Flexplate issue

[66fleetsidewarrior]

I have a 66 fleetside that has a 327 with a 2 speed cast iron powerglide in it. The motor had something bouncing around the number 6 cylinder so i am trying to swap it with a mystery motor. I am told that it is a 350 but not 100 percent sure yet. will run casting numbers when i can. The flexplate that i pulled off of it would not bolt up to my powerglide so i was going to swap the plates but it doesn't match the old one. Could it be a 400 crank because a 350 crank should be the same bolt pattern? Is there something I am missing here that anyone would have any insight on? thanks.

[Captainfab]

I'm not sure if the cast iron poerglide converter has a different bolt pattern, as I have no experience with them.

Regarding the engine. All Chevy V8's from '55-'85 have the same bolt pattern on the crank flange for the flexplate/flywheel. If your new engine is '86 or newer, you will need a flexplate for the one piece seal crankshaft, as the bolt pattern is smaller. Typically the flexplates will have 2 different bolt patterns on them. However it is possible that the flexplate on your new engine does not have both. Also there are 2 different diameters of flexplates, 12-3/4" (153 tooth) and 14" (168 tooth).

[PoDuck]

The cast iron powerglide needs a different flexplate than any other transmission. The bolts won't line up on the torque converter. It appears that you are saying that the flexplate won't line up with the bolts on the crankshaft. I have no idea why that would be.

It wouldn't matter if you were putting in a 267, 350 or a 400, all Chevy small block cranks I have ever come across have the same bolt pattern.

That means I have no idea why your bolts won't line up, unless I'm misunderstanding where the problem lies.

[tincan1966]

The flexplate from the 327 should fit the new engine. Only concern would be IF the new engine is a 400 then you'd need a flexplate with a counter weight(external balanced) Other than that, there shouldn't be any reason you can't swap flexplates.
Have any pictures you can post showing your fitment issue?

[gimmy 64]

could it be that your 350 is a olds or buick they are differant than chevy. you need to run numbers and find ouy what motor you have

[PoDuck]

I was just thinking about it. '86 and newer crankshaft flanges had a 3" bolt pattern where 55-85 cranks had a 3.58" pattern. A good indication would be if the valve covers on the engine bolt on in the center. If they do, you have a post '86, if you instead have 4 outer bolts on each cover, it could still be an '86 motor, but you'll have to determine that by the distance between the bolts on the crank flange, or by looking up casting numbers.

If you have the newer small block, you'll also need to make sure you get a weighted flexplate, no matter what transmission you have. You will also need a different starter.

You'll certainly need a new flexplate. You will need to know what year the engine is, and the distance between the bolt holes on the torque converter. You can then get the correct flexplate.

[Captainfab]

Pretty much what I posted above.........

Originally Posted by PoDuck

I was just thinking about it. '86 and newer crankshaft flanges had a 3" bolt pattern where 55-85 cranks had a 3.58" pattern. A good indication would be if the valve covers on the engine bolt on in the center. If they do, you have a post '86, if you instead have 4 outer bolts on each cover, it could still be an '86 motor, but you'll have to determine that by the distance between the bolts on the crank flange, or by looking up casting numbers.

If you have the newer small block, you'll also need to make sure you get a weighted flexplate, no matter what transmission you have. You will also need a different starter.

You'll certainly need a new flexplate. You will need to know what year the engine is, and the distance between the bolt holes on the torque converter. You can then get the correct flexplate.

[PoDuck]

Huh, how did I miss that. lol

[66fleetsidewarrior]

Found a universal flexplate that will bolt up to both a th350 and a powerglide. It was a different bolt pattern for the new one piece rear main seal crankshaft. What starter will I need now? I know the new flexplate has a larger diameter than the old one. The block is from 96. Thanks.

[HOTFUN]

I have just taken apart for restoration an original 66 truck with a 327 powerglide(aluminum case) and them went to take apart my parts truck which was a 66 327 factory turbo 400. The flex plates are just what Capatin Fab said above for size. The powerglide used a 153 tooth and the turbo 400 was 168 tooth. The starter was missing on the turbo 400 but checking the parts store website they also list different starters for the powerglide and the turbo 400 which makes sense since the ring is larger on then the other.

[PoDuck]

Since you determined it was a '96, I would just get a starter for a '96 c1500 or something else that had a small block in it that year. I looked them up though, and they are fairly spendy compared to older starters that should fit, like the 1987 starters. They are almost twice the price.

If you want to guarantee it will work without researching further, go with the '96 one. I can't tell you what is so different about them that they cost so much though. If you want to see about getting the less expensive one, get the parts guy to pull both a '96 and an '87 starter and see what the differences in them are that aren't purely cosmetic.

If you find a good parts guy, he may be able to tell you about the internal differences. Unfortunately, those are few and far between.

[Captainfab]

All you need for a starter is one that has the staggered bolts, which are for the 14" 168 tooth flrxplate or flywheel. You do not need one specifically for a '96 350. If you need something to tell the dude behind the parts counter, ask for a starter for a '77 C10 with a 350 engine and a TH350 trans. Unles you still have a points distributor. In that case ask for one for a '73 C10 with a 350 engine and TH350 trans.