Military DB4

[6.2 turbo]

It idled up and down,pretty much any were it wanted to. I think the four plunger .310 DS4 or DB4 is probably the biggest size needed to get 400 + hp. The problem I see with the DS4 is that it 's cam ring has no lobe. The other problem is that the fuel metering solenoid needs to be tight shut at full throttle . Excellent plunger filling design on the DS4. I have considered trying to run one of these with a push button switch or pwm,no computer,the advance could be made mechanical. I'm not convinced that the stock prechambers are bad. My 6.2 had the smallest precups ,and I put the big pump on and the horsepower was extreme. but only untill it broke the cam pin,and seized the plungers. I later changed to turbo precups,but didn't notice anything,keep in mind there was lots of variables in my testing as I was always changing multiple things at a time,and getting very frustrated and confused. I discovered my 6.2 ran better with the timing retarded than advanced. I have seen egts on this thing over 1600,not sustained, and the cyls and pistons are fine. It didn't melt anything. It didn't crack the block or crank. It just blew head gaskets,and spun the main bearings, maybe from a bad homemade girdle ? I'm convinced most my tuning problems were from the dished pistons.. Did you notice more power with bigger prechamber openings ? This is something I might try for my 92.

 

[vdb11]

Some very good thoughts/ideas here.

Slim Shady, I have read/heard from others that what you are saying about pre cups is exactly right, the smaller cups tended to be more efficient, while sacrificing some power and keeping heat, while the larger cups increased power but efficiency went down. In addition, I saw somewhere that someone who owned a 6.2 and a 6.5 said that the 6.2 did a much better job of getting up to operating temp than the 6.5, which supports your idea that the small cups keep heat in the head. I will be running "T" cups on mine (factory).

I have also thought about the governor as well, I did not realize the metering valve was such a restriction. What do you think was a good solution? Is there anyway to adjust the metering valve to open up almost the whole way? That rough idle that you had is odd.

When you had the charge holes widened, did you have the slots in the head enlarged too? I do not know if I will have that done at all, as I will not be going nearly as large as your pump.

 

[6.2 turbo]

I did not touch the holes in the head. Who is doing the machine work for you ? The throttle idle screw can be adjusted lower,and the governor linkage adjusted inside,also max the full throttle so that the governor arm hits the housing. The inside one will have to be set on the vehicle to get it to idle without turning the actual idle screw. This helps a little. Basically you try to get get as much travel as possible without binding. Some metering valves have the pin farther away from the valve. So I made one that the pivot point was very close together,this helped pretty much. I also cut the valve on the side that is slanted,and made it straight. This makes a very touchy throttle,and tends to lope always, except full throttle. Very hard to drive. A slotted or v shaped metering valve hole would also work better if it was done with edm instead of a dremel tool and a chainsaw sharping bit. I got so fed up with the metering valve ,that I drilled a hole in the head directly into the plunger chamber and routed fuel there with a solenoid,this gave it lots of fuel,but at part throttle it surged randomly . This idea would have worked better if I hadn't used hose and used hard line instead,and had a separate fuel pump just for that. Instead I used charge pressure . I also cranked the charge pressure to around 150 psi,but it would drop to 80 -100 psi at full throttle. I want to study the ag style governor on the DB4, it looks like it will travel lots farther,a very confusing setup,at least to me. It has lots of springs, and I could barely get it apart. Also a good tight head and rotor and perfectly fitting plunger makes a huge difference in the fuel output. The perfection that these parts must fit is insane. I put one pump together with a head and rotor the felt snug,but it was still to loose to even start. When they don't start hot they don't feel loose either.

 

[vdb11]

I am having Davies precision machine do it. I talked to Gary Monday night and he remembered working on one a while ago once he saw the rotor. Anyways, I will probably call him tonight after work, as he is working the late shift. When I talked to him he said he remembers opening up some kind of cavity in the rotor?? I want to come up with a good size without endangering the pump, so maybe .370 to .410??

I will have to do some more research on the metering valve. I wish I had the pump in front of me but its at home. Do you think adjusting the charge pressure helped? Is that harder on the pump to run a higher charge pressure like that? Also, how is that adjusted?

That ag governor sounds pretty cool, definitely let me know what you find out. Hopefully if the plungers and rotor are done right they should be tight, the pump is almost brand new, so the head and rotor should be in good shape.

One more thing, how much did you have the charge holes in the rotor enlarged?

 

[6.2 turbo]

Davies did mine,and the hole he is talking about,is in the drive slot,it was opened from going to 1/2 inch plungers. I just pressed a tiny plug in the hole,but you should be ok. Supposedly any thing over 120 psi charge pressure will seize the pump. You might want to tell them to put two circular grooves in the plungers,like the updated factory ones. This might keep them from seizing ? I didn't know about this when I got mine done. I'll see if I can find my old rotor and get the charge hole size.

