aaronz28

i just pulled the 302 out of my 69 Z and am installing a 421 sbc that i built.

The flywheel/clutch/pp assembly is about 3-4 seasons old with less than 1500 miles on it -

was planning simply to re-use everything on the new motor - However, i didn't realize the starter/flywheel size thing until it was too late - -

so now, I HAVE to run the 168 tooth flywheel and starter (and larger bell housing) - but i'm wondering if it will be the kiss of death to bolt that slightly used clutch and pressure plate to a new flywheel? RAM makes a 168 tooth flywheel with both the 10.4 and 11" clutch bolt patterns... so i could get by with the new flywheel, new starter, and new bell housing.

i tried drilling the block for the smaller starter - but i'm getting starter gear hang up problems (Like being required to have about 1/8" of fender shims between the starter and block to get the engagement correct and the starter gear still hangs up - I'm thinking i might have drilled the starter hole slightly on an angle - anyhow, at this point, I just think it would be better to use the larger flywheel and correct starter.

thoughts???

wmf62

if they were both in good condition, I'd be tempted to reuse them; but, really, in the big scheme of things, a new pressure plate/disc are not that expensive...

as to drilling for the starter.. you can get one of the old cast iron open bottom bellhousings that use the starter that bolts into the bellhousing (rather than into the block) and use that instead.

Bill

vetrod62

Ok, A little confused, What block is the 421 built from??

Any block designed for a block mounted starter should work with any after market mini starter. They are drilled for both sized flywheels. Your clutch, disc and flywheel should be fine, if they are strong enough for the new engine.

DZAUTO

It would be built from a SB400, depending on bore/stroke combo. I built a SB420 for the jet boat.

JohnZ

You need a 444 or 621 bellhousing, to accommodate the 14" 168-tooth flywheel, and a starter with an offset cast iron nose.

MikeM

You can have the 153 tooth flywheel balanced and use it along with the Z 28 clutch. No need to go to the larger flywheel.

I don't understand having to drill the block for the starter either.

vetrod62

Tom, I know that a 400 block is needed. In my garage are a 395" ( my 4.25"B x 3.48" S) and a 436" (a friends 4.165"B x 4.00S) engines installed in our early vettes ready to race.

The question is for any one, What block for these big inch SBC does not accept common mini starters. And why does the OP need all these changes?

First a SFI shield, flywheel, clutch and disc should be used with that power level. All 400 engines can be internally balanced to avoid externally balanced dampers and flywheels.

So where is the OPs problem?? More facts, better answers. Jim

Auto Gear

OE Block? Dart (Little M, Dart SHP), World Products and I believe PBM all have aftermarket blocks.

aaronz28

the block is a 1973 400 block. the rotating assy is internally balanced -
i have a zero balanced SFI flywheel and clutch assembly that is the 153 variety.

the 400 block is only drilled for the larger 168 tooth starter.

there is NO available mini starter on the market that has the offset holes.
they have two sets of starter holes, but they are inline - this doesn't allow for a 400 block to use the 153 tooth flywheel starter -

its confusing indeed unless you know the differences involved....

simply put - chevy had 2 different sized flywheels, 2 different sized bell housings, and 2 different starters - which had different bolt patterns - and some blocks were drilled for both starters - some were not.... mine is not.

when i drilled and tapped the hole (a blank casting boss was present) it must have been drilled off just enough to cause the starter gear to hang up....

vetrod62

I hate a mystery. My research shows that some unusual engines used the staggered starter bolt starters. All the GM , dart and World engines I have done were the in-line starters. Live and learn. Any way , your solution would be to use a flywheel tapped for many clutch patterns. What is your clutch?? Borg & beck, Or long? Any after market sfi flywheel should be tapped for both 10.4 or 11" . Yes a new starter needed.

I have a Hays 10-130 ($289 Jegs price ) with one run on it for sale super cheap from a customer that should work for you. PM me if interested.