Quick question Are the automatic flywheel the same for a 400, 430 and a 455 If not, is there a different part number on the flywheel? Thanks
They're the same except for balance...right? The way I understand Buick balanced their engines: each original flywheel/flexplate was balanced to the engine it was installed on. It's not a straight replacement. Replacing the flywheel/flexplate requires match-balancing the new to the old. Am I wrong?
Nope, there is a standard flexplate with a spec weight and position, and it was common to all 400/430/455 engines. I think what your thinking about is the ability to install weight pins in the harmonic balancer, in the holes provided.. which the factory did to fine tune the balance at the factory. Those holes for the weight pins in the stock type balancer are shown below. JW
I knew they did that with the damper. I thought they selectively/individually drilled the flexplate/flywheel at the same time, making the flywheel match-balanced to the specific engine. In other words, "custom fitted" at both ends of the crank. If that's not the case, that's very good news.
Pretty sure Jim has a standard flex plate master he uses on all his engines. So if you ever need another, he match balances the replacement to the master. He did that with the replacement SFI flex plate I got from him.
Finally got photos of two of my Buick 455 flexplates. Both have one or more "custom" holes in them punched by Buick, to match them to the engine they were installed on. I was fairly sure Buick screwed with the flexplate/flywheel to "final-balance" the engine at the rear, just like they pounded pins into the damper at the front. Educated Guess: Find fifteen Buick flexplates, you'll see fifteen different flexplate weighting schemes. Flexplate 1. Multiple holes on the opposite side of the "standard" counterweight; on this particular engine the "standard" counterweight was too light. There's three pair of holes to fit two different torque converter bolt circles. (Note the red (small bolt circle) and yellow (large bolt circle) holes on one of the three pairs.) The larger torque converter bolt circle has rectangular witness marks from being used. There's some round, and some "oblong" double-punched holes opposite the counterweight to alter the balance. Flexplate 2. On this engine, the "standard" counterweight was slightly heavy. One hole punched to lighten the offset weight. Note that there's only one set of three torque converter bolt holes. That's another difference in the BBB flexplates. On engines that have not gotten a PROPER aftermarket balancing, be very careful replacing flexplates/flywheels. The "new" flexplate should be matched to the old one to keep the "factory" balance standards.
One of the benefits of having a TSP built engine is that Jim uses a master flex plate that all his engines get balanced with. If you need a replacement flex plate, as I did, Jim can match balance the replacement to the master.
Taking those two flexplates and measuring the offset weight amount, and then laying them on top of each other would answer the question for you. It is my understanding that all flexplates and flywheels had a blueprint offset weight position and amount, and the holes you are seeing are for correction of a specific flexplate to that blueprint standard. I can tell you this.. we balance every assembly with a "master" flexplate. Then the flexplate that is going to be used is bolt on the crank, and re-spun. Now the tedious process of drilling or welding on new weights begins.. this used to have to be done with every aftermarket flexplate, and the worst offenders were actually the "made in USA" big dollar "the Wheel" SFI flexplates. I had the opportunity to do two flexplates on one assembly once, both of them the big dollar units.. and believe it or not, they had completely different corrections done to them, to get them to match the "master" we use. That was the day I stopped overpaying for flexplates. In about 2018-19 PEP came out with a blueprint duplicate flexplate, with both the correct offset (all previous SFI plates were flat) and the correct offset weight amount and position.. We have used about 20 of them now, and only one had to have a single drillpoint worth of weight removal, to match it to the master flexplate. This plate is the "end all, be all" for SFI Buick BB flexplates, I use and recommend it to everyone. The correct offset keeps the ring gear in the correct place, to avoid starter issues, as well as keeping the converter mounting position correct. Plus, if you take some teeth of it, you just buy a new one for around $100 bucks and replace it.. no worry about match balancing it. Probably the best aftermarket replacement product to come down the line for the BBB in 25 years. It's correct, SFI rated, and doesn't require a second mortgage to buy it. JW
For my stock GS that were in the middle to high 10's I always put t stock flexplate in there.Never had any problems.The more you touch,the worst it gets,my motto.I have been doing this for a long time,build engines that are still running from 20 odd years ago.And most of them were not grocery getters.Bruno.
Yes, the PRW was the one I was using before the PEP flexplate came out.. The PRW plate has some issues.. JW
Jim, I'm guessing the PRW was the one on my engine originally? The only problem I had was with the starter. Solved that with the Robb Mc Starter which enabled me to shim the pinion gear away from the flex plate. When I switched to the newer flex plate, I had to remove the shims as the pinion was now a mile from the flex plate teeth.
The SAE handout you hosted on this site--now saved somewhere else--specifically says that Buick final-balance is corrected by running the engine under it's own power, and driving pins in the damper, and punching holes in the flexplate; or drilling the manual trans flywheel. https://www.diyauto.com/manufacture...nference-bb-handout-booklet-scan-by-jim-weise Page 8, top left. I've got no evidence that that balance system changed over the years. The flexplates are balanced to the engine they were originally installed on. A PROPER aftermarket balance will fix all that, but it isn't cheap. It does solve the problem of having to match-balance flywheels and dampers to the original parts, IF (big IF) the replacement parts are made properly. This is not a given, as JW and LARRY70GS have more than adequately shown. For the record, problems with aftermarket parts are not limited to Buick. I bought two aftermarket flexplates for a One-Piece Rear Main Seal Chevy 5.7L; compared to a used OEM flexplate, one was too heavy, one was too light. My machinist drilled the heavy one, and welded tabs to the light one to match-balance to the OEM flexplate.
I know this is an older thread. Where can I purchase one of the PEP flexplates? I am in the process of making some changes to my motor and would like to upgrade since the rotating assembly is going to need balanced. Thanks, Chris
