1955 12 Valve NAPCO Clone

[1985-GMC]

Nice work! How tall are those 36s, Ive heard they are only about 33". You should just step up to 37s.

[Luther Grimace]

I haven't measured them but they are a little taller than my buddy's 35x12.50R15s. You know how they run small. They are prolly right around 33 or 34 inches. I want some of those new 37 BFG hummer tires but I am satisfied with these...and they were free! I guess nobody likes the bias plys.
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[blackdiesel]

hey are you using your mechanical fan??

[Shaun1162]

Great looking build! Man, can't beleive anyone would scrap that '55!

[Luther Grimace]

No I won't be using the mechanical fan. And thanks! I like that dually!
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[Luther Grimace]

Do yall think I should put a fuse inline on the positive battery cable? This might be a dumb question. I have never seen one on a positive battery cable going to a starter. I hope to get a video of it running up soon.

[6BT 56]

Dont put a fuse in. It would need to be in the 400 amp range to support what your cummins is able to pull thru that 2/0 batt cable. A shut off swich as close to the batt as possable incase of a problem is a good idea tho.

[Luther Grimace]

Alright I was just gonna check. I didn't think it would. Does anyone have experience bleeding these clutches?
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[blackdiesel]

Originally Posted by Luther Grimace

Alright I was just gonna check. I didn't think it would. Does anyone have experience bleeding these clutches?
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Gotta be done from the bottom! Pull your slave out if the bell housing and push it on with your hand and let it suck fluid to it. While working your bleeder of course.
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[Luther Grimace]

Are you talking about the allen screw next to where the line attaches in as the bleeder. I wonder if I could find a bleed screw that would fit that thread pitch?

[blackdiesel]

I must be thinking of A nv4500 slave/master as far as the bleeder goes. However bleeding any slave and master cylinder is easiest from the bottom. break the line loose if you have to to purge the air

[Luther Grimace]

Originally Posted by blackdiesel

I must be thinking of A nv4500 slave/master as far as the bleeder goes. However bleeding any slave and master cylinder is easiest from the bottom. break the line loose if you have to to purge the air

You are the man blackdiesel! That did the trick last night. Bled the clutch right out after 10 pumps or so.

Got a wild hair last night.



I'm hoping to find the #6 knock I have had since a month after I bought this. Dieselwrencher had mentioned that it could possibly be a wrist pin bushing and that is what I am hoping for.

Here is the video I promised of it running.

[blackdiesel]

Did you crack your injector lines loose to find the down cylinder before you popped the had off?
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[Luther Grimace]

Yeah the noise comes from #6 and weakens when I crack the line. There is no telling how many miles this engine has. I was told it was up in the 300-400K range but who know since it didn't have an odometer. Is it really expensive to bore these engines and put new pistons in? I am just getting freaked out about having to spend money on this truck. The number 6 piston kinda rocks side to side when you push on it. But most of the others do as well. I was just happy not to see major scarring in any of the cylinders. I wish they had liners though.

[blackdiesel]

A sleeved engine would be nice. But my local machine shop charges 16 per hole to bore. But if you have no scarring, check out for a taper or out-of-round condition. Look closely at the top under the carbon ring and see if you can see any evidence of a broken top compression ring. These engines have two and an oilscraper. Not uncommon to break rings. Worst case scenario, pop that piston and rod out and look the wrist pin over, however I've never had much trouble out of those. Lastly slap a p-pump on there! Haha
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[blackdiesel]

Send me a pic of the head above #6. Check it for cracks in the valve seat. Had a lot of issues with the early first Gens trashing heads 8705777488
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[Dieselwrencher]

Also keep in mind these engines have more cylinder to piston clearance when they're new compared to a gas engine. This clearance is to allow the piston to swell without the piston sticking in the bore. Around here, I can get a block o-ringed, decked, bored and cleaned for $550. Without o-ringing it'll be $300.

And on the cracks in the valve seats, just because there is a crack doesn't mean it's junk. If the valve and seat seal, you can run it a very long time. Usually the heads that are junk have long and deep cracks. IH casted heads are really bad for this. But the non IC first gens were prone to cracking more due to the 9mm hole for the nozzle to pass through.

[blackdiesel]

Originally Posted by Dieselwrencher

And on the cracks in the valve seats, just because there is a crack doesn't mean it's junk. If the valve and seat seal, you can run it a very long time. Usually the heads that are junk have long and deep cracks. IH casted heads are really bad for this. But the non IC first gens were prone to cracking more due to the 9mm hole for the nozzle to pass through.

Exactly. However we're trouble shooting a down cylinder so gotta look @ all options!

Good price on the block work w/rings btw...

[Dieselwrencher]

Originally Posted by blackdiesel

Exactly. However we're trouble shooting a down cylinder so gotta look @ all options!

Good price on the block work w/rings btw...

I totally agree. I have a really good machine shop for the 5.9's. Technically this cylinder isn't dead, it's hitting and when it's hitting it's knocking. Since he's already ruled out injectors and rod and main bearings, the last piece to the equation is the wrist pin and bushing. If it were a valve it would be losing compression. Bla bla I have seen bad injectors create a knocking situation, but the noise doesn't go away. (Stuck pintle wasn't a cool find)

Luther, you get that rod/piston out yet?

[Luther Grimace]

Sorry if I have been a bit disconnected guys. It has been a hectic last couple of days at work. I managed to pull the pan and get the rod and piston out tonight and sadly this is what I found.




What are my options here? I checked on some machine work but I don't know if it wouldn't be better to just swap out the long blocks. I found a P-pump long block for $550 that had 250K on it. I'm almost thinking I should do that compared to machining this block. This is a major road block for me budget wise.

[blackdiesel]

Originally Posted by Luther Grimace

I was just happy not to see major scarring in any of the cylinders.

And that didn't scar the cylinder? Machine shop can bore that cylinder out and press in a sleeve so you can run a standard piston or just leave it over bore and run one .010 or .020 in that cylinder. (yeah yeah i know what you're thinking... It'll "throw it of balance" but this was the recommended repair procedure they told us in Cummins class for the b series)
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[blackdiesel]

I'm sure I've even got a good std piston laying around id give ya if you sleeve it
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[Luther Grimace]

It did scar the cylinder but it was down low in the bore and didn't see it til I got the piston out. I have heard that is a recommended repair. I guess because the mass is the same? If I just get one bored I guess I will still have to strip the block down completely for machine work? I just wonder what the cost would be compared to me buying a used long block. The machine shop I talked said 380 to clean, bore, hone, and install cam bearings and freeze plugs which seems high. I'm sure if I just bored 1 hole it would be considerably cheaper.
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[blackdiesel]

Like i said my machine shop is 16 per hole to bore. Personally since it could easily have half a million miles on it and the history is unknown, id freshen them all up but i have gotten by with much less in the past.
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[Dieselwrencher]

Don't let the machine shop bs you. There is only one cam bearing in the block and it is behind the gear housing. $550 for a long block isn't a bad price. Does it have the fuel system? Let's see a pic of the cylinder wall. If you can get all the aluminum off the wall, you might be able to hone it out and run it to save money. I've got a couple of non ic pistons. If you want send me your injectors and I'll have my brother check them while it's apart.
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