What flywheel with TH400 + trans brake???
- Thread starter wb's87
- Start date
The motor is not stock. It's a brand new build. 109 stroked, all forged internals, full roller. It has a stock style flywheel that was balanced with my rotating assembly.
- Joined
- May 26, 2001
A forged rotating assembly will be neutral balanced, and a new SFI flexplate which is also neutral balanced should be used.
To machine a used, stock external flexplate for neutral balance is insane?
Any off-the-shelf internal balance flexplate will work for any properly neutral balanced rotating assembly, and it should be a SFI unit.
I would hope you also have a new, neutral SFI harmonic balancer, not a stock one that also has been machined?
To machine a used, stock external flexplate for neutral balance is insane?
Any off-the-shelf internal balance flexplate will work for any properly neutral balanced rotating assembly, and it should be a SFI unit.
I would hope you also have a new, neutral SFI harmonic balancer, not a stock one that also has been machined?
FASTV6HENRY
Member
- Joined
- Feb 16, 2012
Yes you can use your stock flex plate. And your drive shaft needs to be cut approximately 1-2 inches shorter (measure to be sure) and use a th400 yoke. I actually had a complete new drive shaft made when i put my th400 in.
Nick I think insane is a little strong. Maybe "not the very best choice" would be a better choice of words. Fact is most folks that get engines built for these cars don't have an unlimited budget. In a perfect world everyone would have a aluminum TA block, billet crank, billet rods, forged pistons, billet roller cam, roller rockers, 14 bolt aluminum cnc ported heads, BHJ balancer, SFI neutral flexplate, etc etc and a wife that smiles when he writes the check for the 25 thousand dollar motor for his 30 year old car that always seems to be broken down. In a non perfect world many folks have to squeeze the budget a little to end up with a good running car that will still make them smile when they push the go pedal. I always encourage my customers to consider a internal balance when ordering a build. That is a no brainer as far as I am concerned. When I tell them that the best choice for this is to use a BHJ and SFI flexplate many just can't go the 800+ that accompanies that choice. Most of my customers have to watch the budget and cut a little where it matters the least. I tell them that the next best choice is to use the TA neutral "stock style" balancer along with a budget neutral flexplate. If that 500 dollar choice still gives them heartburn I then tell them that I have had good luck machining the stock balancer and flexplate to neutral for which I charge about 200 dollars. By good luck I can say that I have done about a hundred motors like this and have never had a single field failure.
Here is my justification. I do my balancing in my shop with a CWT balancer and do a very exacting job of it. If someone is going to cut out something due to budget I feel there are a lot of other things that are more important to not cut cost on. Maybe you have seen otherwise but the only failures I have seen on OEM flexplates have been starter teeth related. If the flexplates don't fail when they are out of balance (ie external) they are under much less stress when they are neutral balanced. From the factory they are bolted to a torque convertor and as a unit that creates a huge unbalanced combination when they are external balanced. To me it only makes sense that if they survive externally balanced that they would fare even better if they were neutral balanced! Think about that. Surely you would agree that is reasonable to assume.
I can state that often the same customers that choose this saving for budget reasons also tend to not update the rest of the drivetrain as well. Engines with this balance combination regularly damage trannys, break driveshaft yokes, strip ring gears and break axles. Yet to date none of them have exhibited flexplate or crank failures due to this balancing technique.
Currently about 7 out of every 10 "109" motors that I build get this combination. Without naming anyone there are several other engine builders that use my shop for machining and they have adopted this cost saving idea on some of their builds as well. Their success has also been a testament to this technique.
Would I do this on a stage motor? Absolutely not. I would also not suggest it on a motor intended for power levels exceeding the 700 to 800 range.
Here is my justification. I do my balancing in my shop with a CWT balancer and do a very exacting job of it. If someone is going to cut out something due to budget I feel there are a lot of other things that are more important to not cut cost on. Maybe you have seen otherwise but the only failures I have seen on OEM flexplates have been starter teeth related. If the flexplates don't fail when they are out of balance (ie external) they are under much less stress when they are neutral balanced. From the factory they are bolted to a torque convertor and as a unit that creates a huge unbalanced combination when they are external balanced. To me it only makes sense that if they survive externally balanced that they would fare even better if they were neutral balanced! Think about that. Surely you would agree that is reasonable to assume.
I can state that often the same customers that choose this saving for budget reasons also tend to not update the rest of the drivetrain as well. Engines with this balance combination regularly damage trannys, break driveshaft yokes, strip ring gears and break axles. Yet to date none of them have exhibited flexplate or crank failures due to this balancing technique.
Currently about 7 out of every 10 "109" motors that I build get this combination. Without naming anyone there are several other engine builders that use my shop for machining and they have adopted this cost saving idea on some of their builds as well. Their success has also been a testament to this technique.
Would I do this on a stage motor? Absolutely not. I would also not suggest it on a motor intended for power levels exceeding the 700 to 800 range.
- Joined
- May 26, 2001
Richard, I do not recall any issue that we have not been on the same page, but stand by with my position on these 2 parts!
If someone is building a performance engine and cannot afford the proper parts, they should wait until they can afford them.
A SFI flexplate is about $120-130, and a steel TA SFI balancer list is $290.
Having seen many stock, cast iron balancers give up on stock engines, I would never use a stock one on a performance build.
A balancer should have a tight fit on the crankshaft like the TA unit to do its job properly, not a loose slip fit.
I have replaced many stock flexplates due to cracking, and any mods to it would make it weaker.
https://www.ebay.com/itm/BUICK-231-...401447604955?_trksid=p2385738.m4383.l4275.c10
http://www.cottonsperformance.com/proddetail.asp?prod=JW93007
https://www.summitracing.com/parts/jpt-93007l/overview/make/buick
http://www.fullthrottlespeed.com/tu...ine-parts/buick-shortblock/buick-balancer.htm
lhttp://www.taperformance.com/search.asp?nobox=&scat=&stext=flexplate&stype=&sprice=&pg=3
http://www.taperformance.com/search.asp?nobox=&scat=&stext=balancer&stype=&sprice=&pg=4
