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Discussion Starter #1
Guys I’ve decided to post on here as I had very good luck years ago on a 4bt conversion and 7.3IDI also. I’m not here to build up a race engine but I am looking for maximum MPGs. This is a lowered, light 74f100 that a 1993 6bt will be going into. Engine currently is stout with 322000 miles that will be getting a good cleaning and all new gaskets. The 5 speed is very clean but will get a rebuild that I already have all new bearings and kit for along with new input shaft because a few teeth have a few spots on them. I had the 9” pumpkin rebuilt with a Daytona large bearing kit added and a factory 31 spline limited slip with factory 2.47 gear set out of a car. What I need help with is possibly three things at the moment. Looking for help on turbo, injectors and fuel pin. I’m thinking I may go non intercooled at first so that’s something to think about on these parts also. Fuel economy on this highway cruiser is top priority.

Fuel injectors are wore and hazy and all signs of injection pump being stock. So I want a injector that is very efficient but if going up one size helps in wanted outcome that’s ok. I want real word advice on fuel pin if I should just turn my factory one or is there a proven aftermarket for a bit more upper rpm power with no extra smoke on low rpm range? And last with more boost comes more fuel so I’m lost on sticking with my factory H1c that is tight and seems like no issues or a slight up grade for overall help for my MPG goals? Sorry for long post but I really looking for real word help because buying parts over and over gets expensive! Thanks for the help in advance guys, Greg in Texas.
 

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Adding fuel without intercooling is a recipe for melted pistons. Minimum instrumentation required is an exhaust gas temperature (EGT) gauge. A boost gauge will help you sort out your fuel modifications.
 

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Russ I understand that very well. When I pull the engine and clean up the manifold it will get tapped for the pyro before it heads for ceramic coating. I do not plan on using a engine fan as I bought a 4 core aluminum radiator and will try to use a stock 93 intercooler as it is the narrowest one I’ve found. My issue is if I cannot make work behind the radiator I’m not cutting up my front grill to make work. Most of the conversions I’ve seen guys swapped to 78-79 grill that is more open.
 

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Nice project. A few things. First off the injectors. The IC 6bt had an odd ball injector. The were 6x.009 tips with 145 deg spray angle. The early non IC engine had 4x.012 tips with 155 deg spray angle.The 6x tips are only about 85% the flow capacity of the 4x.012 model. The smaller holes atomize the fuel a bit better and the smaller cups in the pistons made for a better burn. It was mostly a smog thing. All this being said, whether you change injectors depends on how much power you plan to make. The stock size can do way more power than the engine currently has. You definitely want to have those either rebuilt or replaced. Over time, the pop pressure decreases which essentially changes the timing as to when they fire. Makes for a poor running engine. If you want more, a common unit would be the 5x.012 tips.Those could probably carry you to 400 HP or maybe more. As Russ mentioned, don't even think about turning up the power without an intercooler. More power takes more fuel and the boost to burn it. As boost goes up the heat level in that compressed air goes up dramatically. Can easily get 300 deg F or a bit more. Hot air has less oxygen and makes poor power. Now for the turbo. The stock H1C that you have was OK for the power level the engine was set up for, but if you want more you need to consider a better turbo. The base HX35W found on the P pump model is much better. Boost will come on quicker. If your were going into a higher power level, the HE351W or HE351cw would be possible options. Have to remember that you base engine had 160 HP and 400 lb ft torque. That's nearly as much as a 429 CJ ford had and it all come on down around 1700 RPM. Remember, as you turn up the power the torque goes up too. A few adjustments to the HP and the torque can be north of 600 lb ft. The Ford 9" is a super rear end but it's not unbreakable. Dodge trucks used a Dana 80 which makes the 9" look small. You mentioned you're ceramic coating the exhaust manifold. Very good idea. You want to keep the heat in there because that's the energy that drives the turbo. Also, consider coating the turbine housing on the turbo. Before I went to that expense, I'd want to be sure of my final selection on turbos. Another trick that can gain you some power is a bit of minor porting work on the exhaust. Place a manifold gasket on the head ports and mark it with a felt tip pen. Might spray some silver paint on the area first so you can see the mark. Gently grind any metal inside the mark to make sure the ports are even. Then take the exhaust manifold and do the same only with that one you remove the mark. That small step from the smaller head port to the larger manifold port will increase the gas flow and help turbo boost a tad. It's not gigantic, but every little bit helps. You mentioned no engine cooling fan. I assume you plan on some electric fans. Even with a 4 core radiator, it can get hot.
 

