I bought my 350 about a year ago out of a 74' GMC full size PU. Unfortunately i left the flexplate in my friends garage and he inadvertantly threw it away thinking it was for his 302 Ford that he was doing a auto to manual conversion on. Now i need to buy a flexplate and am unsure of how many teeth it had. If I get one out of the JY out of the same year truck will it bolt to our third gen 700r4's? It is true that two-piece rear main seals have a different flexplate than the one-piece? Any help or advice would be greatly appreciated.
-Bob

 

It doesn't matter how many teeth that flex pate had; what matters, is how many your setup needs now. Which is probably different.

The 74 motor almost certainly had a 168-tooth (14") one, and you probably would be better off with a 153-tooth (12.8") one.

The 2-piece and 1-piece rear main seal cranks are different, and take different flex plates. They will not interchange.

Get the flex plate, starter, and starter bolts for a 82-85 Camrao / Firebird 305. It will be what you need.

 

I know RB is the master here, and I have much respect for his advice and wisdom. But I humbly ask to make but one, small notation:

did you use the 305 starter, or the 350 starter? if you used a 305 starter, than ignore me. if you used a 350 starter, then you'll need the starter bolts and flexplate for a 350, which is 168 teeth, 14". get it for a 74 GMC van or p/u (whichever it ws you pulle it out of.) so, you need to ask yourself: DO you feel lucky? well, DO ya? PUNK? seriously, though. did you use the starter that was on the motor when you yanked it? or did you buy it elsewhere?

I had this problem when buying parts new for my car. i bought the wrong fuel pump, water pump, and about 12 other things that i had to return or exchange because i had to figure out what came from a 78 corvette, and what came from a 82 trans am.

 

I have yet to get my starter but i will most likely be going with the 305 setup since they are a dime-a-dozen in the local yards. I dont feel lucky, why, do you? Thanks, Bob

edit: yes i do have a 2 piece rear main seal. Pertaning to my orignial question; will the flexplate from a 305 third gen fit with my 2 piece rear main block ?

 

That's for 2-pc RMS. 86-up will be for 1-pc and will not fit a 2-pc crank.

 

No.

350 does not mean it has a 168 tooth flywheel. Some have that, some do not.

As a matter of fact, follow all the starter / bellhousing T56 threads. All factory third gen 350s came with 153 tooth wheel and a starter that other than the front "cone" is externally the same as a 305 starter. However, that front cone doesn't fit in the T56 bellhousing.

If the block has staggered bolt holes (one fwd. of the other,) and not the parallel ones, you need to go 168 tooth wheel and equal length bolts and correct starter. OR there are aftermarket starters which will fit that block and a 153 tooth flywheel.

If the block has the parallel bolts, you use a 153 tooth flywheel, unequal length bolts, and the correct starter, or aftermarket starter works too.

Everything I have in SBC is 86 & newer and is drilled & tapped with all 3 bolt holes so either starter works.

-Matthew