I read a post in the C3 general section about a '71 LT-1 with 89K miles on the engine...supposedly all original and unmolested. The first thing that came to my mind was, WOW that's a bunch of miles on a hi-revving, built for racing, mouse motor. My experience is that flat tappet valve trains don't typically last that long. With all the lifters rubbing on the cast iron cam lobes, OEM rocker ***** galling and excess valve clearance from the lock nuts loosening. Let's face it folks, those solid lifter valve trains are really crude by today's standards.

I know that there are exceptions to every rule and this 89K LT-1 might be one of them. In your experience, is it possible to put on that many miles and still survive? Even if it was lovingly driven by a little old lady who never revved it to its full potential and often short-shifted from first to fourth, it seems unlikely to me. What's your take?

 

Why not? The only difference between a solid and hydraulic valve train is the clearance, and the solid lifter lobes have clearance ramps designed to gently close up that clearance.

 

89K is not all that many miles.

 

All depends how it's been driven and maintained. If that little old lady who short shifts and doesn't rev the motor too high owned it then you could go 89K miles x 2 with no problem. Maybe even more than that.

 

My '71 LT-1 with original motor and 88k on the clock, ran like a raped ape right up to me tearing it apart for a full restoration.
Tim

 

If it has had periodic valvetrain adjustments, regular oil changes with the proper ZDDP oil and not beat hard it could very well be fine. The ramp rates, lift, spring pressues and hydraukic intesity of the ramp profile are very mild in those cams. Much milder than many basic modern hydraulic flat tappet cams.

 

In the 60's when I was a kid I ran the GM 30-30 solid lifter cam in my 55, the same came that came in the 365 hp vette's, the 67-68 early z-28 camaro's which I bough a new one in 68, and the first lt-1 vette for 70, that 30-30 set up was hard on the valve train with the 30k's clearence's, never had any problems with the lifter's but once when street racing one night and broke a push rod, the 71-72 lt-1's have a great street cam with the clearences dialed back, haven't had any problems with my 72 lt-1, I run poly locks and street roller rockers, if you good adjustin solid lifters just "set it and forget it"

 

That's a very mild cam overall with mild springs and no reason for it not to last 100K plus.


JIM

 

I don't know I think people just forget, when I first started driving in the 60's a 50,000 mile V8 was considered to be a mid to high mileage motor, now it's just barely broken in. If it had 75,000 mile or so you would never be able to sell it.

 

in the 50's to the mid 60's I think people were still using non- detergient oil, with factory recomended 5k oil changes, " its ok honey we can go a little further I'll stop at western auto and pick up some oil, its on sale for .45 cents a qt." they knew better, they wanted to sell you a new car, when I rebuilt my first motor in auto shop when I pulled the intake it had mud clean to the bottom of the intake, I'am thinkin it had about 80 k on it.

 

It should not a problem for those that know what there doing.....most of the posters have never used a Vette as a car and are newer to Vettes and without any experience to maintain a solid lifter car or even a hydraulic one....a lot of DIYS participants here are in way over their head on many subjects...and this does contribute to a large amount of new replacement part failures..{starters and cams are a couple areas}.....these cars are not hobbies and more than mere nut and bolt wrenching...but they eventually for the most part do 'learn

 

The springs in a LT-1 and a 307 2bbl motor are the SAME! LT-1 cam had long clearance ramps on the cam, thats why it spec'd out at 254@0.050 lift, it wasn't lifting that valve very quickly. I run more aggressive profiles with around 120lbs on the seat and 310lbs over the nose and the longest one is at around 45K miles in my buddies 68 Z/28 right now. Some of the current aggressive fast ramp stuff, I don't know how long it will go even running quality motor oils. Better to be safe than sorry. I have a few favorite Ultra Dyne lobes, I have Bullet Cams grind for my rebuilds. They sould great, rev high and hold lash well, can't ask for much more than that

 

What's neat about the LT-1 cam is it actually runs pretty darn good on the street. I used one with some REALLY nicely ported heads (came off an 8 sec N20 car) on a stock sump piston 350 for a time in my car. Threw some 1.6 rockers on it. It was a heck of a lot of fun and ran strong...with 7000 RPM never an issue. If the heads are strong..you'll be amazed at how well a *mild* cam can run...and not be eating parts.

PS- somehow those stock cast pistons, cast crank and etc etc survived all those high RPM passes! That engine was original/untouched out of a '71 Chevelle!

JIM

 

That early 30-30 LT-1 cam is the one I'm familiar with...a lot of clack-clacking going on under the valve covers. I was not aware that GM changed the solid lifter cams in the subsequent LT-1's.

 

The 30-30 cam was never used in an LT-1.

 

OK then, the valve lash was .024/.030" on 3972178. And I suppose the cam grind was changed the next year to better work with the reduced compression of those engines.

I still think 89K miles is a lot for a high-winding, solid lifter mouse motor.

 

Jim you can't be doing this. You have to have 4340 grade crank, rods, forged pistons to do 6000/6500 rpm in your hydraulic cammed engine or it will fall apart lol.

All kidding aside its amazing how things have changed. 3.70,4.11 gearing used to be commonly ran around with many people had no problem with 4.56 on up gearing. Everyone had factory rods no better then 5340 steel cranks. Now most are worried about even going past 6000/6500 rpm with far better parts today.