CcanDo

We are of the opinion the bell housing should be DIALED IN as part of the engine major overhaul and/or assembly.

There has been discussion about using offset dowel pins,tolerances and procedure. Flywheel run out can be either front to back and/or side to side. Run out side to side is thought to have a maximum acceptable of .005. That tolerance is the maximum amount the flywheel can be off centerline from the crankshaft. The same.005 applies to the drive plate and bell housing center line.

Some have found the most accurate method of locating and holding the bell housing , over size the bell housing dowel bore,install a loose fit bushing and weld the bushing into the bell housing.

However,for dowel alignment a special fixture is required. The fixture is bolted to the block,a special bit is run through a collet in the fixture and then a stepped,knurled dowel pin is installed in the block.

Future overhauls won't require new dowels unless these original dowels are worn. However, the bushing may require replacing.

Lack of centering the flywheel,drive plate and bell housing may create negative effects on starter engagement,vibration,crankshafts and transmission life.

Is there a market for a professional, inexpensive kit that includes the fixture,precision drill bit ,dowel pins,aluminum or steel bushings and instructions ?

BenPerfected

What are you aligning...transmissions? All my bellhousings are really doing is holding the starter and oil coolers. Even with transmissions is the play in the flexplate enough margin of error?

MOBILEMERCMAN

What drives and trannies? You may be over thinking it.

Mbam

It is a problem, we have advocated it for years. Have seen bad align bore/hone jobs that moved the crank over .060 up in the block.

It’s not a big deal on a Bravo as you are referencing the coupler centerline with the alignment tool anyhow, but on a transmission the pilot center line is referenced via the flywheel housing to the dowel pins.

When I was in the engine business (in another decade) checking/fixing this was part of our build.

Tilton already makes the fixture & pieces, we have them.

BenPerfected

I learn something on OSO most days. Never new this was a an issue...isn't for me anymore as no more transmissions ...just Bravo hassles!

CcanDo

Hi Ben, First, the flywheel is centered on the crankshaft.(The flywheel bore and/or crankshaft flange may require polishing.)Therefore,there is no concentric run out to discourage consistent starter engagement and there should not be vibration from the internally balanced flywheel.The starter gear engagement quality is then only subject to cut of the gears and radial run out. However,we know the ring gear shouldn't be shifting from side to side as it rotates,because the flywheel was just centered to the crank shaft.

Second,the drive plate is measured at the outer edge while using the crankshaft pilot bore for the dial indicator locator. (I have been told,the Dubai team replaces the hub and springs after every race)

Third,the bell housing transmission bore and bolt circle is then located by using the crankshaft pilot bore as a locator. The bore and bolt circle are both measured.Subject to the bolt circle and bell housing showing conflicting numbers the bore may require filling and machining.

Mark from Bam states in one of the threads,run out should not exceed .005"

Global still hasn't come up with the drive saver. We want to use a set and put them between the gimbal flange and drive line.

Would you care to meet us at Texoma over the week end ? We will be taking the Skater.

BenPerfected

Cat,
Texoma is a great thought and offer, but I am committed for this weekend....could I get a rain check? I could be scared at much above 100 MPH! I will bring a diaper...
My Drive Saver was a "stock" piece that was really just a replacement for the steel adaptor from Stellings...I think as that was about 6-8 years ago! If you are using a HD flex plate with your transmissions, they are likely serving the same purpose as the DS in the Stellings drive line.
I am absolutely confident that you will sort this all out.

CcanDo

Ben,
As said before,you always welcome....come anytime or we'll let you know when something might seem of interest....Perhaps when we splash the Motion....That is not far off now.

The drive saver is interesting not only as a dampener but as a circuit breaker for electrolysis. The drive saver should stop electricity before it goes into the driveline or engine.

CcanDo

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