Technical Dowelpin fitment

Hi,
I bought a flywheel for my flathead 8 ba from a well known speedshop, when I try to put it on I found that the dowelpin hole was to large, I mailed the shop and told them the problem.
They answered that the fitment is not critical, the bolt will hold it tight to the crank.
My opinion is that, the dowelpin should have a snug fit in crankflange and flywheel and the bolt just hold them together. What do you folks Think?
I am from sweden so you have to look over my English.

Regards Rickard

 

Your English is fine.

 

The dowels (you should have 2...are both loose??) locate the flywheel, bolts clamp and should not really have any role in locating or driving the wheel. What you think is mechanically correct. I would consider that a defective flywheel...
if you wind up stuck with it because of bad treatment by seller or because shipping is too much I would have a machine shop drill out the dowel holes on proper locations and bush them to correct size.

 

Or make stepped dowels.

 

You really need an accurate measurement of the dowel pin and the hole in the flywheel. Pretty easy if you have a good micrometer (do not use a dial caliper...) and a set of precision gauge pins. A slip fit of .001 is very acceptable. Like Unkl Ian suggests, a stepped pin looks like the solution.

 

Thank you guys!!!!

 

The dowel pins are what actually transfers the torque of the crankshaft to the flywheel. As Bruce said the bolts are for holding to the crankshaft not for transfering the torque. Tell that well known Speed shop the flywheel is junk. The only way the flywheel could be used is if you go threw the trouble of having oversize dowel pins made.

 

I told them what you say "The dowel pins are what actually transfers the torque of the crankshaft to the flywheel" in a mail two Days ago, but they have not answer yet. I Think this very old speed shop losing a customer.
Thanks Ronnieroadster

 

Does this speedshop have a name ?

 

Yes! the name is Speedway motors, they have measure the other Wheels they have in stock and the hole are the same size as mine. So i guess they have more junk flywheels.
Thank you guys!!

 

There is a zillion flywheels bolted to engines that don't have dowel pins, Ford small blocks for one, 221 through 351, one offset hole so they only will go on one way as they carry balance weight but do have six bolts...The 8ba has four bolts and two dowel holes and can go on two ways and it doesn't matter because it carrys no balance weight...To me as long as you use the best bolts for max strength it shouldn't matter as long as the dowels stay in the crank..If the engine is apart you could turn the dowel holes into bolt holes, should be able to tap the crank for m14x2 [dowels are .468] and drill the flywheel to 14.5mm...

 

If by measuring you find that the holes are too big, the proper fix is to re drill and bush the flywheel down to correct specs.

Modifying pins, cranks and drilling holes is a modification to accommodate a fucked up part. Now you have 2 bastard parts that only fit with each other.

 

A couple of thoughts here ...

1. The factory dowels are stepped already (part #B-6387). Is is possible that sometime in your engines past they have been replaced with straight dowels so that your dowels are actually too small?



2. Can you make a bushing to slide over the dowels to match the flywheel holes? There is a dowel retaining plate that goes on before the flywheel bolts so this would hold the bushings in place.

 

Or maybe drill and ream new dowel pin holes the correct diameter 60 degrees from the oversize holes.

 

I had the same issue with our flywheel. Had a machine shop knock out some stepped pins. Fit perfectly.


Posted using the Full Custom H.A.M.B. App!

 

I have made new pins, so I guess it will work now.I bougth a new flywheel becauce I already had one with to big holes and I got another one.

 

Im going chime in even though many will disagree with me.A standard hardened and nitrided dowel cant take much side pressure before it will crack and snap off.Dowels are typically used for locating but not for transferring torque.
Built many dies and molds in my years and used plenty of dowels so I have seen first hand that they break off pretty easy when used for the wrong application.Had plenty of customers insist on using dowels to keep inserts and components from shifting and most of the time they broke when items tried to shift or had any misalignment at all..Makes sense that the bolts should do most of the torque transfer instead of the dowels as they are softer and can handle some side movement before breaking.