360 balance problems

[dusterz]

I have a problem with my 360, I don't think its balanced correctly.When I first got it running I noticed a vibration around 2800 rpm, felt like a wheel out of balance,not it, so I checked the driveshaft, not it, noticed the output shaft was a little sloppy,not sure what the specs are for that,so bought a , tci super street fighter tranny, tci 3000 stall, new driveshaft, and a new rear yoke, about thirty five miles later I blew the front pump seal out while warming it up in the garage to check the timing,while doing so I noticed the vibration around 2500 rpm and up.I'm thinking the guy who built the motor diddnt balance the flexplate correctly. my question is how do I get it balanced right? do I need to take it all apart again or is there another way.
I've had nothing but issues with this thing since i did the engine swap.
Its a mild race built engine, supossably 400 to 450 horse. any help would be greatly appreciated

 

[fishy68]

In stock form the 360 is an externally balanced engine so it requires the correct 360 harmonic balancer (check to make sure it has that first) and the correctly weighted torque converter or a B&M or TCI flexplate with a notch cut out to balance the engine so a standard neutral balance torque converter can be used. What converter do you have in it? Is the flex plate stock or an aftermarket unit?

 

[kursplat]

the only way to know for sure it's balanced correctly is disassemble it and have the balance checked by a shop you trust, who should give you a print out with all the weights. if you do, take the TC and flex plate with you

good luck

edit: the guy who built it should know if it was balanced internally (not stock for a 360) or externally (stock 360)

 

[moper]

Find out if he internally or externally balanced it. If he only had the factory balancer and it was external then you need the correct flex plate. (B&M makes it)
If he internally balanced it and didn't have a balancer, and you used the factory 360 balancer, you need a new balancer. If the whole car shakes, the pump seal blew out already, and it doesnt start being felt until 2500, my money's on the flex plate.

 

[dusterz]

I bought the b&m sfi flexplate for the ext. balanced 360, but the motor was built about five years befor I finally got it in the car and it was then that he told me to get that flexplate, supposedly he spun it with a different carnk since mine was allready iin the car, and he said it would be good, from what he told me the motor was built and balanced for someone else, but they never paid the bill, so he sold the heads off it then he sold me the short block.
I kinda figured I'd have to pull the motor back apart to have it checked, btw the guy that did it retired about two years ago and since then I've heard of other people having proplems with stuff that he did.
so i think that i have a 4500 dollar boat ancor, I wish i woulda went with the 360 crate engine insted.
thanks for the input

 

[dusterz]

ya he retired and moved to montana, he did tell me that the rotating assembly was balanced, but ive heard hes in trouble with a lot of people that he did work for he used to work at a local auto parts store here in town b4 he left i've had the motor apart 4 times for different things, heads leaking,wrong head gaskets,twice! motor apart twice to check the bearings cause of the antifreeze getting into the oil, i think im gonna have to start over, again.
thanks for the help

 

[moper]

Sounds like you have a source of decent parts, but you need a real performance shop to sort it out.

 

[kursplat]

...supposedly he spun it with a different carnk since mine was allready iin the car, and he said it would be good,

ya, that kind of defeats the whole point of getting it balanced :shock:

 

[pettybludart]

Do you have a new dampner or are you using an old one?They tend to seperate,pushing the rubber ring out.I had this happen to me,causing a vibration,changed it for a new one.Fixed.Just sayin..