95' Junker Drag Truck

NickTF said:
Can you expand on this or is this top secret?
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madmikeismad said:
I was curious too.
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tireburner27 said:
I have been a fan of this thread to. I was curious about alterinh the shims to.
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Each barrel is supported with (2) external shims, one under each ear of the barrel and then the bolted down tight against the shim. If you put thinner shims under the barrel, it essentially makes the pump have more stroke. .035-.040" thinner shims equates to .035" - .040" longer stroke which is good for another 30-40 cc's.


The downside of this modification is it reduces plunger fill-time while adding an equal amount of required filling requirement so it's not a common modification for high rpm pump setup. In fact, some shops will install thicker shims to "destroke" the pump to help with higher rpm performance.

The plunger always sweeps the same vertical distance. Thicker shims adjust the whole barrel and therefore the spill-port higher with relation to the plunger so it reduces the effective injection stroke of the plunger while increasing the fill stroke. Thinner shims do the exact opposite, they lower the barrel and spill port with relation to the plunger which increases the effective injection stroke while reducing effective fill stroke.

Moving the spill port higher or lower will change the timing of the pump and variation in thickness of shims from one barrel to the next will change the phase timing of the pump. Since there are 360* in a circle, and 6 cylinders, ideally you'd want 60* of phase difference between each cylinder. Just like racking the barrels without bench testing will provide max fuel delivery with unknown balance, shaved shimming on the barrels can also provide more fuel delivery but without bench testing, phase and flow balance may or may not remain balanced.
 
This seems like it would be a redundant mod on a 160 pump to remove shims as they already have a short window for fill time. With the high rpm fueling issues you have it seems as though adding a small amount to the shims would be more logical?
 
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He's force feeding the pump at high rates of pressure, so perhaps it won't be counterproductive. Yes it's shorter fill time, but he's also running abnormally high fuel pressure if I remember correctly and you're still doing so.
 
What about loosening the hold down nuts on the barrels for easier starting? I did it by mistake and my truck fires up with 2 seconds of cranking or less. Cold or warm start. It's 40* in the morning here. I have them at about 5 ftlbs. If I snug them any tighter it starts hard and lopes badly when idling in gear at a stop light. Time for a new pump?
 
Big Blue24 said:
Mine seems to go full travel around 55-60 psi. Works great for the current 5x.018's.

In an attempt to get maximum fueling out of this 160 pump, I've got some upgrades planned.

1. Swap out the DDP 042/024 DV's for something more aggressive....

2. Try out this monstrous set of 5x.025" VCO injectors I recently acquired...

3. Alter the shims on the pump barrels....
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More power? Work on that 60ft, and go hit a test n tune with a well prepped track! I found an old thread that said turbomatt (one of Garmon's guys) hit a 1.59 60ft with pretty much your same setup. That alone ought to put you in the low 11s, if not high 10s! By what I saw in Arizona when your truck shocked the slicks in Second Gear, if you can hit em like that off the line you'll be able to hit a 60ft in the 60s, if not the 50s!
 
**Update***


The inevitable happened, it looks like the headgasket finally blew on the Junker Drag Truck. It was a good one with over 240K miles stock then about 10k miles tuned up with lots of boost, timing, and fuel.

During the minute-long burnout contest, it spit some water out of the overflow tank, I assume that is probably when the headgasket initially failed. I then ran quite a few 11 second passes after that NHRDA Arizona event back here at my home track in Las Vegas. On my last track outing, the truck developed a severe oil leak that appeared to be coming from the rear main seal. I limped it home and it's sat parked in the garage since May.

This is the burnout that I believe started the head gasket failure:

https://www.youtube.com/watch?v=5DR41DG_nk0




This past weekend I started pulling it apart, planning on doing a rear main seal. When I pulled the turbo drain, the oil level was high but still poured out normal appearing dirty black oil. I then pulled the oil pan drain plug and about 1 gallon of un-mixed, pure-looking antifreeze came out, then a small oily mix layer, and then the remaining oil. I then pulled the overflow tank and it was full of clean engine coolant. I then pulled the radiator cap and it was low on coolant and had black sludge build-up deep inside, definitely mixed coolant and oil but no "milkshake" as is commonly found. I drained the radiator and it had clean coolant for the first few gallons then mixed amounts of oil floating on the top layers of the last gallon or so.

JunkerMixFluids1.jpg


I pulled the oil filter and punched a hole in the bottom, it was 100% oil, no coolant present. I might have gotten lucky where the coolant didn't make it into the engine oil till after the motor was shut off and sat for several months in the garage.

I then pulled the oil cooler and pressure tested it to make sure that wasn't the source of fluid mixing.... the oil cooler tested out leak-free meaning it was not the source of oil contamination.

JunkerMixFluids2.jpg


JunkerMixFluids3.jpg


JunkerMixFluids4.jpg


I then started tear-down on the cylinder head so it can be removed for gasket inspection and replacement. It looks like there might be some surface leak evidence at the rear of the head. Won't know for sure till the head is pulled and inspected for leak signs.

JunkerMixFluids5.jpg


It's ready to pull, just need a buddy to help lift the head.
Headgasket1.jpg



Using a cardboard box seemed to be a simple method for sorting the used head bolts, pushrods, and rocker assemblies.

Headgasket3.jpg
 
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Sorry to hear about the head gasket failure. Atleast its towards the end of season.
Are you going to stick with the stock bolts or anti up and go with studs? Also r you going to do any port work to the head while its off?
 
Are you still running stock valve springs? I can't really tell because of the smaller picture on my phone but I don't believe they are... Point being do you think you're losing top end due to float?

Edit: also looking forward to see where your spray is landing and condition of the internals!! Fingers crossed!!
 
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