427 SO Flywheel question

[Specialk]

I have a few questions. I was trying to bolt an 11" Centerforce clutch to a 427 flywheel today. The bolt pattern on the pressure plate was too wide to fit the flywheel. It almost appeared that the flywheel was setup for a smaller clutch. All the information I have been able to find seems to indicate all 390,427, and 428's came with 11" clutches. I am using a Tremec TKO trans

1) Any clues as to what I have here? I do not know for sure what the flywheel is from. I assumed it was setup for a 427.

2) Are 427's and 390's balanced the same? are they Internal or External balanced?

3) Any suggestions on what brand and style of flywheel to buy new?

4) Any clutch suggestions, like who has the best setup for a mild sideoiler?

Any input you experts have on this will be very helpful to me on this frustrating issue. Thank you.

[Tom Kirkham]

Kris,
We have had some flywheels that would not take the larger 11 and 1/2 inch clutch. I believe that the 390 flywheels were not drilled for the big clutch.

2. 390 and 427 are both internally balanced and take a neutral balance flywheel. The 428 is externally balanced.

3. McCleod flywheel and clutch. We are also very happy with the Center Force dual friction clutch. The stock 390 flywheel is cast iron. It is NOT the hot set up. Just think about where the flywheel will go if it explodes. The 427 had a steel flywheel from the factory. I much prefer the McCleod aluminum flywheel. Also be carefull as some of the Hayes and Weber flywheels only have the steel friction liner out to 11 inches and not the full 11 1/2. I would highly recomend the 11 1/2 clutch.
Good luck
Also in a similar vane the 390 truck bellhousing and the passenger car bellhousing are not the same depth. The truck bellhousing is about 1/2 inch deeper. The Lakewood scatter shield is the passenger car depth. Also when using the Lakewood and any other bellhousing it is HIGHLY advisable to check and make sure that the bell housing is concentric with the crankshaft.

[ERA535]

Kris-

410's and 428's are externally balanced, 390 and 427 engines are internally balanced.

I used the next step up from stock clutch in ERA 535 and was fine - easy pedal etc.

When I put it together originally I got a clutch set up from Summit that the bolt holes wouldn't match the flywheel - maybe you have the same problem?

Pat

[Specialk]

Tom and Pat,

Thanks for the info. You confirmed what I had hypothesized. It looks like a new flywheel is needed. I love this forum!

[Mr.Fixit]

Don't skimp on the scattershield either. If you have ever seen the results of a flywheel explosion, this advice is obvious. I like my feet and all ten toes.

[A Snake]

Just an adder to Tom' note on concentricity of the bellhousing. This is not just for the bolt holes. It is to assure that the "hole" in the center is lined up with the crankshaft.

The bellhousing is mounted on the block without the flywheel. A dial indicator is mounted on the crank flange and the "hole" is "swept" with the dial indicator by rotating the crank. It is a job for an engine shop to perform. If things don't line up, they have the necesssary equipment to make adjustments.

On the flywheels, I bought 40# steel unit (McCleod) and had about 18# machined off. Best of both worlds. Lighter than stock for quick revs and the toughness of all steel construction.

One other note that I haven't yet heard anyone mention about flywheel weight. A heavier flywheel dampens the effects of a "lumpy" camshaft, making the idle a little smoother. The lighter flywheel lets the engine lope more.

[Mr.Fixit]

The heaviest flywheel you need is the lightest one that will still let the engine idle.

ASNAKE: I always do the bellhousing runout check with the flywheel in place. It gives a great stable surface for the magnetic dial indicator stand to hold onto. You can't have the pressure plate in there though. Check both concentricity of the bellhousing to the crankshaft centerline as well as parallality of mating surfaces (90 deree difference). Offset dowel pins are available to correct centerline problems, parallel corection needs to be done at a machine shop that can Blanchard grind.

[A Snake]

Right on Mr.Fixit. My dial indicator has a large magnetic base and the dial itself has 1 1/2" of stroke, so using the crank alone worked fine for me, but I must admit the flywheel is more forgiving and takes less screwing around.

I think we should add a note here: Check ALL aftermarket bellhousings for concentricity and square (parallel surfaces on flange to block face and trans face) before using them. Don't just assume because they're new they must be right. Most of them are not.

BTW I love those offset dowel pins! What a breeze to use!