M1007 - CUCV Suburban Clone Build Thread

Barrman

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Todays Topic is injection pump timing. I have owned a 6.2 or 6.5 for almost 11 years now. I have replaced at least 6 injection pumps on varies engines in the same time span. I have also been looking for an accurate way to set the IP timing after pump replacement or to just baseline a running truck.

That sounds easy and simple to someone who grew up with timing lights and distributors. Except it is really a voodoo black magic hole you fall into with the 6.? engines. First there are different timing definitions.

A gear on the crankshaft turns a timing chain with connects to a gear on the camshaft. Then another gear sits on the camshaft gear which turns the injection pump. All 3 gears have big dots on them that have to be lined up in a specific way during engine assembly or timing chain replacement. Really very simple. But any 6.? internet search pops up an amazing amount of people who can’t play connect the dots and are working on an engine. That is one kind of timing.

Inside the IP are many moving parts. They change relationships with each other inside the IP as fuel pressure and rpm change. Totally different timing but just as important as the dots on the gears if not more so. Also something that 99.99% of the people will never touch and can’t change.

The goal is that fuel will be sprayed into the combustion chamber right at or just a hair before the piston gets to the top of the compression stroke. How do you measure that? Some engine makers make it easy. There are markings on a rotating part of the IP and markings on a rotating part of the engine. Basically another version of connect the dots. Line them up and all is well. The M35 multifuel trucks use this method and I approve.

GM did not do this. They wanted to set the timing of the IP fuel delivery based on the actual combustion event. Which is very hard to see inside the engine. I am not sure how they figured it out but they ended up putting a line on the IP housing and a line on the engine block. Then they assumed that every single injection pump would be made to have the exact same tolerances as the ones they tested. So with that in mind they didn’t ever publish timing figures for any of their mechanical injection pumps. Just line up the lines and let it run.

Reality is that each pump has sometimes hugely varied tolerances and each timing chain is of a different length to some extent. Which means fine tuning when the combustion event happens can have a very big effect on how the engine performs. Most people online agree that “going a line width advanced “ is good.

Turning the IP housing as it is mounted in the engine valley toward the drivers side of the vehicle will make the fuel going to the injectors arrive sooner than turning the housing toward the passenger side. But, how much sooner? What timing is just right? How do you measure it?

I have found two ways to measure it:

Several companies make a transducer that clamps to the outside of the metal injection lines. That electrical signal is then sent to a box which magically makes a signal just like spark going down a gasoline engine spark plug wire. Clamp a generic timing light to that wire and point it at the timing tab on the front of the timing cover to see where you are. Just like a gasoline engine. Except it isn’t. Where on the injector line do you put the clamp? Next to the IP or next to the injector? When does actual combustion occur in relation to the fuel going down the pipe? No one knows exactly.

I have such a set up. It gave me a strobe light that worked just like a gas engine timing exercise. But, it was never consistent. Even the same engine in the same truck gave me very varied results each time I tried it. It was good for getting engine rpm only through a rpm showing timing light in my experience. Time for another method.

The other method is probably what GM used from the start. Kent Moore, Snap-On and a few other companies including Ford made devices that put a clear “window” into the glow plug hole. Then a sensor is plugged into that and makes the light of actual combustion the trigger to an electrical signal for a regular timing light. The catch is nobody has made them or their “window” in almost 30 years.

Snap-On went a step further and made a machine called the MT480. They called it the Lumymag. It had the probe in the glow plug hole and a probe that went in the tube on the timing tab to produce an rpm read out. The MT480 had two big analog dials to show rpm and timing advance or retard in degrees. Finding a working MT480 with all of the probes and the adapter to go in the glow plug hole is tough. I bought a set up 5 years ago at what I thought was a good deal. It didn’t work.

Snap-On later came out with a MT1480 lumy mag II. Same idea, different sensors and digital read out. Of course the probes on the MT480 and the MT1480 don’t interchange. It seems there is always at least 1 MT1480 on eBay. They also seem to never have the probes. Last week I saw one where I thought the probes were hidden in a bad photo. I took a chance and bought it.

