Hi, I know we have a lot of smart people out there and I'm looking for technical help. I have 72 Pinto Super Stock Modified Compact whith a hp 2.0. It has a 4 speed with a 9 inch with 6:50 gears, center force clutch. The compression is 13:1 with 560 inch lift cam. I can't seem to kep flywheel bolts in the car. I shear them off after a few runs and it eventually tears up the end of the crank. I've tried the 10.9 metric bolts and even drilled and tapped the crank/flywheel 7/16-20 to run the chevy flywheel bolts that have a shank. I switched because I heard the 10.9 and stock bolts are threaded all the way and it creats a shear point. The 7/16-20 chevy bolts have a shank so I figured they'd work better. This wekend the bolts let go and the flywheel came off and the motor died. I'm hoping I didn't hit the valves. Does anyone have any good ideas. Thanks, Don Please e-mail me @ Donald.Corneau@GZA.com
I don't have much experience with drag racing but....
Is flywheel too light?
Not enough sliping of the clutch?
Too much traction?
Gears?
Internal harmonic vibration?
Just a few things that poped into my head......
Like they say, "if your not braking traction your braking something else."
Bill
Hello pinto1955,
You have tried all the bolt options I know about.
Have you tried installing hardened dowls between the bolt holes?
from Pintony
i had the same problem on mine a long time ago. i took it to a local REPUTABLE crank shop (velascos in downey, ca.) and had them redrill the end of the crank for 1/2" bolts & i dowel pinned the thing to death. (several smaller dia. dowels & one larger dia one as a locating dowel) had the flywheel modified accordingly and the whole assembly (everything including all the motor internals) balanced.
NEVER had a problems again
Thanks to all for the good ideas. I think SRT and Pintony has the best as I've considered dowel pinning the flywheel and crank. One thing I didn't cosider was going to the 1/2 in bolts and posssibly using locktite. SRT did you also use lockwashers? Hopefully I didn't do too much damage to the engine with the flywheel coming off the crank. Thanks to all of you for your ideas. I'll keep you posted. Don
IIRC on the lock washers. No. The bolts did have a shoulder on them though.
SRT,
Were these aftermarket bolts from a speed shop and if so by who? The only aftermarket bolts I've seen is ARP and they're 1/2" x .750. for a Pontiac.Did you use fine thread or coarse? Or did you use plain grade 8 bolts? Sorry for all the questions but I'd like to do this for the last time. Thanks, Don
they were grade 8's and the machine shop provided them at the time they were doing the work.
speed shops around here at that time (1972) didn't have any such thing on the shelf as a line of prepackaged hi-perforformance fasteners
SRT,
Thanks for the information. I went down to the local hardware store and bought six 1/2x20x1.000 grade 8 bolts and some 5/16 & 3/8 dowel pins. I'm going to pull the motor this weekend and see what the damage is. It'll also give the chance to put the new McCleod flywheel in also. I also saw on the Jeg's online catalogue a set of 1/2x20x1.000 used on pro-stocks for 69.00. They had a 240,000psi rating. Might look into those also. Will definitely use the red locktite this time. Once again thanks for everyones input. Don