PFF - Pennock's Fiero Forum, PDA Edition

Best flywheel for a 3.4 V6/60 with a 5-Speed Getrag? (Page 2/2)

lou_dias

OCT 11, 01:42 PM

Be careful with flywheel weights.
IIRC the pre-88 flywheels weigh 12 lbs.
88 flywheels weigh 15 lbs.

I believe this is why the 88V6 is rated for lower hp than the pre88 2.8's.

82-T/A [At Work]

OCT 11, 07:45 PM

For what it's worth, I watched a ton of YouTube videos, and found several websites that showed before and after dyno curves, and there seems to be a 1.5-2% increase in horsepower across the entire RPM range with a lighter flywheel (some were lighter comparatively than others). They all seemed to say the same thing though, not to expect a better quarter mile "drag time" with a lighter flywheel, but that the flywheel helps on road courses (as you guys said).

Regardless, I'm not building the car to drag race, but to enjoy the car through upshifts and downshifts.

ericjon262

OCT 12, 12:23 AM

quote

Originally posted by La fiera:

I have the same set up as well with wider hardened steel washers in between the bolts and the aluminum flywheel to give it more area of clamping force but I use blue Loctite on the threads. Reason being because I do lots of transient on/off the throttle and the on full power is longer and more repetitive than average.

I'm sure whatever washers you are using have sharp edges removed, and were carefully inspected, but ARP's instructions explicitly state to NOT use any kind of washer under the bolt heads.

quote

Originally posted by La fiera:
The washer acts as a buffer between the bolt and flywheel spreading the force over an much ample surface. The problem with aluminum flywheels is that if you don't take into account the aluminum expansion rate depending on how fast you heat it up, the gap between the flywheel and the bolt shrinks which is great but it starts to gouge or eat the aluminum over time if you don't use a washer and a gap gets created and that is when the flywheel gets loose even though the bolts are in the same place they were torqued.

This is a documented material property, in engineering terms, it's referred to as "creep" it can occur with or without cyclic load changes.

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"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."

I invited Lou Dias to trash me in my own thread, he refused. sorry. if he trashes your thread going after me. I tried.

pmbrunelle

OCT 12, 09:43 PM

I don’t see why a suitable washer couldn’t be used beneath an ARP bolt.

Probably some folks used soft washers beneath a highly-tightened ARP bolt, and then when the washers creeped, customers blamed ARP for bad bolts that loosen.

Their instructions most likely originate from problem customers in the past.

ericjon262

OCT 12, 10:43 PM

quote

Originally posted by pmbrunelle:

I don’t see why a suitable washer couldn’t be used beneath an ARP bolt.

Probably some folks used soft washers beneath a highly-tightened ARP bolt, and then when the washers creeped, customers blamed ARP for bad bolts that loosen.

Their instructions most likely originate from problem customers in the past.

I agree, I didn't inquire as to why my Coyote bolts have heads that are as big as the washers I was going to use, so I omitted them.

La fiera

OCT 13, 10:09 PM

I'm sure whatever washers you are using have sharp edges removed, and were carefully inspected, but ARP's instructions explicitly state to NOT use any kind of washer under the bolt heads.

Yes its very obvious! That's because the Coyote engine doesn't have an aluminum flywheel.