Rebuilding the jeep engine PART FOUR-TIMING!

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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Rebuilding the jeep engine PART FOUR-TIMING!

Post by john barton » Wed Sep 06, 2006 7:19 pm

In a previous part, I mentioned that it was not necessary to know the 4-cycle engine theory to rebuild this engine. It does, however, help a little to understand some of it when dealing with setting up the timing. In a 4 cycle (also called 4 stroke) engine, the usual description of this cycle starts with: the intake, then compression, then power, then exhaust stroke. During these 4 strokes the crankshaft rotates twice.

Turn the crankshaft clockwise, looking from front, (nut on front/or with flywheel bolts) until the front- #1 piston is at the top. #4 (back) is also at the top.
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Both are at the position called TDC- top dead center. You don’t need to worry which stroke is involved at this point. Until the crankshaft and camshaft are in time, just realize that the crankshaft turns twice during the four stroke cycle, and that the camshaft turns once- (half speed).

When the cam gear is installed- temporarily as in one of the pictures below, you can see the relationship. Cam gear is twice as large as crank sprocket. When connected by chain, the crankshaft must turn twice to each cam revolution. This is because while the pistons must go up and down twice (2 crankshaft revolutions) to complete the 4 stroke cycle, the valves must only work once for each cylinder (1 camshaft revolution) during the 4 stroke cycle. I have all the camshaft parts laid out.

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Both types, rope and the newer modern timing cover seal are shown. When the old steel retainer is removed, the asbestos rope seal must be removed. Clean up the surfaces and install new type with seal driver…a large ½ drive socket that fits diameter of seal, also works.

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Note the dots on crankshaft sprocket and on camshaft gear, turn cam gear until they are lined up. Take camshaft gear off, lube camshaft spacer/thrust washer, and put in place behind gear. The holes in front of camshaft are offset- the gear will only fit one way. Slip chain over sprocket, then place chain over cam gear- keeping it in the same position…watch dots and camshaft holes, and wiggle gear until bolt holes line up.

When in time, the timing marks on both gears will be in line.

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Place special washers- have a curved surface that fits in cam gear- and bolts, and torque them to 35lbs. Bend the tab on the washers over.
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Place spring in camshaft hole, then thrust plunger. These provide thrust when cover is installed to hold camshaft in place. Put oil slinger on crankshaft in front of sprocket. Install timing chain cover. This probably wont be coming off, so I do use some sealant.

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I labeled the bolts sizes. 3 are 3/8-24x3/4, the last is 1”- doesn’t specify where the longer one goes, but- two of the top bolts also get a clip- one holds the oil line that feeds the filter, the other holds the steel fuel line going to fuel pump. It may also be for the different front (reinforced) mounting plate? While the other bolts for oil pan are 5/16-18 x11/16, the four across the front are only x1/2”. The parts books are a little confusing concerning oil pan bolts. They list 4 different sizes, but they add up to more than required, and only two sizes have descriptions of where they fit. The short ones in front are so they don’t pierce the timing chain cover. You need to use a little care here with gaskets. The oil pan gasket is already in place, when you put timing chain cover on- make sure you don’t push pan gasket out of place. No pulley guard for now

I put the flywheel on now because it helps visualize timing with the markings. Put back engine plate in place. Two bolts thru the flanges will hold the plate temporarily. Bolt up flywheel. Two of the bolts are dowels or shouldered. Make sure timing marks are visible in timing hole. It will go on in two positions-correct and 180 degrees out. Torque to 40lbs.

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Now that everything is hooked up, you can see the valve timing relationship. Turn the engine clockwise (viewed from front again). As #1 travels down, notice that the intake valve opens. #1 is on the intake stroke. Watches #4, as it travels down, both valves are closed. #4 is on the power stroke. Ignition has just fired in #4. It actually occurs just before TDC- takes a few milliseconds for explosion of fuel-air mixture, and for the power to develop that pushes piston down.

This may be a little confusing, because most manuals, etc. deal with #1 when setting ignition timing and installing oil pump. However, we have just set the crank-cam timing and #4 is on ignition? Easy to fix…!

Before that, set the valve clearance. If you turn crankshaft another half turn again, when #1 starts up, it is on compression. When it reaches TDC again, both valves are closed. This is when valves for that piston are adjusted (when each piston is TDC for ignition). The tappet is not on a cam lobe, and valve is held closed by a spring. Adjust clearance using two ½ inch open-end wrenches. Special thin tappet wrenches are available, but not absolutely required. The clearance on chain drive engines is adjusted to .014 or 14 thousandths. You need a set of feeler gauges that has a .014 piece. Since the tappets and stems have been ground, you may need to play with adjustment to get them close. Hold the tappet with one wrench on the flats. The adjuster is like a regular bolt. Turn right (clockwise /in) to turn it down into tappet, which opens/increases clearance. Turn left (counterclockwise/out) to close/decrease clearance. Valve clearance is important. Too much and engine will clatter as tappet hits bottom of valve stem. Too little and valves will open too soon.
It usually takes a few times to get exact adjustment. You adjust, try feeler, adjust, try feeler again, etc. The clearance is ok when gauge slides with a little resistance.

