So....you suppose.....

[Not A Duster]

....that 1/2" of end play on the camshaft is a bad thing? :shifty:

 

[restoman]

Nah. It's riding in an IRON block, and besides, that's what shim stock is for.


Your 340?
Do tell.

 

[Not A Duster]

Your 340?
Do tell.

Well first we go back to last July & a thread with almost the same title:

http://www.moparnuts.com/forums/showthread.php?21088-...So-do-yer-suppose....&highlight=

And then finally this weekend I pulled the engine out of the Demon.

It started as a couple hours screwing around removing the timing cover to see if our suspicions regarding the timing sprocket were correct. Turns out they were. the entire front row of teeth (double roller thankfully...) on the camshaft sprocket were sheared completely off, explaining why we found all of it's teeth in the oil pan. But get this: the chain is still tight, still - no good reason as to why it happened in the first place. Or why the oil pressure suddenly dropped to 20 psi on the highway.

So......next I pulled the oil pump out - I'm thinking maybe I can salvage the beast for another summer or two - until I'm feeling a little more comfortable with my job situation to spring for a full rebuild. Turns out the screen in the pickup failed to do it's job, and there is a piece of sprocket tooth jamming the pressure relief valve open in the pump, but no signs of material in the rest of the pump or oil filter. (Which I cut open for inspection.) I guess I know why the oil pressure dropped suddenly. But still no clues as to what happened to the timing chain sprocket. So next I pull the headers, carb & intake - in the process of yanking the intake I am reminded how flaky all of the bolts & holes for the intake, headers and valve covers are - worn, slopped out, helicoiled, oversized, this motor has been in & out of too many cars with too many sledgehammer mechanics doing the work. I decide that if I can save the short block, I'll just temporarily put on the Edelbrock heads I bought for the "new" motor & move them over whenever that engine gets built.

So....off with it's heads.

Yeesh - bad stuff stuff there - too numerous to mention. Valves & seats are are OK, but the guides and seals are fubared and for some reason the heat crossover passage on the passenger side head is full of oil - black skanky oil..... and so on. No matter - nice new heads on the shelf. Anyways - I pop out the lifters, & put them into a nice partitioned box, and decide to spin the cam by hand to see if it binds or does anything bad.

It moves 1/2 - 3/4" to the back. Seems the welch plug at the back of the block has come loose allowing the cam excessive free play. Not enough to leak oil, mind you - it's till there - barely. Guess I know what happened to that sprocket now - if the cam shifted far enough backwards, it would have pulled that top sprocket out of line with the one on the crank...binding the chain at speed. I'm lucky only the front row tore away. At that point I had no choice to yank the engine out of the car completely.

Shit.

I am now contemplating my next move.

-Bruce

 

[restoman]

Crap, that sucks.
Was this engine put in the Demon untouched or was it a rebuild ?

 

[dustergal]

Aw man!
I wish you were closer, I have a nice running 318 you could pop in there until you get something else built.

 

[Stretch]

That is precisely the reason why I always put red lock tight on all freeze plugs. I wouldn’t reuse the lifters or the cam at this point. 3/4 inch of forward and rearward movement surly did damage to the lobs and the lifters. If the engine is out anyway I would take a look at the rods, mains and cam bearings. If something made it to the pop of valve something may have gone through the bearings as well.

 

[Stretch]

Here’s a question. How is it that the cam pushed the frost plug out of the back of the block? The oil pump drive gear is angle cut, as is the cam gear. The cams rotation against the oil pump drive gear should force the cam forward against the thrust plate.

 

[Not A Duster]

Yeah - I've been thinkin' about that very question all day Stretch.....but I'm at wurk now so I can't take a closer look at it until I get home - Best I can remember, there was no visible damage to the oil pump drive gear.

It was the end of a couple long days when I finally encountered this, so attention to details may have been lacking - I do know that it did move - and the welch plug does not look right. It also appears that one of the other freeze plugs back there has been seeping antifreeze as well. Not enough to contaminate the clutch, but enough to leave visible fuzzy material around it.

 

[Dr.Jass]

I wrote a brilliant response to this, and the fucking site ate it.

I'll post it again when I have more energy.

 

[Not A Duster]

Well - that's kinda disapointing.

Been there tho - 1/2 hour typing and *poof*

 

[Dr.Jass]

Yeah, and that's what it was, too... a little over half an hour. Argh!

Now I have to post the fast version, as I'm absolutely exhausted and exasperated for reasons totally not pertaining to the board.

OK, here's the deal: the angle cut that pulls the cam forward against the thrust plate works only when the cam is powering the oil pump--at cruise or acceleration. Under deceleration, that same gearset works to pull the cam backwards against the rear core plug, which in your case apparently has a funny accent since you say it's Welsh. The situation is worse under compression braking, since the crank is really dragging on the camshaft but the load (per RPM) on the oil pump does not change, so that backwards pull is more significant. It would certainly push the core plug out, though.

If you don't see where I'm getting this, I can tell you how to demonstrate it rather easily and quickly with the engine torn that far down.

Long and short of it: Your cam and lifters are junk, just as is your timing set. Other areas I'd check:

• Crank snout where the timing gear resides: If the timing gear's not a snug fit (I mean any wobble at all), the crank is junk. There is not a timing set on the market that corrects for lateral movement of the cam, so that rearward tug could have damaged the crank. This means a new crank, since yours is iron.
• #3 main bearing, on the thrust surfaces: See above... if the cam's been out for a walk, it's dragging the crank with it. Look for abnormal wear on the forward face.
• Lifter bores: Again, if the cam was moving back and forth, the odds are good that the lifters were being dragged around against their will. If they're ovalled your only choice is to either spend a pile having them bushed, or find another block. A lifter in an ovalled bore will not spin, and will wipe the cam in short order. Check to see if the lifters will rock in their bores.
• Pushrod cups/rocker arm cups: Perfectly shiny and hemispherical. If they're not, that would indicate a wandering lifter or lifters. Side loads on the rockers would also be evidenced by uneven valve-tip wear or uneven marking of the rocker shafts. This would explain why the valve seals and guides are junk... but the heads are not likely the problem and new guide liners and seals should make 'em A-OK. However, if they're 587 or later castings, they're not worth the investment.

That's the short version. The long version was so much better, but even this much is beyond the energy I have at the moment... I'm more wiped than your timing set at this point.

I will answer further questions happily.