I have a gen 3 5.3 and I have ended up with a set of 243 heads and when I was taking them apart i seen they have 5.7 stamped on the inside will they work on the 5.3?

 

243 heads will work on a 5.3 but you may get better performance staying with the smaller bore head such as the 706/862's.

GM started putting 243 heads on the 5.3's and the aluminum 5.3 I have on the stand right now has 799's which are essentially 243's

 

Ok thanks I just didn't want to put them on and the valves hit or something trying to get my truck back running with out buying another set of heads

 

That will depend on what you got going on for a cam but if its stock you'll be fine.

 

I have a 585 life cam in it i also have springs I can put in the heads anything else you can think of?

 

What is your camshaft duration?

 

I'm not sure right off I'll look in the morning and send you a reply

 

Duration @ .050" is 228°/230°.

What vehicle is this going in?

Good cam for a light car with lots of gear and/or converter, in a 5.3; will be TERRIBLE in a truck. If the 5.3 is SBE, it will be gutless down low due to the drop in compression (243 has larger chambers than stock 5.3 heads), regardless.

I'm not seeing it as a real harmonious combo, in case you can't tell.

 

It's going in a 2007 GMC canyon

 

Ok thanks which set of heads will work better the 706 or the 862 i may try to find some

 

706 & 862 are basically the same head.

Not a matter of "bore", as such; it's chamber volume.

706 & 862 come on 4.8 and 5.3 motors from 99 to about 06. EXTREMELY common.

I think you could probably trade your 243s for the others without too much trouble. Or, use RB04Av's Patented Copyright Exclusive 2-Step Method for turning anything you have, into anything you want: (1) sell the thing you have, (2) use the cash to buy the thing you want. MAGIC. Harry Potter would be proud. They're a good head for some situations, just, not the one you're in.

 

706 and 862 are identical. Just different manufacturing method.

 

I agree if mill the 243 it pretty much a wash ! Sell the 243s ,put that money towards making your 706 perform better , with a CNC program run on them. Even hand ported 706 will spank stock 243s. At a bare minimum go to 1.95 intake and best vj you can find from a pro .

 

If you have not firmly made up your mind on the cam, look at various stage 1 and 2 truck cams from various vendors. Be much better off with a 212/218 type cam. Really about anything with duration in the 2-teens. Even a single pattern 216/216 would be great.

 

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