350 flexplate on a 307?

[rich67]

will a 350 flex plate work for a 307?

[MARKDTN]

Yes, same thing. But both have to be either internally balanced or externally balanced.

[rich67]

wud the stock one b externally balanced?

[rich67]

i guess my question would be how to tell.

[rich67]

307 has very small harmonic balancer on it

[GASoline71]

Stock, 350's are internally balanced (unless they've been messed with). Not 100% sure about the 307's... but I'd like to assume that they are too.

Gary

[kwmech]

It will interchange as long as it is an early 350, just make sure of the diameter so the starter will work properly

[Wrenchbender Ret]

A 350 from 85 on back will fit. Like Mech says check the dia. of the plate & the mounting holes for the torque conv.

[MARKDTN]

Sorry, I meant 2-pc rear seal and 1-pc rear seal. All 305 and 350 are internally balanced. You just have to have the correct one for the type of rear seal you have. Through '85 I believe all are 2-pc rear seals. '86 up, all production cars got 1-pc rear seals. The Crate engines can be had both ways.

Bottom line is that all Chevy V8s (assuming correct crank type seal) will bolt onto each other. The same flexplate works for everything but a 400 small block and a 454 big block. These are the only 2 externally balanced. So for a 2 pc seal motor the same flexplate will work for 262, 283, 302, 305, 307, 327, 350, 366, 402 and 427.

[mmiddle]

Yep what he said 2x^^^^^^

400 skinnies are External balance. The flywheels on these engines have a big weight tack welded to them and a notched harmonic balancer. All other SBC's have a smooth balancer and no weights on the flywheel. There are differences in the balancers between the years and CID's but they all will work.

[rich67]

thanx so much for info folks. new update. motor is original 307 so 85 and back. 2 piece rear main. flex plate came off a mid 70s 350. 307 has very small balancer on it. flex plate has a slug tacked on it and a rectangle weight both on motor side of flex plate. have another flex plate from a 305 it has nothing on it. im assuming first mentioned flexplate will not work but one from 305 will. seems very confusing. lol im trying to find out from previous owner if crank in 307 is original.

[mmiddle]

most flexplates will have a small weight on them to balance the plate. A 400 skinny has a real big weight, nearly the size of a brake pad.

Confusing???? You should see the issues with F**D! Everything on them are different even from year to year.

[kray59]

Why are you replacing flexplate ? going from standard to auto ? if available i would also use balancer off 350 that i got the flexplate from .

[jaketynan96]

i have 82 chevy and it had a locked up 350 in it so i bought a rebuilt 305 that had nothing but the innards heads intake and carb i went to put the flexplate from my 350 on and 5 out of the 6 bolts fit but the last one wont thread in uness i do it first, but then the flexplate goes cockeyed and wont stay flush any one got any ideas?

[GASoline71]

Yep... get the correct flex plate for a 305.

Gary

[jaketynan96]

i thought they were the same though? would taking the crank out of the 350 help? i spent my last little bit of money on the 305 and cant really afford to have it down too much longer

[GASoline71]

I don't think you can use a crank from a 350 in a 305.

Gary

[jaketynan96]

hm chevy has funny way of doing things i guess if i ream the holes out a little bit(each one same amount) would that throw off the balance

[MARKDTN]

Are you trying to put a 1-piece seal flexplate on a 2-piece seal engine or visa-versa? That won't work. The balancers will interchange and almost everything else external, but the flexplates have a different bolt pattern. DO NOT make the holes bigger. If you have a like for like swap it will fit. Even 400 and 454 will fit-they just won't be balanced.

As cheap as a flexplate is, just go buy one for your new engine. What year is the 305?

Your 82 350 is a 2-piece seal, the end of the crankshaft has a flange on it like this.
http://www.thirdgen.org/forums/tech-...-will-fit.html


A 1-piece seal crankshaft is round all the way. like this http://oppositelock.kinja.com/1pc-or...siv-1705492654

[MARKDTN]

Originally Posted by GASoline71

I don't think you can use a crank from a 350 in a 305.

Gary

Yes you can. They are balanced differently, but that can be done at a machine shop as part of a rebuild. They have the same casting numbers, same dimensions, etc.

[hamjet]

The 305, 86 and up had 1 piece rear main seal. it used an externally balanced flex plate, can't use it on the 83 350 which was 2 piece rear seal, which used a flex plate with no weights. flexplates aren't expensive,($35.00).. just get the right diameter one to fit the starter, 153 or 168 tooth.. BUT, first you have to know if you have a 1 or 2 piece rear main seal.. Boy Markdtn, I have to learn how to type faster, LOL

[67 chevelle]

Originally Posted by hamjet

The 305, 86 and up had 1 piece rear main seal. it used an externally balanced flex plate, can't use it on the 83 350 which was 2 piece rear seal, which used a flex plate with no weights. flexplates aren't expensive,($35.00).. just get the right diameter one to fit the starter, 153 or 168 tooth.. BUT, first you have to know if you have a 1 or 2 piece rear main seal.. Boy Markdtn, I have to learn how to type faster, LOL

dead on , one piece seal engines have a neutral balancer , excluding 383-400 crank engines , and a weighted flexplate , the old 2 piece seal cranks were asymmetrical on the back flange for balance , discovered that on the first zz4 I built 25 or 30 years of using the same balancer , and they change things , atleast they dont leak as bad

[jaketynan96]

no it turns out the threads were screwed up on the flange lol soneone screwed it up previously i was so hapy whe it turned out to be that and they both had teh same flanges and were i believe 80-84 blocks

[jaketynan96]

neither of which are the original engine originally had 305 someone put in 350 now putting a 305 back in because its all i can afford