 

[6.2 turbo]

The rotor that Davies did has .100 thousands holes,they are stock,but he added two more. I do have a stock rotor from a tractor DB2 that has .110 holes,these are the biggest I can find at the moment.

 

[Slim Shady]

There are some issues with messing with the pre cups, Right now I would say don't do it, untill you have a know good motor and have data onhow it runs then play with that. They MUST be machined, variations in the machining make a big difference in cylinder balance. Take my word for it.

 

[turbonator]

Some very good thoughts/ideas here.

Slim Shady, I have read/heard from others that what you are saying about pre cups is exactly right, the smaller cups tended to be more efficient, while sacrificing some power and keeping heat, while the larger cups increased power but efficiency went down. In addition, I saw somewhere that someone who owned a 6.2 and a 6.5 said that the 6.2 did a much better job of getting up to operating temp than the 6.5, which supports your idea that the small cups keep heat in the head. I will be running "T" cups on mine (factory).

I have also thought about the governor as well, I did not realize the metering valve was such a restriction. What do you think was a good solution? Is there anyway to adjust the metering valve to open up almost the whole way? That rough idle that you had is odd.

When you had the charge holes widened, did you have the slots in the head enlarged too? I do not know if I will have that done at all, as I will not be going nearly as large as your pump.

are you planning to keep your truck as a daily driver or are you building it for full throttle tractor pulling? i dont know if you ever heard 6.2turbo's truck run with the modded pump..... so.....http://youtu.be/rvlIQIIJjms

i dont think he was running this as a daily driver... in your search for power, you might be wise to look at water meth and or propane injection to aid in making more power as well, could be a bit cheaper and loads more streetable...LOL...

 

[vdb11]

Hmm I wonder if I should even have him touch them then. I may leave them go. I am thinking somewhere between .370 and .410 inch so hopefully I shouldn't run into the cavity problems.

I agree Slim Shady, I was going to have mine machined since my pass. side head was running circle precups while the drivers side was running the factory "t" cups, but my machinist wouldn't even touch them, and neither would his buddies. I just bought 4 new cups instead, I am happy with that decision.

Hey turbonator, thanks for showing that video! I didn't realize you had videos 6.2 turbo, although I like the sound of that lope, it would be totally impractical for a DD, which my truck will be. Hopefully I can avoid that as I won't be going quite as all out. I like the idea of watermeth and propane but not the extra plumbing I wouldn't mind doing both but I think that will have to come after the WTA intercooler, which comes after the solid axle swap, which comes after the exhaust brake, which comes after the injection pump

I think these old 6.2/6.5s are an addiction......

 

[turbonator]

Hmm I wonder if I should even have him touch them then. I may leave them go. I am thinking somewhere between .370 and .410 inch so hopefully I shouldn't run into the cavity problems.

I agree Slim Shady, I was going to have mine machined since my pass. side head was running circle precups while the drivers side was running the factory "t" cups, but my machinist wouldn't even touch them, and neither would his buddies. I just bought 4 new cups instead, I am happy with that decision.

Hey turbonator, thanks for showing that video! I didn't realize you had videos 6.2 turbo, although I like the sound of that lope, it would be totally impractical for a DD, which my truck will be. Hopefully I can avoid that as I won't be going quite as all out. I like the idea of watermeth and propane but not the extra plumbing I wouldn't mind doing both but I think that will have to come after the WTA intercooler, which comes after the solid axle swap, which comes after the exhaust brake, which comes after the injection pump

I think these old 6.2/6.5s are an addiction......

IMO if you weigh the pros and cons, you will make up the extra hp with water meth and or propane.... and as for plumbing, well it is no more involved than that.... if you check on the other site one of the mods did a water/meth setup for something like 250 bucks... and propane, well i am not sure what is all involved, but there is a real gain from it... what say you slim/6.2turbo?

 

[Acesneights1]

Hmm I wonder if I should even have him touch them then. I may leave them go. I am thinking somewhere between .370 and .410 inch so hopefully I shouldn't run into the cavity problems.

I agree Slim Shady, I was going to have mine machined since my pass. side head was running circle precups while the drivers side was running the factory "t" cups, but my machinist wouldn't even touch them, and neither would his buddies. I just bought 4 new cups instead, I am happy with that decision.

Hey turbonator, thanks for showing that video! I didn't realize you had videos 6.2 turbo, although I like the sound of that lope, it would be totally impractical for a DD, which my truck will be. Hopefully I can avoid that as I won't be going quite as all out. I like the idea of watermeth and propane but not the extra plumbing I wouldn't mind doing both but I think that will have to come after the WTA intercooler, which comes after the solid axle swap, which comes after the exhaust brake, which comes after the injection pump

I think these old 6.2/6.5s are an addiction......

