HoppedZ

I purchased a 94 Z M6 to use as a project and it has a bad engine. I plan to tear it down and inspect it and do a budget rebuild. My plans are to get the block prepped, cylinders taken 0.030 over since it has 200,000 miles on it. New pistons, Eagle crank and reuse the stock rods with ARP bolts.

I plan to use Mr. Gasket 0.26 compressed head gaskets and have the stock heads decked for flatness with a 3 angle valve job. The cam will be a Lunati hydraulic roller that operates from 1800-5800 rpm.

The car is a project and not my daily driver that will mostly see street use and an occasional thrashing at the drag strip. My goals are 330-350hp at the flywheel.

I have rebuilt 4 small block chevy's but never an LT1. Any tips on the rebuild for this newb?

Thanks

SwampWS6

iTrader: (7)

Port the heads, a good spec'd cam, 1.6 roller rockers, PCM for less mail order tune, and maybe some 30lb injectors. And why buy a new crank and pistons but use the stock rods??? Just curious on that one....

KyleW707

If you're only looking for 350 at the flywheel, save your money on the pistons and crank, if they're not part of the reason for the engine being bad.

fbody_brian

Well just because it has 200k on it doesn't mean it will have to be bored out. I'd tear it down and check everything before making decisions on what parts to replace. 330-350 at the flywheel is easily attainable with the stock bottom end.

SS RRR

iTrader: (2)

There is absolutely no reason to buy a new crank if the stock one can be used, especially for your HP goal. The stock crank can take an astronomical amount of abuse. There is not a lot of history of people breaking the stock crank no matter the application. At that mileage, more than likely the block will have to be bored. If so, get new hyper-u pistons and reuse everything else in the rotating assy. You'll save yourself a bunch of money.
To read up on the LT1, get this book:

cardo0

Before cleaning the LT1 block u need to remove a steel ball in 1 of the vertical oil galleys. Then ensure u replace it before assembling the block. This is described in the book listed above.

cardo

ahritchie

iTrader: (1)

I second the suggestion to upgrade rods as well while it's apart:

bowtienut

iTrader: (1)

Do you have a story to go along with that picture?

Stock rods are fine for what the OP said in his post.
Just make sure you resize the big end with those ARP bolts installed and torqued.

ahritchie

iTrader: (1)

Yeah, 3 years back I had a similar lunati voodoo 60121 cam only 145K LT1 build which had a mild rebuild with new rings, bearings, hone, BUT didn't put ARP rod bolts in it. I over-revved it to 6600RPM or so at the drag strip (my mistake, 6spd), and sent a rod out the side of the block! Lol...quite the loud noise and quite a mess on the track! That's why my current 383 build is overbuilt for my needs...I can beat on it, rev it to 7K on accident all I want and not break it or worry

SS RRR

iTrader: (2)

^^^ That's not the fault of the rod, but rather the rod bolt failing. With the OP's HP goal there's no reason to "upgrade" anything since that power level can be obtained at or near stock RPM.

ahritchie

iTrader: (1)

Just curious, how do you know by looking at the carnage, if it was the rod bolt vs. rod? I wondered myself, thinking should have gotten ARP bolts, but I'm no expert on catastrophic engine failures...It looked to me the rod bolt was in one piece but the rod certainly isn't Cause and effect I guess?

OP, HP is addictive, maybe consider some used ported heads instead of spending money on a valve job and decking them; you'll be pissed when a mild bolt on LS1 beats your cammed LT1....you'll add another 50+ HP, just saying!

SS RRR

iTrader: (2)

Deductive reasoning. The stock LT1 rotating assembly does not have a lot of failures regarding crank or rods from over the years. However there are a plethora of those who've reported rod failures using stock bolts and revving to the moon. Perhaps your case is different, however it would be a rare incident if the rod itself failed.

bowtienut

iTrader: (1)

I'd back up even one more step and wouldn't necessarily blame the rod BOLT either. Whether you stick with stock bolts or upgrade to ARP bolts is less important than measuring the rod big end with your bolts of choice installed and torqued, and you'll probably find the big end is ovalized and needs to be resized. They DO go out of round in normal use in stock engines. That condition can go only so far until you break through the oil film in one or two spots ....generate extra heat in the rod.....the material loses some compressive stress at the elevated temperature AND can even yield......it relieves some of the preload on the bolt......and.....your margin to failure just keeps getting smaller and smaller. It's a vicious cycle; each time the damage happens at a lower rpm than it previously did.
ahritchie, that one missed shift was only the last straw that broke the camel's back.
Rebuilding the shortblock that's in my car, we found big ends up to .0015" out of round, and that came out of a 80k mile car that never saw 5500 rpm.

Catmaigne

iTrader: (6)

lol .30 over

Catmaigne

iTrader: (6)

If all you want is 350 flywheel then just put some bolt ons on it.

HoppedZ

The engine has a rod knock so before tear down I am assuming a few of the bearings and probably the crank is toast. If the cylinder bores are within spec I will just have the cylinders honed to restore the cross hatch and get a fresh set of standard pistons. I suspect the cylinders are worn beyond standard spec. I'll know more when it comes apart next week.

As recognized above the stock rods will continue to live well under the power level I'm looking at. Ifthe stock parts are trash I'll need to go another route.

HoppedZ

Excuse my misplacement of the decimal 0.030. Happy now

bowtienut

iTrader: (1)

If you find a spun rod bearing or ANY signs of heat distress, throw the rods away!

ahritchie

iTrader: (1)

Interesting....how much does it cost to have rod's resized though (not to mention cost of ARP rod bolts)? Seems like for minimal more $$ you could just buy brand new forged rods (with ARP bolts included... my forged Ohio H beams with ARP 2000 bolts go for $389 in the new 383) are good for 700HP for added insurance? Just throwing that out there....OP may get greedy and need a 200 shot of nitrous down the road!

bowtienut

iTrader: (1)

I certainly wouldn't discourage him from going that route. Depending on his machine shop capabilities and/or pricing, it may make sense for him.