95' Junker Drag Truck

That's kinda crazy. I wonder what the Georgia boys do different to keep them in place


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It could have been the head gasket he used. I know he stated during the rebuild process that he was not using a cummins head gasket. I believe he said it was a Victor Reinz gasket.
 
While I'm not running 80+ psi of boost I am running 29* timing, nitrous, o-ringed block, and 150ft lb torqued bolts. So far so good for me.
 
^yup. It appears that nearly everyone overlooks that detail.


That and the ether.
 
They also run well over 100psi of boost. Compression isnt the reason they don't blow head gaskets.
 
97rada said:
That's kinda crazy. I wonder what the Georgia boys do different to keep them in place


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Click to expand...
I've spoken with a few of the "Georgia Boys" one factor is they utilize fire rings in lieu of my .010" protrusion o-ring setup.


Zmm828 said:
It could have been the head gasket he used. I know he stated during the rebuild process that he was not using a cummins head gasket. I believe he said it was a Victor Reinz gasket.
Click to expand...

Yes, it was a .010" over Victor Reinz gasket.

YOUNG GUNS15 said:
While I'm not running 80+ psi of boost I am running 29* timing, nitrous, o-ringed block, and 150ft lb torqued bolts. So far so good for me.
Click to expand...

Spencer, don't take this the wrong way but torque which is directly proportional to cylinder pressure is the single most important factor in determining how much force is present in the motor to lift the head. My quick spooling twin setup is now making north of 1700 ft-lbs to the tire, this is tremendous amount of lifting force and more in the realm of common 1000 rwhp motor setups although admittedly my HP power is in the low 800 range.

Hurley said:
^yup. It appears that nearly everyone overlooks that detail.


That and the ether.
Click to expand...

I might be joining the ether club, going to run a .020" over gasket this time around. I have (2) exhaust valves that are barely contacting the piston on cylinder #1 and #3 or 4, I have .047-.048" clearance so it looks like on my current setup, .050" is the minimum needed for everything to clear at full temp and high rpm. The thicker gasket will also help lower the torque/peak cylinder pressure a little so killing 2 birds with 1 stone.

kleann said:
They also run well over 100psi of boost. Compression isnt the reason they don't blow head gaskets.
Click to expand...

Remember that their 100 psi of boost does not happen sub 2000 or maybe even sub 2500 rpm. This pushes the torque curve higher in the rpm range and helps save gaskets, fire rings, engine bearings, rods, cylinder blocks, and transmission parts.

Any way you slice it, 2000 ft lbs at the tire is danger zone for 12 valve Cummins utilizing a wet block. Pushing that torque higher in the RPM range is one key factor that I cannot duplicate with my current low useable RPM range with the factory 160HP Pump Cam.


I'll give it a shot with the new to me used studs and a Fel-Pro made in Britain (mysteriously close resemblance to genuine Cummins) .020" over gasket this time around. Will try to be better about re-torques and taking it easy the first 20-30 heat cycles. If it doesn't work this time around, going to have to pony up for some high $$$ fasteners and try a genuine Cummins gasket which I'm told are now all made in China....
 
Yep, throw that same torque at another 1000rpm higher and all the sudden your making a pile of power. Easier said than done.
 
Just throwing out my experience with high timing so far. I made only 350ft lbs less than you will haha
 
OK will. Here is what I got..
Going from an he 351 secondary with a gt4202 primary
Ran a best of 92mph in the 1/8 and 112 in the quarter.. With a 12.02
I did this at 70psi with 40 on primary. No idea what drive was..

Only change I made was going to a 62/65/14 with small internal gate.
Ran 11.99 at 113 with 50psi overall 27 psi on primary. Without paying with secondary gate.
Went to a7x12 injector, down from 7x14 then,
Screwed a cheapo import brass boost controller into gate hose., went 93.75 in 1/8, best mph by 1 full mph in 1/8...At60psi total 25 from primary.. 10psi less than I was running overall... I don't believe injectors made a difference in this case, no difference in driveability, just a loss in heat some..

Would have been a117mph pass or so in 1/4. I an pretty sure you have a lot to gain by changing secondary to something else.. Something that can apply more turbine torque and compress air easier. Like a62/68/14.. I honestly believe the lack of drive pressure would gain you a ton, move torque up in power band and limit it a bit..
 
Blue said he was kicking around 1700lb ft and 7xxhp.. Yeah there is some to be gained with limiting tq!
 
I think the greatest benefit right now would be from a 13mm.


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In order to fit the new studs, the rocker towers need to be machined for both valve cover clearance and to accommodate the shorter length of the arp studs.

Per ARP's instructions, the bolt/stud seat on the rocker tower needs a 0.200" recess by 1.10" wide.

MillRocker1_zps3f754c90.jpg


Used Chinese combo mill/lathe machine that I picked up off Craigslist for a couple hundred bucks:

MillRocker2_zps141ca4f7.jpg


Took a light pass to ensure the rocker tower was fastened somewhat square and true, ARP's instructions state that the machined recess needs to be within 0.005" of parallel with the bottom of the rocker or perpendicular to the stud.

MillRocker3_zps8cab52b2.jpg


After several small .010" deep passes with the 3/4" end mill, the recess was complete.
MillRocker4_zps3c41f099.jpg


They didn't turn out perfect, but decent considering I didn't have a proper machining vise or way to tram the old worn milling head. I did have to go slow and it took roughly 5 hours start to finish to complete the setup, milling, and re-assembly of the rocker assemblies.

MillRocker5_zpsa6c3021c.jpg


After a thorough cleaning, I reassembled the rockers with some assembly lube to help prevent a dry start-up.

MillRocker6_zps5414940f.jpg
 
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