I just recently bought a bare pair of 5.3L heads, and plan to have a local shop port them & put bigger valves in. I do not plan too mill/deck them. What are the biggest valves that I could safely go with without sacrificing power?

 

Most go with a 2.02, but some have been getting good numbers with a 2.05. Jay@Absolute Speed had a new development with a 2.04 valve that seemed to be doing alot of good. I'd say a 1.57 on the exaust if you plan on sticking with stock CI. Anything bigger than a 2.05, I believe, will start to shroud the combustion chamber and cause lack of power.

 

Keep the exhaust valve stock and replace the intake valve with the valves from your LS1 heads.

 

2.02" intake and 1.575" exaust with stock seats.

 

I just got them today! So 2.04 intake and 1.57 exhaust?

 

Mike... Keep Me/us up to date with your heads. I too just picked up a bare set of 5.3s, and am planning on doing the same as you. I'm running a 230/230, 578/578, 112 cam, and I'm going to run the 2.05/1.57 valves. Where does one get the valves from??

 

Unless you're going to swap intake valve seats, 2.02 is the biggest you may be able to run on a stock seat.

 

Do you think it'd be beneficial to go to that big of a valve? It's cool if the seats have to be changed, that's not a big deal. I wanna make a bad *** set of heads.

U can get valves at almost any of the sponsors sites. Look for manleys or even better ferrea 6000's.

 

great info on this thread.. I'm looking to do the same and need to get the specs together

 

Also, what size pushrods will I need? I don't really plan on having the heads decked or milled or anything.

 

Will i be able to run a 1.60 on the exhaust side with stock seats?

 

If the chambers are not properly opened up to the 3.900" bore (they are 3.800" stock) a 2.00" valve would be too big. We do these with anywhere from a 2.02-2.05 intake and a 1.55-1.57 exhaust. My car went 9's on the spray with just a 2.02 and the stock exhaust valves of 1.55

We do the CNC porting of these heads at around $699 per pair, that includes the entire intake port, exhaust port and combustion chamber. Hope this helps.

 

So a 2.02/1.55 would be a good combo to run??

 

I wanna know the same thing.

 

Just a little late to the party, aren't ya?

Valve sizes are mostly dependent on things like displacement, bore size, RPM, etc. A lot has changed since this thread was started in 2004, but try taking a look at what sizes some of these aftermarket heads have and pay attention to what kind of applications they're intended for. You might find a trend or at least get an idea.

 

No need to start a new thread if I am looking for the same info.

My combo is in my sig...

 

Like I said, a lot has changed in the last 6 years so your best bet is took look at current trends within the aftermarket. What hasn't changed is that you can still ask 20 guys on ls1tech what's the best valve size combo, and you'll still get 15-20 different answers. There are also much more recent threads asking the same thing, so the replies are likely to be more relevant than this 6 year old thread.

Also, no one is going to put forth much effort to help you out if the most you can muster is "combo is in my sig". That is a very lazy response, so don't be surprised to get some very lazy answers. I know I'm feeling too lazy to look up your cam specs, and too lazy to ask you what RPM you're turning or what port work you would do as well. Hell, I might be too lazy to respond to this thread anymore, lol.

 

Lunati Voodoo # 60511,
IN/EX 222/228,
Gross Valve Lift IN/EX .567"/.567",
LSA / ICL 113/109,
Valve Lash IN/EX Hyd/Hyd,
RPM Range2000-7000.

 

Promise?