1993 Quad4 GTZ: Project WTF

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Rettax3
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Re: 1993 Quad4 GTZ: Project WTF

Post by Rettax3 »

GT_Indy wrote:The only things I can think of is the bolts might be over torqued and stretched, bolts might be bottomed out, the crank/flywheel isn't a true flat surface, or the bolts might not be good quality.
I've read about people getting an expert machine shop to machine the crank and flywheel with dowels to help relieve the bolts of the shear forces, that could be a possibility.

Being an aluminum flywheel I wonder if aluminum creep is happening (I know Aluminum can dent easily), where the metal deforms under the bolt heads and it becomes loose enough where the bolts can shear off. (Because the friction between the flywheel and crank gets reduced).
I wonder if he needs something like this made of strong steel to help clamp the aluminum flywheel to the crank:
plate.jpg
More likely it is that the bolts are UNDER-torqued. Even if they were to OE specs, switching out to aluminum should have a different, and higher, torque-spec. Aluminum compresses differently than steel, of course, and is softer. Think about aluminum cylinder-heads, that frequently use torque-to-yield bolts to retain tension against them. Typically, bolts will get work-hardened and fatigue from insufficient torque causing vibrational impacts against them. I like the retaining-ring idea, I have something similar on the flywheel of my V-8 Indy, although that was more to hold a bushing to center the flywheel onto the hub -when this car was being built, no one was offering Northstar flywheels yet.

Despite the performance enhancements, I would be hard-pressed to go aluminum for a flywheel. Even with my GTU, the F40 transmissions suffered more frequent issues, even complete failures, with lightweight flywheels, it puts more stress on the input shaft and softer synchronizers because it transmits more vibration and doesn't absorb the power-pulses from combustion as well. It just seems like a lot of reliability issues over these. :pardon:


1989 SuperCharged 3800 Srs-II (First)Six-Speed GTU
1990 Turbo 3.4 5-Speed T-Type
1990 4.0L 4-Cam 32-Valve V-8 5-Speed Indy GTi (Project)
1990 Stock(!) 3.1 MPFI Auto Indy
1995 LA1/L82 4T60E Z-26
1995 3.4 DOHC Turbo 5-Speed Z-26
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GT_Indy
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Re: 1993 Quad4 GTZ: Project WTF

Post by GT_Indy »

yah under torqued can be a posibility as well. I was assuming it happened when the softer aluminum creeped and I was thinking that steel ring I put a photo of might be useful in keeping it all torqued down.

Yah the flywheel mass helps to balance the whole engine. I feel like a lighter flywheel would be pointless unless the whole rotating assembly gets weight reduction and was digitally balanced.


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Rettax3
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Re: 1993 Quad4 GTZ: Project WTF

Post by Rettax3 »

It isn't just a balancing issue -yes, on many engines, the flywheel and/or harmonic-balancer are actually part of balancing the crankshaft, rods, and pistons. The farther out to the ends of the crankshaft, the more effective the balancing effect a little weight can be, so the factory can use less weight overall thus improving engine performance and response. It doesn't matter for that part of it how heavy or light the flywheel is, just that it has the right amount of weight at the right radius either added or removed on one critical spot to balance the rest of the rotating mass.

BUT, the flywheel also is meant to deliberately add rotating mass, to absorb the shock delivered to the crank through the connecting-rods, since there isn't a constant stream of power applied in a reciprocating engine (it isn't a jet... :wink: ), and to help get the engine in position for the next combustion event without loosing momentum. The smaller and lighter the engine's rotating mass is, and the fewer the number of cylinders it has, the more critical it is to have a good mass on the flywheel.


1989 SuperCharged 3800 Srs-II (First)Six-Speed GTU
1990 Turbo 3.4 5-Speed T-Type
1990 4.0L 4-Cam 32-Valve V-8 5-Speed Indy GTi (Project)
1990 Stock(!) 3.1 MPFI Auto Indy
1995 LA1/L82 4T60E Z-26
1995 3.4 DOHC Turbo 5-Speed Z-26
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