Yepper, 100% agree, it's the carbon build up that sometimes makes you have to use the Brass Punch to get em out but the Dead Blow Mallet is generally more than enough to put em in,

They really shouldn't just fall out, but I've seen it on the 6.9, 6,2 and on the Volvo Diesels, I just haven't done a lot of 7.3 work other than my own truck.

 

Got it. I had taken one of my old pistons to my shop today and cut it in half to see how much material is there when you start shaving them. At its thinnest part in the center it’s roughly .575 so I think we have enough material to put a dome in it. I have heard that shaving it down straight across about .040 will get me roughly 17.5-1 compression which is good. I don’t know if this is true but I guess it gets the top ring hot when you do this. We were going to take the pistons and put a dome to it rather than just cut it straight across. We have full CNC so it’s very doable . Is worth it though? Does cutting the piston down .040 really get heat to close to the top ring?

 

I gotta say a 150 is pushing the limits of stock rods as I know of 2 people who have spit out rods on stock rods with a 150.
also with a 150 a intercooler is required if you ever want to be able to use it. I would recomend water meth as well. also if all you are going for is 300 whp a 110cc pump and a 257 turbo will do that. why go for more fuel than you need to accomplish your goal?

 

I have been debating stepping down to the 110 but I also am probably getting the psd rods due to for only another 400 bucks of getting my reconditioned I can have the bigger rods. Trying to keep it all flowing machine shop is moving slow and been hit with medical. Bills recently so I’m taking it one step at a time I guess

 

If you can get ahold of Justin you might ask him how much he shaves the pistons. He also does ceramic coating which I think is almost a must with 150cc's of fuel. That's going to be a lot of heat.

I don't think it will transfer too much heat to the upper ring, the pistons have a deep skirt and the oilers underneath to keep em cool. If it gets too hot the piston itself will fail. Although too hot ring temperatures will cause them wear out quicker and scar the cylinder wall.

110cc's is probably plenty if you plan to tow with it. If its just a "fun" truck the 150 would fit the bill although it's a bit in price jump

 

watch that 17.5 to one compression ratio. one of our old members here did that, and he had to use ether to start the engine because the compression was just too low.
one running it ran great after it built some boost, but it would not start due to the low compression.

 

The newer versions of the deuce and half military trucks as everyone seems to know them by, are MTVRs and the use an automatic ether injection system whenever it is below I think 40 degrees. Besides this no glow plugs, no grid heater, no block heater. C12 engines are a beast never have issues starting as long as the batteries are food and a fuel canister of ether in it. I was going to look into doing this if it gives me issues starting. Obviously Iv learned this doesn’t impact the motor (unless different go or grid heaters are envolved) so I’d simply unwire the plugs and use ether. I am a little worried about off boost power but I think it will be fine.

 

Who has experience with the R&D cam? I am considering running this cam but not familiar with how regrinds work. Would the pushrods have to change? And I found stock cam specs while it is an inprovment I would like to see a lot more exhaust opening but it it probably difficult with being a regrind and I do understand new blanks cost way to much . Any input would be helpfull

 

Well, we're going to see soon. I've got one in my '88, that is still not fully together yet. Didn't need pushrods- plenty of extra take up room in the lifters on my build.
Part of the problem with valve opening is that there's very little clearance around TDC - like 1/16" of an inch or so. And the piston can follow the valve up within 1/32" or so(.030"). So everything has to be just perfect at that spot on the cam for it to work.

Also, I think if you take too much off the lobe, you lose the case hardening done. The main body of the cam is a ton softer than the lobe surface, which is around 50 HRC(I saw 56 HRC on a stock 6.9 cam, 53hrc on the heel of a R&D, and 50HRC on the heel of a Torque cam. All really good numbers. The body was like... 30HRC?).

Fortunately, our cams use roller lifters and don't wear the lobes like solid lifters do, but still, having good hardness is important for longevity.