Where did you buy them ?

 

[vdb11]

Aces, I bought them from GMpartsguy over at the place, he should be calling me back any day now to tell me they came into his shop. Unfortunately, these cups are apparently hard to find and need to be purchased from a GM "vintage" warehouse (isn't that sad?) so they take a while to get here. He was lower than other online places and the local dealer, about $40 a piece. Still a tough pill to swallow but thats how it goes I guess.

turbonator, I did see that thread, and I think I will eventually pursue either water/meth or propane, although I would like to see what I can get "drug-free" first. The idea of keeping the inside squeaky clean with water is a pretty attractive idea to me though. I see you guys are planning WMI.

I have heard propane can be like nitrous, very addicting and it often doesn't end well

Anyways I really didn't mean to steal your thread 6.2 turbo, I apologize. I appreciate the info you have given me, I will call Gary tonight, I am still debating as to whether or not expanding the charge holes is needed for my use. Any updates on that DB4 governor, what rpm is it designed to run?

 

[6.2 turbo]

I looked at the DB4 governor,and not sure if its worth the effort. Plus the throttle arm will be on the other side. I tried propane once,it did help some,but at higher rpms ,when there was less unburnt diesel it no longer helped. Also I didn't like that changed the timing. I want to try an intercooler before trying water injection.

 

[vdb11]

Agreed, I would like to do a WTA set up before I start injecting water/meth. I have been looking at the manual on stanadynes website, trying to understand how everything works a little more. Do you guys think a little stiffer gov spring would keep the gov from closing the metering valve as early? Also, I can see what you mean 6.2 about trying to get as much travel as possible. So if I am understanding this right, if the spring screw on the rotor is adjusted to the same position as a stock pump, the plungers will move the same distance as they did before, regardless of size (assuming enough fuel comes through the charge passage from the metering valve), but with every charge and discharge, the pump will inject more fuel than the stock pump, regardless of load or rpm. So even at idle, each discharge is sending out more fuel assuming the screw is in the same position, so I can expect a mileage decrease?

Although the spring adjustment screw will probably not be in the same position as before. BTW, what is the factory setting on those screws, is it a certain torque? or plunger to plunger max travel spec?

Thanks again, 6.2 do you have any pics of what these circular grooves might look like in the plungers?

 

[turbonator]

Aces, I bought them from GMpartsguy over at the place, he should be calling me back any day now to tell me they came into his shop. Unfortunately, these cups are apparently hard to find and need to be purchased from a GM "vintage" warehouse (isn't that sad?) so they take a while to get here. He was lower than other online places and the local dealer, about $40 a piece. Still a tough pill to swallow but thats how it goes I guess.

turbonator, I did see that thread, and I think I will eventually pursue either water/meth or propane, although I would like to see what I can get "drug-free" first. The idea of keeping the inside squeaky clean with water is a pretty attractive idea to me though. I see you guys are planning WMI.

I have heard propane can be like nitrous, very addicting and it often doesn't end well

Anyways I really didn't mean to steal your thread 6.2 turbo, I apologize. I appreciate the info you have given me, I will call Gary tonight, I am still debating as to whether or not expanding the charge holes is needed for my use. Any updates on that DB4 governor, what rpm is it designed to run?

the WTA coolers sold on ebay,(about 16x20?) are not much of an improvement over no IC at all... when you freshened your motor, did you upgrade your waterpump/rad as well? just askin because more fuel also means more heat... on a side note we have a WMI system on our pugg, it is a push button(hurst shifter handle for nitrous) system that is activated by a boost sensor... works good although it has passed mostly water.....

 

[vdb11]

Yeah I actually had the water pump go out two months before the planned rebuild so I installed a pump from a year 2000 6.5, along with a new fan clutch, and a plastic fan off a Duramax. I believe the rad is not too old, i think the PO had replaced it. It runs right around 190-195 (has a 190 delco t-stat). the other day towing a 8k load of straw (only about 45 mph though) and running too much boost, I got it to almost touch 210 going up some grades. it cooled down quickly though. It does have 2 inches of hardblok in it so I figured it might run a little warm.

I was thinking of the ones on the frozen boost website, they look pretty legit but I don't know. It seems to me like they would be more effective than an ATA. How much water do you guys use? I would like it to be on a push button or manual switch so i only use it when I really need it. The biggest reason I would use it is for EGT purposes. Does it seem to lower EGTs well?

