3.8 information - balancing

keithnh

Newbie
Need to know how to distinguish a fully internally balanced Buick 3.8 from one that requires external balancing. If there is such a distinction. Appears there is with Chevy V6 between 1 and 2 piece seal motors. I am trying to convert my 1984 motor from automatic to manual transmission and shoehorn a conversion flywheel into an H-body bell housing. I believe the H-body was 153 tooth my Cutlass flexplate is 160 tooth. My 84 engine is a low mileage smooth running motor I don want to have to disassemble to balance. Flywheel selection is slim but widens if I know it is neutral balance.
 
Just got my Buick V6 book that says all Buick V6 engine are externally balanced. I get on the Advance Adapters website where they offer the CF700010 160 tooth flywheel for all Buick 231, 299$ .. for internally balanced engines .. ??? Does this mean you are supposed to disassemble your motor and have it balanced internally, something the factory didn't do, just to use their flywheel? From my reading so far both flywheel and balancer are not neutral by small amounts accomplished by drilling the flywheel or flexplate mostly or sometimes adding a weight and the balancer by varying its thickness. I have not purchased a flywheel yet. May see if a tire balancer can indicate the offset and see if I can drill a flywheel that bolts to my engine properly to duplicate my current flexplate. Have my balancer rebuilt if it needs it. Was told washers on the flywheel mount bolts, and longer bolts in the right place works too. Just saw flywheel shims meant to space a reground flywheel surface back to original .. one could be fabricated to be placed on bolt-head side with raised portions to vary weight possibly as well. There must be a certain weight at a certain location from the dowel that when compensated for would allow any flywheel that fits otherwise to work.
 
The ONLY way to do it properly is to COMPLETELY dis-assemble the engine & have it balanced PROPERLY. Anything other is just a guess & COULD end up being another HORROR story. Lots of those out there.
I'm sorry, as I'm sure this is NOT what you wanted to hear.
 
Well you might be right but Im not going to do that. I don't accept that is necessary yet either. My Buick book does say production engines are balanced with the flywheel. The engine is smooth running now and changing to a heavier flywheel from a flex-plate shouldn't affect balance if weighted the same. Should get the same level of smoothness possibly alittle more as the heavier flywheel should make smoother idle but accelerate slower. Ive never heard of engines requiring rebalancing when changing flywheel weight. Im building a Harley sport 1100+ engine now as well, they just guestimated the balance on my 86 engine and then mass-produced balance by casting voids in the wheels(crank) that are identical, I did hand balance that as I changed pinion shaft and desired a smoother than factory engine .. they used to hand select the 4 gear drive cams to mate together from several different sizes for fit as well, I don't believe gm went that far on an engine for a passenger car, that would make a nightmare for replacement parts. They probaby just guesstimated a value and all flywheels are set at for a given application. I could be wrong, maybe thats the nightmare Im in right now. No mechanic Ive ever spoken to acknowledges an issue concerning that tho. The machine shop does shows a 200$ fee for flywheel balancing.
 
According to my 2001 information, all Buick V6s are externally balanced. If you can find the information, you could have a neutral flywheel balanced for your motor if you know the weight angle and offset. I wouldn't be surprised if you talk to advanced adapters if they could balance the flywheel for an externally balanced engine. Having said that, it can only be within OE standards of balance and a proper balance is always more desirable, but could be done if you ever take the motor apart.

Doing a satisfactory job of converting an internal flywheel to an external flywheel should be done with the proper equipment because even if you get it perfect to factory specs, it is still with factory tolerances.

You might have a talk with T/A:
http://taperformance.com/proddetail.asp?prod=TA_2038L

http://taperformance.com/products.asp?cat=59

Keep us posted on your project, it is interesting and it would be good to have your choices and results on the board.
 
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