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1969 R685 engine ID for cam replacment


AMGeneral
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Hello fellows,

I have posted here before, I now am running into a problem with my 69 R685,

Last week while hauling stone for a local job, I noticed a noise from the RH side of the engine, not really a knock, but a rythymic high pitched tapping. Upon getting home I pulled the valve covers to find #3 and #5 intake valves with about 1/4 inch lash.  

I pulled the rockers and checked the push tubes for bending or deforming, all good, It seem to me I am gonna be replacing the cam and tappets now.  

 

 I am fairly sure this is not the factory engine for this truck as I believe the  Tip turbine aftercooler did not come out till 73?

My problem is that at some point it has had a Mack reman engine installed before I ended up with it, and there is no serial number stamped anywhere on the front cover or behind the injection pump, or anywhere on the engine for that matter.

I am wondering now whether I need to order parts for an EM6, T675 or T676 engine.

 

Pics attached

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If the block is out of a cabover the number is clear on the back of block, right below where block and head meet, will be hard to see in a r model, have use a mirror maybe, a reman mack engine should have a tag on it, maybe torn off.  looks like a T676, but cam and lifters might be the same on a 675 and 676 engine.    terry:MackLogo:

Edited by terry
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30 minutes ago, terry said:

If the block is out of a cabover the number is clear on the back of block, right below where block and head meet, will be hard to see in a r model, have use a mirror maybe, a reman mack engine should have a tag on it, maybe torn off.  looks like a T676, but cam and lifters might be the same on a 675 and 676 engine.    terry:MackLogo:

Thanks Terry, I will check there,

Would a factory New short block be stamped with a serial number? I have noticed that the bell housing and injection pump drive are still painted the gold color the Maixdynes were painted from the factory but the engine itself is Mack gray.

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On 7/7/2020 at 9:27 AM, j hancock said:

The AMBAC pump number 313GC5126P2 was used on the ENDT676 285 HP engine. 

 

 

Thanks Mr. Hancock, Than information confirms my suspicion on this truck, The Mack museum and my local dealership state that this truck was built with a ENDT 675/ 237 Mack engine.  I am guessing it had a ENDT676/285 swapped in sometime before I got it.

 

At any rate, I cannot find any numbers stamped on the block or front cover anywhere, so I have no clue on the serial # for this engine.

My suspicions were confirmed though, after pulling the oil pan this morning  I could clearly see that #3 intake valve cam lobe and tappet have some serious damage, I got most of the engine torn down today and will hopefully get the cam and tappets ordered tomorrow.

Edited by AMGeneral
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My 4 valve 350 did exactly same thing as yours. Are you able to find a cam and lifters I ended up getting a used cam and lucky enough to find new  lifters locally. I have a extra set  of lifters if you can't find any

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I talked to one of the fellows at Watts Mack, The cam is no longer available, the tappets are possibly, but  both were available aftermarket, all total for cam, 12 tappets, upper and lower gasket kits and a new rubber insert for the front motor mount is roughly $3500 with tax and shipping.

My oil pump holds a steady 25 psi at idle hot and 50 to 60 above 1600 RPM, both verified with a mechanical gauge, I may go ahead and replace the relief valve and spring in the pump while I am in there.

Edited by AMGeneral
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On 7/10/2020 at 10:21 AM, fjh said:

new style lifters are of  better design the original lifter had the hard surface silver soldered on the new style seem to be one piece these never or rarely fail !

I hope so, I really don't want to have to upgrade to a newer truck, I talked to one of the guys at Watts, PAI produced parts are no longer available, they are checking other aftermarket sources for cam and tappets.

 

I know the cam is available through Federal Mogul, but the tappets may be the problem.

Edited by AMGeneral
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  • 2 weeks later...

We have replaced several cams on those motors over the years, it pays to have a fleet of trucks, on road and retired, all with the same engine.  Not sure if the cams are different between a 237 and 283, we haven't needed to scavenge our retired 237s yet for motor parts.  I'm vaguely aware there's a couple different head bolt differences, not sure beyond that!

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  • 2 weeks later...

Sorry it took me so long to update this thread, It's been busy here,

Long story short, I actually ended up sourcing a New camshaft and 12 new tappets from Capitol Reman in CO, they stated that PAI in GA still produced the parts, part # PAI272949 or ECM-9002 for the cam and EML-8583 for the tappets.

I did measure all the surfaces before installation and noticed that all cam lobes had at least .015 wear on them when compared to the new one.

I got a new upper and lower gasket kit from my local Mack dealer as well as the 2 rubber inserts for the front engine mount.

I did inspect and clean my oil pump and found several metal shavings that were not allowing the relief valve to move at all, after assembly and cam break in time  I now have 45 to 55 psi oil press at idle hot and 85 to 90 psi hot at 1600+ rpm w/ 15w40 Rotella oil. It barely made 20 psi at idle before the repair.

It runs sweet and smooth ,I guess it's ready for another 20+ years!!

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