Cylinder head advice

[65standard]

I have a 2000 LQ4 and MT1 for my '85 C/10. This early version 6.0L has iron heads and dished pistons for a 9.4 CR. I'm looking to swap in aluminum heads with smaller combustion chambers to raise the compression and shed some weight. I'm looking to keep my power range from idle to 5500. Any recommended casting numbers I should be looking for?

[Vandals909]

I bought a lq4 it has the 317 heads. I have been looking for the last couple days on the best setup.

If you want to increase compression look at the 799 cast # heads from the 05+ 5.3l trucks. They are the same as the 243 heads.

If your going to go boosted seems like l92/heads seem to be the most recommended. They will however cost you more as they need a rectangular port intake.

[65standard]

I have a 2005 5.3 long block from a Tahoe. I will check out those heads. Maybe they will work on my 6.0 and bump up the compression too. Thanks for the information.

[BR3W CITY]

5.3 heads are pretty commonly used.

I prefer the 317's from the LQ4/LQ9. If you want some more CR, have them milled and cleaned up (ported if you want to spend the extra $). Amount you mill controls compression bump.

[Cobalt964ruf]

317 heads are 243/799 heads structurally but have lower compression, larger volumetric chambers. by milling a set of 317 heads you end up with 243/799 comparable heads. I would likely just start with the 243/799 heads and save some time.

[BR3W CITY]

Yes and no. Milling the 317's puts the chamber size closer to the 243's, but it also changes the way in which that volume is distributed. When run with oversize valves, the flow #'s can be tempting. Its essentially what Texas Speed does with the 2.5 heads. If I'm putting work into a head at all, then its not much extra time.

[Cobalt964ruf]

it depends on the op's desired outcome

[Cobalt964ruf]

brew, it depends on the op's desired outcome. 243's are a proven performer and a good all around head whether na or boosted. 317's milled .030 puts you at 67cc chambers, not quite the 64cc the 243's are. unless the op has a milling machine and the knowledge themselves to do it. starting with 243's is likely a better option, and less time. 317's have the same valve size and similar volumetric structure in the chamber areas, yes you can make them work like a 243 or at least similar but at what $$$ cost and time loss? your killin me man lol

[boostedc10]

Based on what the OP is looking for the 243 would be the way to go.

Cobalt964ruf is right, the chambers are better in the LS6 head right out of the box.

Even with a mill the 317 doesn't flow as well.

Now if it was boosted and I was on a budget I would just use the 317 because you can make up the loss with more boost or timing.

[BR3W CITY]

I'm suffering from a bad case of not reading full posts

I was under the impression the OP had already got some stock heads and was thinking of swapping them for 243's. IMO in that case putting a little work into the 317's is still a worthwhile consideration.

Since it sounds like he's purchasing outright, then a clean set of 243's are a legit option. Seems like they are costing a tad more right now, but if you can put up with the ppl on LS1tech's for sale area they sometimes crop up on the cheap.

FWIW, my love for the 317 is as such; I can get them for dirt cheap, and including the machine work I can see great flow #'s through the low .600's lift. Since you can choose the amount of milling to occur, and use head gasket thickness as needed, it allows a huge amount of flexibility in ongoing builds. We've put together a few setups that allowed the customer to "grow" the build with the heads, being able to go from N/A to boost or nitrous setups with somewhat ease. By no means is it the be all end all solution, just one we've been extremely happy with under the situation.

[homemade87]

One thing to consider also , If you go with an unmilled 243 head you can use stock push rods . This saves a $100.00 and the problem of checking push rod length if using oem cam . They will be a direct bolt on with stock parts .

[65standard]

I have the stock 6.0 iron heads now. I don't know what number they are. I'm looking to build a high torque low RPM motor. My thinking is to use aluminum heads with smaller combustion chambers to raise the compression. Smaller valves and ports will be better to keep the velocity up in the lower RPMs. Aluminum will be better at reducing spark knock on a higher compression motor.

I have a 2005 aluminum head 5.3. I don't know what heads they are, but if they raise my compression to 10.5:1 or higher and the valves aren't too small, I'll use them. I'm also okay with buying any other set of heads that will be best for my high torque, low RPM motor.

Thanks for all the tips and info guys, much appreciated.