ACE1252

I seriously disagree with that....(I assume you are referring to 4 bolt mains).

If that was the case why bother with four bolt mains on any engine(btw LS1 has 6 bolt mains..yeah, guess they are irrelevant...)....plus if the main caps distort under high rpm you are in a world of hurt....bearings will wear out of round I'm guessing....you can then count on spinning a bearing soon.

chrism400

Dude, we are talking about a 7k maximum Chevy smallblock. The mains aren't even close to being the rpm limiting factor. What you are all worried about rarely happens in our motors. In this discussion, they are completely irrelevant.

Denny McLain

In a stock or semi-stock vehicle........Nada, zippo, nope. Probably not a tinkers dam even in a pretty heavily modified one unless it's turning a zillion rpm or has a pretty HD power adder. More than likely marketing and perception than anything in a mass produced production vehicle as the Corvette is and always will be, GM's performance benchmark and GM needs to make distinctions whether real or perceived.

Quite honestly the original question falls under the guise of………”If ya got to ask, you probably don’t need to know.” A more appropriate question might be: What is the most effective shift point? These cars can rev quite high as compared to the stock LT1 redline and not blink an eye when it all said n done. Since when was a small block Chevy ever considered anything except a higher rpm screamer??

Where in the world did all this burn out friction stuff come from and what does it have to do with anything??? Hey……….type on dudes.

rskrause

Well put.

Rich

chrism400

Come on Denny, Physics 101. F=MA or Fun = Mash Accelerator !

showstoppers-96-Z/28

i have my shift point set at 6100 RPM's, i've been told you can spin the stock bottom end as high as 6500 - 7000 and not have an issue as long as you have a strong top end to keep up.

jclark311

Well i am glad i started this discussion, i think most of us are in agreement, you can rev an LT1 safely above 5800, i think for me i will set the rev limiter at 6100, and shift at 6k, i just know that as long as there is no valve float, you get more horsepowerr that way, hey keep in mind, i am reading the stock tack, maybe i am shifting at 5800, who knows how accurate that thing is.

mattbailey

I turned my stock bottom end cam only to 67-6800 for best et's. Never a problem. My new motor should take whatever I can dish out as well

ACE1252

I'm not disputing the fact that a 2 bolt can be turned higher than the stock rev limiter. As a matter of fact I plan to go around 6200 myself after my cam install.

I just wanted to point out that it is safer to do it with a 4-bolt rather than a 2-bolt. It's a matter of keeping the main caps from distorting. The better you can do that, the less chance of bottom end failure.....and the fact is a 4-bolt will control cap walk better than a 2-bolt.

I will also agree that the valve train is more of a concern than the bottom end on a stock LT1.

I reviewed the buildup of the LS1 that Horsepower tv broke(have it recorded on the computer). They took out a rod bearing and not a main bearing.

chrism400

That's right Eric, a 4 bolt will help the "cap walk" phenomenon for sure. I was just pointing out that a stock motor, or stock motor with cam has other issues way before the mains become a problem. If you look at problems guys have after a cam swap, it's almost always a rod bearing failure and not a main bearing. I happen to think it's due mainly to dirt or some foreign object loosened up during the install that gets into the oiling system. Adequate oil pressure and volume play a part here too - the older the engine, the greater the bearing clearances become while the oil pump, with age, starts to lose pressure and volume. It's a double edged sword. At high rpm, centripetal forces are pushing the oil away from the center of the crank. You need an adequate volume of oil to keep up the supply or else the forces will sling it right by the rod bearing and cause a failure. A neighbor of mine had an insane 287 5 speed Vette. He ran 2 bolt mains with studs for years up to 8400 rpm. As stated earlier in this thread, the valvetrain is the big culprit we need to worry about first. With any application, it would be wise to experiment with shift points to see where the best et is achieved. Unnecessary rpms on the motor are just that - unnecessary.

Denny McLain

That's really quit good and on the other hand.......short shifting can leave a lot on the table. Pro Stock, Pro Stock Bike...leave, shift point, shift point, shift point and shift point. All must be perfect or you loose.

95ttoplt1

Sorry I didn't realize he was still using a stock cam.

My car with the stock cam was fastest in the 1/8th shifting at 6200 according to datamaster.

jclark311

Thats what i thought, 61 to 6200 feels reel good. At 5800, your leaving horsepower on the table, with the stock cam.

stereomandan

Not according to dyno charts that I have of stock M6 LT1's, but you can experiment and find out.

Dan

95ttoplt1

Every car is different, I didn't expect it to do what it did and neither did anyone else. Maybe it has something to do with the higher mileage motors retarding the cam slightly due to a streched timing chain.

But thats just a idea.