I stroked my 460 to a 545 using Scat's parts. I had the engine balanced internally. The flexplate that they sent and I installed was for an externally balanced engine and had a weight welded on it. I found out after the engine would start vibrating around 2500 rpm and was so bad that I wouldn'g run it to 3000 rpm for fear of damaging the engine. I talked to Scat and found out that they had sent me the wrong flexplate. After talking to them, I ground the weight off the flesplate - it was accessible from the access opening at the bottom of the engine. My problem is that I still have a noticable vibration, nothing like it was before but enough that I notice it. I'm thinking that I have to get a new flexplate from Scat that is balanced for an internally balanced engine, at no cost to me of course.

Does it make sense that the flexplate could be out of balance without the weight I cut off enough to still vibrate the engine?

 

what sort of dampner did you use?

 

I used a BB Ford 6.7" damper supplied by Scat.

 

who did you get to balance your engine? there is no way anyone would balance your rotating assembly without using your flexplate and harmonic balancer. if they did, then you need to take your engine apart and send the assembly along with the correct flexplate (either internally or externally balanced) along with the balancer (which are all neutral balanced) to a reputable shop to have it rebalanced. if it was balanced without the flexplate and balancer, no matter what flexplate you put on it, it will be out of balance to some extent. it needs to be balanced as a complete assembly.
if the shop would of balanced the assembly correctly they should of caught the fact that the flexplate was incorrect.
even though in theory the flexplate is suppose to be neutral balanced for an internal balanced engine, it should always be balanced along with the rotating assembly as manufacturing tolerances can mean it is not 100% neutral balanced.
you can try putting a flexplate on it, but i don't think the vibration will ever go away unless you rebalance it again.

me 2 cents

Rgds
Mike

 

Thanks Mcdonaldm,

Scat balanced the rotating assembly. Obviously, they don't do it with the flexplate. I have a machine shop that can balance the flexplate I have but I think that Scat should give me the right flexplate. I'm thinking that if they can balance the flexplate then with the rotating assembly already balanced it should work.

Thanks for the input, I'll let everyone know what happens.

 

okay makes more sense. thought you had it balanced by someone else.

getting the correct plate might help. might not though.

did you buy a complete assembly from Scat? crank, rods, pistons as a balanced assembly?

if you bought a complete kit, then everything should be balanced out. but if you just bought the crank and added rods and pistons, then everything would of needed to be rebalanced with the new parts taken into consideration. also to what standard did Scat balance the assembly to? just because their advertisement says they are balanced, does not mean they are perfectly balanced by any means. lots of stories on other boards of aftermarket cranks needing work to get them perfect from the supplier (not only balancing, but finish of journals and sizing of journals).

not trying to be a downer on your project, but you might just always have a slight inbalance even with the correct flexplate installed. unforetunetly in todays economic reality, the only way to keep costs down is mass production and minimal labour input. Quality control adds a lot of extra money to the product, so that is why the same product from a good supplier will cost more than from a bulk reseller. the good supplier spends more time checking and fixing the factory work to make it acceptable to them.

hope it works out for you

Good Luck
Mike

 

you CAN balance the rotating assembly without the flex plate and dampener (actually on a BBF the dampener is NOT the issue it's the spacer behind it that is important)

you can't get that flex plate right just by grinding that weight off you need to have the correct one, also make sure you don't have a hatchet weight spacer behind the harmonic dampener

 

Thanks for all the input. Yes I bought the whole rotating assembly from Scat & had them balance it. Since I did buy everything from Scat and they sent me the wrong flexplate, I figure that they owe me the right one. Anyways, I'm currently fixing a leaking rear main seal. Once I get that done, I will finish up the flexplate problem.

In pulling the engine mount bolts I did notice that it appears that the right motor mount bolt that is inline with the engine appears to have allowed the engine to be moving a little bit (the motor mount was shiny), though the bolt & nut seemed tight when I took the bolt out. I'm going to make sure that they are tight when I reinstall the motor mount bolts. If this bolt was allowing the motor to move, it could have affected my feeling a vibration.