Clean Out Plugs
 

Does anyone know where to get the proper plugs for a Flathead Mercury V8, with the 5/8" clean out holes in the crankshaft ? I have Dorman Number 555-010 Plugs, but I don't see HOW they could possibly fit since they are slightly larger than the 5/8" hole ! I've ruined 2 plugs already. Any help appreciated. Also, I've been on line, checked with about a dozen vendors, and no one seems to habe this simple little part.

Re: Clean Out Plugs
 

The traditional hot rod way has been to tap the holes and use screw-in plugs and Loctite.

Re: Clean Out Plugs
 

You have to tap the plugs in with a punch. It's best to grind a suitable punch to a domed shape to drive them in. I used a smaller diameter flat ended punch and knocked a hole through the end.

Re: Clean Out Plugs
 

You appear to have the correct plugs. 8CM-6307 cross references with your Dorman number. They are supposed to be .628 in dia. Or more likely a metric plug 16mm (.6299 )
I always installed them with a loosely fitting pin punch, or a steel bar in the center of the cup. And a 3-4 lb hammer !
If the punch fits too tight you will have a difficult time removing it as the walls of the plug collapse in from the press it.

Re: Clean Out Plugs
 

Exactly how I have done it.

Re: Clean Out Plugs
 

Ld, what method are you using to install the plugs that's causing the failure?

Re: Clean Out Plugs
 

The Dorman plugs are just made incorrectly .They are actually .625" at the closed end, and flare out to .650" at the open end. Ain't no way that oversized plug is going to fit in that hole. That's why I'm asking where to get other types. I already know how to install them, just need a quality part to start with. Thank ya'all for your responses, keep em comin !

Re: Clean Out Plugs
 

I have used these plugs. It may be that the old staking is getting in the way. I used a tapered reamer to "smooth" the opening at the outside. As someone said above, drive the plug using the center of the plug, not the outside edge. Stake these in place!

Karl

Re: Clean Out Plugs
 

Once you have them in, then 'stake' the outer edge with a pointed punch - in about 3 or so places around the perimeter. A stock 49-53 oil pump can blow the plugs out if you don't stake them . . . ask me how I know such things! LOL

Re: Clean Out Plugs
 

Sounds like a vote for threaded plugs.

Re: Clean Out Plugs
 

Yep - that is what I have in all my racing cranks. ;)