JD camshaft overlap

Shortrun · Nov 27, 2019

Hi. I am working on a JD 5030t, 5 cyl powertech engine. I want to know the valve overlap spec for the cam.
Or just in general what the overlap is for a diesel engine.
Any help would be great.
Thanks.

MikeJM · Nov 28, 2019

That s tough to measure and compare. Most of the time cams are compared at .050" lift number. But more often than not they do not publish that information.

The stock ones I ve measured had no overlap at .050" the Ford 456 cam had around 16 degrees of gap. The 466 Deere had around 24 degrees of gap at .050".

My old ford manual indicates 17 degrees of overlap, but has not specs on lift.

My performance cams have around 12 degrees of overlap at .050" thousandths.

Shortrun · Nov 28, 2019

Thanks Mike
Good information.
I think that 0.050 is measured at the valve stem. And the degrees are crankshaft degrees and not camshaft. Is that correct?

Also i have seen just about all the cams i can find info on (cars motors) are about 55% on the before TDC and 45% after TDC. So for example intake
opens at 15 degrees BTDC and exhaust closes at 10 ATDC. Is this the normal?

I appreciate the help.

VicS · Nov 29, 2019

Think the .050 is measured at the lifter

Shortrun · Nov 29, 2019

Thanks Vics
Nice picture. The small engine world is very different from the tractor / diesel one. Great learning experience for us.

MikeJM · Nov 29, 2019

Yes, the .050" is measured at the cam tappet. And it s measured in crankshaft degrees with reference to TDC or BDC so finding TDC accurately is critical.

Intake center line falls in around 99 to 107 on most everything I ve measured and setup.

What are you doing with that hideous engine? That thing looks like a bear to work on.

Some cam numbers:
Deere 466 @ .050"

Intake opens 12 B TDC
Intake closes 22 A BDC
Exhaust opens 13 A TDC
Exhaust closes 16 B BDC

Ford 456 @ .050"

Intake opens 7 B TDC
Intake closes 20 A BDC
Exhaust opens 10 A TDC
Exhaust closes 27 B BDC

Ford 5000 from ford service manual, no spec on lift.

Intake opens 10 B TDC
Intake closes 34 A BDC
Exhaust opens 37 B TDC
Exhaust closes 7 A BDC

VicS · Nov 29, 2019

I'll try for my cam card.

Shortrun · Nov 30, 2019

Thanks. I sent Vogel a note.
But with all the good information i have recieved here i am starting to get a pretty good idea of what my cam is. Plus i have been trying to make my own measurements.

VicS · Nov 30, 2019

As you can see I just took a picture of a degree wheel then my grandson blew it up to size on our printer and glued it to a piece of cardboard. Vogel must have compensated for worn gears because all figures were right on.hope it workes for you.
Hi

Shortrun · Nov 30, 2019

I stole your method.

535353m · Nov 30, 2019

I am sure that one grind is not a fit for all,different strokes,types,sizes and much more,head flow,card or injected,high rpms,low torque,how do we know what we need to be as good as it gets ??????

MikeJM · Dec 1, 2019

You are correct, not one grind fits all applications. But the cam events must happen at a certain point for an engine to run. Plus low speed applications tend to have conservative cams in terms of duration and overlap.

The trouble with the engine shortrun is working on is it has no timing marks or key on the cam. The injection pump lobs are on the cam as well with unit pumps for each cylinder. The timing procedure involves special tools to lock the cam at a certain timing position.

Shortrun, if you could determine port closure on the #1 pump in relation to the intake centerline for the same cylinder then you could set the injection pump timing at say 14ish degrees BTDC and see where the intake centerline falls and see if it makes sense. The pump timing will have far more effect on how that engine runs than the other events.

Shortrun · Dec 1, 2019

Yes, if i could find a way to see when the injector for cyliner one is triggering. Or pump closure. That would be the best.

Since i know so little about diesels i dont know if this is possible. On an engine that is all apart like mine is now. Can i supply fuel to the injector pump
at about 60 psi. Then slowly turn the camshaft by hand. A wait for the spray of fuel coming out the (now removed) glow plug hole? I really have no
clue.

But if i can this would be better than using the valve locations to time the cam.

I dont know what "intake center line" is?

Shortrun · Dec 1, 2019

535
I agree. If i had actual information on my cam i would not be guessing. Just doing the best i can with what i have.

MikeJM · Dec 1, 2019

Intake centerline is the relation of the camshaft intake lobe center and the crankshaft measured in degrees after TDC.

60 psi won t open an injector, they pop open above 3,000 psi usually.

But 60 psi supplied to the pumps with the injector line disconnected should indicate when the pump begins it s injection event. This is known as the spill port method. You can do a search about it, lots of information and videos on it. Depending on the delivery valve spring in the unit it may or may not flow fuel with 60 psi applied, also, make sure the fuel rack is set to run when you try this. It should get you heading further in the right direction.

Shortrun · Dec 1, 2019

Ok on the cener line.
I will reasearch spill port. I had actaully read that but did not understand. I do now, so i will check if this will work for me.
If it does this will be more accuate timing for my camshaft.
I read many engine inject close to 14 BTDC, as you mentioned. Is that a number i can assume is right (close) or are there some
John Deere that are far from that?
I guess the range is 10 to 20 degrees BTDC, outside of that the engine will not run.

MikeJM · Dec 1, 2019

Different engines run best at different pump timing. Some like more timing than others. For performance and emissions it s probably around 14 degrees. It will likely run best from 10-20, but most engines will run from 40 degrees BTDC to 10 degrees ATDC. I ve even seen engines run 180 degrees out, not well, but run. You situation is more complicated because the intake and exhaust are also tied in and too far off and stuff starts hitting pistons and valves.

Shortrun · Dec 1, 2019

Thanks. Part of the cam i will check is to measure the exhaust valve to piston clearance as the piston approaches TDC on the exhaust stroke. If this is
good it will be a good indication the timing is close.

Shortrun · Dec 27, 2019

I like to finish a thread when i can. And not leave folks hanging when they read through in the future.
In the end the motor starts an runs pretty good. I used all the information i got here, and really appreciate those who took time to help me.
I ended up watching the intake and exhaust valves overlap. Then took the center point of those 2 positions. Next i took that cam center point and placed it about 3 deegrees before top dead center on the crankshaft. ( i wanted to be sure i was advaned and not retarded) locked the cam shaft gear to the camshaft. (Just tightened the big bolt holding the two)
I didnt have any problems getting some oil pressure. Also no problems bleeding the fuel / injectors.

VicS · Dec 28, 2019

Appreciate the results. Thanks

showcrop · Dec 28, 2019

Interesting, Thanks

buickanddeere · Jan 9, 2020

Rather limited on lift and duration as the valves have to be closed when the piston is a TDC.
Unless valve reliefs are cut into the pistons at the expense of compression.

JD camshaft overlap

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