It showed up yesterday and it had the probes. I hooked it up and it worked! Glorious day. Except the numbers for the timing didn’t make sense. Which brings up the next part of the timing puzzle. What are correct timing numbers? No one knows because GM never published them. Snap-On has a wonderful 18 page manual for the machine but no specs are published.

Another problem is the “offset.” Anyone that has used a timing light knows to aim at the timing tab and where the balancer timing line is strobe lighted is the degrees advance or retarded the timing of the ignition. You ever wonder what those round tubes attached to and at one end of the timing tab since about 1976 is? That round tube is a holder for a timing probe. The exact same timing probe the MT1480 uses.

All 6.? engines have a timing probe holder. All 6.2 engines as far as I can tell have the probe holder offset 9.5°. That value is entered in the MT1480 and it adjust for that. I think but have not been able to verify that the early all mechanical IP 6.5 engines also had a 9.5° offset. So, I put 9.5° in the machine and got 24° advance at idle. What?

There are a few people using the MT1480 that post to wildly different forums about their timing experiences. The generally accepted timing baseline is 8° advanced at idle and somewhere between -2° to +3° at 1400 rpm. I was at 24° at idle. How is it even running? I looked at the timing tab and noticed it gave reading to 16° advanced and that took about an inch of space. Yet, my probe holder was at least 3 inches to the retarded side from the TDC mark. That should be more than 9.5°. I went over to a m1009 and looked at its probe holder. It was almost on top of the TDC mark. So I had the wrong offset for a 2005 GEP 6500.

Doing an internet search for 6.5 diesel timing probe offset introduced me to an entirely new black hole. It seems the DS 4 electronic injection pumps used on all 1994 and newer 6.5 engines have an offset setting inside the IP that has to be set with a special scanner. Nobody needs to hook up a MT1480 so no listed offset that I could locate.

I have a 6.5 timing tab in my class and a 6.2 timing tab as well. I think I will just try and figure out how many millimeters per degree and try and figure out the probe holder offset. I just used 30° yesterday and that gave me a baseline of 3° at idle and -4° at 1400 rpm. I moved it to 5° at idle and -1.5° at 1400 rpm. I have to drive 500 miles the next few days and I will see if it made a difference. Once I know the proper offset, I will fine tune it for boost, turbo lag and EGT.

Unless someone knows the offset. Do share if you do.
 

Barrman

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The gist of the long thread yesterday is that I don’t know exactly what my timing is because I don’t know the timing probe offset. Yet, I now have an accurate timing reading that is repeatable and I advanced the timing a bit.

I wrote that and went for a 231 mile drive into the hill country for a family event. Texas yesterday had a huge dust storm atmosphere and 26-40 mile an hour northwest winds. Guess who got to drive at 70-75 mph directly into that wind? Sitting still at stop lights had the truck rocking. Definitely two handed driving on the open road.

But, the timing change did some real noticeable good. Two months ago driving into a similar wind I was at 4-6 psi boost up hill with EGT wanting to creep past 1150°. Yesterday I was on dozens of steep grades at speed with the cruise set. 8 psi boost and exactly 1000° EGT at 75% throttle. Those numbers were so rock solid repeatable that after the first few times I actually stopped watching the gauges more than the road. I would just look and confirm those readings as part of my sweep.

We started the drive at 81° outside temperature. I never got the coolant over 202°. Which is right about where the thermostat gets fully open so perfect. So I plan to drive home Friday. Loosing the 1300 feet of altitude we gained yesterday and hopefully without the huge head wind. I am expecting just as good of numbers again. I doubt fuel mpg will be very good because of the wind. Then next week I will do the timing probe measurements and see if I can get some exact information before I advance it anymore.
 

The FLU farm

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While I understand your quest for perfect timing, aren't there too many potential variables?
Let's say that the balancer's markings aren't right on, for example.

