Pressure Plate Bolt Clearance Options

[aggiezig]

Howdy 914World

I am in the process of reassembling my car and decided to go ahead and mount the clutch and pressure plate to the flywheel. I've only done this a couple of times before on VW beetles, so not a whole bunch of experience here but seems pretty straight forward.

When I mated everything up together, I noticed there was quite a bit of gap between the pressure plate ears and the flywheel mating surface (probably .25" or so). But, I figure this may be normal and the ears cinch up when you go to tighten the PP down.

However, I did run into an issue when snugging everything up. There doesn't appear to be enough clearance around the PP to use regular hex head bolts. IE: the socket can't fit on the bolt head. Also, by the time I got them as far tightened as I could, the heads were at or below the level of the starter ring. Is this normal? Should I be using allen head bolts here for the clearance?

I read on this post about machining clearances out of concern that perhaps my flywheel was machined improperly. On that diagram, my "A" measures 21.60MM which would appear to be out of spec.

Here are some pics of the situation:

(IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-19557-1550037644.1.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-19557-1550037645.2.jpg)

(IMG:http://www.914world.com/bbs2/uploads_offsite/i.imgur.com-19557-1550037646.3.jpg)

What do you guys think? Is this normal / do I need allen head bolts? Or, is something strange going on here.

[Mark Henry]

(IMG:style_emoticons/default/blink.gif)
That looks like it's sitting wayyyy too deep.
It should only be inset about the thickness of the washer, maybe a hair more.

[barefoot]

Are those the OEM bolts ?, look a little large to me. I had to use a fairy thin wall socket but was fine with that. Your clearance looks tighter than mine was.

[ericoneal]

I just did my clutch, here is a picture of mine if that helps.

[aggiezig]

(IMG:style_emoticons/default/blink.gif)
That looks like it's sitting wayyyy too deep.
It should only be inset about the thickness of the washer, maybe a hair more.

That's what I'm afraid of. If that is the case, does that mean my flywheel is toast? Going to be pretty upset if so because the engine builder signed off on it. I knew it had been "lightened" but wouldn't think that would screw up this clearance if done properly.

Are those the OEM bolts ?, look a little large to me. I had to use a fairy thin wall socket but was fine with that. Your clearance looks tighter than mine was.

They are not OEM bolts and that could be part of the issue. These bolts have a 13mm socket head.

I just did my clutch, here is a picture of mine if that helps.

Thanks for the pic, that's helpful. Your bolt heads appear to be sticking out a bit more than mine do.

[jcd914]

To me the concern is not really the position of the bolt heads, if you can tighten the bolts to proper torque they will do their job. Or you can use allen bolts.

The issue I would be concerned with is the machined step from the surface the pressure plate bolts to the clutch surface of the flywheel. You said yours measured 21.6mm and the spec is 22.5.
That means as yours sits now that pressure plate is compressed 0.9mm farther than designed.
The fingers of pressure plate will be recessed in further than normal, farther from the throw out bearing and the pressure plate may not be able to move away from the clutch disc enough to release the the clutch, it may bind mechanically.
I have never seen a pressure plate mis-machined in this manner before always the other way around, the step being too deep.
I would probably disassemble the clutch and pull the flywheel and carefully measure it using the specs in the other thread you refer to. See what you have to work with.

Jim

[rgalla9146]

To me the concern is not really the position of the bolt heads, if you can tighten the bolts to proper torque they will do their job. Or you can use allen bolts.

The issue I would be concerned with is the machined step from the surface the pressure plate bolts to the clutch surface of the flywheel. You said yours measured 21.6mm and the spec is 22.5.
That means as yours sits now that pressure plate is compressed 0.9mm farther than designed.
The fingers of pressure plate will be recessed in further than normal, farther from the throw out bearing and the pressure plate may not be able to move away from the clutch disc enough to release the the clutch, it may bind mechanically.
I have never seen a pressure plate mis-machined in this manner before always the other way around, the step being too deep.
I would probably disassemble the clutch and pull the flywheel and carefully measure it using the specs in the other thread you refer to. See what you have to work with.

