Question about Lifter Oil Gallery Plugs

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70Hardtop

70Hardtop

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Hello, i am assembling an LA eng. 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
 
That guy is a nutcase. They need to be installed.
 
Umm, if they are not installed you have no oil pressure, he is a freaking fool!
 
thanks. But it didn't answer the other important part of the question -is it possible that one of them can block off the oil feed to the front main bearing? And i can see his point - the thrust plate will go a good way to sealing the ends and especially if using silicone. But the core plugs are there for a reason. I will have to check out another block to see how far into the gallery the oil feed to #1 lies.

Just edited this now to add this: 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.
 
70Hardtop said:
thanks. But it didn't answer the other important part of the question -is it possible that one of them can block off the oil feed to the front main bearing? And i can see his point - the thrust plate will go a good way to sealing the ends and especially if using silicone. But the core plugs are there for a reason. I will have to check out another block to see how far into the gallery the oil feed to #1 lies.

Just edited this now to add this: 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.
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The short answer is yes , but you figured that out yourself. Early engines used the thrust plate to seal the passages. Their thrust plates were machined flat to seal these passages. New thrust plates may not seal and hence the need for core plugs.
 
Begging to differ. I have pulled a bunch of LA's apart and have never seen sealer or plugs in one. It's your motor build it like you want.
 
66fs said:
The short answer is yes , but you figured that out yourself. Early engines used the thrust plate to seal the passages. Their thrust plates were machined flat to seal these passages. New thrust plates may not seal and hence the need for core plugs.
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Thanks, its the answer i was looking for. 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. Thanks
 
dartjack said:
Begging to differ. I have pulled a bunch of LA's apart and have never seen sealer or plugs in one. It's your motor build it like you want.
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Thanks for informed answer! Obviously the first two replies came from people who were text book builders, maybe had never seen a real engine pulled down.
 
All but one small block I have tore down had the plugs. I am building a 1971 318 right now that never had the plugs. Did the factory just forget them? Who knows. But I can say that is the way it came from the factory, as I got the car from the original owner, and that engine had never been toughed. Bearings looked fin. So there was never an oil pressure issue. That said I put them in. Why take the chance.

One thing I have been reading on is drilling a small hole in the plugs, and a small hole in the cam plate over top of them. This is done to help oil the timing chain and make it last longer. I am thinking about giving it a try, as every small block I have tore done seems to have an over stretched chain. I do not think they get enough oil from the fact. So we will see.
 
604 said:
All but one small block I have tore down had the plugs. I am building a 1971 318 right now that never had the plugs. Did the factory just forget them? Who knows. But I can say that is the way it came from the factory, as I got the car from the original owner, and that engine had never been toughed. Bearings looked fin. So there was never an oil pressure issue. That said I put them in. Why take the chance.

One thing I have been reading on is drilling a small hole in the plugs, and a small hole in the cam plate over top of them. This is done to help oil the timing chain and make it last longer. I am thinking about giving it a try, as every small block I have tore done seems to have an over stretched chain. I do not think they get enough oil from the fact. So we will see.
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340's and HP 360's used a double roller timing chain and sprockets. They had one special bolt with a hole drilled through the center to oil the chain. It was on the upper drivers side, if I remember right, of the thrust plate. I have checked 340's, run very hard with over 100k miles that were still within spec for chain stretch. This does not bleed pressure off of the lifter gallery.
 
66fs said:
340's and HP 360's used a double roller timing chain and sprockets. They had one special bolt with a hole drilled through the center to oil the chain. It was on the upper drivers side, if I remember right, of the thrust plate. I have checked 340's, run very hard with over 100k miles that were still within spec for chain stretch. This does not bleed pressure off of the lifter gallery.
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Yea,
All early SB are oiled that way with that bolt. Not sure what year they got rid of that. I know my 71 318 had it. Problem is it just catches a little oil drain back from the lifter valley. It is rather doubtful if much reaches the chain. I believe that is why they went to that little metal tab. To try to get the oil out to the chain.
 
Yes if you drive the galley plug in to far it will restrict or block off oil flow to # 1 main. I have pulled apart several LA engines and some had the plugs and others did not. I always put them in just to be on the safe side. Measure the depth of the # 1 main feed passage from the front face of the block, make sure your plug is a little shy of that measurement , trim if needed on a belt sander ant drive her in flush w the face. That easy, No worries.
 
thanks for the input guys, here in Australia i have now talked to quite a few people and Mopar mechanics who say that they have never seen an LA engine WITH the plugs. And i havn't either. So that's weird. We had 273's early on (from the US), some 340's (numbering only about 345 from the US) and mostly 318's and 360's. Many of our blocks came from Canada, South Africa and Mexico and assembly was done here.