I would adjust for best performance, then take a reading for future reference, not worrying about what the number is.
 

Barrman

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That is a good point. Not only could the balancer be off a bit. But the pointer itself is adjustable. There are a lot of variables for someone who reloads and messes with BMW’s. Variables are very annoying. But, it I can get repeatable reading for my engine to base changes off of. I will be happy.
 

Keith_J

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To make things more difficult, the DB2 injection pump base timing varies with injected quantity as IQ has the end of injection timing physically set. The start of injection varies with IQ, a longer stroke causes the rollers to contact the cams sooner.

The centrifugal advance is set by transfer pump pressure, this is then offset for part throttle position by the cam and lever.

The other type of distributor injection pump design has a variable end of injection timing system, this is the Bosch design used on the White Multi fuel engines and many others.

What this means is a very complex timing curve based on throttle position, engine speed, fuel temperature (partially compensated with bimetallic spring) and injector pop pressure. Then there is start of ignition since this is dependent on temperature, fuel quality ( cetane index) and compression ratio.

The best you can do is follow the TM, then use your ears to fine tune. Fortunately indirect injection is far less demanding in the timing department.
 

Barrman

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Thanks for making it more simple Keith. I did find a GM publication with a static timing spec. I am looking for dynamic timing though. I have looked through the CUCV and HMMWV -30 TM’s and have not been able to find any dynamic timing numbers. I did find several people referring to the “military spec of 4° advance at 1400 rpm.” Those were all 15-20 year old post with dead links.

I had more power than ever on my hill country trip this past week. EGT’s were lower as well. 14 mpg going against that crazy wind and 16 mpg coming home with a cross wind and riding the boost wave for an hour in Austin traffic. Not a good mpg situation.
 

Keith_J

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All dynamics are set during calibration. Even the timing mark can be reset, using the proper tooling and measurements.
So when you install a turbo and tighten the leaf spring screw, it slightly advances the max fuel timing as the plungers, shoes and rollers now contact the cam lobes sooner.

When I was playing with base timing after a pump replacement, I advanced the pump and pressed the cam ring plunger at idle, slightly retarding the timing. As long as idle RPM dropped, timing was not overly advanced. Energizing the cold start advance solenoid with the engine hot would noticeably increase clatter, pushing the timing plunger would smooth this out and increase idle speed slightly.

I've been tuning engines by ear most of my life. I did such a road side timing fix on my Boy Scout Troop bus when it couldn't make it up the Kerrville hills on I 10..all by ear. Plus the 1500 foot elevation there needed more advance.

Remember, diesels operate with burn duration set by injection window. On thermodynamics, it is termed heat addition under constant pressure. Otto cycle thermodynamics is heat addition at constant mass.
Timing requirement is vastly different. Diesels are very sensitive at idle and low power, gasoline at wide open throttle and peak torque range.
 
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Barrman

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It is for sure a rabbit hole to go down.

I found 2 data points to go with. I am not sure I trust either though.

This one:


Is a very old thread on CK5 by a guy that at the time of the thread had a 6.2 with a Banks set up like mine. His 1300-1400 rpm timing sure did pop positive and back to negative in a wide swing so it seems a bit off to me.

I think this might be what people are calling "military spec."


I haven't been able to find a real TM that correlates though. Anyway, chapter 4 deals with how to set the timing dynamically. It talks you through the Kent Moore tool and the Snap-On MT1480. It is for a 6.2 engine so the timing tab is for sure 9.5° offset. But, it gives the degree span from the top of the balancer to the timing tab as 72.5° on page 4-14. That is new information to me. My timing tab I am pretty sure from looking at it with my eyeball and looking at pictures is at 90° to the top of the balancer. 17.5° difference between the timing tabs. Add in the 9.5° and 27° should be my offset to enter in the machine when using cylinder #1. I guessed and used 30 the other day.

