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Discussion Starter #1 (Edited)
1972SL350 has started the reassembly.

Does anyone really replace the lower rails/guides?

Will reinstall the cams and sprockets to assure that rotating the crank will not screw timing.

Then will replace the guides and rails.

Basically treat the cam replacement and the rail/guide/tensioner replacement at separate operations.

 

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One of the BW Old Guard/R129, W204 Moderator
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1972SL350 has started the reassembly.

Does anyone really replace the lower rails/guides?
engine in car, forgo replacement. Engine out of car... Replace. Timing Cover is nigh impossible to remove with engine in car, due to the oil pump drive chain...
 

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Good to SE Aaron working on a good car for a change:). I hear stories about some plastic parts, although I can't remember what they are or what they do. How about some pictures of those things when you get to them. Mine is a 73, so the information might be helpful. Good luck!
 

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The '72 and '73 both have metal backed guides. They do not break. Check them for excessive wear. Also check the tensioner rail for excessive wear.

The tensioners wear out. I was surprised how weak both of mine were compared to the new one I bought. Need to submerged it in oil and manually pump it up.

Lower guides showed almost no wear so don't worry about them.
 

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Discussion Starter #8
We have all the parts, including new chain and tensioner. Will skip the lower guides.

BTW, the journals on the new cams mic out virtually identically to the ones that came out.


The '72 and '73 both have metal backed guides. They do not break. Check them for excessive wear. Also check the tensioner rail for excessive wear.

The tensioners wear out. I was surprised how weak both of mine were compared to the new one I bought. Need to submerged it in oil and manually pump it up.

Lower guides showed almost no wear so don't worry about them.
 

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R/C107 Moderator
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If they mic out like that the oiler tubes must have been clear.
 

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^^ which brings us back to the no oil pressure quandary
Indeed.

As for the seeming randomness of the low oil pressure condition, it cant be out of spec clearances etc. I keep coming back to a clogged/blocked pickup tube. Or my other thought(admittedly half baked) is that the tensioner was failing and as it is oil controlled(right?), maybe it was bleeding off the oil and causing a low pressure situation. why that would be effected by simply restarting the car..thats where it starts to not make sense. I will know more after we remove this tensioner and i have a look at the guts.

also shortly after the cams and chain is replaced we will be doing an oil change and poking around, perhaps with a borescope in the oil pan, looking for anything that shouldnt be there.

one thing i noted early on was how grooved the long bent chain rail on the pass. side was i would estimate the grooves to be about 1/8th inch deep.

and the reason the valve covers were ever opened is dad started the car one day and heard a buzzing that he estimated to be at about 100 hertz(hes a speaker guy) he immediately shut the car off.

and the only thing i could see causing that is is the links of the timing chain buzzing on something, tho when i came over and the car was restarted, there was no buzzing.


one question i have is why were the cams in dads motor on the "off" sides of the cam lobes not shiny, or looking like they were in contact with anything

like in this pic. see how the "off side" has no polish, or machined look to it, like it was never moving against a part?



and in this pic, stolen from a timing chain guide i found(and most every other cam iv ever seen) has a nice, machined look all the way around



could this have just been caused by an iffy valve adjustment? or? i cant imagine(doesnt mean its not true) that it left the factory like that.

any thoughts on that?
 

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And these engines are solid lifter. Not hydraulic like a few years later.
 

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Discussion Starter #19
I'm obviously concerned about the oil pressure situation. As I've said before, it happens in maybe one of ten starts. Did not happen until midway through my roadtrip in San Francisco. Has probably not happened in the past 100 starts though. (Not since Cortez, CO in mid-Sept.) It always cleared on restart. I keep hoping it is gone permanently.
 
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