5.3 Cylinder Head recommendations

lolthisisnuts

Not-quite-so-new-guy
Feb 2, 2021
11
3
Hey All

I have an 83 el camino with a 5.3 LM7 out of an '05 Silverado that is a street/strip car. I have a BTR stage 3 truck cam and a 2500 stall converter. I'm looking to upgrade cylinder heads. Would love some recommendations.
 

motorheadmike

Geezer
Nov 18, 2009
7,034
113
Ottawa, Ontario Canada
Don't bother.
 

Injectedcutty

G body LS mafia
Supporting Member
Nov 24, 2014
5,774
113
Louisville, KY
^^^^what he said. Just do a spring kit in the 862 heads and send it. They flow plenty for what you're doing. I have a similar cammed 5.3/80E in my Cutlass with a 3400ish stall. Running stock internals, stock heads but BTR springs. Running full tube headers and full exhaust and it breathes just fine.
 

Streetbu

Know it all, that doesn't
Supporting Member
May 22, 2011
2,476
113
Central NY
What heads do you have now? If anything send them out to be cnc ported by Katech. Only $499. But for a NA setup, you probably won't feel much via the butt dyno.
 
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motorheadmike

Geezer
Nov 18, 2009
7,034
113
Ottawa, Ontario Canada
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64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
2,889
113
Upstate NY
The 706's are not an issue - small chamber to keep up the compression and flow just fine until you get over 7500rms with a 5.3. I'll guess that you don't plan to be spending much time in the 8000rpm range? Correct me if I'm wrong. An LS has two distinct advantages over anything built before it - the bottom end can withstand 7500rpms in stock form with 200k+ miles on the odometer, and the stock heads flow almost double of anything old school Chevy or Ford for the same displacement.

If you want to make silly, dumb power on stock heads the 317's will outflow everything else, but it will take 20psi of boost before you see any benefit. 243/799's are the best bet if you want to keep it NA with a stock head, but again, you need to see 7000+ on a 5.3 before you notice much of any advantage.

I had a set of 317's on a 421c.i. motor with 18 psi of boost and it ran very well once it was cranked up to 6500. The issue was that we rarely ran it over 6500 and the bottom end seemed sluggish (to me). I swapped on a set of 706's fresh from the boneyard with a quality one angle valve job. They increased the compression almost a full point with the 421 and the bottom end became just absolutely stupid with throttle response BEFORE the boost hit. At 14 psi it's a tire smoke machine before 50mph.

My point is that your 706's will out run your Gen 3 LM7 rods before you need to worry about a head upgrade for anything that you want to drive on the street. Let the LS advantages do their job.
 

64nailhead

Goat Herder
Supporting Member
Dec 1, 2014
2,889
113
Upstate NY
Forgot to mention, price out a set of 243 heads. In my area everyone thinks they are gold. I was fortunate enough to find a core motor for $250 with a set of 243's on it, but generally they are $400 just for rebuildable cores - totally not worth it IMHO.
 

Supercharged111

Royal Smart Person
Oct 25, 2019
2,154
113
Colorado Springs, CO
Forgot to mention, price out a set of 243 heads. In my area everyone thinks they are gold. I was fortunate enough to find a core motor for $250 with a set of 243's on it, but generally they are $400 just for rebuildable cores - totally not worth it IMHO.

To hell with 243s, get the 799s that are falling off of trees from every single 2007+ truck motor. Or don't and send it.
 

Northernregal

Sloppy McRodbender
Supporting Member
Oct 24, 2017
2,100
113
Red Deer AB
To hell with 243s, get the 799s that are falling off of trees from every single 2007+ truck motor. Or don't and send it.
Or watch Richard Holdeners video series on LS heads and realize the 706/862 is the best NA head you can get for anything under 370 cu/in.

Also the best for boosted HP among the stock offerings.
 

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