Okay, Looking at a set of heads with 2.055/1.60 valves, can they be used on stock LS1 shortblock? I want to use a nice cam, so fly cutting will already be planned...
Thanks
Charlie

 

Will be close. After you get over 2.02, it seems that any gains by going larger are negated by valve shrouding.

 

Like previously posted once you get over the 2.02 size you really don't see enough pick up to make it worth it. We did some flow bench testing a number of years ago on our 5.3l heads and found that a 2.04 valve actually lost midrange and posted the same top end flow results as the 2.02 valve we use in them now.

 

That is because you had them on 2.02 seats.
2.055 on correct seats with proper bowl work will yield benefits over 2.02.
Ideally IMO, keeping the valve train the lightest has its benefits as well as well as a matched valve train.

 

Will it work? Yes.

Will it work well? Probably not.

 

Well if thats the case what benefits have you seen? It seems like you must have done the testing on this to prove that statement?

 

Try that Chris1313 guy for example. I'm pretty sure his 346 put down 520whp with 2.04" valves.

2.04" valves are only 52% of the bore on an LS1. The LS3 uses intake valves that are over 53% AND has a wider valve spacing.

 

Mamofied is 2.055/1.6...people seem to do just fine with Mamo's work.

 

I was looking at your guy's heads... What combo can give me 450whp and at least 410wtq? I want reliability so i'm using stock rocker arms.
Thanks

 

Awww do you even know what size valves are on the car in your sig??

Stock bottom end 346 right?

Prc 227 heads with a 2.06" size intake valve???

http://www.texas-speed.com/p-1163-pr...der-heads.aspx

 

dose a flow loss on a bench mean a hp loss?

 

Yes I know what valves are in those heads. This is a complete aftermarket casting head that does not have a stock valve seat. Why would we go and spend all that time and money to make an aftermarket casting and leave a stock valve seat in it?

Do you know what an aftermarket valve seat is?

 

IMO, a 2.055 valve will work on a stock bore. This is the largest that I would use. I hae seen a 2.08 valve flow more on a flow bench. But it didn't make anymore power on the dyno. You will have to change the seat for any valve lager than a 2.04, but this has nothing to do with the bowl area. It has everything to do that the outside diameter of the valve will be on aluminum instead of steel.

 

Thank you... that's all I wanted to know lol. Maybe I'll play it safe and stay with 2.04s or find a cheap set of prc's

 

LOL, you must like net-wars.
IMO No, not necessarily. Flow numbers are merely like a measuring stick (like dyno numbers). There is quite a few other factors to consider.

 

I'm guessing this is where volumetric efficiency comes into play?

 

I ran a set of ETP 5.3 (2.055 intake, 1.60 exhaust) heads on my ls1 motor with a 228/228 112 cam. Did not see much gain over the stock 241 heads, but the ETP 5.3 heads are setup for a minimum 4" bore.

What is the valve angle of the head's you are looking at?

 

No that is big shop talk...just a simple garage wrencher here...

OP just states he wanted to know about large valves, not stock castings and stock seats...your post didn't explain all options and could be read that going anything bigger than a 2.02 valve is a waste...

 

Ive got a set of 243 heads that I just had valve jobed. Im on my first ls build so when the machinist said he used 2.055 / 1.60 valves I didnt hesitate nor did I research valve size and seat combinations for these heads. So the heads were valve jobbed with the stock seats. Now I find out through major head porting companies TEA, AI, ect.... that the stock seats on the 243 wont allow any bigger than a 2.04. So im stuck with new REV valves. Im sending my heads off for cnc port so they are going to replace my intake seats and revalve job. Will the stock exhaust seat fit work with the 1.60? Ive heard you cant go bigger that a 1.575 on a stock seat.

 

1.60" is fine, that's about the max though.