I emailed Rick Ehrenberg from Mopar Action magazine about them, he reckoned that the plugs were a late addition only (late 318 and 360), kind of an insurance. But he didn't specify anything else, and i wouldn't take this view as gospel.

Swinger 340, i sort of did what you said, well actually after i drove the plugs in, i then went and checked another block to measure the distance from the front face to the beginning of the oil feed holes. Then measured the depth of the core plugs (including the thickness of the metal) and luckily they will not interfere. But just to be sure, i will use an oil priming rod in the oil pump on the end of a drill through the distributor hole and with the lifters out, i can see if oil is being fed well into the galleries at the front.

As for the timing chain oiling, i wasn't sure which came first, the hole in the bolt method or the tin hat dripper. I have used both in my engine build, can't hurt. There is usually quite a bit of oil in the valley so there should be always plenty oozing out through that bolt. Also, i thought that the lower part of the TC was close or even in, the oil in the pan, especially in street driving when its sloshing around forward and back so i didn't think the chain had too much problems with oil. However if you were sitting at a steady speed for hours at a time and say the oil pan level was a little low, then i could see how the TC might benefit from extra oil. Would better oiling prevent chain stretch though? Maybe if the stretch was a result of wear in the pins rather than the metal itself getting stretched.
 
My 273 had those little plugs in, and I know the motor had never been apart previously. Also, this engine does not have a "holey" bolt, but it does have the oil slinger on the crank snout for chain oiling.
 
65Val said:
My 273 had those little plugs in, and I know the motor had never been apart previously. Also, this engine does not have a "holey" bolt, but it does have the oil slinger on the crank snout for chain oiling.
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I've never seen plugs in any unmolested early, 64-73, small block, and I've done too many to count... Someone may have added them during a timing chain swap? But as we all know, anything is possible...
 
66fs said:
I've never seen plugs in any unmolested early, 64-73, small block, and I've done too many to count... Smeone may have added them during a timing chain swap? But as we all know, anything is possible...
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Nope...still had the nylon timing gear in it. Wish I had taken a pic before I sent the block to my machinist.
 
THOSE PLUGS ARE FOR ROCKER SHAFTS. NO PLUGS BEHIND THUST PLATE.Some thust plates have a 1/16 hole drilled in for timing chain oiling others have a hole drilled in 1 of the cam plate bolts. Had small block mopars for 42years.
 
The original unmolested numbers matching 318 in my 71 Dart didn't have any plugs behind the thrust plate. I put it back together that way. Carried 70lbs oil pressure cold and 35lbs warm at idle for the 3 yrs I ran it till the day I sold the car.
 
I have had them for 40 yrs..and all mind have had plugs in them...and i put plugs back in them....

so it is your choice to plug or not to plug..
 
sleepyhead416 said:
THOSE PLUGS ARE FOR ROCKER SHAFTS. NO PLUGS BEHIND THUST PLATE.
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...then why is there only 2 in a freeze plug kit?? If for the rocker shafts, wouldn't you need 4?

This is what mine looked like upon disassembly (not quite as clean, though). It is the original, numbers, never been apart before( according the orig. owner) 273 2 bbl engine. Also had the orig. nylon timing gear and s-t-r-e-t-c-h-e-d timing chain to prove it.

camthrustplate001-1.jpg
 
70aarcuda said:
I have had them for 40 yrs..and all mind have had plugs in them...and i put plugs back in them....

so it is your choice to plug or not to plug..
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Could it be an assembly plant issue...some did and some didn't???...or, 273's did and 318's etc. didn't???? (shrug)
 
I've been told, FWIW, that not all thrust plates are machined on the back side... As I said, FWIW... A friend with a lot more experience than I said the plugs were for the non machined thrust plate.
I've only had a couple of 'em apart, and seen with and without, and no I haven't seen the un-machined thrust plate.
That and $2 will get ya a large coffee...
 
the 2 on the rear are threaded pipe plugs thats why there is only 2 in the kit.
 
65Val said:
Nope...still had the nylon timing gear in it. Wish I had taken a pic before I sent the block to my machinist.
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I've seen people replace the worthless nylon toothed timing gear with another worthless nylon gear, on a 70's Chevy LT1 no less. I will never be convinced they are facory. Chrysler did not use plated plugs. Who knows, the Factory had fixes for certain problems. Maybe that would explain your plugs. That being said, it is a small matter and does not really matter. I see no harm in using them, extra Insurance. I personally do not use the plugs.
 
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