Image

In the picture, you can see that I hold two wrenches in one hand, hold feeler with other. After major adjustments get the clearance close, by changing which wrench is on top, I can increase or decrease clearance by squeezing wrenches together. I adjust to a loose .014, then make final closing while sliding feeler gauge between tappet and valve.

The firing order is 1 3 4 2. Turn crank half turn again until #3 is coming up to TDC, both valves closed, … adjust them. Same for 4 and 2- half turn, adjust. Try to get clearance exact now. Normally, you will need to adjust again after engine is run in a few hundred miles. But, sometimes it is not necessary.

After #2 is adjusted, another half turn should put you back at TDC for #1 with ignition. This is where you need to be for final steps. If not sure, turn crankshaft until you have seen all the strokes:
Piston going down with intake open- INTAKE
Piston coming up with both closed-COMPRESSION
Piston going down with both closed- POWER
Piston coming up with exhaust open- EXHAUST

You want #1 at TDC, both valves closed, at ignition. This is important because oil pump and distributor must be installed in time to crankshaft and camshaft. You can actually install oil pump in any position, install distributor, and wire from wherever the rotor points, to spark plugs, in firing order. But, for the sake of future jeepers and our kids…. lets try to make all jeeps match the books!

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Note how in TM9-803, the #1 spark plug wire is always at 5 to 5:30 clock position, looking down on distributor. OK, for the second photo- you have to turn it upside down and imagine looking at the distributor on the right
side of the block! Strange- manuals refer to engine sides as if you are sitting in jeep- but describe rotation as your looking at front of engine!

This question has come up on G503 many times. When the oil pump is removed, it must be re-installed in time! If you have seen these discussions, there is always a question about finding TDC for #1 at ignition. You can’t trust the flywheel, whistle devices, thumb in #1 spark hole, etc. With head or valve cover off, you should be able to see and establish #1 TDC exactly.

When oil pump is installed, the drive gear engages with the gear on cam. When the gears engage, oil pump turns- The top of gear has an offset slot.

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So, you need to turn it back, engage gears, with slot winding up in correct timing position. The bottom of distributor shaft has corresponding key, with offset, that fits into slot. The oil pump drives the distributor. Look down through distributor shaft, slide oil pump part way onto mounting studs. With long screwdriver turn oil pump gear so slot points to 9:30 clock position with fat part on top. When oil pump is pushed to final position, the gears engage, and it should turn to 11/11:30 with fat part still on top.

Put one nut on to hold oil pump in position. Install distributor, you need to wiggle it to get key into slot (remove anti rattle spring for this part). If oil pump timing is correct, the rotor on distributor, will point to 5/5:30. Because of offset, it will only engage in one position. If not correct…drop oil pump and adjust gear position accordingly. Try distributor again until rotor winds up pointing to 5/5:30.

Crank, cam, oil pump, and distributor are now all in time! You can wire spark plugs just as shown. As I mentioned above, you can install oil pump and distributor in any position and wire spark plugs from wherever rotor points. Just go around distributor cap counterclockwise in firing order. But all manuals show #1 firing position as 5/5:30, so we should do it for uniformity.

I’m not making final distributor installation now because of painting etc. When you do install distributor, turn body so coil-wiring terminal is near 11 o’clock. If you haven’t turned engine…rotor will still be pointing to #1. With ignition mark on flywheel lined up with marks on cover,turn body clockwise until points just open. Tighten distributor clamp- should be close enough to get engine started…!

In the final post, I’m going to show all rest of the bolts and plugs, etc. As I mentioned, this engine is replacing a MB motor in a GPW. For this post. this will essentially be a short block with remaining parts coming from other motor.

No one has posted their methods….come on!
John
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Post by tsmgguy » Wed Sep 06, 2006 8:15 pm

Just superb, John, Thanks! Much appreciated.

With your engine already assembled, it is easy to tell when #1 is at TDC with both valves closed as you can slide the feeler guage between both #1 intake and exhaust tappets and lifters. Put another way, the lifters are exerting no pressure on the tappets with the engine cold and both valves of any particular cylinder closed. This would not be the case with #4. This is your tip off.

Thanks again; this one is a keeper!

