I was noticing that a lot of you guys here have modified the redline on your cars. What are the power characteristics of this motor? Does the LT1 even make good power that high in the rev band? Also, just out of curiousity, where is the fuel cutoff? I accidentally spun my car up to about 6200 RPM (there was gravel where i was racing, and i didnt know it) and i thought for sure i would slam into the rev-limiter, and nothing happened. Can a stock motor handle 6200 RPM and not be destroyed? I am relatively new, and i would like to learn what my car can take before i cause damage

thanks,
trav

 

Well to give you an idea I have my rev-limiter set at 6000.My trip to the dyno showed peak hp at 5600.I think the basic rule is shift 300-500 over your peak hp.Right now I have my shift points in the 5900 range.

 

Most of the people you are referring to have probably upgraded their valvetrains--if not they should have if they are spinning that high. I would not rev a stock motor past 6000 myself--but that's a personal choice. With an upgraded valvetrain designed for higher RPMs, people are spinning the stock bottom end to 6500 in some cases, with some claiming even higher--I would not go there however.

My advice is that if you have a stock longblock, keep the rev limiter where it is.

With a built motor, the limits are as high as you design for--7K rpms is not unheard of, although I think the stock computer won't go past that. With an aftermarket computer (& built motor to handle it) people are going over 7K.

 

I'm shifting @6200 with an upgraded valvetrain. I'm with RobK, I wouldn't go over 6000 on stock internals. It might not hurt anything, but it won't help you either.

John

 

thanks for the info,

trav

 

I think the consensus was that if you have under 50k on the stock bottom end then rev it to 6500 (if you want) and more than 50k 6000 rpm max.

Personally, I never rev my car past 5500 or 5600 (on my autometer tach, near 6k on the stock tach). You can feel the car stop pulling after 5k. With an upgraded cam that makes power past 6k and some nice strong valve springs you can rev up to 6300 6400 easy. Some with solid roller setups rev to 7k like it's nothing.

So for the most out of a stock motor, don't shift after 5.9 or 6k.

 

I have 180 passes down the track with my STOCK valvetrain going to 6,200 RPM. No problems here. Yes, the dyno shows I'm dropping power up there, but 3rd gear more than makes up for it. I have tried short-shifting into 4th many times, but my fastest E.T.'s have been when I stay in third and ride it out past the finish line.

I'm not saying YOUR stock springs will handle it, but mine have.

 

Interesting. I fail to see how the milage of the bottom end has much to do with the safe limits. Considering, the 3 limiting factors of the botom end on LT-1s are cranckshaft bow/ due to a heavy crankshaft. (get a forged/ lightened crank to solve this problem.) Piston ring washboarding (get good rings and run tight clearanced to solve this one) and crankshaft twisting on its own axis. Balanced rotating assembly balanced compression and a good damper will solve this one. Piston ring washboarding isnt a worry unless you are at high RMPs for a reasonable time, like in autocross. so wear on piston rings probibly shouldnt effect us here, besides, many LT-1s with 50k miles if maintained will still be withing factory spec on ring clearances. The damper might get old and need to be replaced but wear there come more from taking it off the wrong way then milage. With a fluid damper I would have no problem taking a stock bottom end to 6500 regardless of milage. I would like a to make sure the crank was lightened and balanced first but thats not always an option. Gm went with a nodular iron crank for this reason. As for the valvetrain, according to GM research the stock rockers are only good to 6200 Run alumnium roller rockers after that. Im still un-eazy taking my stock lifters to 6500 but it seems like they are doing ok. but I think I'm pushing the envelope there. Most stock -bolt on LT-ts ive seen peaked hp between 5200 and 5400. like somone said, shifting 300-400 past that is ideal. So there is really no reason to go past 5800 unless like one guy said, he is running out of gear, of course a slightly streatched out gear raito would be better for his times but that may not be possible/practical.

 

Good discussion... I mentioned that the mileage is important in determining your MAX rev point... mileage should not determine when you shift. A brand new engine with very tight tolerances and unstressed parts and everything in good mechanical order will be safer to rev to 6500. I mean I'm sure there are a lot of other factors than mileage but you can't discount it either...

 

<------- had limiter set at 6900 with my cc306... no problems at all.

 

There is almost never a point in turning a stock LT1 more than ~5,800rpm, you will go slower.

Rich Krause

 

at what point would a fliud damper be worth installing...?

 

I have been spinning My stock bottom end to 6500 rpms for 4 years now. Have hit the rev limiter at 7000 too many times to count. The car dropped a valve reasontly and put a silver dollar sized hole in the piston(#8 cylinder). I rebuilt a stock bottom end with ARP rod bolts and maincaps. Within 10 minutes of starting the motor while test driving it I hit 7000 rpms and it stayed together. The Lt1 stock bottom end is strong and will take alot of abuse if taken care of properly.
HVY SS

 

I am spinning a completely stock bottom end past 6500 pretty often. No problems as of yet (70k shortblock).


My buddy is turning his up to 7k, no problems yet either. A well taken care of car, with regurlar oil changes etc should hold up fairly well. Some do bite the dust earlier than others however.

 

6800 on stock components. Not a stock bottom end by no means. Fully blueprinted and all ARP bolts/ Studs. Engine doesn't even flinch. Valve train is comp cam Pro Magnum rockers, twisted flow hardened pushrods.
No way I would twist it like this without ARP fasteners and a fresh rebuild to tolerances.

Base your rev limiter and your shift points on your cam though. Thats whats important.

-Shannon