6200 is LT1 limit

[sothpaw]

Just FYI,

I was surfing the net last night and I came across an interesting
site where a corvette owner blew his LT1 because the rev limiter
was 6400 rpm, against his mechanic's advice. This engine had
the stock bottom end but the diff. had new 410's in it.

So, anyway, this is just one data point. But I will set my rev
limiter at 6150 rpm when I do my mods this spring.

 

[vetteguy]

Good idea Sothpaw. I would stop @ 6100, just to be on the safe side. :L Guy

 

[Mad-Mic]

i doubt it blew from winging it to 6400 rpm. sounds like something else was wrong or he did this everytime he drove the car. 6100 is all you need imo on the stock lower end btw.

on a well maintained and tuned motor it would take along time to blow it winging it to 6400 rpm if the redline is 6000 rpm. GM gives you alittle more play than 400 rpm even with a rev limiter.

 

[UB2 SLOW]

I got the LT4 Top end and stock LT1 bottom. I have my rev limiter set at 6400 and my shifts set to 6200. I have made about a hundred passes at the track and who knows how many times I have maxed it on the street and I have no problems. YET!

 

[sothpaw]

stock rev limiter

MadMic,

The stock limit is 5850, so 400 would be 5250.

UB,
This guy was autocrossing it pretty hard with 410 gears in a 6
spd. I bet he spent a lot of time up there. And, like I said, this
is just one data pt and your car is another. There will be some
tolerances in actual engine components; maybe that is enough
to explain the difference.

 

[92ghost]

I think Sothpaw is correct. Autocrossing does put a lot more stress on the internals than 1/4 mile drags. My thoughts are this: autocross will use the compression to slow down the vehicle, I'm not sure but I think this puts stress on different parts of the rotating assembly. Then all of a sudden you mash the gas for acceleration which shifts the stress point once again. I'm not an engineer or stress anaysis expert, but I think this combination of rapid deceleration and acceleration puts a heavy toll on the rotating assembly. More so than drag racing. I've heard from several people that have taken the stock LT1 to 6400 and even 6600 RPM during drags and have not experienced any problems. To be safe, I would not go over 6200. BTW, what is the difference in the rotating assembly from an LT4 and the LT!. I know the top end is geared more for higher RPM on LT4 but the crank (LT4 has undercut fillets), pistons and rods/Pins etc. Are'nt they the same?????

 

[Vettelt193]

The real issue with high RPM is the probability of problems... The higher the RPM, the more likely a problem will come up. If anything is even slightly off, high RPM will really make that problem come out. With that in mind, if something does break or go wrong at a high RPM it is much more likely to cause major damage to the engine.

For the High RPM/stock bottom end guys:
Some guys have the right combination of luck and skill to have no problems... most aren't so lucky and blow things up.

 

[UB2 SLOW]

Southpaw, if he was autocrossing then yes I can believe it. You will spend more time hitting the limit than you will with drag racing.

92ghost, you are correct, autocrossing is more demanding on a car than drag racing. The LT4's bottom end was reinforced and had some slight changings to handle the higher RPM's. I am not sure what all the changes were, but the crank, pistons and I think the timing chain were different. The LT4 had a higher compression ratio vs the LT1.

 

[sothpaw]

I agree with Vettelt193.

What I was always interested in was that "safe" rpm limit where
99% of well maintained engines will not blow up.

If you tell me that at x rpm, 3/4 cars will be fine but 1/4 will blow
up, that is too risky for me. Major engine damage is too expensive.