Yet they sell flywheel bolts with flat washers for the high end HEMI stuff. Hence my question. More of a curiosity than anything I guess.

The bushing example makes good sense. I guess I didn't really think too far into how much heat gets built up in the flywheel.

You know I'd never have a car with a flex plate!

I think I'll stick with the lube under the head, loctite on the threads and torque 'em down. Now instead of being nervous about the lack of washers I am paranoid they will cause problems.

Always ARP. You should see the bolts that I got from one of the vendors. They are grade 8 with the heads ground down. Very scary especially when I ordered them with all of the face plated 9310 gears. Nothing leaves my shop wearing hardware store bolts, especially on the rotating assembly. ACE is not the place for flywheel bolts.

Millions have not been built with 750hp moving 3600lbs through a solid disc clutch/aluminum flywheel to plant sticky 10.5" slick tires at 5000 rpm. That begs the question.



Some of the flywheel bolt manufactures that cover the entire motorsports spectrum *do* offer flywheel bolts with washers:

Example #1

Example #2

Example #3

I though maybe I was missing something.

Yes, I actually do think ARP has tossed this idea around lol.

Sorry to necro, but for anybody who might still come across this thread, which they will because I did while looking for something else, I feel like it's important to correct misinformation even though I realize none of it was given intentionally.

The bottom line is, none of the answers is actually correct in this thread for about 95%, maybe more, of applications. The reason being, about 95% of manufacturers use PLACE BOLTS, which you can read about at the following link and I guarantee none of you ever heard of them otherwise they'd have been mentioned in this thread, on critical fastener locations like flywheel bolts, oil pump bolts, camshaft retainer bolts, etc.

https://www.earnestmachine.com/sites/default/files/products/imported/BHP.pdf

You will be able to identify Place Bolts by the undercut in the bottom of the head and the six cut out lines in the top of the bolt head. This design allows the bolt to create far more clamping power than a standard bolt, even when using a lock washer.

If you remove a place bolt on any application that is the ONLY kind of bolt that should go back in that application location. Generally these are used on applications where the bolt is not particularly long, since longer bolt bodies are able to provide their own additional clamping spring tension, and where they are both difficult to get to if a bolt were to come loose AND would be likely to create a catastrophic end result if they did.

Did not intend to step on anybody's toes, but sometimes, like I did, you might go half your career AFTER professional schooling, and have never heard of them, until somebody slapped me upside the head with that information. Hopefully, some of you here or others who come along later, will be better informed for the info. Good luck.

Very cool and thank you for the explanation and link. "Now I know!"

I'm into bolts. Nice article. I've paid for flywheel bolts twice from "Mopar vendors" and received regular Grade 8 bolts at a big price. These guys make me very mad sometimes.

interesting article breeze. thank you sir !
i learned something, so you can say you taught an old dog.

In the pic are stock bolts and arp, was told 45 years ago at my first car repair job to never use any bolt that did not have the cutout head on a flywheel. Now I know exactly why. Notice the arp has even more contact area on the flywheel than stock bolt no cuts in head and they are undercut. I do all mockups to check and correct flywheel runout with 7/16 head bolt washers, even with a new flywheel the place bolts distort the [censored] of of the washers, worse on a used wheel. That is why I never use washers. Thanks for the info

I've wondered about the same thing. There are examples of both washers and non-washer flywheel bolts. I use washers if there is space for them. Typically you need a chamfered washer with a high strength bolt since the bolt will have a radius under the head. I don't think there is a problem if you use the correct washer for the bolt and if you have the clearance.

so using a flexplate, i use the ARP bolts with no washers, correct ?
or use grade 8 flat washers if i have the clearance ?

Just adding photos for reference since I am in the middle of trying to undo numerous mistakes on a car I bought last year.

Even without washers they bolt heads can hit... the previous owner tried to add clearance by using a hand grinder on the heads of the flywheel bolts, but it was not enough.

Looks like AMK has them for flywheel applications https://www.amkproducts.com/bulk-fasteners-products/?Product_ID=12702

Gus

That happens when people use a flywheel that has been cut a few too many times

Gus

I believe you are probably correct. the face of the flywheel is basically even with the ring gear.

Yep only good for an engine run stand now.

Gus

I was surprised as I read through this and was commenting to myself about "they are place bolts". Surprised it was a post from the past. Place bolts are used in several other locations including flex plate to tq, alternator bracket, cam, power steering valve.

Me too.
Glad to learn the automotive term “Place Bolts”.

In mining they are commonly called “Double A”
like the link to earnest machine has typed on the right.

I understand the undercut head because in Mech Engr education
class time is spent on “Stress Concentration Analysis”.

I now am wondering about whether
the six cut marks on the upper head surface are “cosmetic” just for human eyes to see
or are functional in that they affect either stress concentration
or act similar to “toothed lock washers.”