Boom!!!

That was the sound that came out of my Model A today, as I accelerated hard in 3rd gear. Everything was doing fine, it's pulling as hard as a Model A will, then BOOM! A really loud explosion, for lack of a better description. It was sudden, shockingly loud, and startled me quite a bit.
I put it in neutral and coasted into a parking lot, looked under it and there were no vital fluids leaking. No huge gashes in any cases, so I fired it back up. It will run in any gear, but not over about 1,500 rpms, before it starts to vibrate. It idles fine and there are no strange noises. Just the initial BOOM, then the vibration above 1,500.

It's a stock 4 banger with the stock 3 speed transmission.

Any ideas?

 

Tire blowout.

 

1500 rpm in nuetral, or driving ? If driving I would say drive train,like, differential. If out of gear,I would say something in the dizzy. Are you running an aftermarket ignition with mechanical or vacuum advance ? if its the stock ignition, check the advance weights and ajoining mechanisms. A backfire may have caused them to jam up somehow,giving you just static timing with no advance/retard

 

Backfire? Is the muffler hatched? As rubberrodder mentioned it could be an ignition issue.

Do a cylinder balance test to make sure it's firing equally on all four. Pull and then reconnect one cylinder at a time while watching the rpm drop.

 

No, it sounded like a grenade went off under the car. The vibration is both in neutral and if you drive it above 1,500. It wasn't a backfire type of bang and it runs fine. It seems like I fractured the flywheel, or something in the clutch, but everything still works as it should. It's really strange, but that seems to be normal for me.

 

Mainshaft bearing in trans? Does it vibrate at a stand still with the clutch depressed? Cracked gear on mainshaft?

 

not sure about A trans.

but when I detonated my 39 box,BANG, cluster gear rooted, reverse idler gear rooted.

I was still able to drive the truck up my ramp and into trailer.

amazing, once I pulled it apart and saw the chunks out of the cluster

 

I didn't try it with the clutch depressed in N, I'll try it and see tomorrow.
Thanks!

 

It ended up that one of the 4 blades on the fan turned loose and hit the hood side panel. Thanks to everyone that offered suggestions.

 

Dayum, I had my money on a blowout. Almost as funny.

 

haha. hey better sumthn stupid and cheep like that then sumthn vital. ive had goofy shit like that happen before.. awesome.

 

OK,EVERYBODY AT ONE TIME:

"I WILL NEVER NEVER NEVER USE A MECHANICAL FAN AGAIN."


peice of junk fans.i have NEVER had good luck with a mechanical fan.

-danny