over revved motor?

[jveik]

i have a 383 stroker in a pickup i just got it liscenced and i was eating lunch with a buddy of mine and when i went to leave, my truck wouldnt start because the electric choke opened up... so i took the air filter off and covered the carb opening with my hand to choke it because i didnt want to wait for the electric choke to cool down again. i had my friend start the truck while i was holding my hand over the carb. problem is, when he got it to fire, he revved it like crazy right off the bat. this is no little rev either... i would guess it probably hit at least 8000 rpm and it was bad enough that it flipped the v belt for the fan and alternator upside down in the grooves of the pulleys. i flipped the belt over and breathed a sigh of relief because it seemed that no damage was done. however, i took it on the interstate and realized that once the motor hits about 3500 rpm, it shakes the whole truck violently. this is with or without a load on the motor, because i revved it to 3500 in the driveway in neutral and it did the same thing... any ideas out there? im hoping that i didnt screw up something in the bottom end, but that would be my luck... could the balancer or the water pump pulley have been tweaked to cause this violent vibration? it doesnt seem to have as much oil pressure as before, but i dont hear any knocking either... hopefully you guys have some idea as to what the problem might be... thanks in advance for any help

[MrPbody]

Since it "flipped" the belt, I would first look at pulleys, the fan and harmonic balancer. Look for "wobbles" or things off center. Pay particular attention to the outer portion (inertia ring) of the balancer.

If no sign of trouble there, do a compression test. You will probably find a bent valve.

Cut the oil filter open to be sure you're not "grinding up" anything. If the paper element is full of 'glitter", you may have hurt a bearing. It happens... Sorry.

Jim

[big dwag]

After this happen what kind of oil pressure do you have? Is it lower than twenty or does it go down to zero while its idling? I know u don't want to hear this but u could have spun a bearing and you might not hear a knocking noise, I have had this happen to me before. I looked at it this way, It gave me a reason to rebuild my motor just to make it better.

[jveik]

my oil pressure will run between about 40 and 45 when not idling and anywhere from 20 to 40 idling. i think that might be because i am only running 5W-30 in it. i might dump out the oil and throw some 10-40 to see what it does. i was talking to an old timer at a local shop yesterday and took him for a spin in it and he seems to think the bearings are fine and most likely i spun the outer ring of the harmonic balancer and threw the motor out of balance, since it is an externally balanced engine. i hope "old-timer" is right. im taking it to the local dyno shop to have the guy there take it on the road for a test drive and if its the balancer ill throw another one on there. thats all i know for now...

[MagicRat]

Originally Posted by jveik

my oil pressure will run between about 40 and 45 when not idling and anywhere from 20 to 40 idling. i think that might be because i am only running 5W-30 in it. i might dump out the oil and throw some 10-40 to see what it does. i was talking to an old timer at a local shop yesterday and took him for a spin in it and he seems to think the bearings are fine and most likely i spun the outer ring of the harmonic balancer and threw the motor out of balance, since it is an externally balanced engine. i hope "old-timer" is right. im taking it to the local dyno shop to have the guy there take it on the road for a test drive and if its the balancer ill throw another one on there. thats all i know for now...

Let us know how it turns out.

I wonder if you floated the valves and, as mentioned above, smacked a floating valve with a pistons and/or broke one or more valve springs ...... which might mean that the valve is now floating at 3500 rpm.

FWIW, this had happened to a '77 Trans Am I bought a few years ago....

[jveik]

im gonna get my timing light back from a buddy of mine in a few days and see if the outer ring is messed up on the balancer, but i have combed the internet and not run across anyone who has had that happen on a balancer that is only a year old or less. most of the problems i saw on the internet involved a balancer that was really old and the rubber ring had decayed to allow problems to occur... have any of you guys heard of this happening on a relatively new balancer?

i had around 36 degrees total timing set at the shop although i dont know what the baseline advance was set to. that would help me out so i could see if it isnt on the mark anymore. ill have to call up the dyno shop i took it to and see if it is in thier computer or something... ill let you guys know what happens

[jveik]

well i got ahold of the shop and he told me it should be set around 12 baseline and it was right on the money. im gonna take it to the shop and have them tear into it since i have not the space nor the tools to do it myself. his hypothesis is that i probably bent a connecting rod and this is causing the terrible vibrations when i get the motor above a certain point in rpm. if that is the problem ill have to get a new rod and have the rotating assembly re-balanced so it has to come completely apart. while he's at it ill have him throw new main and rod bearings in it and rings just to be sure none of them are messed up. that rev might have cost me quite a bit lol... it's a good thing i work union or i would never be able to afford this crap lol

[jveik]

i changed the oil in the beast the other day and it now has great oil pressure as i am now running 10W-40. i also came to teh conclusion that the vibration is being caused by the water pump pulley because when the belt is not connected the motor will rev up smooth as pie, but when you put the belt back on, it does the violent shaking again.

as a side note, would this likely be why my waterpump/alternator belt keeps popping off the pulleys? whenever i try to rev the damned thing, it pops off and the way i can tell is that the water temp guage will start rising so i have to pull over and use a socket and crowbar to reinstall it. it is really starting to get on my nerves...