360 stroker with vibration

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Wayne Rider

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I am new and inexperienced but learning fast and going broke even quicker. LOL I have a 1972 360 bored .30 and stroked with a Scat Crank and Eagle H beam rods Icon pistons 11.5/1 and rings Edelbrock rpm performer heads and intake Denon 850 cfm carb Lunati voodoo cam 552 lift 297 duration with pro form roller rockers . Any way I started and ordered wrong pistons first time ,came out of hole , then got right pistons and my rods barely hit cylinder walls , had to trim cylinder walls a little . Then pushrods were too long had to buy cut to fit push rods. We finally got motor done and went to work on car . 1975 Dodge Dart Sport got motor in and 727 tranny with B&M holeshot 3000 stall torque converter Had drive shaft made for 4.10 geared 8 3/4 sure grip rear. Got car started and got cam broke in but motor sounds good no knocks or anything but a really bad vibration. The crank is internally balanced the balancer is also Scat and internally balanced flex plate is Jegs brand internally balanced torque converter is neutral balanced but a bad vibration. All parts are brand new nothing was ever used. My machine shop says pull motor and bring crank pistons rods etc and they will balance each cylinder. CXar is already painted and I don't want to pull motor if I don't have too. Does anyone have any ideas other than pulling motor ? I have spent a lot of money so far and don't want to take any short cuts now but I also don't want to do a lot of work if there is a better idea.
 
If you have a 4-Post lift, engine can go out the bottom. IMO, it's a bit more work, but way less risk of mucking up the paint.
>Headers can stay on the engine.
>Trans can stay mounted
>hood can stay on
>leave the upper control arms on the car/you may not have alignment problems.

However; with alloy heads, and since the engine has to come apart anyway; I would still yank it out the top, leaving the trans behind..
 
"Don't want to take any short cuts", "don't want to do a lot of work", and didn't balance a mismatched bottom end... No wonder this is in the "Jokes and Funny Stuff" forum.
 
I thought 360’s were externally balanced I know mine is that is why my b&m flex plate has a cutout section to mate it to the 904 trans
 
Oops... yeah that is the PITA of 360s IMO. The external balance. If I had 2 setups a 340 and a 360, Id have a dedicated transmission and flex plate or flywheel etc. for each engine I would just have those two components sitting waiting to be swapped in as a unit.
 
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Take the engine out and have it looked at... do it now or you WILL do it later
 
Thank You all for your comments. I bought car with a lot of new parts with it, they were stroking a 318 . I thought I was making it better and I said I was new to all this. I thhought as long as everything was new and crank , balancer, flex plate and torque converter were all internally balanced I would be okay. Obviously I am not I just waned to know if anyone had any useful advice now that I am in this far. It is not a shame to be ignorant but it does cost a lot
 
You may just need external balance 360 Harmonic balancer flex plate and Torque converter if your rotaing assembly is setup setup for external balance.
 
Did you have the crank/rods/pistons ballanced before assembling the engine?
If it was a rotating from scat cranks it would already be balanced. At least that’s the way mine came. With a scat harmonic balancer. Had machine shop mill counter weights and balance my old B&M flex plate. Engine runs like a top. Can’t say enough about scat cranks, they provided what they said and answered all my questions, no matter how stupid they were.
 
If it was a rotating from scat cranks it would already be balanced. At least that’s the way mine came. With a scat harmonic balancer. Had machine shop mill counter weights and balance my old B&M flex plate. Engine runs like a top. Can’t say enough about scat cranks, they provided what they said and answered all my questions, no matter how stupid they were.
Rotating assembly
 
What torque converter you running. If you went for the internal balance on your 360. Then you will need a neutral balanced converter, flex plate, and dampener.

You didn’t buy a balanced rotating assembly to begin with piston, crank, rods etc. therefore you needed to have those parts balanced before assembly.

I hate to say it but the best case scenario is probably blow it apart again and have a machine shop balance it, better yet maybe have them short block it for you.
 
Pull the engine, and have it balanced.
I hope you did not run it long enough to beat the bearings out of it, there is no easy fix at this point with mis-matched parts.
 
I’m surprised the machine shop didn’t strongly suggest that you balance the engine if they know the story behind it . Which Im sure you probably told them .

We are jumping to the conclusion that what he feels is indeed a vibration from rotating assemble being out of balance .
Please describe what you are feeling and what rpms it occurs.
 
If it was a rotating from scat cranks it would already be balanced. At least that’s the way mine came. With a scat harmonic balancer. Had machine shop mill counter weights and balance my old B&M flex plate. Engine runs like a top. Can’t say enough about scat cranks, they provided what they said and answered all my questions, no matter how stupid they were.
If you bothered to actually read what he said, it wasnt a complete "rotating assembly" bought as a ballanced kit. It was bought as individual peices, and that requires ballancing. Pretty simple
 
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The problem will end up being external you all are sending the guy down the long expensive road...acting like experts . This forum is a joke sometimes because you all act like everyone has an endless checkbook and everyone is building a race engine.
My experience with out of balance motors on the dyno is that they shake most noticeably at around 1500 to 3000 rpm.
 
Your engine... You do what you want
I've been down this road listened to people tell me it was the engine it was a bad pressure plate...all I'm saying is check the external easy stuff first don't tell the guy that he needs the rotating assembly machine shop balanced as the first move...for years Ive seen it on here its always the most invasive expensive thing given as advice. I'm glad I know what I'm doing and can keep a car running... feel bad for those that ask here. OP do me a favor PLEASE come back here and tell us what it is/was... :lol:

to elaborate further how did I know it wasn't my engine? I pulled the 340 and dropped a 318 in and, THE SAME VIBRATION like said been down this road. Its a process of elimination and yes get the checkbook out...if money is an issue you'll get upset fast. I did however get real good at getting a 4 speed out in less than an hour :)
 
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