Triumph TR3 drawing

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Triumph TR3 FAQ page

Fixings for aluminum flywheels

More tales of flywheel woes.
Those of you with aluminum flywheels - buy pt. no. 200-8572 for 3/8", 200-8573 for 7/16" bolts, from ARP. These inserts are easily fitted, and will allow the bolts to pull up properly. Use on both 4 and 6 cylinder.

3/8" bolts - pt no.206-2802 (6 per set) , no washers required, thanks to inserts. Use ARP thread lube not loctite.

7/16" bolts - pt no.200-2802 3/4" heads (6 per set) ditto.(for 4-bolt 6 cyl& Spit, 4 or 8 - bolt TR 4 cyl.)
7/16" bolts - pt no. 230-7303 5/8" heads (3 per set)ditto (for 8-bolt 6 cyl& Spit)

All this stuff is made in the US! We use ARP fasteners anywhere possible.
Jon Wood


Ditch the bolt lock plates and just use locktite. Make sure the bolts don't interfere with the block since they won't have the thickness of the plates under them. ARP bolts for an MGB will work nicely in our flywheels, but you have to grind a little off the end or they interfere with the aluminum seal housing. The plates aren't very hard steel and can cause more problems than they solve.

Tony Drews


Lock tabs are made of soft material. The steel of the lock tab can and sometimes will compress where it is squeezed between the bolt head and the fly wheel. The clamping tension of the bolt on the flywheel is then reduced. The effect is as if the bolt had loosened, without it having done so. This occurred on my own Morgan, with a TR-4 engine, when the car was about 16,000 miles from new. It manifested itself as a rattle when the engine was gently revved from idle. The noise sounded like it was coming from within the timing cover, but it was noise transferring down the crankshaft from the rear of the engine. The bolt were found to be "loose". They were not stretched and the lock tabs were still bent over and locking the bolt heads. Since then, (1966) I have used high strength loctite and no washer on an iron flywheel or metric "wave washer" style lock washers, which are hardened steel, on alloy flywheels. On high performance engines we use bolts that are harder and higher strength than the original "auto" bolts. The best standard bolts were labled "BEES" on the head. We have only had one "tractor motor" flywheel ever come loose since, and it was full race engine. The driver had been revinig the engine to near 8,000 rpm coming down the switchbacks on the backside of the Pittsburg Vintage GP where he had not wanted to upshift and then immediately down shift into 1'st gear for the next hairpin corner.. The failure did not occur that weekend, but the next race weekend where we found the front generator end frame lower ear broken off, then shortly thereafter all 4 ARP flywheel bolts sheared and the flywheel lost its attachment to the flywheel completely. The dowel pin also was sheared off.. There is obviously a resonant frequency somewhere north of 7600 rpm that was inducing these failures. We normally insist that drivers keep the revs on a full race engine with steel rods, crank, alloy flywheel, light pistons, etc.below 7200 rpm which has been safe and reliable in a engine properly assembled with all of the correct necessary parts.

Regards, Greg Solow

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