Howard
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Post by john barton » Wed Sep 06, 2006 8:45 pm

Thanks Howard...good point..
I have been trying to make these posts shorter than longer...I keep whittling them down. Thats why more scans than photo's- download easier. Also shows why people need to have original manuals, Look at details you get from pictures..what rubber wire covers looked like, coil ground strap, 90 degree resistor/connector in coil wire, etc.
I wanted to include section on how to install oil pump on engine in jeep...also had a section about gear drive camshafts..
for the record...it is exactly the same...! cam turns opposite direction..
but oil pump and distributor go same direction as this engine...everything is the same..
But!!...there were no gear drive engines in WWII...so it technically goes on cj forum..
But, thank you for another way to do it...when valve cover is off ...I just watch valves while turning...
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Post by Baz Ford » Wed Sep 06, 2006 9:27 pm

John,

You may cover this on your next post, but after setting up timing as you advise, I always paint a white line on the crank pulley and a matching line on the timing case, to make use of a timing light dead eassy.

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Post by Derek Eddlestone » Wed Sep 06, 2006 11:14 pm

John,

I've rebuilt a few of these and I enjoy reading about other peoples work.
Put oil slinger on crankshaft in front of sprocket.
Is it worth noting that the slinger goes on the crankshaft exactly as you have laid it out in your photo. I've found them fitted both ways in equal numbers and if there are two ways to fit something........... :roll:
One thing I do in a slightly different order to you is adjusting the valves. I fit the cam and the valves, then after fitting the crank, I'll rig up the timing chain so that I can set the tappet gaps without having to overcome the drag of the pistons as I spin the engine over. It's probably overkill but I use a dial gauge and the 'rule of 9' to set up the gaps. I also set them at a 'tight .013/loose .012 which seems to make the valve train quieter. Before the howls of anguish rise, can I say that I've done this for many many years and many tens of thousands of miles and it does no harm at all. I just have a dislike of tappet rattle. I have an engine in for rebuild at the moment and I'm going to use your method of setting the tappet gaps at TDC because it sounds more efficient than my way.
Thanks for your post John and I'm looking forward to the next section.

Derek.


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Post by Fred » Sat Nov 04, 2006 4:12 am

Hi

Be carrefull with the valves setting, if you set them too tight as you do, because you know better than the engine designer, you will get a quiter valve train but they won't close properly and finally burn.

Cheers
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Post by Derek Eddlestone » Sat Nov 04, 2006 7:09 am

Fred wrote:Hi

Be carrefull with the valves setting, if you set them too tight as you do, because you know better than the engine designer, you will get a quiter valve train but they won't close properly and finally burn.

Cheers
Fred,

I understand your concern but I've been doing this for many years now and have covered tens of thousands of miles without an adverse effect on either of my engines. At one time I used to lift the head off to check the seats for signs of burning but stopped after there was never any change. I looked for seat recession by reularly checking the tappet gaps. I'm simply stating what I have done and not suggesting that anyone else does the same. The engineers at the time were dealing with the metallurgy, fuel and oil technology that was available in the 1930s and I'm taking the gamble that things have improved since then.

Derek.

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Post by Lou L » Thu Aug 30, 2007 6:18 pm

Hi John,

I see in the TM that they list a felt washer behind the oil slinger on the crankshaft. I pulled my timing cover to change that seal and see that I did not have one. Is this necessary ?


Lou

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Post by Harold » Mon Nov 19, 2007 11:35 am

Great write up!!!

One thing I have had trouble understanding is valve adjustment. The manual says to adjust the valves on the heel of the lobe--I take it this means the bottom of the lobe. Finding this is not easy---TDC doesn't seem to be at the heel of the lobe---I have adjusted my valves at TDC but had a presitant taping. Finialy, I put a feeler gage in the gap and followed it down--tighten the gap up as it got wider and as soon as it tighten up--backed off and set the gap exact. VERY time consuming, but I have stop the valve noise and my jeep runs better than it ever has, smoother, quiter and has a lot more power.

Most likely, this is not the correct way of adjusting the valves---what I want to know is---just where on the cam lobe do we want to adjust the valves?? Everyone seems to do it differantly---how close is close enough---comments?
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Post by john barton » Mon Nov 19, 2007 12:56 pm

the heel of the lobe is the round part
the toe is the sharp part...
you adjust both valves for that cylinder when it is TDC for compression
both valves are closed...held down by spring..
remember it can also be TDC for exhaust...that valve will be open..

that is why I do it in sequence...firing order...
when doing it with engine in jeep...can't really see cam...but you don't need to
adjust it while assembling....readjust after a few huindred miles..
but assemble correctly and you can use flywheel and distributor
to make sure you're on TDC compression or firing for that cylinder

there is a chart...when you are at TDC #1 ..it shows all the other valves that are closed....goes on to #2 etc...
I just prefer doing it in sequence...can check, turn, check, etc..

correct adjustment is important so ramp of cam lobe pushes/hits
tappet smoothly...too much gap...slams into tappet and valve doesn't open in time...too little gap and valve works before it should..

