I was just reading another thread on vibration dampners and internally/externally balanced blocks, and I have a problem that may be related, but just don't know.

I took the 460 out of my 74 F250 over the winter to change some things, and now that it's back in, there is an engine vibration that shakes the truck a little at all speeds, but is most noticeable at idle or slow speeds. It's driveable, but pretty annoying.

When I took the engine out, I replaced: oil pan & pump, water pump, valve seals, flexplate, starter, and distributor. At first I thought it was vibrating because of bad timing, but I set #1 piston to TDC when installing the new dizzy, then moved timing to about 14 degrees BTC. The truck has good power and doesn't bog down, so that leads me to think the vibration is caused by something else I replaced.

The flexplate only went on one way, and looked as thought it was balanced (got it at Advanced Auto). Is it possible my vibration is caused by the flexplate being slightly out of balance? Anyone had that problem with a new flexplate? Is it possible to figure out if an improperly balanced flexplate is causing it without taking it all apart again? Also, if the flexplate is not balanced right, is there anying you can do to balance the engine without taking the flexplate back apart?

The engine mounts are tight and not misssing any rubber either. I'm out of ideas and need some advise.

 

I am not a 460 guru, but I have read on this page that the early 460s had internal balancing and the newer models have external. If you mixed the balancers and flywheels you would get vibrations.

You mention using a flewxplate. Did the engine originally have a flywheel? Maybe this is a cuase of the vibration. Or if you are using a different balancer.

Good Luck.

Jim Henderson

 

I am using the same harmonic balancer that was on the engine. It's an automatic tranny, so it has a flexplate. The stamping on the block shows it is from the mid 70's (it's not the original engine based on the VIN number), and I thought those were externally balanced. When I got my flexplate, I ordered one for a 74 and it had a weight welded to the backside, so I assumed it was correct. I just didn't know for sure if that's what's causing the vibration, or if some flexplated ever come balanced incorrectly from the factory.

 

the 74 should have been a nuetral balanced flexplate, and shouldn't have a weight attached, the 78 and earlier engine were internal balanced, 79 and later are external balanced. The harmonic dampners are the same for both external and internal balanced engines the difference is the spacer behind the dampner, the early ones are just a round spacer the later ones have a "hatched" weight cast on them. If you got a flexplate that had a weight on it, then you got the wrong one if your engine is from the mid 70s, one way to tell here would be check the block casting number, if it's D9TE then it's a later model externally balanced engine, and should have a weight on the flexplate, any other casting number on the block would be an earlier model internally balanced unit, and should NOT have a weight on the flexplate.

 

The best way to find out which crank you have is to look at the casting numbers on the crank itself, I believe the internally balanced cranks have a 2Y casting and the external have 3Y, not exactly positive on that though . (monster correct me if i'm wrong) but the block should have nothing to do with the balancing, he could have an internally balanced crank in a D9te block.

 

the crank casting numbers you listed are correct but he cannot have a factory internal balanced crank in a D9TE block without major work bieng done to the block for clearencing the internal balanced cranks have larger counter weights which hit the bottom of the cylinders in the later blocks, but you can put the later external balanced cranks into the early blocks they will clear fine. the only other way to have an internal balance crank in a D9TE block is to convert the crank to internal balance with the use of a LOT of mallory metal and the balancing will end up costing about $600 by itself. So for the most part you can tell on a stock rebuild about the balance by the block casting numbers.

 

I checked this morning and could only make out the first 3 letters on the block...DIV....so, this means I have a pre-78 block and needed to have the flexplate without a weight on it?

I think I'm going to take it to a tranny shop this time to have it replaced. Taking the engine out and putting it back in a few months ago just about killed my wife and I (couldn't get anyone else to help). Don't think I could talk her, or myself, into taking all of the stuff apart again.

 

Is the weight spot welded just inside the ring gear? Is it possible to see the weight or the back of the welds from an inspection cover? If so, maybe you could drill out the welds and drop the weight out of there.

 

it's not spot welded trust me they are welded solid then after you cut the weight off would have to have it spun aned make sure it is nuetral balanced so it would have to be out of there in anycase, so might as well put the right one in.

 

Thanks for all of the advise. Got an estimate of about $400 to replace the flexplate from a good tranny shop (including new flexplate). I'm thinking of talking to Advance Auto about splitting the cost of the job since I asked for a flexplate for a 74, so it shouldn't have had a weight on it. Don't think they'll go for it though.

 

Thanks for clearing that up monster, I guess I learned something today.