5.7 vibration at @ 2500 rpm after rebuild...

[piratedude]

Had new engine built and now running good but vibration under load at @ 2500 rpm. Boat shakes and vibrates like a bent blade on prop...prop good though. Shop who put engine in says they will adjust accel pump on carb next spring when i can run it under load at lake...does this sound right?

 

[kwoolard]

Re: 5.7 vibration at @ 2500 rpm after rebuild...

I'd have them recheck the engine alignment to the gimble bearing.

 

[Alpheus]

Re: 5.7 vibration at @ 2500 rpm after rebuild...

Does the boat shake at 2500 rpm out of the water?

You shouldnt take your engine above above idle if you are running on muffs but if you take the engine up till it starts to vibrate take the out drive off and see if the vibration goes away. You can narrow it down to see if its the engine or drive line...

 

[rjedney]

Re: 5.7 vibration at @ 2500 rpm after rebuild...

did you use the correct fly wheel? Accel pump only works on fast throttle movement. Out of shaft aligment will burn out your coupler. never seen one shake until it melts out the rubber bushing. Two piece rear seal engs. use netural balance fly wheel. single piece rear seals use balanced fly wheels 350 and 4.3 fly wheels are interchangable on late years engs. 400 and 383 stroker use yet another fly wheel. I have every engine set up made hope this info. helps you.

 

[proshadetree]

Re: 5.7 vibration at @ 2500 rpm after rebuild...

1955-85 Small blocks have a crank Flange bolt pattern of 3.58. 1986-up have a crank Flange bolt pattern of 3.00. Can not go old to new. All small blocks are internal balanced but the 400. 383 are a cross beard beast that need what the manufacture of the kit states for them. This was my understanding.

 

[proshadetree]

Re: 5.7 vibration at @ 2500 rpm after rebuild...

I was replying to the post above me, if you would have read before typing. Unless you are running a stroked version of the sbc it is difficult to get the wrong flywheel. Now if he had it done by a shop with several projects running at the same time flywheels could have been swapped. Being I did not start this thread I do not know what the original poster had done or not done. I would assume a shop would align the drive after building an engine but who knows? Thats what it has to do with it.

 

[oops!]

Re: 5.7 vibration at @ 2500 rpm after rebuild...

i had several vibration issues.......it is not the acellerator pump.

did you change engines?....if so you may have the wrong coupler....the distance the shaft goes into the coupler will produce a vibration......

also the spring washers in the mount hardware will make a difference.

and the flywheel that is allready posted is a major for vibrations....especilally at higher rpm.

if the rebuild shop just pulled a block off the shelf built the motor and then sent it to a shop to be installed.....the boat mechanic may not know about the different couplers.....everything will fit....but it wont work.