John
Last edited by john barton on Mon Nov 19, 2007 5:22 pm, edited 1 time in total.
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Post by petesilfven » Mon Nov 19, 2007 3:40 pm

A method I learned a long time ago while working with high performance motorcycles using cams with long quieting ramps was to adjust the valves as folows.

1. Adjust the exhaust valve when the intake valve has just closed completely.

2. Adjust the intake valve when the exhaust valve has just started to open.

This procedure puts the tappet of the valve being adjusted on the heel of the cam lobe.
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Re: Rebuilding the jeep engine PART FOUR-TIMING!

Post by Daveyk01 » Wed Nov 21, 2007 10:10 am

John, as the obvoius expert <g>, I have a question. I followed your instruction for setting the oil pump and distributor on my flat head 134 (actually out of a CJ3A - I think). With my rotar at 5:30 (oil pump slot at 11 with offset to left (fat part on top), the GAP is wide open.

Isn't that the oposit as it should be?

Since my timing it most likely gear drive, does that change the procedure?
Dave


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Post by john barton » Wed Nov 21, 2007 11:29 am

Hi..no you are correct....just need a little adjustment

same procedure for chain and gear..

go back and read last 3 paragraph's
you need to turn distributor body...that is the final adjustment..
put ign mark on flywheel in line with marks on rear engine cover...timing hole

now visualize rotor turning counter clockwise...turn distributor housing so points are just opening...
tighten housing...that will be close enough to start...
there are ways to do it with mutli meter or simple light circuit, etc...but that is too much!!..

after it is running, warm, rpms adjusted...then do final timing with timing light or vacuum gauge..
not an expert...just a lot of jeeps!!
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Post by Daveyk01 » Wed Nov 21, 2007 12:46 pm

john barton wrote:Hi..no you are correct....just need a little adjustment

same procedure for chain and gear..

go back and read last 3 paragraph's
you need to turn distributor body...that is the final adjustment..
put ign mark on flywheel in line with marks on rear engine cover...timing hole

now visualize rotor turning counter clockwise...turn distributor housing so points are just opening...
tighten housing...that will be close enough to start...
there are ways to do it with mutli meter or simple light circuit, etc...but that is too much!!..

after it is running, warm, rpms adjusted...then do final timing with timing light or vacuum gauge..
not an expert...just a lot of jeeps!!
john
Thank you I feel a little better now. Boy changing a dang oil pump is a lot more complex than I thought <grin>.

I used a condom on a hose push down in plug #1 to find TDC for cylendar #1 TDC. The condom/balloon trick seemed to work well.

Following your instructions exactly (I have an IAD distributor) puts my rotor right at 5:00 and looks like it would be making contact with the #1 plug terminal on the distributor cap. At this point, the points look wide open. If I turn the distributor so that they are just opening, to me, it looks like the rotor is directly in-between the #1 & #4 plug wires or #1 and #3? One or the other.

Do I need to put white paint on the crank case wheel and timing geer cover in order to use a timing light that I don't have? That way if I ever get one.... For now I may plan on spinning the distributor until is sounds good and doesn't hesitate on gunning the excelleration?

BTW, I have the 5 degree mark centered the best I can in the timing window using a mirror. The mark on the engine houseing seems long gone. I'll look again.
Dave


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Post by Daveyk01 » Wed Nov 21, 2007 1:18 pm

john barton wrote:Hi..no you are correct....just need a little adjustment

same procedure for chain and gear..

go back and read last 3 paragraph's
you need to turn distributor body...that is the final adjustment..
put ign mark on flywheel in line with marks on rear engine cover...timing hole

now visualize rotor turning counter clockwise...turn distributor housing so points are just opening...
tighten housing...that will be close enough to start...
there are ways to do it with mutli meter or simple light circuit, etc...but that is too much!!..



after it is running, warm, rpms adjusted...then do final timing with timing light or vacuum gauge..
not an expert...just a lot of jeeps!!
john

Okay another question:
If I turn the distributor so the points just open, the rotor stays at 5 oclock, that puts the #1 plug wire below the rotor at 6pm? I thought the rotor turned CCW during engine operation. Doesn't that put the #4 plug to fire? If it turns CW then we are okay?

Does the spark fire when the contact closes or when it opens?

"Turn it CW until the points just start to open. "

What if they are open already, then I guess CCW until they just close and the CW a tad to leave them just open.
Dave


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