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I run a smaller intercooler on my 4bt. On a long steep hill, I sometimes have to back off on the fuel. I use a very conservative 1,100 degrees F as the "Chicken-out-point". The engine is 33 years old and I do not absolutely trust the accuracy of a gauge that I bought "off the shelf" at Autozone. I had a core 6bt that someone exceeded the design limits (Pulled Texas Canyon, heavily loaded, with a hot "tune"). Piston #4 was pitted, piston #5 had pot holes, and #6 melted through. At 75 years old, I am not wildly enthusiastic about removing, rebuilding and replacing engines, thus a more conservative approach.
 

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I'll chime in. I have a bit of experience with what you are wanting to do. I bought a 1993 W250 with 6bt new off the showroom door and owned it for 17 years. Been messing with these engines ever since & I'm in the Cummins diesel business & have worked on hundreds of these engines over 26 years.

There is some good info mentioned here & some not so good.
Because you are going for max mpg & only are wanting a slight bump in power and I'm, guessing on a tight budget, the below is my suggestions.

Stick with stock fuel pin & turn to the deepest setting of pin.

If you want to go non-IC, with your IC inj pump/engine that's fine, it can be done safely. Remember a original non-IC engine had a different higher flowing inj pump from factory than the IC ones. The non IC pump had larger, higher flowing DV's (delivery valves) & ran higher timing ( 1.4 vs 1.25 ) & 40hp larger flowing injectors, right from the factory. You won't melt anything even if you add some more power than your IC engine came stock with, if you pay attention to your pyro gauge and water temps. Yes, a IC would make you even more efficient but as mentioned, I'm guessing your doing this on a budget. You can always install one at a later date.
Just make sure you buy a decent gauge/probe kit, such as an Autometer or Isspro & install probe in the rear 3 cyl runner just before the T3 turbo flange. Cummins has tested the 6bt's at 1250 deg's for hours on end, with no damage. 1300 for 1 min straight with a 5 min cool down before running 1300 deg's for 1 min & 5 min cool down cycles all day long, with no damage. We have tested tons of pyro's accuracy and the good ones ( Autometer & Isspro ) were all well within 30degs of gauge reading. It is good practice to say to yourself 1200 deg's is max for any steady load. If you need to push much harder for a short under 20 sec run, at say 1600 deg's, this is a non issue. I've been there done that many times & so have hundreds of others. 22 years later engine still runs like a rapped ape & still has original stock pistons.

1st gen IC injectors are not 6x10's as mentioned, they are 6x9's. With high mileage, they would enlarge to 10's with fuel erosion but along with that, the VCO sealing area will be worn out, pop pressures drop on average 40 bar & that's the reason they lose their efficiency & need replacing.
I can build you a bit larger set of inj's at 6x11 145 deg ( sorry, I have no access to 6x10's, as I'm not aware of that size available ) or as Charlie mentioned a set of 5x12's which are not capable of making 400hp without a super modified VE inj pump that takes modifying internal parts of the inj pump etc.

Run your H1C and install a 16cm non waste gated exhaust housing. Certainly DO NOT install a HE315CW unless you want to lose 1.5 - 2 mpg. A HE351W which is a completely different turbo than a HE351CW would work but is not needed unless you decide to go with more power than what you mentioned.

Hope this helps.
 

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Discussion Starter #8
I appreciate the help and all info giving. I was looking at the 16cm housing on eBay as I figured the 12-14 might be to small and cause to much heat. As far as power I only want more if it really helps me in the fuel mileage department. I will do the fuel pin stock as that free and who does not love free! Injectors I would not mind a factory rebuilds I’m just scared of everything on ebay and internet as you may not get what you actually payed for. I have a friend that bought some cheap Chinese injectors and his truck runs great and he offered me his injectors as he didn’t send in cores and it was a 92 truck. Money wise i figured I’ll have $5-7000 in it all after interior is done so money has not been a real factor on this one. I’m thinking this will be my last build. I’ve spent to much of my life in my shop time to start traveling so that’s why the Cummins in my f100.
 

