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I bought a new to me M6 Z51 wth 65k miles, and one week into ownership the timing chain lets go. This part been discussed in another thread of mine but long story short I'm blaming it on the 25% underdrive pulley. I pulled one of the heads and I've got valve impact on every piston. I'm trying to keep my spirits up and turn this into a build opportunity -- I'd like to get around 500whp out of it. My question is: what is the most cost effective way to go about this? I have a friend who can do most of the engine work outside of machining for about $1k in labor, and we could do a heads/cams upgrade. We'd still have to send the block out for piston replacement. Is this my best bet, or is a drop-in engine (LS3 + mods?) replacement going to be more cost effective?
if it was mine, (and assuming that the cylinder walls look ok), I'd get the valves replaced and the heads freshened and run it as is. Maybe measure the piston top to deck measurement on each cylinder to make sure you haven't bent a connecting rod.
You can overbore very little on that block with the miles on it you will probably end up having to replace it if it needs oversized pistons. A lot of people cut notches in factory pistons for PTV clearance and don’t have an issue.
If you honestly want 500 rwhp then buy a crate LS3 and put a BIG camshaft in it.
You can overbore very little on that block with the miles on it you will probably end up having to replace it if it needs oversized pistons. A lot of people cut notches in factory pistons for PTV clearance and don’t have an issue.
If you honestly want 500 rwhp then buy a crate LS3 and put a BIG camshaft in it.
I was under the impression I wouldn't need to overbore since there doesn't appear to be any cylinder wall damage. Is there a possibility I would need to? Or could I just get away with honing?
You would almost need to disassemble it to measure cylinder diameter and taper. You could just give it a quick hone and throw new pistons and rings in it but it probably would run as good as what you have now.
Obviously, along with stroker crank, $$ heads, intake manifold, etc, etc. obtainable but would it be fun to drive? I doubt it. Have to make 600 crank to make 500 to wheels.
Last edited by farmington; Dec 5, 2018 at 11:25 AM.
Obviously, along with stroker crank, $$ heads, intake manifold, etc, etc. obtainable but would it be fun to drive? I doubt it. Have to make 600 crank to make 500 to wheels.
wut
since when do you need a bigger motor and baller heads to make 500 on a ls3
All you need is longtubes a intake and a btr 4 cam. I came close without longtubes and like 1,500-1700 in mods from bone stock. Car drove perfectly fine for me between a good tune and learning not to try to drive at 900 rpm in 6th gear.
He has a LS2.
500 rwhp with only a BTR4? Gotta be a record. And then did u wake up and realize you were dreaming?
btr 4 z06/zr1 manifolds ported stock intake manifold and some back room deal cnc porting on the stock heads + flex fuel
budget setup that worked I said like 1500-1700 in mods from stock not 400
You’d be surprised how much better the z06 manifolds are. Same exact setup/dyno/week we picked up around 60whp doing the swap not longtube numbers but $100 vs $1200.
I was under the impression that they were still talking about the crate ls3 needing a massive cam and more displacement new heads ect to make 500.
Last edited by Shortpersonbk; Dec 5, 2018 at 02:10 PM.
When you have that type of contact. It puts a lot of pressure on the all the mating surfaces. The rod bearings should be checked, check the rig lands for cracks and wrist pin surfaces.
Those are cast pistons, and they do not like being beat on. I would replace all the pistons, and while the engine was out, replace all the bearings as well.
Check for bent valves, cracked rockers, bent pushrods, damaged lifters, and other signs of valvetrain damage. Replace anything that's even remotely suspect. This would be a good time to do the valve guides and seals too, and maybe a new set of springs. Obviously, it's the perfect time for a cam swap too.
The motor can likely be rebuilt very successfully and can be made to make good reliable power for a long time. But this isn't the time to try and save money by reusing parts.
Answer me this , who from and when did you buy the car and was it after only ONE week that the timing chain broke ? If it was a dealer , take it back and get a refund !
I do not think a timing chain should break after ONLY 65K , unless the motor was beat on .
Did you get a GM VIS report , Vehicle Build and Warranty History to find any old problems? Did you get a warranty with the car ?
Were you racing and over revved or just driving ?
Ed
Impacted pistons - fix or replace engine?
