I have a 93 with a hot cam, double valve springs, self aligning roller rockers, stock pushrods, and lifters. What is a safe limit for occasional drag racing?

 

After a similar mod, I re-set my rev limiter to 6100 rpm and have bounced it off the limit several times - no ill effects.......according to my last dyno run, the engine was just starting to roll off (RWHP & torque) at 6000 so I'm going to be leaving my limiter at the 6100 mark........I'm sure there are others that twist their engines tighter but I want mine to live a little with all those new parts.

:seeya

 

When I first installed my Hot Cam I got a custom computer chip from Ed Wright. I thought he had the rev limiter set at 6300 as that's what it showed up as on the dyno. I didn't have the best valve springs on it, and one could start to see a dip in the dyno graph right in the upper RPM's which I believe might have been minor valve float.

Eventually I got everything I needed to tune the car myself and I couldn't resist taking a look at the Ed Wright chip. To my suprise the rev limiter was actually set to 6500! I got to looking at some dyno graphs from some friends a little bit closer. Sure enough, all 3 different dynojet's that we had used were about 200 RPM's off from what the rev limiter was set at.

I wouldn't have set the limiter to 6500 intentionally, but by this point I had pounded the crap out of it both at the track and at the dyno with no ill effects. I decided that it was safe so I left the rev limiter there. When I later installed my MSD ignition box I wanted to use it's rev limiter instead of the factory one. As such I set the limit in the computer to 6600 and set the MSD to 6500. Later when I upgraded my cylinder heads I went with HUGE valvesprings along with lightweight titanium retainers and undercut valves. Back on the dyno the fluctuation at the top of the power band is gone and it pulls hard all they way to the rev limiter.

Some people will tell you that the stock LT1 won't take anything over 6000, some people say 6400. I say it's all :bs I know at least one guy who routinely spins his to 6800 with no ill effects, several forum members also turn pretty high numbers on stock bottom ends. The valvetrain is the biggest limiting factor on the stock engine.

Would I want to turn 7000 on a stock bottom end? No, but it's a lot stronger than people give it credit for.

 

Nathan right, my stock bottom end with 98,000 miles shifts at 6300, they make great power. :thumbs:

 

My rev limiter is set at 6200 rpms. A little conservative, but my horsepower peaks at 5900.

 

My rev limiter is set a 6,900, but my valvetrain isn't stock. I've also recently acquired some loud lifter ticking.

I wouldn't recommend pushing your self aligning roller rockers, stock pushrods, and lifters past 6,400. Get your car on the dyno and see were the hp peaks.

 

Get some comp cams pro-magnum lifters if you're gonna spin it that fast. They'll handle the high RPM's a little better than the stock ones.

 

:yesnod: Yep, I'm working on it. They were unavailable when I did the H&C swap. I'm also considering a couple of "other" ;) mods when the intake is off.

 

It's all in the valvetrain. I have an Ed Wright PCM with a 6600 rev limit, an MSD that cuts spark at 6400 and my shift point are at 6200. I plan on tweaking the program and raising the shifts to 6300. :D