carbed86fox

is it really that big of a difference to change the valves in 5.3 heads to ls1 valves?

KCS

iTrader: (20)

It can be. With a good valve job and minimal blending, they will outflow 243/799 heads, produce a higher compression ratio, and cost just as much, if not less than the 243/799 heads.

chrisfrost

iTrader: (8)

The 5.3L heads have the same valve seats as the 241's and the 243's so in My opinion You can do better by leaving the 1.89's and the 1.55's and just cutting the inner diameter of the seats a little larger . They can be cut to the same as a 1.94 leaving the 1.89's in without as much shrouding by the valve or the side of the combustion chamber . And the exhaust 1's can be cut to the same as a 1.6 . So think about it and take You're pick .

KCS

iTrader: (20)

Do what?

carbed86fox

how much would it cost at the machine shop to get the valve seats cut to put the ls1 valves in?

wildcamaro

iTrader: (15)

Probably the same price or more compared to buying a set of ls1 heads for $100, but the you would have to mill those to get the compression back up, so pick your poison...

KCS

iTrader: (20)

It depends on the shop, but $200 is pretty much standard.

KCS

iTrader: (20)

Exactly, and then you're limited by piston to valve clearance.

AGearHead4Life

iTrader: (5)

I'd like to know this as well. I wish somebody had a flow sheet of difference.

I just did this to my 5.3 but didnt have $ for a flow test. I am about to see dyno differences soon, but it wont be a measurement of just the larger valves because i also milled .030" and home ported them.

carbed86fox

i have some ported ls1 heads on my car right now but i would also like to see how big of a differnce the bigger valves and more compresiion will do let me know when you get those dyno numbers back

sidearmbandit

iTrader: (1)

Here is what my 2.02/1.60 5.3's did on the flow bench. Can't tell you how they ran because they've never been installed. Project is getting canceled and they are actually for sale in the classifieds.

AGearHead4Life

iTrader: (5)

Daumn! Looks like I need to invest in some 202's!

Got a for sale link?

wildcamaro

iTrader: (15)

Hey sidearm where those 5.3 heads ported as well? It seems hard to believe that just swapping valves netted that much of an improvement!

AGearHead4Life

iTrader: (5)

I've pretty sure they were ported. Not only from the numbers, but look on those Combustion chambers.

sidearmbandit

iTrader: (1)

Yeah they were ported/polished as well. I know it won't be a direct comparison to his question but they aren't going to flow that well with the smaller valves either.

Sale link:

https://ls1tech.com/forums/parts-cla...s-goodies.html

carbed86fox

i already have some ported ls1 heads so i might just check my ptv clearance and see how much i could mill them

omc8

iTrader: (7)

I understand ,I have considered doing 1.94 Intake and 1.59 Exhaust on 5.3s and get them ported. The cheapest route would be just do the the Intake side and swap your LS1 2" over , and run with the 1.55 .The 5.3 already has 1.55 on the exhaust side. Get a performance VJ and some light hand port and call it a day.

AGearHead4Life

iTrader: (5)

That is the route I took... Stock LS1 2" valves and a home port job and then milled .030".

AGearHead4Life

iTrader: (5)

To answer the orignal question, I dont think you'd see much if any gain from just the 5.3 to LS1 intake valve swap. They flow the same as they are in stock form. But like others have said with a port job and a cam that needs to breath you will see a difference.

I finally got my 2" valve, .030" mill and home port 5.3 with LS6 cam through a 80e dyno'd. 329 rwhp and 334 tq.

Now itching for a larger cam and stall...