Would you rebuild a 56k mile L82 motor?

[Tom R.]

At some point, I'm planning to restore an 1978 L82 M21 Pace Car that was autocrossed. It was a mechanically neglected highly optioned Pace Car well documented and I picked it up for the right price. When I got it it was barely running. All I've had to do is rebuild carb, set timing and now it cranks everytime I pump gas pedal several times. So, as I begin to put plans together for the car, curious how others would approach the engine...rebuild since I'll have it torn down for gasket replacement. Are there other factors I should consider?

[Timothy B.]

Re: Would you rebuild a 56k mile L82 motor?

Tom

Before I did anything I would do a leak down test to reveal any problems in the valves or cylinders, 56K is not excessive miles so you may be just making a bunch of work for yourself. All that may be required is to carefully locate the oil leaks, repair them and then clean it. That's much easier than $$ for nothing, whatever you do don't let machine shop cut the heads, deck the block etc.

The L-82 is a four bolt motor with HD rods and nice hydraulic camshaft, only problem is it's loaded with emissions stuff.

[Michael D.]

Re: Would you rebuild a 56k mile L82 motor?

Since it's already torn down, rebuild it.

[Michael W.]

Re: Would you rebuild a 56k mile L82 motor?

56K miles is nothing on an SBC, hardly broken in. I'd leave it alone.

[Paul J.]

Re: Would you rebuild a 56k mile L82 motor?

Since it's already torn down, rebuild it.

Michael, he implies that it's not torn down yet.

Tom, what are your plans for this car? Show it? Drive it? Travel in it? All three? The answer to these questions will determine what you should do.

My experience has been that factory assembled engines last longer than rebuilt ones of equal parts. It is common to see 180k+ miles on a factory assembled Chevy V-8, but you'll never see that on a rebuild (despite the few exceptions that someone will post). While a fresh rebuild would be very dependable, what about 60k miles later, especially when compared to a similar factory assembled engine. My 78 L-82 was my everyday driver, and I used it for trips also. It had enough repair issues on it's own without bringing engine dependability into it.

If your going to travel in it and you're not removing the heads, I'd do as Tim says and fix the leaks and clean it up. However, if it's just for cruising and shows, why not go into it while you're there and everything is easy to reach?

The guy that painted my car did Vette restorations in a small garage behind his house. He had several engines rebuilt with less than 50K miles on them, only because that is the way he did it, or so he said. There was nothing wrong with those engines.

Paul

[Duke W.]

Re: Would you rebuild a 56k mile L82 motor?

I would raise the CR to the 10-10.5:1 range. You can buy a KB hypereutectic piston with a big enough dome to accomplilsh this with the OE 72 cc heads, and you can also probably find a forged piston (The OE pistons are forged) to accomplish the same objective.

The second thing I would do is massage the heads, however, this is only worthwhile IF YOU REPLACE THE OE SINGLE CATALYST EXHAUST SYSTEM WITH A FULL DUAL EXHAUST because any improvements to internal engine flow will be mostly negated by excessively high back pressure from the OE system.

The OE rods are okay. The only thing you need to do is torque the caps, check the big end ID for dimensional conformity to OE specs. Don't bother to change the bolts, which will require having them resized.

If you kept track of which bores the lifters were in you can probably reuse the OE cam. Just check the base circle to top of lobe dimension for wear. If they are within a few thou of OE, it's okay to resuse as long as you marked the lifters for installation into their original bores.

Bore wear may be such that reboring is not necessary, just honing, and if the crankshaft spins freely, it doesn't need align boring/honing. In fact, all the bearings are probably reuseable. With only 56K miles there probably isn't much internal wear, even if the engine was "abused" as long as nothing broke.

Duke

[Peter G.]

Re: Would you rebuild a 56k mile L82 motor?

I would NOT do it unless you cannot get a good tune-up on the engine, or has leaks or excessive blue smoke out the exhaust indicating internal engine failures. 1978 engine..to me that is a low mileage car and engine. Divide the mileage on the car and engine by the years of age. That is less than 2k miles per year.

I also agree that factory engines last longer than rebuilt one. Maybe because rebuilt ones are usually "beefed up" with more horsepower and compression?

Just my $0.02.

[Michael D.]

Re: Would you rebuild a 56k mile L82 motor?

...Michael, he implies that it's not torn down yet....

Ooops. I read it as already torn down. I'm gettting in too big of a hurry.

[Tom R.]

Re: Would you rebuild a 56k mile L82 motor?

Thanks for the great comments but realize I should have provided greater detail. Basically, the restoration would be to make it a candidate that can be campaigned for Top Flight...so exhaust mods would be out of the question. Its use would be limited, on my watch anyway, to cruise-ins and shows. Perhaps, a long trip for working out kinks and flight judging. Let's face it...the 78-82 team has very, very few "restoration" candidates to judge so this would be among the few that would test their skills. And the leaks are not as bad as those on my 35k 78 anniversary vette...which i'm putting back together.

Also, it currently has dual exhaust and no cat converter. One of the other things I did to get it running smoothly is trace all the emission hose routing and get them back to specs...EFE was attached to carb and other goofy connections. But where I was going here is I'm not seeing blue smoke but the exhaust does have its non-emission control scent to it like that characteristic of the early C3 and C2 years. (Is that nicely worded or what?). So, I think rings are ok but the leak down sounds like a "to do."

[Joe L.]

Re: Would you rebuild a 56k mile L82 motor?

At some point, I'm planning to restore an 1978 L82 M21 Pace Car that was autocrossed. It was a mechanically neglected highly optioned Pace Car well documented and I picked it up for the right price. When I got it it was barely running. All I've had to do is rebuild carb, set timing and now it cranks everytime I pump gas pedal several times. So, as I begin to put plans together for the car, curious how others would approach the engine...rebuild since I'll have it torn down for gasket replacement. Are there other factors I should consider?

Tom------


Why would you tear down the engine for gasket replacement? Most of the gaskets and seals can be replaced without complete engine tear-down. The only exception would be the head gaskets which would require only cylinder head removal. I doubt whether these gaskets need to be replaced as the factory used steel shim-type gaskets. Otherwise, I'd only replace the gaskets or seals that seem to be leaking.

My expectation is that the only internal parts you'll need to replace are the timing set components. This can be done without any major engine tear-down. At the same time, you can replace the front cover seal, front cover gasket, water pump gaskets, oil pan gaskets, and rear main seal.

[Tom R.]

Re: Would you rebuild a 56k mile L82 motor?

Tom------


Why would you tear down the engine for gasket replacement? Most of the gaskets and seals can be replaced without complete engine tear-down. The only exception would be the head gaskets which would require only cylinder head removal. I doubt whether these gaskets need to be replaced as the factory used steel shim-type gaskets. Otherwise, I'd only replace the gaskets or seals that seem to be leaking.

My expectation is that the only internal parts you'll need to replace are the timing set components. This can be done without any major engine tear-down. At the same time, you can replace the front cover seal, front cover gasket, water pump gaskets, oil pan gaskets, and rear main seal.

My use of "tear-down" was, perhaps, too aggressive for what I intended. By tear-down I meant pull the oil, pan, valve covers balancer, front cover and carb. If the heads leaked...those as well. Hardly tear-down I know.