MaroonMonsterLS1

I know an old school trick with SBC was to put 305 heads on a 350, port em, and put in bigger valves. These would boost compression and still flow pretty well.

Is this a direct bolt on like it was in the good ol days? I want some practice porting heads anyway and figured i could pick up some 5.3 heads pretty easily for cheap.

.boB

iTrader: (1)

Yes, they're a direct bolt on. The advantage is that they have a smaller chamber, and bumps up the compression. The down side is that they have small valves. You can port them as much as you want, but unless you put bigger valves in they won't flow as well as stock 243's.

http://texas-speed.com/p-1172-prc-st...-castings.aspx

I'll be using a set of these, but with different springs to match the cam I'll be using .

MaroonMonsterLS1

Yup, sounds just like it used to be. Bigger valves shouldn't be too big of deal, but the compression bump will be nice

01WS6/tamu

iTrader: (37)

I had a 06 chevy pu I put a budget 5.7 LS1 into and threw the stock 5.3 heads off the truck on the LS1 with no mods and a super baby cam. It was one of the best running LS1's ive driven outside of one with heavy mods. I sold the truck and the motor wound up back in a buddy's TA and he swears it would run circles around the stock LS1. So in a nutshell for a poorboy job with 0 high performance aftermarket parts the trick still applies

JakeFusion

iTrader: (7)

5.3s are pretty cheap from the likes of TSP or AI. And in ported configurations you can see 45-50rwhp.

96capricemgr

iTrader: (1)

which 5.3l heads? the later ones actually got "LS6 heads" 243/799 castingsnot as small a chamber as the earlier heads but smaller chamber than the LS1 and better flow.

An earlier 5.3l might have 862 or 706 heads yes they have a small chamber for great compression but some of the 706s have porosity issues.

So which casting are you looking at?

HCI2000SS

iTrader: (2)

OP, i'm running PRC 5.3 heads (862 casting on a 61 cc) from Texas Speed. They have the bigger valves, port and polish, etc...for the money they do really well once they are worked over good

LS1HIGHLIFE

iTrader: (8)

Can you elaborate more on the issues with the 706 heads? I've been running them for a few yrs now. Only issue I have is burning oil. I've since converted to LS6 PCV and will be replacing the vale seals soon.

96capricemgr

iTrader: (1)

Google Castech and you will find more info than I can offer. It was only some of the 706s made by one of the manufacturers.

LS1HIGHLIFE

iTrader: (8)

Mine are Castech heads. I haven't had these problems. I did find a thread where on guy mentioned it was Castech's other casting that had the issues, not the 706s.

https://ls1tech.com/forums/13917658-post2.html

96capricemgr

iTrader: (1)

That is the only time I have seen anyone suggest that, EVERYTHING else I have read says it was the 706 that was the issue and not even all of the castech 706s just some.

Js4718

What other mods were done or required? Was the computer reprogrammed? Long tube headers? Stock compression or changed?
I have built a 5.7 ls from an iron block with 706 heads(changed springs), flat top pistons, mild truck cam, full length pacesetter headers. Stock program, air intake, intake manifold, throttle body and valves. Exhaust is currently open and it seems sluggish for what it is. Not sure if finishing the exhaust will fix it or if it needs other things. Stock converter also, I didn't go to a higher stall.

G Atsma

Keep in mind this is a 4-yr. old thread. You MIGHT get an answer.

chaseamb05

When you say direct bolt on do you mean I will be able to use the same intake manifold on the 350 or will I have to buy a new one

RB04Av

Not sure what you mean "same intake manifold on the 350".

This is a LSx motor forum. There are no "350" motors on here.

Apart from that, yes, if you have some one or another LS type motor (4.8 / 5.3 / 5.7 / 6.0) in the early 2000s kind of age range, then yes,

Not the same deal as the old small block Chevy 350, but the principles aren't that much different. The bore & stroke inside the block might change but the external dimensions of bolt-on parts like the intake manifold remain the same within the family.