steven mack

What flywheel and clutch setup can I use with a 406 motor and a 4+3 trans?Thanks

LD85

easiest way is to use the 4+3 clutch, 4+3 Pressure plate, 4+3 153 tooth flywheel and bell housing, IF you use a Balance plate behind the Flywheel

or

buy a 400 BH, 11" clutch, 11" / 168 tooth flywheel and a new Hydraulic slave and probably a starter

or

you can maybe find an external balance 153 tooth FW and eliminate the balance plate

all of the above are for a 2-piece rear seal.

steven mack

I think I get it now I can use apre 86 4+3 fly wheel with the balance plate behind it.

LD85

Yep, I assume that your 400 crank is a 2-piece

Also, check your starter holes to make sure your starter will bolt onto the 400 block, because some of the 400 blocks had diagonal mount holes,,,, you might have to drill and tap a starter bolt hole or buy a starter with a diagonal bolt pattern.

steven mack

Thanks Larry,yes it is two piece

383vett

Is it hinged in the middle or does it bolt together?

LD85

The reason I ask is that you can conceivable use a 3.750 stroke 1-piece seal crank with the larger 400 main bearings or run main bearing spacers on the 350 mains and make a 406 as well.

redrose

balance plate is not desireable as flywheel/crank bolts are known to loosen after extended useage.

better; use 70-90 BBC flywheel p/n 3963537, casting #3935411 (giggle 3963537 for sources new, prices $190-$210)...this is a 153 tooth, 16 lb GM perf part for two-piece seal cranks...looks similar to the lightweight 4-3 flys but has a counterweight cast in for 454 apps...the counterweight is in the correct position for 400 sbc but is very, very slightly heavier than 'detroit balance' for the 400, ez for your machine shop to balance to your 406 (several 'cobblers' have run this without 'trimming' the weight and report no noticeable vibration)...MAXIMUM clutch diameter on this fly is 10.5'' (vette 10.75'' press plate/disc 85-88 will bolt on but fly face is only 10.5)

also consider using one of the many 153 tooth 30+ lb flywheels used on numerous sbc-1's 1985 and earlier on vettes and camo's...extra weight WILL reduce vehicle accel a bit but engine will feel smoother at low revs/cruise and will be MUCH easier to start from '0' vehicle speed at stoplights/etc without embarrasing stalling...these have a wide mass of iron near the outer edge that can be readily drilled/machined to achieve 400 balance...flys with casting # ending with 'N' are preferred.

steven mack

Thanks for the info Guy's I appreciate the help.

coupeguy2001

Now if you want to:
If you use the weighted harmonic balancer, you can use a truck 2 piece crank flywheel that uses the 11 inch clutch and the 90 truck bell housing. Just be sure you get a zero balance flywheel without the weights, or if you are inclined to, you can get a proper size weight made, and drill and tap two holes for the weight on the backside of the flywheel. If you blow it up, you will want to rebalance the next engine won't you?
The clutch is also hydraulic like yours, you just have to make a new clutch line, or match one up at Checker or autozone because theslave cylinder is in a different location than your original.
You will also have to use the front Y pipe that has no pre-cats. Or, if you prefer, find an 85 corvette front Y pipe, because it does not have the precats on it.
Then the larger bellhousing will fit.
You can use the larger clutch, and fine 26 spline clutch disc to match the 4+3. Be sure to use the correct thowout bearing. Remember Chevy made a long one and a short one.
If you need a pic of it, I have one set up on my engine run stand, and can send.
You will also have to use an late C3 starter or one off of a truck because the flywheel is larger, and your starter will not fit.
How you can tell the 10.5 inch starter: the bolts are lined up
How you can tell the 11 inch flywheel, the bolts are staggered.
A lot of the 400 blocks made it into trucks. Your block should have been drilled for both starters, and will have 3 holes on the starter pad. Therefore, any "pick-ur-part" wrecking yard will have what you need at really reduced prices.
Just look around the trucks with an engine, and what the last person didn't take is usually scattered around that vehicle.

USAsOnlyWay

Centerforce sells a 2piece RMS, external balance, 153 tooth flywheel.

I run it on my stroker.

steven mack

Thanks again for the ideas.i have seen the Center force ones.I am trying to keep the cost down on the short block so I can spend more on a good set of heads.

steven mack

Hey guys I found a 153 teeth 10.5 400 factory flywheel casting # 3791021 date code d170.Anyone know what year 400 this came on or how I can find out ,Thanks

redrose

factory never put a 153t fly on a 400...if what you have came off a 400, look at the engine side of the fly for 'removal' of weight to get correct external balance...if no "N" after the 3791021 this is not a 'nodular iron' fly and may fail at high rpm (shoe size adjustment may be in order afterward), ok for start-up/low engine speed

1985 Corvette

How will the 4+3 hold up behind the 406? I've got one and wondering about the limits of the trans power wise.

steven mack

I don't know how it will hold up but I guess I will find out.

steven mack

Redrose I found The flywheel on ebay .It does have material removed on the back for external balance.

LD85

My 4+3 lasted for one hard drag run,, I hope yours lasts longer than mine.

steven mack

What broke Larry the 4 spd or the the overdrive section ?I thought from some posts on hear that the 4 spd section was pretty strong.If you just use the overdrive for the highway.

LD85

Correct, the OD took a dump, 1 - 4 was fine.