Bast*** "Machine Shops/Engine Rebuilders" !

Back in the 1970's I trusted a machine shop to do some decent work for me on small block Mopars in Salinas, California. In 2005, I returned to the same shop to drop off a 318 for a stock rebuild.

This week I find the timing cover is pitting, resulting in a coolant leak around the water pump bolt that secures the belt-adjusting-brace for the alternator. When I removed the timing cover, I noticed the timing chain did even look damp with any oil (photo #1).

So I rotate the crank to line up a see thru spot in the camshaft gear to inspect the thrust plate bolts. What do I find? The lower bolt on the driver's side missing. The upper bolt on the passenger side without an oil hole evident (photos #2 & #3).

So I pull out parts from a 340 I dis-assembled a couple of years ago and I found the thrust plate and thrust plate fasteners in a plastic sandwich bag. Not sure, but the one bolt with a drilled hole doesn't look factory to me. The head is flat and shiny (photo #4; I am sure it works just the same).

So it's off the the fabricator to drill another bolt for the 318 (5/16"-18 per FSM). Just upsets me that after paying thousands of dollars for a rebuild that I have to back-track and cover all the non-sensical errors.

In a machine shop's defense, so far I can find no mention of the special bolt in the reprint of the "Plymouth 1965 Service Technical Manual" (photo #5). On page 9-40 the manual instructs to place the chain case cover over the locating dowels. Well, I have never found locating dowels there (as far as I can remember). The suggested torque is 15 foot-pounds for the cover and 30 foot-pounds for the water pump. However, on page 2 of the "Tightening Reference" chapter, the chain case cover (cast) torque listing is 30 foot-pounds, not 15 foot-pounds. The thrust plate torque listed is 210 inch-pounds (210 divided by 12 = 17.5 foot lbs).

On page 9-38 they make a big deal about using tool C-3509 on 273/318's after having first removed the oil pump/distributor drive gear. This is supposed to keep the camshaft from contacting the rear welch plug (when installing the timing chain sprockets/tightening the camshaft bolt).

Makes me wonder if the drilled bolt was a later factory change since no mention of it in the FSM. Did the poly 318 use a drilled bolt? Thank you.

I believe the 318 Poly had dowels for the timing chain cover- the '65 FSM would have been referring to that since LA 318s didn't happen until '68.
As far as the bolt with the oil hole, I wouldn't lose too much sleep over it. Even Ma Mopar couldn't decide if it was worthwhile. I've had virgin small blocks apart that used 4 standard bolts, 3 bolts with an oil drip rail and a bent "finger" to go into the fourth hole, or four bolts with one drilled. When using the factory timing chain tensioner (V6) on a small block (which replaces the cam plate), it's only drilled for 3 holes to begin with... My impression? Chrysler saw no difference over the years and eventually phased it out. So, as long as it's apart, put it back together whichever way makes you comfortable and forget about it.

i just tore down a '79 360 and the thrust plate had the three solid bolts you describe and the lower ds bolt is not there, there was also the oil drip plate in the lower bolt.
no bolts with a hole drilled in the..

I have found a few things over the years in Factory Service Manuals that didn't make sense. One is for my 05 Ram SRT front brake calipers. If I remember correctly, it shows something like 245 lb/ft torque. I've never tried that much. Similar bolts in rear show maybe 120 lb/ft.

So, as long as it's apart, put it back together whichever way makes you comfortable and forget about it.

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Exactly.

The early small blocks came with a drilled lower bolt. Later on they went to leaving one lower bolt out and using a drip rail. Either will work when the engine is fresh and the oil stays clean. The drilled bolt can clog on high milers with sludgy oil deposits. That's not as likely to happen with the drip rail system. With today's better oils, either setup should work fine.

The bolt with hole gets oil from the very front corner of the valley, not pressurized, about 3/8ish of an inch below the 1 inch front valleys drain holes.
There's tons of oil in the valley returning from the heads and lifters .
I think the whole bolt with hole etc is related to type of chain, (link/roller) gear type (plastic), that was installed at the factory, - replacement chain/gear type likely changed thru the years, - fasteners didn't . .jmo

My 65 273 Commando had a cam thrust plate and 4 bolts. No drilled hole in the lower bolt and no drip tab. Never seen a Mopar small block with alignment dowels for the front cover either. Did have an oil slinger too. 65'

The LA 318's arrived in 67, I know because my Dad bought a 67 Fury wagon and I was happy to see the LA engine under the hood.

They stopped installing the drilled bolt and left out one bolt. Not sure when this happened but in your case it is correct. Some also had the oil drip tray that guided the oil to drip on the chain. Again, not sure what years used that.