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For what your doing, the 16cm is a good compromise on spool up vs fuel mileage. I sell a fair share of 16cm housings for the 1st gen crowd. You want/need to keep boost under 10psi as much as possible to get good fuel mileage. Going over 10psi isn't going to hurt anything but fuel mileage. So the name of the game is as much under 10 psi the better. The lower the better, as long as egt's are expectable & useable. I run 5psi on flat ground & 525+/- for egt's at 60mph.
As for your buddy buying cheap Chinese inj's, good luck on that one. lol
If the 92 inj's he gave you haven't got over 200k on them, they should be fine if you get the pop pressures re-set, as they will be as much as 40bar low vs spec of 245bar.
Nothing wrong with saving $.
 

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Mark, my lousy typing or bad memory, the IC injectors are 6x.009. I'll be sure and correct that. Bosch isn't exactly the best at telling you anything though. I had a listing of injector orifices by CPL. The 160 and 175 HP were both .009. 180 HP was .0095 and 215 HP was .0105. When I mentioned the 400 HP point, that's what the injectors should be able to reach, not necessarily the pump. We have guys running 5x.012 injectors on a VE pump 4bt reaching near 300 HP. Since a 6bt is 50% larger I figured it could do 400 HP. One thing I'm wondering on this project is front suspension. The 6bt weighs about 500 lbs more than any engine that would have come in an F100. Might need F250 or F350 springs up front to handle the load.
 

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Charlie, no worries on the 91.5-93 inj nozzle size. No one person can know it all or remember it all. I stick with generally the mech inj engines because of this. After 26 years, I'm still learning stuff. I've recently dug deeper into the valve train of the Cummins engines and understanding the effects of pushrod flex, retainers & keepers, valve springs geometry etc vs hp & egt's etc. Just because the stock pushrods can make over 700hp doesn't mean they are the most efficient etc.

Yes, you are correct on Bosch not supplying much for info.
You are correct on the 160hp, 175, 180 & 215 sizes but remember the p7100 inj's are all 5 hole vs the VE ones being 4 hole for the 89-91 non-IC & 6 hole for the 91.5-93 IC VE inj's. So stating hp to a nozzle or inj is no longer a good practice. Companies used to be all over the place on hp rating for inj's & nozzles & I used to see up to 50hp differnce in power rating for the same inj or nozzle. The public got real confused & I don't blame them.

The 6bt is not 50% larger, it is 33%...3.9 vs 5.9 and power is not on a sliding scale.
5x12's in a VE pumped engine are 350hp at max with just a fuel pin, gov spring & turning original inj pump up to just under runaway, with just these parts, even with the best turbo(s).
As mentioned, it takes modifying internal parts in the VE to go farther.

The p7100 is a different story, as it has a higher injection pressure than the VE so it's capable of making more hp with the same nozzle size.
Take the 370hp marine engine for example. It uses 5x12 155deg inj's & runs 22degs timing from factory to achieve this power. Also the wider spray angle of 155 vs 145 makes more hp & is more responsive. The high timing play's the largest part of making this power for a 5x12 inj in a p7100. Yes, you could install performance parts & turn the power up of the same p7100, using the same 5x12 inj's & make say 500hp if you had enough turbo/air.

All of the above is based off of 12mm inj pumps of course. Larger is a whole different story. The highest hp I know of with a 5x12 155deg inj's is 700hp with a 13mm inj pump & custom ground cam in inj pump. But this is not a good practice for inj pump longevity as a 13mm pump needs bigger inj's to stay alive for long term.
 

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Discussion Starter #12
Thanks for comments again. My truck sets low with drop beams and cut factory coils. Ive got a factory set of oneton springs out of a 72 I’m going throw in there and try. Depending on how it sets I may cut a few coils out to get it to set how I want. My thoughts is I may have to cut a few inches out of the oil pan if needed. My oil pan in my Mercury was cut down for engine to set as low as it could.
As far as power again I think I would be super happy with around 500lbs torque as that’s where most of my low end 460s I’ve had should have been around. I built them all with c6 autos and 2.47-2.50 gears. Great cruisers but still not good on fuel.
 
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