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millco

Help! How do you do an 'OverHead'?

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Okay,

We are learning how to do overheads on different engines. For most types it is pretty straight forward. The ones I'm having trouble understanding are where you bar the engine over with the accessory drive pulley to a mark (A, or B, or C) that is equally spaced 1/3 of the way around the pulley. I am having trouble understanding the manual in how you know where you are when you come up on a mark. I will re-read the manual today and see if I can't watch the valves as I bar it over to see where it is.

I just thought I would ask in case any of you had a better idea of how to explain it. Sometimes the book and or the instructor just can't get through my thick head to get me to understand.......

:coal

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sounds like you are learning the good ole 855 cummins, IIRC all it is is that when you come up on A two of the cylinders are at a position where the cam is on the base circle for the valves and the injector at the same time, I don't remember which cylinders correspond to which letter, I think it was A=1+6 B=2+5 C=3+4

so on A 1 and 6 are all on the base circle of the cam so you can set the lash for the valves and injector.

on B the same for 2 and 5

on C the same for 3 and 4

IIRC I set mine for .015" intake and .030" on the exhaust and set the injectors at 72 in/lbs for the non top-stop and 74in/lbs for the top-stop style.

I know that's not the recommended way to do the injectors but it does work rather well and at the time I couldn't afford a dial-indicator

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sounds like you are learning the good ole 855 cummins, IIRC all it is is that when you come up on A two of the cylinders are at a position where the cam is on the base circle for the valves and the injector at the same time, I don't remember which cylinders correspond to which letter, I think it was A=1+6 B=2+5 C=3+4

so on A 1 and 6 are all on the base circle of the cam so you can set the lash for the valves and injector.

on B the same for 2 and 5

on C the same for 3 and 4

IIRC I set mine for .015" intake and .030" on the exhaust and set the injectors at 72 in/lbs for the non top-stop and 74in/lbs for the top-stop style.

I know that's not the recommended way to do the injectors but it does work rather well and at the time I couldn't afford a dial-indicator

GOD I HATE THOSE!!!!! Our bigger tractors have a 855 cummings..lol

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Steve, don't say that; you'll give me a pre-disposition!.......lol

I later realized I forgot to mention it is a L10. I think it is the same thing....

I think what you described is how to do it. I think to tell if you are a turn off you would just 'feel' the valves to make sure they are closed and that you can adjust them.

The book we have for a N14 says to not go over 25 in lbs so you don't damage the injector..... I don't know what all that is about.....

(I better read the book today.... Wish we had the one for this engine....)

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I think you were lucky if that is all you 'bent'!

From what I can tell, these are a bit hard to work on or at the very least a guy better follow the book to the letter!

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IIRC that is one way of doing it, I think there is another method. I haven't been on the 855, We just did the N14, and the jakes on it. and it was the same way. But you had to set it over 2 revolutions of the crank.

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Yeah, what he said!

I don't know what was going on that first day when we were looking at the book.... We neither one were seeing straight I guess. The next day after posting this question we looked at it again and it made perfect sense.

You bar it over to one position on the accessory drive pulley (A or B or C). We got lucky and when we came around to A it was ready for #1 to be adjusted (Top of the chart in the book!) Then you just bar it over to B and do the next cylinder that is ready, I think it is #5. I didn't memorize the 'chart', so I was just going off of firing order. I will have to check the chart and see if that is right. It seems like it should work......

You can only do one cylinder at a time since one will be in firing position and the running mate will be starting intake stroke. Next time you come around to A you would be able to do #6.......... Hopefully that makes sense.

After learning this we went over to a 900MBE Mercedes. That was a little un-nerving as the book doesn't talk about any timing mark. We couldn't find a mark anywhere. You bar it over and look for over lap in the valves (Exhaust closing and Intake opening). Stop when you get it and then adjust the running mates valves.

It is amazing how many different ideas there are out there and how many differnent ways they made engines! Pretty wild really......

I guess I'm gonna have to learn how to read and then be able to follow manuals at this rate........LOL

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deutz engines are the same way, when #1 overlaps you set intake and exhaust on #4, intake on #3 and exhaust on #2

when #4 overlaps you set intake and exhaust on #1, intake on #2, and exhaust on #3, then to make it fun the engineers decided that #1 is the rear cylinder...

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