O, ok. I’m not familiar with SBCs later than the 70s but my buddy bought a new long block from somewhere and it was supposed to come with the damper installed and the flexplate. When it arrived it had neither. They refunded him some money and told him what to buy. He thought it was strange and asked me. I had no clue. Thanks for educating me!
The engines they built starting in 1986 had a one piece rear main seal. This required that the crank flange be round, so they could not put a counterweight on the flange, so the weight moved to the flywheel/flexplate. They use a smaller bolt pattern for the crankshaft to flywheel bolts. So...all the 86-up small blocks use a neutral damper, but a weighted flywheel. 400 is the only small block with a two piece rear seal, that used a weighted damper and flywheel.
My buddy got good information from the supplier but neither of us had ever messed with the one piece seal engines. So when he asked me, it sounded kinda wonky and since they had screwed up not putting the damper on in the first place it made us kinda question their advice. So, early bolt pattern with a weight - would be a 400 flexplate? Do the SBC and BBC flexplates have the same size weight?
No, he didn’t give me any numbers or anything, just that it was a one piece rear main seal. It’s not a stroker 383 or anything, just a 350. I’ve got a couple flexplates with weights lying around that fit the early crankshaft bolt pattern, now I’m wondering if they are BBC or 400 SBC.
look at the weight, the 454 is bigger., also, not all BBC use the weight, only the 454 does. The 366/396/402/427 are neutral.
@bchctybob Just to fill in the gaps for future reference, can you post the part numbers the builder supplied to your friend? 350 one piece main weighted flexplate and neutral balancer, right? Tooth count? Might help the next guy!
As far as 2 piece seal small block flex plates go the only difference between a 350 (or smaller) and a 400 168 tooth flex plate is the counter weight. In the early 80's one of my brothers bought a beautiful black mid 70's K 10 long bed that had 400 emblems and was sold to him as a 400 but after he had his transmission shop buddy rebuild the transmisson and replace the flex plate it picked up a bad vibration and he brought it over to me an my other brother an I got it on the hoist and after doing a bunch of studying figured that it had a 350 rather than 400 and I took a hammer an chisel and knocked the weight off the flex plate and that ended the vibration.
My buddy lives about 700 miles south of me and like many of us old guys, he isn’t always easy to get info out of. I’ll see if he can get us some pics or at least numbers to fill in the blanks. I bought my roadster from a trusted friend but it had a nasty vibration at around 1500-2500 rpm. It also fouled spark plugs in about a few hours of driving. It came to me with a fresh 283, 3x2 Rochesters and a TH350. It turned out that he had installed a new flexplate during the installation. The ink stamped number on the new flexplate was correct for a neutral balance 283-350 but it has a weight on one side. Problem solved. I dug out a flexplate with no weight and bingo, no vibration. The fouling plugs problem was just as simple. After determining that it was oil, not fuel, I checked the hose going to the vacuum modulator. It was wet inside. I changed the modulator and no more fouled plugs. I wish all of car life’s problems were so simple.
Does 10243880 mean anything to you? He says it’s supposed to be 92-2000 Vortec 350? He didn’t specify if that was a casting number or stamped on the pad.
For those of us who've spent a lifetime on 1st gen SBC engines the 1986 and later one piece main seal SBC are like having to learn it all over again! I got my 1990 SBC engine for my '39 in 2019 and had all sorts of parts I planned to use p and discovered none of them worked. And of course I had to learn what to buy, and how things went together too as I began ***embling the rebuilt short block. It was really an eye opener to discover cams, oil pans, the rear main seal ***embly, flywheels, timing chains, etc. were all different! Luckily the heads are interchangeable so my first gen Dart heads bolted right on, and I could use the 1st gen distributor with the 1st gen Edelbrock intake. And lucky too that the block was fully machined for a 1st gen mechanical fuel pump! Just had to buy the operating rod, and plate to mount one.
I might be mis-remembering, but it seems like the bolt pattern on a weighted flex plate is different than that on a 1st gen SBC crankshaft? I know they'll only go on one way when I installed the flexplate for my 2nd gen SBC.
My friend Danny and I graduated from high school in 1968 together. He was one of the guys who used to come hang out while I was working on my cars at my parents house. We’ve always done car stuff together although we ran in different social circles. Here’s a typical Saturday at Mom and Dad’s place. The guy with the beard is MVV on here, he’s dropping off his Anglia so I can build some headers on it. That’s Pete Hea****’s Hemi powered Bantam and our next door neighbor’s flatbottom. Danny isn’t in this photo. At the time, he was driving a Pontiac powered ‘49 Stude pickup (he still has it) and was building a Falcon Ranchero with a Comet front clip. (It came out *****in) So these days we text a bunch. Questions back and forth. He asks me something and very often I look up the answer here and text him the answer. He’s not on the HAMB. He got caught up in the LS-in-everything wave for a while but he has recovered. He recently bought a nice “barn find” 1940 Ford Deluxe 2dr sedan. It will be a driver, so he’s sticking with mostly the good old tried n true 350/350/8” Ford combination. I think he was caught off guard by the differences in the later sbcs, I know I was.
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