sprink58

My brother is replacing the POS 350 he bought from A & L Engines out of Miami in his '83 Formula F-3.

He is buying a recently re-built 1972 406 Chevy that will get his 12 5/8" Mercruiser flywheel as well as all the accessories and brackets from his current 350.

Will his flywheel need to be balanced for the 406 since 400 cu in SBC's were all externally balanced? Does he need to use the harmonic balancer from the 406 or the 350?

Will his current starter bolt up to the 400/406? ( I think it will using his current flywheel).

The crank flange bolt pattern should be the same since both engines are 2: piece rear main seal.

Any other issues other than the brass freeze plug/head gasket/water pump?

This could be a perfect replacement for him.

Thanks in advance.

dereknkathy

there is an add-on bobweight for 383-400's. goes between the flywheel and crank. 30 or 40 bucks on ebay. i don't know if the bobweight is any good or not. all 400's use the big flywheel. i would look for a real 400 clutch flywheel. must use 400 balancer. jegs sells one for 85 bucks new.

FIXX

iTrader: (2)

+1,,the bob weight thingy dont work so well,,he will need a 400 flywheel and a harmonic ballancer..

fireboatpilot

Personally I wouldn't buy a 400 SB from anybody without the flywheel and balancer on it. Any 400's I have ever bought or sold come and go with their matched flys and balancers. I try not to break up the sets. Also buy after market parts in sets then they stay with the blocks. What happened to the originals? So I am assuming that he hasn't heard this engine run? Sounds like another red flag. Tell the seller to purchase the correct parts and install them so you can hear the engine run. If everything is OK, you'll pay him the money for the parts. I'd hate to see you buy a mooring anchor and on top of that have a new 400 fly and bal. added to your loss.

sprink58

I understand...he wants to use the small flywheel and keep his No 1 set up. I think the flywheel can be balanced by adding weight aka "Mallory Metal".

I thought I knew all there was to know about 400 SBC Chevy's...but I guess not. Was there ever a 400 sold in a vehicle with a manual transmission as original? Everyone I have seen or known of had an automatic and therefore a flex plate. The crank flange bolt pattern is the same for all 2: piece rear main seal small blocks...at least for the dozen or so I have been involved with. I have put the parts together and have seen 327~350 flywheels go on 406's but was never involved in the balancing process. I recall that the balancer stayed with the engine and something tells me the flywheel was matched up to the harmonic balancer?

sprink58

Is this it?

http://www.smileysracing.com/shoppin...i=47115&c=1396

JD33

Yes that is the add on flywheel weight. I've used them in a few dirt track engines I've built for people in the past, they work ok but of course not the best way to do it.
You want to find out if the 406 your buying has a stock GM crankshaft or a aftermarket crank; you can buy afermarket ones for a 400 that are internally balanced like a 350.

JD33

Also check the starter mounting holes on the block, not all 400 blocks had both sets of holes drilled. May not be an issue since all production 400's had the big flywheel which used the staggered bolt pattern but if you try to use the smaller dia. flywheels from a 350 etc. they used the straight across bolt holes which may not be there.

FIXX

iTrader: (2)

the 400 also came in early gm p/u with a 4 speed..also keep in mind that the smaller diameter flywheel wont accept a merc alpha coupler,,mr will work but not a alpha.

dereknkathy

jegs has a 400 flywheel for 74.95 plus 10 bucks shipping on ebay. there are also used orig flywheels on ebay for 80 to 100. use the big flywheel. go to a starter rebuilder and get a staggered-bolt starter nose, or whole old-style starters are 30 bucks or so. don't use small flywheel.