repairing block drain and manifold drain

D

dantheman

Member
May 17, 2009
102
Rochester NY
Boat Info
1989 390 Express
Engines
454's
I was wondering I could get some idea's on how to fix the threads in the block and manifolds, I have one of each that i cant get the stock (new) brass plugs started in. I looked up into the manifold with a mirror and can see that the threads are gone, smooth now. The block drain really scares me, the season starts soon :smt043and i really don't want to mess that up. any help would be greatly appreciated, Thanks and happy boating. oh, my engines are 454's
 
dantheman said:
I was wondering I could get some idea's on how to fix the threads in the block and manifolds, I have one of each that i cant get the stock (new) brass plugs started in. I looked up into the manifold with a mirror and can see that the threads are gone, smooth now. The block drain really scares me, the season starts soon :smt043and i really don't want to mess that up. any help would be greatly appreciated, Thanks and happy boating. oh, my engines are 454's
Click to expand...

I run a pipe thread tap through my drain holes to keep them easier to screw in the plugs. I also put vaseline on the plug threads so that they screw in and out easier.

Ken
 
Thanks for the quick reply, that was fast! I hope to be up in the Islands again this year, Last year I stayed in the Lake of the Isles for a week, Just to get away from civilization..
 
If your threads are gone as your say, you may find that cutting new threads with a pipe tap will make the hole too large for the drain fitting to thread in far enough to get a tight thread seal. Also in the block area, be very cautious when running the tap in as to not be bottoming out into the cylinder web.

I would do as the electricaldoctor suggests first and then test the fit on the new drain fitting. If it seems to loose to where your not going to get a good seal, there are several repair options that will work in your situation. Just don't muck it up too bad now and this repair shouldn’t turn into a night mare.

Let us know how it goes.

BTW: Nice Boat
 
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That's the day I purchased my boat back in 06, under the boat they had this thick v-shaped girder thing supporting the boat, I asked them if they would sell the girder thing to me but no luck. But yes, just one jackstand per side.. I've since photoshopped out that jackstand just to be a goof.. I am hoping someone will share some idea's about fixing the manifold that has no threads, I think the block drain can be fixed with a pipe thread tap, any idea's? And thanks BonBini for the compliment. I'm psyched to get it in the water soon.
 
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dantheman said:
Thanks for the quick reply, that was fast! I hope to be up in the Islands again this year, Last year I stayed in the Lake of the Isles for a week, Just to get away from civilization..
Click to expand...

When you come back out of the Lake of the Isles, if you take a left and head due north, you will bump into Ed Huck Marina where we keep our boat. We are on D-Dock in slip #125.

~Ken
 
I'll assume you are raw water cooled.
The sediment and rust in the block maybe filling in the threads so it looks as if there gone. Flush/spray with a garden hose and probe the hole with a small tool to get the crud out and clean the threads out. Then, carefully chase with a tap.

If the threads ARE somehow gone. You need to replace or re thread to a bigger size.
Look to see if the drain is an insert screwed into the block and the plug screws into it? If so replacing is easy with a socket.
If the drain is threaded directly into the block. You prob. need to go the next size up route.
Drill and tap then, install a bigger plug.
Good Luck,
 
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I guessing 3/8. But take your plugs with you when you go buy your tap. Unless you’ve got a few already, but then I suppose you would have just matched one up!

Be Careful on the Block. Best of luck.

Edit: 3/8 pipe
 
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