This should allow me to get spot on readings that I can repeat for my timing. I will try the -3° at 1300 rpm and see what it gives me. I think my -1.5° setting the other day at 30° offset should translate to a -5.5° with 27° offset. Then, maybe work my way to 3° positive at 1300 rpm. I have been doing the advance arm with a screw driver test and still get a change so I am not too far advanced yet.
 

Barrman

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This is a good example of the mixed data one finds when trying to figure out the 6.? dynamic timing numbers:


They build and tune engines, yet admit they don't know how they are getting the numbers they are. Actually, the way they say the numbers are gotten is impossible with the tools they claim are being used for the 6.2/6.5.

A clear pattern has developed through my research. People that use a pulse detector of some kind clamped to an injector metal line that converts the fuel pulse to an electrical signal. Then there are people that use the clear glass in a glow plug hole which converts the bright light to an electrical signal. Timing numbers that could be exactly correct for the chosen method can be as much as 16° off compared to the other method. I wrote about both methods in post #481 a week ago. I hope to hook mine up again tonight and do some more adjusting. Then drive the Cowdog to the not a Rally Rally Friday in Bryan. Results will get posted. As will I think a separate thread dealing with nothing but 6.2/6.5 timing and methods.
 

Barrman

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So, I found another data point. This article was written by a guy converting to a DB2 pump from a DS4 electric pump:

He uses a MT1480 tool to set his timing. He claims the 6.5 timing tab has a 30° offset. Which is what I guessed last week. I think it is actually 27°. He says positive 3° at 1300 rpm is the proper setting.

I hooked it all back up this evening and put in 30° offset to see if my numbers from last week would be repeated. They were exactly. Then I changed the offset to 27°. I got the 8° positive at idle and positive 3° at 1300 rpm People seem to think is best for a turbo. It isn’t the AM General non turbo spec of negative 3°. But, the only 2 people with a turbo who have written about timing with the Snap-On tool both wrote positive 3° was their setting. I did 500 miles with this setting last week and will do anything few hundred in the coming week.

Since I didn’t think to verify the balancer to timing tab alignment when the heads were off 5 years ago. Plus I am still not sure about the exact offset I should have. I think there are too many variables to push the timing any more advanced.

More to follow I am sure.
 

Keith_J

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From my research, offset is used when the magnetic pickup tool cannot be aligned to the fixed pointer.

I did find the IP base timing calibration in the -34 last night. Performed with IP off engine using compressed air to force plungers into the cam ring through the #1 outlet port with input shaft in position for #1 transfer port alignment in the distributor section.

The cam ring position varies in position based on transfer pressure which generally increases with engine speed, this is analogous to centrifugal advance. This is opposed by throttle position via the throttle shaft cam, acting through the external lever on the timing dash pot. This dash pot is a simple piston which receives transfer pressure.

Dynamic timing is therefore a balance of transfer pressure and throttle position. Both can be changed or calibrated..and then there are thermal effects...you can see why computer controlled injection is the norm.
 

Barrman

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No argument from me that when working correctly, computer control is far better. Like you, I enjoy the "art" of getting something just right. Dynamic timing of a 6.? mechanical pump seems to be part art, part full time researcher and part black magic.
 

Barrman

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I built the truck with high speed comfortable interstate driving to get to places where pavement isn’t. Overlanding is a neat idea that I want the truck to be able to do. I think I have the high speed somewhat efficient travel in comfort checked off. Some of the off-road equipment has been simmering in the background for years.

Such as my swing away water carrier and cooking shelf. I built the swing away spare tire, hi lift jack, fuel and CO2 tank carrier 4 years ago while I was still building the truck. I even built the mounting plates for the passenger side bumper back then. But, I didn’t get around to ordering the bearings and mounting ears until last February from Comp4x4. They are who I bought the parts to make the driver side mount. The first time I was very impressed with the product and service.

Not this time around. Nothing showed up after weeks. Then COVID hit. Sometime last April a few of the parts showed up out of the blue. I tried emailing, commenting on their website and calling. No reply to anything. I finally gave up waiting for parts or a refund last fall and sourced the rest elsewhere.

