Anth's Iroc

Heres my question I have an 87 (lg4) iroc with a 700 r 4 tranny.Im puttin in a 85 350 i bought from recon.Now i know these motors are different with the seals(1 piece and 2piece) Which means i have to get a new flexplate.I called b&m today for a part number and they gave me 20230 168 tooth flexplate.Is this correct cause i went in the archives and i saw some post sayin it is a 153 tooth flexplate.I really need the right answer so i can order the right one for my car.

Joshua Leslie

Just count how many teeth are on the flexplate that you have for the 305.

Anth's Iroc

I dont have it out of the car yet im tryin to buy all the parts i need ahead of time so ill have it when im ready.....

Joshua Leslie

Id just wait to buy it until you pull the motor and find out.

Flexplates are pretty plentiful, your local engine shop should have a wide variety available.

Anth's Iroc

But isnt the flexplate on an 87 motor different than a 85 motor.The way i take it there different teeth.im lookin for the 85

Anth's Iroc

Can Anyone Answer this question PLEASE.............

SATURN5

I have a 80 305 with a 153 tooth 12 3/4 dia flexplate with a 88 700r. A 153 tooth flexplate will work.

Joshua Leslie

From past experience, I know the 89 flexplate is to small(the hole where it goes around the crank) to fit on an older motor.

I think the changeover was in 86, so yes, your 87 will proly need a different flexplate for an older motor.

But its really not a big deal, you will proly need a new one, just get one with just as many teeth and you wont need to change the starter.

I think I paid like 35$$ for mine.

Randy82WS7

86 was the year that the cranks went to the round style one piece main seal, there are two of each for each style of crank, its kinda complicated really, just see what crank you have and which plate you have and go from there, theres the 168 tooth 14" one and then the 12.5" 153 tooth one, and then one of each for the one piece seal and ifferent ones of each for the 55-86 style two piece cranks, 14" 168 is WAy more common, 153 tooth was very very seldomly ever used, and to top it off there are three starter nose designs for auo tranneis alone let alone manual, you got the vette ones, then the ones for 153 and the oens for 168, 168 noses have stagghered bolt holes, 153 are straight across, i ownt get into all the manual trans noses, the old oens were cast iron and truck ones were three bolt and bolted to the cast iron bellhousing, all kinds.....

its messy..

Anth's Iroc

Wellfrom what i was told today 85 motor uses 168 flexlpate.I was also told you can use 153 tooth but you also have to a starter with gear reduction and that a 153 tooth fleexplate is for high compression motors.This is what i was told.........

SATURN5

Interesting since I used the stock flywheel from my 80 305 (2 piece seal) that was bolted to a turbo 350. The 700R and converter bolted up just fine....and with a stock 80 Malibu large starter......

Yes..I know...my sig has a T-10 listed,presently swapping to the 4 speed.....cheers, Bob

RB83L69

That is all a bunch of misinformation.

The 168-tooth (14" diameter) was usually used with T-350 and 400, and in trucks with 700s. AFAIK these cars all come with the 153-tooth (12¾" diameter) stuff. Both sizes are available in both crank flanges.

More than likely, you simply need to ask your supplier for the right flex plate for a 83-85 F car. That should fit your block, your starter, and your trans.

The trans does not care which size flex plate you have. THe larger flex plate gives the starter more mechanical advantage on the motor (like a longer wrench handle) and is the only one that the older-style GM heavy-duty starer works with.

My 78 El Camino 305 2-barrel has the small flex plate, for example, as did a 84 Caprice 305 we used to have. My 83 HO 305 Z28 has that same size flywheel, and the same starter as the El Camino. What you need is quite common, you should have no trouble finding it.

Randy82WS7

wierd, i dont see how you come across these small diameter wheels so often, of all the cars and trucks ive torn apart over the years ive only found two ever, i have torn down a bunch of 77-79 305 2 bbl cars and never found a small wheel, so....

something is wrong.... keep in mind that the small wheel requires the nose with the straight across bolt holes, not the staggered ones.,.

wheres the misinformation at ?

JohnnyIROC-Z

It is the small one.I have one hanging in my garage from my 84. If you want to pay shipping, you can have it. Shoot me an email if you do.

Anth's Iroc

Thanks for the offer but i got one today its a 153 tooth flexplate
Thank again