Hi Guys,

I've been searching the forum on this but haven't really got the answers I'm looking for so here goes...

I have a L77 engine (6.0L aluminum block) which has a cracked piston no.7 from detonation. The block is still good and has not been damaged.

My question is, simple do I change to a LQ4 iron block or stick with my aluminum block?

Heads are 821 casting and will be ported.

I will be adding a 2.9L Whipple supercharger, ARP headbolts, forged rods, forged pistons, dropped compression ratio 9.5:1, OEM crank, BTR PDS cam with matched springs, hardened push rods, Melling high volume/pressure oil pump etc Manual transmission- TR6060 for what it's worth.


The my ute weighs about 4000 lbs before taking into account the weight of the Whipple system.

I will be running the Whipple on the standard pulley size (for now) which will be about 7 psi, maybe ill go a little higher in the future with a 10-rib belt set up, but nothing crazy.

As I'm based in South Africa, I'm not so spoilt for choice when it comes to parts and junk yards everything is expensive. I need to do this once and never have pull out my engine again, I can only get my hands on a complete LQ4 engine, so can strip it to only use the block If I go this route, I just want to know if its a no brainer costs aside or considering the mods the aluminum block is good?

If the consensus is to go to the iron block, do I stick with the standard 4.0'' bore or go bigger making it a 6.2L? So 4.065'' bore

I think ill be on the 700hp right from the start with a goal of maybe 1000hp in future, but key factor is reliability and safety with those numbers.

thanks in advance,
Rob

 

I'm not sure how much overbore an L77 block can handle, but if the cylinder walls look good, I see no reason not to reuse it. It's lighter than an iron block by quite a lot. You're already heavy enough, you know? Also, the iron LQ4/LQ9 blocks have been known to get radial cracks in the bores with boost, even with just a .030 overbore. I would NOT try to boost an LQ4/9 block with a 4.065 bore, even if it didn't crack you'd probably have ring sealing problems. Get your present block checked out and if all looks good, run it. I can't imagine it wouldn't be capable of 1000 HP.

 

See if you can get a piston just a little bigger than stock, I would not go .030, I'd try for .005-.010.

I think if you nail the tune it would live a happy life. There are heavy G8s and 5th gen Camaros running 600-800rwhp with a stock bottom end.

 

Appreciate the feedback!

I'm going to have my block looked at properly and if it's good I will stick with it based on the advice I have been given. I will put in a set of forged pistons, forged rod, ARP headbolts and maybe ARP main studs?- Anything else I should be considering in terms of the block?

thanks,
Rob

 

What oil pump will you run?

I'd have the heads decked and I'd run head studs.

 

Definitely head studs over bolts. I really like having the mains studded also, but it really needs align honed also. The stock main bolts hold up fine tho, other than that you got it licked.

 

I have a Melling 10296 (high volume, high pressure) pump

 

So here's an update, my aluminum block was checked for oval-age, the engineering shop said it can be fixed with a 0.010'' overbore.

Now I am in two minds do bore out my existing aluminum block to 4.010'' or do I go with a LQ4 iron block?

Negatives with the iron block is weight and the extra cost of getting the block, which is a complete LQ4 engine in my case (2500 US down here)

Extra costs aside, taking the 0.010'' bore of the aluminum block into consideration, boosted at say 10 psi with forged pistons and rods, compression ratio around 9.5 : 1, will I be safe, or am I better off with the iron block?

 

I don't think .010 over will hurt anything, I'd run it. With good prep and assembly, it should live a happy life. Especially if you drop compression and only run about 10 PSI. Just make sure the tune is spot on.

 

Sleeve it for 500 cubes and make all the powaaaaaa.