Max RPM in the shop ?

[RacerX10]

I have a well built late model motor that I race @ around 8,000 RPM.

Trust that I have a good reason for asking, so I'm just wondering .. what would you engine guys that are "in the know" consider to be a safe max rpm to run this thing up to sitting in the shop.

For some reason I have it in my mind that it's not good to run one up too high "unloaded" but I can't think why that is.

Thanks for your comments !

[50j]

Why would you want to?

[stock car driver]

I try not to EVER start mine at home, no races to win in my shop. I use a winch to unload and pull back into shop if nobody in my family wants to push a little!

[stockcar5]

i rev mine to 3500 or so to make sure my locked out timing isnt moving. other than that i see no reason to rev it at all.

[hpontap]

After the feature I usually just drive my car up in the trailer. Next day wash it and start checking it over. I will run it up to temp and check everything over on the engine also. If it is time to set valve lash or check timing etc, I will run it up to where I need to verify the timing is correct. Depends on the engine combo but usually never 4,500 - 5,000.
Nothing worse than getting to the track and not having the engine run right when you could have checked it at the shop.

[RacerX10]

Thanks for your comments, I appreciate it.

I'm still looking to hear why it's ok to run it up to 8,000 out on the track but not in the shop.

If you must hear a reason to spin it up that far, assume it's for some instrument testing.

[lovinlatemodels]

On the track the motor is under load on and off the throttle if you bring it up to 8 in the shop it will drop off very fast more or less shocking your equipment on the track it works up to 8 in the straight of ways and probly only drops down till about 6 in the corners and drops down slow when you go back to idel JMO. In the shop only ever brought motor to temp too check it out before leaving for track and sometimes to 3500 to 4000 just checking carburator throtle response.

[Egoracing]

I don't remember where I read it but if I remeber correctly they were saying that an engine at no load on the crank at 1/2 normal RPM is in more of danger to itself than a loaded engine at full RPM. The issue is you do not have the drive train dampening the forces of the engine.

[let-r-eat]

Like always you never should rev a cold engine. Friction/oiling etc. An engine doesn't heat the oil enough without load. Promoting poor oiling. IE the need for oil preheating.A warm engine in the shop with no load has the capability of revving up much faster than it does under load. This also makes it far more apt to over rev. Revving it up is not the problem. The problem is how neutral allows this to happen much faster and along with poor oil flow due to lack of heat, you end up with bearing damage, lifter bore damage, etc etc etc..

[merc123]

However on a late model....if you crank one to 8000 in the shop and hold it there.....you can rule out the ignition system. Tells you under a load it is fuel related.

I don't have a late model, but I had a misfire for 5 weeks. It would start at 5800 and stay there. In the shop you could rev it to the 7k chip. Turned out to be bad spark plugs so just because it revs to 8000 in the shop I don't think you can 100% rule out the fire...

[stockcar5]

merc is 100% right. misfires under load can be fuel OR ignition. but i still wouldnt try to rev my car up in the shop to find it..lol. i'd head to my guys chassis dyno and throw the scope on it for $75 and have it solved within an hour.

[RacerX10]

Like always you never should rev a cold engine. Friction/oiling etc. An engine doesn't heat the oil enough without load. Promoting poor oiling. IE the need for oil preheating.A warm engine in the shop with no load has the capability of revving up much faster than it does under load. This also makes it far more apt to over rev. Revving it up is not the problem. The problem is how neutral allows this to happen much faster and along with poor oil flow due to lack of heat, you end up with bearing damage, lifter bore damage, etc etc etc..

None of that makes any sense. You can easily get your engine up to operating temperature in the shop, and the MSD rev limiter will take care of any over-rev issue.

[RacerX10]

The issue is you do not have the drive train dampening the forces of the engine.

That's the closest thing I've heard to making any sense, but I'm still a little skeptical

I did find this googling :

"The pistons, rods, rings, valves, lifters, rockers, cam, oil pump, etc, etc. neither know nor care if the engine is in neutral or drive. All these parts see is loads based on RPM. 6000 in neutral is no different than 6000 in drive. The only difference is the RATE of RPM increase. This does not increase the structural loads.

The crank is the only part that sees different loads in neutral or drive, and the loads are HIGHER in drive."

[stock car driver]

None of that makes any sense. You can easily get your engine up to operating temperature in the shop, and the MSD rev limiter will take care of any over-rev issue.

Are you asking a question or giving answers??

Rev the thing on the chip (8000 at least please) and time how long it lasts!

Post back and let us know the exact time, rpm etc. Then we can use your proven information to answer the next stupid question like this that comes up.

[stockcar5]

6000 in neutral is no different than 6000 in drive. The only difference is the RATE of RPM increase. This does not increase the structural loads.

biggest load of bull$hit ive ever read next to dynomans posts anyway...