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TR2/3/3A TR3 Rear Main Upgrade

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M

markctr3

Senior Member
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Part on the rebuild on my TR3 engine was to install the rear main seal upgrade. Basically, it eliminates the felt seal with a "modern" oil seal. The crank does have to be machined to remove the scroll from the crank and reduce the diameter to 2.5 inches which I did when all of the reciprocating parts were balanced.

There is a problem, however. The aluminum oil seal housing is thicker than the OEM seal, and when you mount the flywheel to the crank, the 4 bolts will hit the new housing! This in NOT a good thing since the crank will no longer spin (this SEVERELY reduces horsepower by 100%). I had to place 2 grade 8 washers between the bolts and the flywheel in order to keep the bolts from contacting the new rear main seal housing.

I was curious if anyone else has encountered this problem...
 
I installed the new type seal with out any problems the flywheel hitting the housing

Don
 
Hi,

I'm not sure what the spacing problem is with that seal housing, but I am pretty certain it's not a good idea to space the flywheel like that.

For one, the flywheel needs a particularly strong connection to the crankshaft because of the heavy, rotating mass. There is a ridged portion on many flywheels that "cups" over the end of the crankshaft and helps keep it solidly in place. Spacing it backward would eleminate that safety margin.

Also, spacing it back will make the clutch cover/throwout bearing spacing incorrect. It will likely cause the T.O. bearing to drag and/or over-engage. At the very least, it will eliminate most of the free play between the T.O. and the release fingers on the clutch cover.

If the seal housing is too thick, you could have it machined down. If you would like, I've got a converion seal housing out in the garage, not installed, that I can measure, for comparison.
 
[ QUOTE ]
Hi,

I'm not sure what the spacing problem is with that seal housing, but I am pretty certain it's not a good idea to space the flywheel like that.

[/ QUOTE ]
I interpreted it to mean that the flywheel bolts were a bit too long & projected through the crank flange far enough to hit the seal. Washers under the bolt heads might allow the heads to interfear with the clutch disc. Better yet, shortening the bolts, would eliminate both problems.
D
 
You're right. The choice was to either shorten the bolts, or place some sort of spacer to keep the bolts from penetrating too far through the crank and making contact with the seal housing. I decided to use the grade 8 washers as a sort of "extended" head of the bolt. I didn't want to cut down the bolts because I didn't have a die or thread chaser of that size and thread pitch. I believe that shorter bolts would been the best idea, but given my options, I did what I thought was best.

Time will tell...
 
Ah, my bad. I misunderstood.

So the bolts are protruding through the flange and catching on the seal housing, right? I thought you were spacing the flywheel itself, which would not be a good thing. But it sounds like the washers are just under the head of the bolt. Better... but still not ideal.

For one thing, those bolts normally have tab locking washers under them. (Unless special self-locking bolts, such as ARP, are used.) Are the tab washers installed? They should be, it's a high vibration area and you definitely don't want a flywheel coming loose! If not installed, would locking washers help?

If you just need to shorten the bolt to a more ideal length, I frequently do this using a Dremel tool fitted with a cutoff wheel. It gives a clean cut that only a little sanding or filing to taper the first thread or two will tidy up... no chasing with a die is normally needed.

A bolt can easily and securely be held in a vise by threading a nut on temporarily, which can also be used to "mark" the cutoff point and help guide a square cut. In addition, simply removing the nut after making the cut cleans the threads well and removes any burrs. I find the slightly more expensive "reinforced" Dremel cutoff disks last a lot longer than the smaller, unreinforced type. Go slow so the bolt won't overheat and lose it's hardening qualities. Be sure when using these tools to wear eye protection.
 
Good advice on the Dremel tool Alan. I did put the locking tabs on the flywheel, and used a spot of loctite as well.
 
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