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Upgrades to get better mileage and performance

gcxcountrystar1

gcxcountrystar1

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I have a 1993 chevy silverado 3500 6.5TD. The engine that is in it came out of a 95. I am wondering what I can do to the engine to get better fuel mileage and performance. I am the second owner of this truck. There are no after market gauges. The only work I know that has been done on the truck is the guy had the transmission rebuilt and had bigger gears put in for hualing heavy loads, and the suspenision has been beefed up some. I am new to Diesels, I am used to rebuilding chevy sbc's. I want to learn as much as I can about diesels, i dont know what it is but i am very interested in them. I am looking for any tips or any information anyone can give me. I will ask questions if i dont know what i am doing. thanks for the help. looking forward to what you guys post.
 
Condition of the injectors and timing chain are critical also. The mechanical injection pumps are more fussy about timing and timing chains than the electronic pumps are because they can't compensate for chain wear as the electronic pumps can. Gearing and tire size are a big factor also. It is possible to get near 20 mpg.
 
Since you dont have EFI, the PMD and chip stuff wont work for you. So I would focus on these for economy, and the glows for convenience. You can look into how it is timed, and advancing it just a tad may help economy and performance.

1) 4" exhaust with 2.25" or 2.5" crossover
4) 97+ K47 Air Cleaner Assem With Amsoil EAa111 Nanofiber filter (dry, vacuum clean element, flows like a K&N, filters like OEM paper)
8) Bosch Duraterm Glowplugs with GlowPlug Override Mod
9) Known good injectors, if you don't know Test/Replace them! (For this I recommend finding only standard Bosch Germany nozzles, and just have yours rebuilt and pop pressures set to 2250psi)

For Performance, the above help tremendously, then you can
1) Turn up your IP to output more fuel, and an EGT gauge
2) Get higher output LP, that will put out 12-14psi, like the Cummins FP953, FASS, Airdog, Etc....which need custom installation with fitting adaptors
3) Change to an adjustable wastegate actuator to get more boost, and a boost gauge
 
Welcome to the site & your 1st post :welcome2: ,

What kind of budget are we working with, how many miles on the engine & truck that you know of, you are a few $$$ ahead of the rest of us since you aren't having to do electronic/programming upgrades we 94+ year trucks have to do.

Above recommendations are good ones, but before getting too deep into mods run as stock until you have established your truck has a good baseline for reliability since you are 3rd or higher owner, with no first hand knowledge of "abuse" visited upon it by prior owners, gauges would be one of my 1st mods as they can help you diagnose any issues not known.

Enough can't be said from the list is a DEEP external cleaning of radiator and AC condenser as these trucks tend to run hot, 210+ on coolant is hot on these trucks, the 260F shown on gauge is too hot & too late, what are you currently showing for your coolant temp on highway?

When you get a moment go to the my profile tab and incorporate your truck info into your signature.
 
The radiator cleaning is part of Daves reliability list he linked to.

Bring up a very good point though, coolant temp, the warmer the better for economy, to the point of bad above 210F. So using the stock ACDelco 195 degree T-stat is a must for economy.
 
wow thanks for all the responses i sleep for 5 hours and you guys are typing your hands off, lol.

well first to start for gears i dont know what gears where put in the transmission, all i know is under 45 mph i have to be in drive and over 45 i have to be in overdrive, if i dont my truck starts bucking around 40 to 45 mph.

my buddy is a chevy mechanic and said that when the guy had the transmission rebuilt they put in bigger gears for hauling so my transmission and the transmission doesnt know where to kick in overdrive and when it should kick out.

if im in overdrive driver and it starts bucking i drop it down in to 3rd gear(drive) and it it stops. right now im avg 25 to 28 mpg on the highway. i dont know if it is good i dont know if it is bad but it is better than what my ranger 4.0 4x4 was getting that i traded for this truck.

as for tire size im runing 245/75/r16. how would i go for checking the injectors and timing chain? is it easy for someone to do that knows nothing about diesel engines?

what is IP and LP and how do i turn them up? as for a budget doc im a disable vet, right now money is tight but getting better mileage is what im going for.

my va check should be coming soon so im getting a nicce chunck of money from that im just trying to get a ideal on what i need and what its gonna cost if the price is right, ill buy it, im a craiglist junkie so i always find good deals.

the guy i got the truck from said that he rebuilt the engine him self only has about 30,000 on the engine and tranny. but i cant take his word for it until i see the paperwork that he said he mailed to me, but gut feeling is i wont see it.

what i want to do is get another engine either another 6.5, or 7.3 or 5.9, and rebuild it myself so i know for sure what has been done to the engine. what type of gauges would you recommend?

i just replaced the antifreeze, and the t stat got the t stat from advance dont know what one it is.
 
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well, I am guessing your odometer is off, and by bigger gears I am assuming that means lower differential gearing, not in the tranny. Not sure he can change the transmission gear ratio changes, but maybe he used beefier planetary or something. Your bucking sounds strange, like the PO messed something up. Perhaps he put in the wrong torque converter with a stall speed of 2000rpm or greater thinking this was "better", or maybe the transmission mount is broken?. Changing the differential gears will affect the speedometer and odomoeter which can be adjusted by modifying the VSSB module.