Last week was my spring break from work. I was able to make everything fit together and finished painting last night. I wanted to try it out at the not a rally rally tomorrow night. It makes the truck look more balanced in my opinion.

It also helps if you tighten the just hand tight bolts before you put over 100 pounds of water on there. That is why it is crooked swung out. I fixed it but ran out of daylight for a picture. 452DD6A5-038E-4A04-9E65-19F0E98D5C6F.jpeg30365019-05B5-4423-97AB-5D0944562BE1.jpegB06C0458-9C4F-488E-8E28-9CBF03C0AA48.jpeg
 

M37M35

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That's a really awesome rig you've got!!

I have a 1994 Suburban with a 6.5 that I'm building up. The 4L80E went out so I found an NV4500 to replace it with . And I'm rebuilding the 6.5 since I'm already that far into it.

The way you're setting your rig up is very close to how I'd like to eventually build mine.

Again, awesome job!!
 

Sharecropper

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So, I found another data point. This article was written by a guy converting to a DB2 pump from a DS4 electric pump:

He uses a MT1480 tool to set his timing. He claims the 6.5 timing tab has a 30° offset. Which is what I guessed last week. I think it is actually 27°. He says positive 3° at 1300 rpm is the proper setting.

I hooked it all back up this evening and put in 30° offset to see if my numbers from last week would be repeated. They were exactly. Then I changed the offset to 27°. I got the 8° positive at idle and positive 3° at 1300 rpm People seem to think is best for a turbo. It isn’t the AM General non turbo spec of negative 3°. But, the only 2 people with a turbo who have written about timing with the Snap-On tool both wrote positive 3° was their setting. I did 500 miles with this setting last week and will do anything few hundred in the coming week.

Since I didn’t think to verify the balancer to timing tab alignment when the heads were off 5 years ago. Plus I am still not sure about the exact offset I should have. I think there are too many variables to push the timing any more advanced.

More to follow I am sure.

I've enjoyed following you guys' comments about proper methods to achieve correct timing. I was hoping you could come up with a reputable way to set the timing correctly with a timing light. Having said that, I will share with you the following - Way back in 1985 I had a GM master mechanic friend of mine install a Banks turbo on a brand new GMC civi 1-ton SRW truck with factory 6.2. When he got to the timing part, he simply aligned the timing marks, tightened the top bolt, and then drove the truck a mile or so up the road and back. He then loosened the top bolt and advanced the pump a degree or so, and re-tightened the top bolt. Up the road and back we went (I was sitting in the passenger seat through this process). He then loosened the top bolt again and advanced the pump another degree or so, tightened the top bolt, and up the road again. On the way back to his shop he said it sounded and ran the way it was supposed to. When we got back to his shop he tightened all three pump bolts and closed the hood. I asked him if he was going to shoot the timing light onto the harmonic indicator, and he said "Naw, that indicator don't mean nothing. Always time a diesel by the way it sounds and runs.". I put over a quarter of a million miles on that truck and never touched the pump again. Sold it in 1994 to my neighbor.

When I rebuilt the pump on my M1028 a few years ago, I used the same method to time the pump. My NA 6.2 runs like it was turbo'd. Come drive it if you doubt that.

Yall probably know that, for the past few years, I have been assembling a new P400, a 700R4 from Bowtie, and a NP241 from Mark Bendler at Kodiak Truck to go into my M1028. The last piece of the puzzle will be a Supercharger from Bullet in Australia. I plan to get this ordered as soon as I get through this next surgery (if I am still alive, I am headed for the pre-op MRI tomorrow). Back to the timing subject - when I get ready to time the pump on my P400, I will go through the same process as before. I will not pay any attention to the timing scale, until I get the pump set where it needs to be. At that point I may shoot the timing light on the scale just to see where it is and write it down in my ledger, however I just now looked at the timing scale on my P400 and, hail, it is adjustable! Here's a photo. Thanks guys for your comments. I will be watching this thread.

