lifter Oil Gallery Plugs - Question

[70Hardtop]

Hello, i am assembling an LA engine. There are two small core plugs at the front that go into the ends of the lifter oil gallery, they sit behind the cam thrust plate. The engine had previously been rebuilt, but i noticed that the previous mechanic had not put them in. I asked another mechanic, he said they are not necessary, he uses silicone on the camshaft thrust plate and lets that seal the galleries.

He said that putting plugs in can block the oil supply to No.1 main bearing, if one of them sits too far in.

Does anyone have any experience with this? I had already installed the plugs when he told me this so now i am worried i might have blocked off the oil hole to #1 Main.

Thanks

 

[70Hardtop]

i went and checked another stripped LA block i had - there are two oil feeds to the #1 main and the feed holes are deep enough back from the from the front of the block so that the core plugs i installed will keep them clear. I can see how a deep plug, or one that is pressed in too far though, will block the feed hole. Always learning.

 

[Juan Veldez]

I looked at the same plugs and wondered if they should be there also. The cam thrust plate has those recesses directly in front of the plugs and I first thought the oil was supposed the flow through there. I looked at a few books I have and they seem to be required. I had a motor shop install all the plugs when they installed the cam bearings, but I wanted to double check. Any one know why those 3/4" dia. recesses are in the cam thrust plate?

 

[70Hardtop]

Thanks for answer Juan. I have since been told that most production engines didn't use the plugs. But not having a great deal of experience on these engines i wasn't sure what to do. The core plug kit i got from Mancini (or maybe Summit) had these two plugs in it. So i assumed they had to go in; - plus i was reading "How to Rebuild Your Small Block Mopar", by Don Taylor and Larry Hofer and it said to install them. Although i have since found a few mistakes in this book, one of which is on the same page, saying that the tin drip feed for the timing chain, if used, has to be put in the same position as the bolt oil feed method, ie top RH side (or left side looking at the engine). This obviously won't fit here (i tried!), it has to go in the two lower bolt holes.

Yes i have now been told that most engines didn't use the core plugs, the machined thrust plate must have been good enough to effectively seal the galleries. And if you had to use a new replacement plate that was not well machined then the core plugs would then be needed. Good question about those recesses in the thrust plate. Maybe they are to provide a clearance if plugs were to be used and if the plugs protruded out a bit? or maybe they actually help seal the oil in somehow (fluid dynamics) -if the plate was completely machined flat here, the oil might flow more easily across the plate? But i'm only guessing

 

[72cudamaan]

I have always put the plugs in. Why would you want silicone in your engine that
can come loose and get into the pickup screen?

 

[Challenger340]

I always use the plugs, no silicone.
The plugs should only be installed "flush" with the front of the block.

 

[btceng]

Good advice. Thanks.