 

Well with my plans chop off .040 I’m not to worried about piston clearance but the valve “lash”in general I was worried about How it in total affects valve timing. I guess I just don’t get how you an grind material away and have the valves open more/ longer

 

You're definitely going to need an ether start system dropping the compression that much.

I never understood how the regrinds work either, I'm sure Google would tell all though

 

Who has lost rods with a 150? It took justin several months to blow up his craigslist engine with his big pump that flowed ~190 Per the man himself NA rods should be good for around 450hp, a 150 pump will make a pinch over 400 if everything is in good shape. Im not saying facts and opinions havent changed, i just might be behind the times.


I have his cam, i cant really compare it to anything, but it seems to work well. My 364 lights by 1800, never seen the pyro over 900 in the DP with my 110 (even trying to get them up). EGTs at cruise are 400-500 at 60. It does take away a fair bit of engine braking, but thats to be expected, still not as bad as a psd or cummins though. Im running other justins push rods, just because i had them, i want to say theyre .020" longer. General consensus is you can run the stock push rods with the stage 1, but i would check rocker position on the tip to be sure.

Im going to disagree with the compression comments. It will be harder to start, but under normal conditions it will start with the glow plug system. That said, why though? If youre worried about headgaskets, 0-ring the block. I spoke with Justin pretty extensively about cutting my pistons, in short, he advised me against it. Think of compression the same as you would porting, the better it is, the better boost will help it. More compression gives you better under the curve torque, lower egts, spools the turbo faster, easier starting, theres really no downside until you start spitting out gaskets. Which even given the IDIs history, doesnt seem to be much of an issue on the 7.3s with studs.

I would coat the pistons just to keep the heat out of the oil, not worried about the pistons getting too hot. As you guys have already hit on, you cant coat the rings, and thats what will cause problems in the long term running hot.

As far as power and what not. I bought the 364 and psd rods because i wanted a 150, and im going to be pulling a 2 car trailer. I dont want an auto, but short of dropping 2k on a flywheel, a dual disc clutch isnt available, thus the 110. Knowing what i know now, i wouldve bought a 257 and 110cc from the start. Especially as i cant even use all the 110 without my coolant temps getting out of hand. Im very very VERY strongly considering trying to sell my 364 and buying a 257. Then if things change and i go bigger, well, i can always throw a 369 on top of it. The 364 would be great if my gearing wasnt so tall, that said, if i stay with the 110, i dont need the extra airflow, and the extra response would be welcome. Also, i really like the idea of compounds, just because. Do some reading on power driven diesel's towing twins if youre curious, pretty impressive numbers and characteristics. When i moved down here to the valley i got to try a little experiment, i wasnt dissapointed. My 92 out towed my grandparents stock 2011 6.7 psd, not by any runaway margin (and i wouldnt be able to sustain it do to coolant temps) but a win is a win and ill take it.

 

I lost a rod at, well, near zero HP. It evidently just snapped during a cold start. No boost, and the end results didn't appear to be caused by bending or other stress - the other 7 looked just fine.
The consensus, after posting pictures here, is that it was just stress in the rod and it just... failed.

Justins rods, on the other hand, had *all* bent before one finally failed.

I've also gotten a couple of JY motors, one a 6.9 and the other a 7.3, with thrown rods. Not sure what caused them, but obviously not a massive power boost... judging by the IP still on the motor.

So, don't confuse 'normal' failure with 'overload' failure.

 

The block has a crack in it. The machine FINALLY called me back and I went and inspected it was in the webbings by a maincap . I was suprsed I didn’t have any bearing issues but he assured he WOULD NOT build this and juice it up. Which really sucks because I have already spent a lot of time cleaning and paint parts for it. Besides the block I have everything else exhaust manifolds I took to work and acid washed and painted extra precups and brand new headstuds never been used pm me is you guys want anything I’m going to sell for basically any decent price including the zf-5. I was contemplating a 12v swap anyhow so I’m going to be looking at some soon. I really do like projects that are unique but I think it’s a sign. Let me know if you need anything