1966 Belvedere Vibration Help - from over the pond!

[mustbemad]

Having had my 318 Poly Belvedere Wagon for seven years, I finally got round to swapping out the tired Poly for a 360LA. Lots of threads on here have been useful!

It came out last year, and the 360 has only had its cam broken in a couple of weeks ago - these projects take a lifetime.....not least of which because parts supply in the UK of anything other than oil filters can be tough!

Having successfully broken in the cam and thinking I could get cruising, I now have another problem

Engine idles nicely at around 800 RPM, but when you then bring the revs up there's some nasty vibration around 1200 rpm which then goes as the revs rise and once again it's smooth - with the 727 in Park, neutral, and the same when you drive it.

Things I've checked:
-Engine mounts
-Transmission mounts
-Transmission fluid level
- Was a new harmonic balancer (could the wrong one cause these symptoms?)
-Anything else that might to be rattling loose.
-Specifically remember torqueing up the flex plate onto the engine and the torque converter
-And had the 3 clunks as the converter went onto the splines

This is the 318 poly swap to a 360, the 318 being internally balanced so I fitted a B&M weighted flexplate so I could use the original torque converter. (No problems with it when it was previously fitted behind the 318.)

Am I missing something obvious? Thanks in advance!

Gerry

 

[BeepBeepRR]

Here is an entire topic on the swap. Maybe you can get some info from this.
http://www.moparchat.com/forums/vintage-mopar-chat/125146-318-poly-la-360-swap.html

 

[mustbemad]

Here is an entire topic on the swap. Maybe you can get some info from this.
http://www.moparchat.com/forums/vintage-mopar-chat/125146-318-poly-la-360-swap.html

Thanks!

Scared me for a moment that I'd bought the wrong weighted flexplate - but it's the right one, thankfully!

 

[440Coronet500]

Are you using the externally balanced crankshaft damper also? 440'

 

[mustbemad]

Will check that out - if it is wrong, wouldn't that cause problems across the whole rev range?

 

[440Coronet500]

Not necessarily, I believe that all 360 externally balanced engines had the externally balanced damper and torque converter from the factory. You've already got the weighted flex plate which takes the place of the weighted torque converter. Now you need to verify if you have the externally weighted damper. It's very easy to verify, the damper will have an offset casted mass on the face of the damper. 440'

 

[70rcode]

Sometime in the distant past, i remember noticing a "factory" 360 H-Damper lightened or carved out on the Back side only.....just sayin,...tom.

 

[mustbemad]

Not sure of this will be of use to anyone, but finally solved the problem. Moral of the story is check and check again!

Turns out I had done everything right, but the aftermarket harmonic balancer the engine builder had given me was the wrong one

A lot of research found that Pro Sport have the same base balancer for both 360 and 318 engines, but convert it to suit the externally balanced 360 with a big weight bolted to it! You guessed it - the one that came with the engine didn't have the weight. But I wasn't to know it needed one.....

Thankfully, the weight is available separately, so more cash sent from the UK to the US economy, and all bolted up and the vibration has gone

Thanks for your help on here, as it made me recheck everything and not assume other people knew what they were doing!

Set me about a month back, but onto the last few bits and hopefully the Belvedere will ride again!

 

[Don Frelier]

Pictures and the celebratory burnout are required.

 

[mustbemad]

Pictures and the celebratory burnout are required.

That will be a first! Very tired Poly taken out - not sure it ever even chirped the tyres!