3.8 E Flywheel resurfacing

Hiya,

My lump is current on a stand for bottom end work, and will be getting a new clutch also. The flywheel is original. I got concerned when I saw the ring gear as the teeth all have a very pronounced chamfer. No teeth are broken but some of the chamfers have gnashing marks from the starter gear which could probably be cleaned up.

After reading a few posts from the archive it appears that the 3.8 ring gears do have chamfered teeth, and did from new so maybe it is fine from that perspective. What does concern me is that it’s been cut before multiple times, and will need to be cut again.

I’m not noticing any specification in the manual for minimum thickness nor am I sure where to measure it? I once saw a nice looking used one on Ebay and it appeared from the photos that it might have originally had a raised area where the clutch disk engages. Is that correct? Mine has none. It had none when I got it 20 years ago. If it had one originally it had already been shaved off and now it needs to be shaved again. How badly might this alter the throwout characteristics?

I noticed that SNG is offering a new steel flywheel but I don’t think it has chamfered teeth, in fact none of the replacement flywheels have them. How would this affect the operation of a 3.8 starter gear? I am somewhat averse to trying an aluminum one with a 3.8L at 1/3 of the weight. I find it twitchy enough and challenging enough to rev match a Moss box with the steel one.

Thanks!

Post a pic: yes, the teeth are chamfered, on the starter pinion side.

No idea about minimum thickness, but that will only affect the TO bearing’s operating distance. Not sure it’ll be an issue even I’d 1-3 mm have been taken off it.

As for the operation: if the starter pinion is chamfered, probably not affected.

When I put the Gustafson, meant for the Jag, on the Rover (and it shared a common starter twixt the two Marques), the pinion engages towards the rear of the flywheel, as opposed to the OE starter, which engaged from the rear.

It worked perfectly.

I’ll snap some picks when I’m down at Drew’s shop on the weekend. The starter pinion I believe is slightly chamfered yes, but it’s fairly blunt.

Do you know if it originally had a raised landing on the face for the clutch disk or was it always flat all the way across?

AFAIR, it’s always flat.

Yes, what Paul says.
Flywheels of this size are virtually always flat with a few industrial exceptions. If it were a “cupped” flywheel, the manual would list a spec for the amount of the step.

I’ve read that if you take too much off the surface of the flywheel you may get to the point where the clearance between the springs in the clutch disk and the heads of the bolts that attach the flywheel to the crank, becomes an issue. Might be worth doing a search…

My engine’s out at the moment if you want to compare any measurements.

I’d guess that could be measured pretty easily by just sticking a bolt through and laying the clutch disk on top. I can lay my old worn one on and see if it comes close to interference. I’ll definitely check that.

This is the thread I remember seeing before. It’s from the XK list, so I can’t be sure it applies to your 3.8 E-Type, but it may help. There are some flywheel dimensions in it too, which may help determine how much has previously been removed from your flywheel.

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On our flywheel, drilled for a diaphram (sp.?) style, the bolts attaching the clutch cover are a slightly odd length - not super odd, but not from your scrap drawer either. Also, we have an after market “modern” starter which works fine without a bevel on the flywheel teeth. Our original 3.8 flywheel did have beveled teeth on the back side. The solenoid-on-the-starter style, of course, engages from the front, the old 3.8 like an old Ford from the rear. Our clutch is an “AP”, and has a very stiff pedal - harder than any car I’ve ever had. Works fine, just a lot of effort (9.5" disk). I almost think all reproduction AP’s might be ‘heavy duty’, which most of us do not need.

That’s interesting Larry. I’ve driven 4.2s with the diaphragm and they were as light as a modern car. The 10" spring clutch is a major workout.

I think I’m going to end up having mine surfaced again. There are just a couple tiny nibbles on the tooth chamfers and I verified that the new B&B pressure plate is very far away from the bolt heads as David warned.

Interestingly the new friction plate is different from others I’ve seen including my old one. Generally the springs are open on one side and shielded on the other. On the new one the spring is visible from both sides. I wonder if they did that because detritus could build up inside the covered side?

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Or the PP yer worried about: it’s the clutch disc.

Correct my mistake. I tested the friction disc

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