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Flywheel Timing

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H

Healeysince59

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When I rebuilt my BN1 engine I used a lightened flywheel that came with the car (basket case). I don't know who did the machining of the flywheel but it was nice work. The 1/4 timing mark had disappeared with the machining. The rest of the machining was done locally by a machinist familiar with Brit iron and having a good reputation. He also balanced everything. Right after he finished my engine and before I assembled it he retired so was not available for consultation.
My question:
What was the purpose of the original 1/4 timing marks? With the flywheel balanced, why should orientation make any difference?
My problem:
I've got an annoying vibration that comes on about 1500 RPM and I'm looking for ideas. As soon as I convince myself it's not the driveshaft (don't think it is), the gearbox comes out and the flywheel and clutch cover plate will be rebalanced. I may go back to the stock flywheel. Not excited about tearing a car apart when I don't even have it together yet.

Marv J
 

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Hi Marv,
When you say you're sure it's not the drive shaft, do you get the vibration only when the car is moving? What's 1500 RPM feel like when the car is sitting still? What a fair amount of people have problems with are the brake drums being out of balance. When they are facing a vibration issue that is.
 
Hi Greg,
I just went out and ran it to eliminate the driveshaft issue. The vibe is there with the car sitting still. Probably comes on closer to 200 than 1500 RPM. It fades a little by 3K. I don't like to rev it much higher unloaded.

Marv J
 
The 1/4 mark (when visible) should align TDC when cylinders one (1) and four (4) are also at TDC. You may already know that, I'm just stating it for clarity, should this thread be searched/used for others.

If you do have to pull the trans, rotate the engine to #1 TDC and remove/replace the flywheel 90 degrees from where it was removed. It would be a good idea to mark the flywheel at this point, for future reference.

It's been fully thirty (30) years since I had a Big Four apart, so I don't recall how many bolts retain the flywheel; if it's four (4), then it's easy...

Have you scoured the flywheel and crankshaft for any possible non-stock identifying marks the machinist would've put on it?

Doing a zero-balance on the flywheel and clutch cover would aid in your quest for smoothness, assuming the flywheel wasn't used to assist the balance of the entire rotating assembly. I've done piece-meal balancing on a six (6) cylinder, when my dampener needed to be replaced (the entire rotating/reciprocating assembly having been previously balanced individually and combined).

Good luck, and please post your solution and results to benefit others in the future.
 
I dropped the flywheel and pressure plate at the machinist this PM. He'll check it as I had it assembled and then 180 away. Should know by Monday.

Marv J
 
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