Jim

(IMG:style_emoticons/default/agree.gif)
The next issue will be fastener clearance at the flywheel-to-crank bolts. If the right distance between the mounting surface and the friction surface was maintained the disc will no doubt be contacting there too.
Best to remove the flywheel and review the basics.
Also, no dowels ?

[Mark Henry]

Are those the OEM bolts ?, look a little large to me. I had to use a fairy thin wall socket but was fine with that. Your clearance looks tighter than mine was.

They are not OEM bolts and that could be part of the issue. These bolts have a 13mm socket head.

I just did my clutch, here is a picture of mine if that helps.

Thanks for the pic, that's helpful. Your bolt heads appear to be sticking out a bit more than mine do.

Stock bolts are M8 with a 13mm head. I'd remove the PP and measure.
If the friction surface is ground too much the clutch disc will hit the flywheel/crank
bolts. You can grind these bolt heads some, but only so far as you still need to get a socket on them.

[aggiezig]

I ended up ordering a new flywheel and checking against mine. Yes, way out of spec. Not sure how the engine builder missed this but too long ago to do anything about it now.

My question now... I believe the flywheel was balanced with the rotating assembly. There is a yellow dot reference to install at TDC. Do I need to have this new flywheel balanced to match the old?

If so, does anyone know of a good machine shop in LA area that won’t charge an arm and a leg to do this?

Thanks

[Jeff Hail]

I ended up ordering a new flywheel and checking against mine. Yes, way out of spec. Not sure how the engine builder missed this but too long ago to do anything about it now.

My question now... I believe the flywheel was balanced with the rotating assembly. There is a yellow dot reference to install at TDC. Do I need to have this new flywheel balanced to match the old?

If so, does anyone know of a good machine shop in LA area that won’t charge an arm and a leg to do this?

Thanks

Both are right around the corner from each other. Dave from TRE uses them and just about every other air cooled German rebuilder in the area. I have used both for 34 years. High quality, reliable and reasonable. Dave at The Balance Shop is a very cool guy and knows his stuff.

[SirAndy]

Should I be using allen head bolts here for the clearance?

That's what i did on mine. So far, so good.
(IMG:style_emoticons/default/idea.gif)

(IMG:http://www.914world.com/bbs2/uploads/post-179-1185423324.jpg)

[type2man]

I ended up ordering a new flywheel and checking against mine. Yes, way out of spec. Not sure how the engine builder missed this but too long ago to do anything about it now.

My question now... I believe the flywheel was balanced with the rotating assembly. There is a yellow dot reference to install at TDC. Do I need to have this new flywheel balanced to match the old?

If so, does anyone know of a good machine shop in LA area that won’t charge an arm and a leg to do this?

Thanks

If you want to balance the flywheel you have to disassemble the engine. No good since its already built. Unless its a fully built engine that will only see high RPM, or if this is your one and only mode of transportation which will see 15k miles a year (which I doubt) then you can live without it.

[aggiezig]

If you want to balance the flywheel you have to disassemble the engine. No good since its already built. Unless its a fully built engine that will only see high RPM, or if this is your one and only mode of transportation which will see 15k miles a year (which I doubt) then you can live without it.

The flywheel is already off and the engine is out of the car. It’s also a fresh rebuild that was balanced originally with the flywheel. So I’m thinking I should err on the side of caution and have it done while it’s all apart.

[Olympic 914]

If you want to balance the flywheel you have to disassemble the engine. No good since its already built.

Not necessarily so. Depends on how your builder balanced the parts.

The machinist that balanced my components first balanced pistons with each other then the rods and crank. Added the fan and balanced that, then added the flywheel and balanced it.

The shops that Jeff posted should be able to balance the new flywheel and compare it to the old one, and match it if needed. If you really want to get picky about it then have them balance the pressure plate separately. Since you may one day replace it.

IMHO