Stumped on my first Flathead Build

macdonge

macdonge

Senior Member
I’m stumped & could use some ideas on where to turn (no pun intended). Was in the middle of assembly of my ‘39 Merc block, bored .060” over and crank main & rod journals machined .010” under. I installed the cam and crank and the latter turned fine in the new bearings. I installed the valves & adjusted the clearances and the crank still turned just fine. I installed the rods & pistons, timing cover and crank pulley and the crank still turned just fine. Then I left it sit for 10 days while I went out of town. On my recent return I fitted the flywheel (taking pains to ensure the flywheel bolts did not contact the rear main seal housing) and then, while fitting the clutch disc & diaphragm, found that the crank would not turn!

Other pertinent information: Main bearing clearances, crank endplay & rod journal/bearing clearances are in spec (all liberally lubed with Redline assembly lube); piston rings are cast iron with gaps of .012” - .015” (pistons & cylinders liberally lubed with engine oil).

I’m afraid to put more torque on the crankshaft bolt for fear I’ll strip the threads in the nose of the crank or shear the pulley key. Is it possible that it’s just ‘stiction’ caused from sitting & at 65 my arms just don’t have the strength to break through it (hard to believe)? Anyone have any ideas?
 

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Remove the last part you installed the flywheel will it now turn? If it turns look at the flywheel surface crankshaft side it may be an interference with the oil pump idler gear cover or the cover bolts.
Ronnieroadster
 
Check your flywheel . from the pic it looks like maybe a late aftermarket flywheel and early engine ?
I have not ran into any no turn problems due to a flywheel being mis- matched but nothing surprises me about this 70 plus year old iron and some of the off shore parts. I would reverse procedure till it becomes obvious , my way of thinking is , it aint gonna change till you start removing and inspecting ,sounds like you already checked all but the flywheel/clutch assembly.
 
Ronnieroadster (and Fordestes) get the boobie prize! Had a close look with a flashlight down between the flywheel and oil pump idler gear cover and - sure enough - two of the cover bolts are contacting the flywheel! It is a PRW Industries piece (Placentia CA), supposedly made for "32-48" flatheads and bought to accept a 10" clutch & mate to a T5. I have the (good) original flywheel so now will have to find someone who can redrill it to accept the 10" clutch. Thanks you guys! I'll sleep easier tonight!
 
macdonge, what is the weight of that flywheel ? I am going to a lighter flywheel and I am shopping around to see what is available.
 
When my wife isn’t looking, I’ll drag the bathroom scale out to the garage this aft and weigh both for you. Stay tuned.


Sent from my iPhone using Tapatalk
 
Always good to see a brave man. Just don't get caught. I still cringe when I think about the time my ex-wife came home unexpectedly and found me using the dishwasher to clean a couple of Triumph motorcycle jugs. (It worked good, too!)
 
I was just wondering the weight , I tried to find it on the web but they don't show a part number for that flywheel , Their catalog just goes back to 1955, do you have a listing for the different flathead flywheels ? I am thinking you got a defective one or maybe a later design, the price range isn't too bad compared to the ones I have been finding ,I assume the wheels are steel s.f.i. cert.
Thanks
 
Fordestes: The PRW flywheel (Speedway #91015627) is steel, SFI certified & weighs 35.8 lbs. The original 11" truck flywheel I have weighs 34.4 lbs. Beast that it is, I thought for sure it would weigh more than the aftermarket piece. Goes to show that they should have removed more material from the front face to avoid the interference I encountered! I'm afraid I don't have the listing you refer to.

Gotta go put the scale back in the house before "she" comes home!
 
No problem, Many thanks , "Speedway " tells me a lot , I didn't know who made speedway flywheels , I ruled the heavy speedway out a while back , I about decided a Centerforce or a Ram Clutches brand will suit my needs . the specs on the two are around 27 pounds , Thanks for you efforts , Good luck with your project , Keep posted on your project.
Fordestes
 
If you are unable to cut the flywheel for clearance you mite consider counter sinking the upper idler cover holes and using countersunk socket head bolts
 
You may want to compare the crank shaft mounting face with the old flywheel , there is a difference in the early and late flywheels, sometimes causing problems with the starter engagement . some say they have not had any problems. but it is along way back into the flywheel after it is installed in the vehicle . just thought I would pass this little bit of info along to you.
 
Great Looking engine, and I'm pleased you sorted the problem. On the upsetting she who must be obeyed years ago i used the oven to heat up a bakerlite cam gear , what a stink, nearly had to stump up for a new stove. it tainted the roasts for some time after haha.
 
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