Welch Plug - In or Out?
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 37
Likes: 0
From: West Michigan
Welch Plug - In or Out?
I'm having a problem with oil pressure on my SBC rebuild. Going through the process of elimination someone suggested the welch plug by the rear main bearing might not have been put back in place which could be causing the problems I'm experiencing.
When I measure with a rod down through the top of the block by the way of the oil passage plug near the distributor, I measure 8 1/2 inches. Does that tell me the plug is in place or the plug is missing?
When I measure with a rod down through the top of the block by the way of the oil passage plug near the distributor, I measure 8 1/2 inches. Does that tell me the plug is in place or the plug is missing?
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
If one of the center plugs by the cam was missing, you would have a large oil leak. Are these the plugs you are talking about? What kind of oil pressure problems are you having?
Gary
Gary
Burning Brakes
Joined: Jan 2003
Posts: 755
Likes: 32
From: Roswell Georgia
Dang!
That tells me your plug is in place. (I went out to the garage and measured the distance on my 1970 LT-1 B Production race engine after finding a rod that would fit inside the opening. My distance was 8 7/16" so 1/16" isn't going to make that much of difference.)
Time to remove your engine, double-check the clearances on your rebuild, and if necessary, re-clean the block. There is no reason now that your oil pressure should be so low with the plug in place and with the proper oil screen pick-up height. Sorry!
Time to remove your engine, double-check the clearances on your rebuild, and if necessary, re-clean the block. There is no reason now that your oil pressure should be so low with the plug in place and with the proper oil screen pick-up height. Sorry!
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 37
Likes: 0
From: West Michigan
That tells me your plug is in place. (I went out to the garage and measured the distance on my 1970 LT-1 B Production race engine after finding a rod that would fit inside the opening. My distance was 8 7/16" so 1/16" isn't going to make that much of difference.)
Time to remove your engine, double-check the clearances on your rebuild, and if necessary, re-clean the block. There is no reason now that your oil pressure should be so low with the plug in place and with the proper oil screen pick-up height. Sorry!
Time to remove your engine, double-check the clearances on your rebuild, and if necessary, re-clean the block. There is no reason now that your oil pressure should be so low with the plug in place and with the proper oil screen pick-up height. Sorry!
Burning Brakes
Joined: Jan 2003
Posts: 755
Likes: 32
From: Roswell Georgia
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Thread Starter
Intermediate
Joined: Oct 2009
Posts: 37
Likes: 0
From: West Michigan
OK, I pulled the engine and took it all apart to get to the cam bearings. Many people asked if the bearings for the cam were install correctly. Having them installed incorrectly may have caused not getting enough oil to the top of the engine. The rear cam bearing shown in the attached picture looks like it did not get installed back far enough. I think the groove that the hole in the bearing is supposed to line up over is still back further. The other bearings look OK. The middle three I can see down through the hole in the main bearing through to the where the cam would be. The front bearing is lined up with a feed tube and the groove can be felt with a straightened paper clip. Any thoughts, is the rear bearing set wrong?
Last edited by Gun Laker; Nov 11, 2009 at 05:17 PM.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
OK, I pulled the engine and took it all apart to get to the cam bearings. Many people asked if the bearings for the cam were install correctly. Having them installed incorrectly may have caused not getting enough oil to the top of the engine. The rear cam bearing shown in the attached picture looks like it did not get installed back far enough. I think the groove that the hole in the bearing is supposed to line up over is still back further. The other bearings look OK. The middle three I can see down through the hole in the main bearing through to the where the cam would be. The front bearing is lined up with a feed tube and the groove can be felt with a straightened paper clip. Any thoughts, is the rear bearing set wrong?
BTW, the other issue - if the cup plug is missing from the vertical passage from the oil pump, oil will merely bypass the filter, however, oil pressure will be unaffected.
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 37
Likes: 0
From: West Michigan
What I understand is that all the oil comes to the bearing groove from an annulus and with the bearing in the right spot, only some oil goes to the bearing, the rest gets diverted to the lifter galleries. If the bearing is not in place, all the oil dumps at the bearing so little oil get diverted to the the lifter galleries, thus starving the lifters and getting little flow out of the push rods. Does that make sense? The welch plug by the filter is in place right where it is suppose to be.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
What I understand is that all the oil comes to the bearing groove from an annulus and with the bearing in the right spot, only some oil goes to the bearing, the rest gets diverted to the lifter galleries. If the bearing is not in place, all the oil dumps at the bearing so little oil get diverted to the the lifter galleries, thus starving the lifters and getting little flow out of the push rods. Does that make sense?...
