Grade 5 or Grade 8?

[Tinkerman]

I'm getting ready to install the flywheel and the clutch pressure plate in my TR 3. My question is, should I use grade
8 bolts or would grade 5 be OK?

Your thoughts, as usual, would be greatly appreciated.

Tinkerman

 

[DNK]

ARP

 

[humanoid]

Grade 8... better to be safe than sorry.

 

[martx-5]

If you don't have the original screws, then according to this engineering chart, the torque requirements for both the flywheel and clutch plate attachment would require a grade 8 bolt. The clutch needs 20 lb/ft, and the flywheel 42-46 lb/ft. The numbers in the chart are in inch/pounds, but if you divide by twelve, the grade 8 falls right into place. BTW, the clutch bolts are 5/16"(.312")x18, and the flywheel bolts are 3/8"(.375")x24.

 

[TR3driver]

For flywheel to crankshaft, Don't use standard bolts at all! Either ARP or reproductions of the original flywheel bolts. TRF P/N is 138527.

Very high, repetitive stresses in those bolts; and you don't want them to fail. There's a reason they cost $2.40 each (more from ARP).

The clutch bolts take a lot less stress, IMO ordinary Grade 5 is fine there.

Just as a general rule, when the original fastener part number is 5 or 6 digits, there is something special about the fastener and ordinary hardware store stuff won't do. But when the original P/N starts with 2 letters followed by 2-4 digits (eg the cover plate bolts are Stanpart HU856), then it's a "standard" fastener and all you need do is match the dimensions in Grade 5 or above.

Don't forget the locating dowels for both flywheel to crank and cover to flywheel. They're important.

BTW, I would also suggest new lockwashers for the clutch bolts; and Loctite on the flywheel bolts. The racers say the locktabs are a bad idea, and Loctite is cheaper anyway. If you do use locktabs, be sure to get new ones.

 

[Cheapsnake]

I'll second the suggestion to NOT go with hardware store bolts, even if they are GR8. Beyond the tensile streength of the fasterner there are other factors to consider such as thread cut and finish and fatigue resistance. ARP is the way to go, cheap insurance. Good luck.

Tom

 

[Brosky]

ARP or verified Grade 8. By that I mean, not Lowes or Home Depot Grade 8.

Grainger or MSC at the least, if you don't go ARP or OEM from TRF.

 

[Tinkerman]

Don't forget the locating dowels for both flywheel to crank and cover to flywheel. They're important.

Randall I just checked and I have one of the locating dowels so I need one of those also. Where would I go to get one of those? I must be getting tired because that was a really dumb question I know that there are two spaces and one dowel pin! Please ignore the question.

Thanks All!!!!

Tinkerman

 

[TR3driver]

I'll second the suggestion to NOT go with hardware store bolts, even if they are GR8. Beyond the tensile streength of the fasterner there are other factors to consider such as thread cut and finish and fatigue resistance.

If memory serves, the flywheel bolts also have larger (and thinner) than usual heads.

 

[TR3driver]

Randall I just checked and I have one of the locating dowels so I need one of those also. Where would I go to get one of those?

Total of 4 required, two for clutch and two for flywheel.

Should be available from any LBC vendor. Stanpart (TRF) numbers are DP608 for the flywheel and DP407 for the clutch (but DP408 should work fine).

 

[Tinkerman]

Thanks All. Have just ordered the OEM type of bolt from TRF. I will use the standard grade 8 bolt on the presure plate. Since I have the locking tabs I will use those along with the Loc-Tite, should cover all angles.

Sure thank you for all your input. Messes up my to-do list for this weekend but better to be safe than "Whoops" on down the road.

Regards, tinkerman

 

[Bob_D]

Does anyone have a Triumph-knowledgeable source (online or phone) for ARP hardware? I'd love to be able to contact a vendor and just ask for rod bolts, head bolts, etc. without having to do the research into part number, etc. Thanks

 

[DNK]

Just order direct from ARP. Cheaper sometimes and they know best.

 

[Safari]

Just did my 6 clutch ordered from Advanced Performance Technology, they have a site and kits.

I used ARP W71634 Washer Chamfered ID $1.32 ea.
ARP FBT716-4 1399, 1500 Kit $18.00

I don't know enough to know if the 3 is the same.

Safari