Mike Gresham, Paris, Kentucky

DSC_0469 (2).JPG
 

Another Ahab

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I asked him if he was going to shoot the timing light onto the harmonic indicator, and he said "Naw, that indicator don't mean nothing. Always time a diesel by the way it sounds and runs.". I put over a quarter of a million miles on that truck and never touched the pump again.
Stories like that (First Person), are the whole reason to keep up with this site:

- Hard to beat the personal "been there/done that" experience of posts like this

Good luck on your surgery. I know you are going to be fine and come out stronger because of it!

I'm sending love to ensure it. Amen
 

chevymike

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When he got to the timing part, he simply aligned the timing marks, tightened the top bolt, and then drove the truck a mile or so up the road and back. He then loosened the top bolt and advanced the pump a degree or so, and re-tightened the top bolt. Up the road and back we went (I was sitting in the passenger seat through this process). He then loosened the top bolt again and advanced the pump another degree or so, tightened the top bolt, and up the road again. On the way back to his shop he said it sounded and ran the way it was supposed to. When we got back to his shop he tightened all three pump bolts and closed the hood. I asked him if he was going to shoot the timing light onto the harmonic indicator, and he said "Naw, that indicator don't mean nothing. Always time a diesel by the way it sounds and runs.". I put over a quarter of a million miles on that truck and never touched the pump again. Sold it in 1994 to my neighbor.
@Sharecropper So could timing being too retarded or advanced cause what feels like less power than another 6.2? Reason I ask is my first M1010 seems like it had way more power than my current one. Both had similar mileage. Both started and ran fine, no smoke at start up or under load. Because my current M1010 feels so much more under powered to what my last one was, I have been getting ready to go down the 454 BBC swap road (already have engine).

If a timing tweak could help resolve that (I know NA will never be a powerhouse) and get me to how my first one felt, I would reconsider the BBC swap.

So what I am trying to see/feel/listen for when playing with the timing?

Thanks and wishing you the very best on your upcoming surgery!
 

Sharecropper

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@Sharecropper So could timing being too retarded or advanced cause what feels like less power than another 6.2? Reason I ask is my first M1010 seems like it had way more power than my current one. Both had similar mileage. Both started and ran fine, no smoke at start up or under load. Because my current M1010 feels so much more under powered to what my last one was, I have been getting ready to go down the 454 BBC swap road (already have engine).

If a timing tweak could help resolve that (I know NA will never be a powerhouse) and get me to how my first one felt, I would reconsider the BBC swap.

So what I am trying to see/feel/listen for when playing with the timing?

Thanks and wishing you the very best on your upcoming surgery!
Mike - timing too advanced or retarded will indeed impact performance. Have you looked at the timing marks on your pump? If not, shine a light down in front of the pump and see if the 2 timing lines line up. My ‘85 civi as well as my current M1028 seem to have the best power with the timing advanced the thickness of 2 marks towards the drivers side. To find the sweet spot, you can follow the procedure outlined in my previous post and gradually advance the pump. There are 3 nuts holding the pump to the engine and these are a bear to get to, but with the correct wrench you can access all 3. Start with the 2 lines lined up and drive it around the block. Then advance the timing by rotating the pump towards the drivers side the thickness of the line. Tighten the top nut securely and drive around the block to see how it feels. Then repeat the process and rotate the pump towards the drivers side another line thickness and see how that feels. Once you find the pump position with the best power, tighten all 3 nuts. I will predict you will find the best power when the line on the pump is past the line on the engine approximately 1/16” inch. Give this a try. It cost nothing.
 

Keith_J

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Another timing trick good for a few degrees is to supply 12 volts to the case pressure solenoid. This is done for cold start, applying voltage lowers the case pressure which advances timing..
If this doesn't produce any noticeable sound change, the injection pump could be defective in the pressure advance circuit. Time for an overhaul. This is one reason for gross timing variations.
 
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