason: spelling