 

[6.2 turbo]

At light loads and idle the fuel output should be the same as stock. I'll see if I can get a picture of the plungers with grooves. I would say the stock leaf spring setting would be 1/4 turn from tight. If you are going to run the leaf spring ,make sure its at least a 7-3 or 7-2. Never seen a 7-3,but have seen 7-1 and 7-0 and 7-2. I have lots of these since I never put them back on. Keep in mind that the plungers are not getting full travel when the metering valve is not opened very far.

 

[Slim Shady]

Just have your machinist match the old plungers they can do that. Make sure you request the parts be hardened. and the fit must be good or the plungers will leak down causing all kind of weird problems. I would not go much bigger than .370 to .380 at this point, anything else will give you durability problems from the head. The head is induction hardened so the hardening is not all the way through. This also presents problems when you try and machine a part to tight tolerances. You HAVE to have the groves.

As far as fuel delivery your output at a fixed throttle position will go up so you will find that the throttle becomes more responsive (touchy to a point) because you are adding more fuel at a garter rate. It doesn't take more fuel to move your truck down the road but you will notice that you don;t need to have as much throttle as you did for a given speed (getting more fuel).

If you stick below
390 I don't think you will need to enlarge your transfer slots. Also you may want to back the screw Spring retainer for the pistons off initially to limit some of the possible fuel issues then turn the screw up a little at a time to get your optimum fuel rate for your setup.

Yeah yeah I know take it from experience, most people talk it, the ones who try it and fail learn the most, costly yes but that is what the ATT paid for is RD research. Most will never know that. I can get heads done for DB2 and DS4 pumps if someone is interested in playing . I also need a victim that wants to try some RD pre cups that has a new 20 to one or better motor. preferably with OBD1. I am getting tired of taking my truck apart and putting it back together. All this will need to be done with a non disclosure agreement for confidentiality.

 

[turbonator]

Yeah I actually had the water pump go out two months before the planned rebuild so I installed a pump from a year 2000 6.5, along with a new fan clutch, and a plastic fan off a Duramax. I believe the rad is not too old, i think the PO had replaced it. It runs right around 190-195 (has a 190 delco t-stat). the other day towing a 8k load of straw (only about 45 mph though) and running too much boost, I got it to almost touch 210 going up some grades. it cooled down quickly though. It does have 2 inches of hardblok in it so I figured it might run a little warm.

I was thinking of the ones on the frozen boost website, they look pretty legit but I don't know. It seems to me like they would be more effective than an ATA. How much water do you guys use? I would like it to be on a push button or manual switch so i only use it when I really need it. The biggest reason I would use it is for EGT purposes. Does it seem to lower EGTs well?

how much boost is too much for you? we run 20-28 psi at WOT with the pugg (2831-5088 IP) and have not missed fuel.... if you are not boosting to match your fuel output, then the extra fuel will be going out the exhaust, wasted...the WMI has worked good to reduce EGT's with 14000lbs on the trailer, and the weight of the truck(truck weighs 17000lbs loaded) keeps the EGTS around 950 on a 2.5km hill..... and slim, would be interested in trying your pre-cups, but we just got a set of Diamond cups machined to try on our 6.2l build..... slim, have you ever looked into machining piston tops like kennedy does on their low comp ones? when you did your pistons, did you shaved them down, or machine them?

 

[turbonator]

Just have your machinist match the old plungers they can do that. Make sure you request the parts be hardened. and the fit must be good or the plungers will leak down causing all kind of weird problems. I would not go much bigger than .370 to .380 at this point, anything else will give you durability problems from the head. The head is induction hardened so the hardening is not all the way through. This also presents problems when you try and machine a part to tight tolerances. You HAVE to have the groves.

As far as fuel delivery your output at a fixed throttle position will go up so you will find that the throttle becomes more responsive (touchy to a point) because you are adding more fuel at a garter rate. It doesn't take more fuel to move your truck down the road but you will notice that you don;t need to have as much throttle as you did for a given speed (getting more fuel).

If you stick below
390 I don't think you will need to enlarge your transfer slots. Also you may want to back the screw Spring retainer for the pistons off initially to limit some of the possible fuel issues then turn the screw up a little at a time to get your optimum fuel rate for your setup.

Yeah yeah I know take it from experience, most people talk it, the ones who try it and fail learn the most, costly yes but that is what the ATT paid for is RD research. Most will never know that. I can get heads done for DB2 and DS4 pumps if someone is interested in playing . I also need a victim that wants to try some RD pre cups that has a new 20 to one or better motor. preferably with OBD1. I am getting tired of taking my truck apart and putting it back together. All this will need to be done with a non disclosure agreement for confidentiality.

i would be game if you sent me a ATT to use at the same time as the pre-cups...LOL