rebuild

[Willdue]

So this winter me and my buddy are gunna rebuild a 6bolt 4g63. Nothings broke on it, juss has high miles. So what should repair to replace/rebuild? And what should we get to hold a decent amount of boost

[noclutch]

Leave it stock

[QuasiMondo]

Before you rip it apart, did you check the compression (140 psi avg, 114 svc limit, no more than 14 psi diff btwn cylinders)?

If that's fine, get a gasket set, crank & rod bearings, and a new oil pump. Replace the stock head gasket with a multilayer steel gasket, clamp down the head with ARP studs, slap on a new timing belt and be back on the road. Don't forget to replace the water pump as well.

If the compression is down, have the block bored out, replace the pistons with the appropriate overbore (Diamondstar motorsport and SBR have replacement pistons that have a slightly raised compression ratio), and follow the steps above.

A stock six-bolt can hold a decent amount of boost as is. As long as you don't have plans of pushing more than 25 psi, there's little that needs to be done to these engines.

[teh DIRT]

umm if compression is down it could be a headgasket, or a leaky valve, or a failed piston ring. Wouldnt just bore it because of low compression. None the less get the block checked out, if it needs to be bored then bore away

[QuasiMondo]

True.

Do a compression test, then a leakdown test to determine if you're leaking from the valve, gasket, or rings. If it's the rings, pull the pistons and bore the cylinders.

[Driven]

umm if compression is down it could be a headgasket, or a leaky valve, or a failed piston ring. Wouldnt just bore it because of low compression. None the less get the block checked out, if it needs to be bored then bore away

I think his point is that typically in DSM's, if they have low compression its the rings. If you are rebuilding the bottom end, I'd recommend having the head freshened up though and of course you're going to replace the head gasket so I don't think those are much of an issue.

Regardless, if the motor has good compression, I wouldn't mess with it. I've witnessed a stock 6 bolt standing up to 38 PSI from a T67 and 136mph traps. As long as you know what you're doing, they'll hold almost anything.