wilpetty
1/2 ton status
replacing 2 bolt main 350 with a 4 bolt main. I know some of you guys said I will need a new flexplate and I went and got one but they are the exact same. Whats the difference in the two flexplates?
CK5
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Difference in 2 bolt main vs 4 bolt main flexplate?
- Thread starter wilpetty
- Start date
Nothing. The post 86 engines use a different style and the small block 400s use an externally balanced flywheel. All pre 86 265-350 should use the same flywheel.
actually...it's not whether the block is 2-bolt or 4-bolt mains but if the block is a 2-piece or one piece rear seal. crankshaft to flexplate bolt spacing is different. you'll need one for a pre '80 block. gosh - wish i was home now, i could get you a part number but Rock Auto says it's: ATP Part # Z111 or DORMAN Part # 04328
wilpetty
1/2 ton status
Awesome
I just saved 35 bucks
I just saved 35 bucks
even the cheaper flexplates have the bolt spacing for both types of torque converters. good luck, sounds like you'll have that thing fired up pretty soon...
wilpetty
1/2 ton status
As soon as my next day that I don't have school I will have it in. Hopefully 3 more days off and it will be fired up. I may yank out my tranny and get it rebuilt though so who knows 
Man I'm having de ja vu through your build. I also have an '86 K5 (my dad's the original owner) and I had bought an engine for it years ago before the days of crate motors, which took me a while to install (life got in the way). It was a four bolt, pre-80's motor but I also had to maintain smog for registration purposes, but most of the stuff bolted back on. The orginal motor and trans had 225k miles on it and actually ran well (but tired). Sure enough, 2k miles after I installed the motor, the trans went out - well, not really but one day it made a hi pitched noise that went away but the pump continued to have a slight whine afterwards (but shifted normally and started leaking badly). It was dumb of me to keep pushing it so it only took a few hours to drop the tranny - the hardest part is balancing the transfer case & tranny on a lift if you're pulling it as 1 unit. Since your motor's out, I would def consider dropping trans now because it wont last too long behind a fresh engine (especially if it's stock or has never been rebuilt).
