General Tech Flywheel Bolts Too Long For Main Seal

[KVH]

I installed the “Viton“ split seal—rear main seal when rebuilding my TR4A engine. From a review of a great number of posts dating back 10 years, I can see folks having issues with the flywheel bolts interfering with the split seal. Despite following the instructions that came with the seal kit, some of us have experienced interference when installing the fly wheel and bolts.

Well, I just checked my flywheel while rebuilding, and I can see that the bolts are interfering slightly with the seal.

In reviewing prior posts, it appears that the use of washers is not recommended. Some form of hardened steel washer “might“ be OK, but it appears that the better solution is to shorten the bolts by about a 16th of an inch, perhaps as much as 1/8 of an inch. That’s the protrusion beyond the crankshaft.

Shorter bolts apparently are not available. I measured the new bolts that I ordered several months ago, and they are slightly longer than the ones that I removed from my flywheel. I am reluctant to use the old ones, and I believe it’s possible even the old ones will slightly interfere.

I’m just wondering if anyone has any violent objection to grinding these bolts a bit shorter as indicated. I see that it has been done in the past, apparently with the concurrence of others here.

Thanks for any advice.

 

[Hamish Racing]

Cut them down. It won’t affect the tensile or sheer strength. and the protruding thread provides no extra area for the clamping force.
Just put a nut on first before cutting that way when you take the nut off it neatens the thread.
just make sure the bolts are very good quality and the right tonnage

 

[KVH]

Perfect. Thanks!!!

 

[KVH]

I guess I'm now wondering: Would you cut the bolts down with a cut-off wheel, or just grind them down with a good grinder? An eighth of an inch might be tricky with a cut-off wheel.

 

[CJD]

I'd use a grinder, but do not get them red hot. That would ruin their heat treating and kill their strength. Work a bit on one and move on to the next in turn to keep the heat down.

 

[poolboy]

Run a die around them after the cutting.

 

[KVH]

I've been very careful in this process, but I'm still at it.

I cut a little less than 1/8 off the bolts and I'm still "almost" rubbing that seal--one bolt is a bit too close. I can tell by a) using a depth caliper; and b) smearing some grease on the end of the bolt and seeing if it hits the seal.

The problem is that the Viton seal appears to be too wide, or it shifted toward the crank.

I'm not taking any more than 1/8 off any bolt, and it appears only that one bolt is the problem currently, about .015 (1/64) too long.

By using a bright light I can see the bolts just reaching the backside of the crank, so I think I'm OK here. Not sure why that one is so close, but maybe the Viton seal is slightly tilted.

 

[DrEntropy]

Use a nut or "thread chasing" die of the appropriate pitch on each bolt before the grinding, file a chamfer at about 15° around the end and unwind the nut/die. Using a regular die can cut into the rolled threads of the bolt, causing a stress riser. May be a moot point now, but something to keep in mind.

 

[KVH]

No, good point. I just used a nut. No die. No issues though because the grind was so clean. I bolted the bolt into a piece of strap iron (below) leaving exposed just the excess to be shaved too. The strap iron was handy to hold on the bench grinder.

 

[KVH]

I just want to add this note: That Viton seal is essentially flush to the rear of the crankshaft receiving flange. That means there will always be interference if the bolts aren’t shortened. The only exception would be for a thicker flywheel or bolts made shorter. My original flywheel bolts were shorter, but even they were a hair too long.

 

[KVH]

After having torqued and installed my flywheel bolts with blue Loctite, and being fairly confident everything is fine, I’m toying with the idea of removing one just to verify no interference. Is there any consensus that it is OK to remove and reinstall one of these self locking flywheel bolts, even if installed with Loctite?

 

[Sarastro]

If you've taken off a couple threads, the bolts will be OK. I don't think there is any problem in removing and reusing those bolts, but as a general principle, I try to avoid messing with things unless I have a good reason.

Blue Loctite is a good idea. That and correct torque really should do it.

 

[bammons]

I asked the supplier about issues with the bolts they sell (TRF) and was told there is no issue and I foolishly accepted that. I just now turn my motor over to get oil pressure and am getting oil leakage from my freshly rebuilt motor. So after holiday company I have to pull the motor to see what the problem is. It the new style Viton and I am a newbie engine rebuilder. I will be highly irate if it is the bolts as I did ask. KVH what do you mean about the seal being too wide? Bruce

 

[KVH]

The seal sits in a machined grove in the aluminum halves, and is tightly squeezed as the lower rear main bearing cap is bolted into place.

The instructions advise the user to try to keep the seal as far as possible toward the crankshaft, but the width of the seal is somewhat of an issue as it extends past the machine surfaces of the main seal machined housing. That’s obviously why the instruction was given.

The amount of interference by the protruding bolts is questionable. My best estimate is that the amount of interference with the seal is only about a 16th of an inch, if that.

When I installed one of these seals about eight years ago I noticed the same issue and took a little bit off the end of each bolt, but I was not nearly as careful. I have quite a leak under the car, but it’s not the rear main seal. It’s my crazy overdrive.

In retrospect, I would think that I probably have a little interference with that eight year-old seal, but not materially. I rather doubt that if you’re seeing an oil leak you could say with any level of assurance that it’s because of bolt interference with the seal.

There are so many other reasons you could have oil back there. One, of course, would be the oil pan. Another could be a transmission leak. Yet a third could be a leak from the rear main seal that may have occurred whether or not the bolts are impacting the seal.

I could imagine situation where the bolts simply rub a slight depression into the seal and not completely destroy it.

All I’m saying is I would not rush to pull the engine. Who knows, you might have succeeded in pushing the seal far enough toward the crankshaft that your bolts actually do not interfere.