25-28mpg is kind of unlikey with a turbo 6.5, so I would be trying to verify the speedo is accurate, as well as the odomoeter.
 
when i got the truck filled up the tank in the town i got it from, drove 2 1/2 hours doing between 70 - 75 mph and only went through a 1/4 tank of fuel. i know my speedo is correct police here in town have radar set up and when i go past it says im doing the correct speed.
 
gcxcountrystar1 said:
wow thanks for all the responses i sleep for 5 hours and you guys are typing your hands off, lol.

well first to start for gears i dont know what gears where put in the transmission, all i know is under 45 mph i have to be in drive and over 45 i have to be in overdrive, if i dont my truck starts bucking around 40 to 45 mph. Look in glove box should be some codes in there letter & number those are RPO codes which tell which options came with truck I suspect with it being a 3500 code GT5 or 4:10 rear end gears which is what we were asking about


my buddy is a chevy mechanic and said that when the guy had the transmission rebuilt they put in bigger gears for hauling so my transmission and the transmission doesnt know where to kick in overdrive and when it should kick out.

if im in overdrive driver and it starts bucking i drop it down in to 3rd gear(drive) and it it stops. right now im avg 25 to 28 mpg on the highway. i dont know if it is good i dont know if it is bad but it is better than what my ranger 4.0 4x4 was getting that i traded for this truck.

as for tire size im runing 245/75/r16. how would i go for checking the injectors and timing chain? is it easy for someone to do that knows nothing about diesel engines? Ask guy who installed the replacement engine if new injectors & chain were installed then if not or no idea I'd suspect you are due for a set as 100K on injectors is about normal life for them

what is IP and LP and how do i turn them up? as for a budget doc im a disable vet, right now money is tight but getting better mileage is what im going for. IP=injection pump yours is mechanical vs most here having electronic one, LP=lift pump electric pump mounted on frame rail driver side looks like a GM gassers fuel filter, if weak will starve the IP and impact performance, for budget lets go with stock stuff 1st

my va check should be coming soon so im getting a nicce chunck of money from that im just trying to get a ideal on what i need and what its gonna cost if the price is right, ill buy it, im a craiglist junkie so i always find good deals.

the guy i got the truck from said that he rebuilt the engine him self only has about 30,000 on the engine and tranny. but i cant take his word for it until i see the paperwork that he said he mailed to me, but gut feeling is i wont see it.

what i want to do is get another engine either another 6.5, or 7.3 or 5.9, and rebuild it myself so i know for sure what has been done to the engine. what type of gauges would you recommend? Boost & EGT at minimum, trans temp is handy if towing

i just replaced the antifreeze, and the t stat got the t stat from advance dont know what one it is. Can you post p/n of the Advance stat as they often recommend the wrong type, what antifreeze color came out when drained and what did you put back in
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GCX I added comment in blue as far as skill requirements if you have basic mechanical skills folks here can get you through any questions you have, don't let it being a Diesel worry you, this is probably one of the easiest of Diesels to work on you will come across.

As far as new engine to rebuild; if you want easy I'd stick with the 6.5 for the reman engine, another source is a 6.2 engine for bottom end stuff with 6.5 turbo upper end, many folks going that route as those blocks are easy to find as US gov surplus.
 
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buddy said:
The radiator cleaning is part of Daves reliability list he linked to.

Bring up a very good point though, coolant temp, the warmer the better for economy, to the point of bad above 210F. So using the stock ACDelco 195 degree T-stat is a must for economy.
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Agreed Buddy I wanted to add the DEEP cleaning part as some folks just gloss over the rad cleaning as hose off just the outside.

GCX by deep clean I mean the rad comes out, and with garden hose pressure only flush the fins/core from the back side to front as that dead space between the 2 cores is a vacuum and you won't believe the crud in them, takes about 3 hours to clean it, I use AC core foaming cleaner to get the crud it's alkaline so don't get it on the paint of your truck, some guys use foamy bathroom cleaner, simple green works, dilute purple power also works full strength can attack the aluminum, why I like the AC core cleaner as it's safe to use on finned aluminum cores.

With rad out if your AC condenser is still pressurized with freon you can do it in the truck same way back side to front flushing (taking care to not get cleaner on the truck paint), I don't recommend a pressure washer as they can bend the fins over, also I like to use the hot water heater drain for cleaning mine sort of 2 birds one stone work flush the crud out of the heater and the hot water cleans better.
 
Speedometer and odometer both being correct is a rarity in these trucks. The same goes for the fuel gauge. You might get 300 miles on the first 1/4 tank but the rest of the tank will only go 100 miles. Verify the odometer with mile markers or gps. I have yet to see 20 mpg in any of my 6.5 trucks. I did get 28 mpg one time with a 91 with a 6.2 n/a. lp is the electric fuel pump mounted on the frame rail under the driver seat. The IP is the injection pump. Lots of good reading in the FAQ stickies at the top of the page. Welcome aboard.
 
Welcome to the site and congrats on the find.

My speedometer is also spot on and I'm running oversized tires (before it was off with the stockers) so check the odometer as Buddy suggested. When compared against two different GPS units (both of which validate each other as accurate) my odometer is off by 6% which I credit to the tires. In my case, the odometer is short on actual distance traveled. So, get out a GPS or borrow one, zero the trip meter on both the truck and the GPS and head out for a short road trip, weather permitting. You'll know the accuracy within 30 miles and 100 will give you a spot on percentage as to what is what. I hope your's is correct because we'll be asking you for advice on how to get those mileage numbers for our trucks.
 
the part number for the t stat is Part No. 14039 Stant 195 Degree Thermostat, it was the only place around here that had one other places told me it would take 2 to 3 days to get a t stat i dont know why, no one had them in stock and i had to wait over night for that one. i just looked at my radiator and the fins look pretty messed up, so im gonna call some friends and see if anyone has a spare they wanna sell. as for antifreeze its what ever my dad had laying around, it was a 50/50 mix when i drained it it was green had a lil brown tint to it through
 
AC Delco is the best T stat for these trucks. I used a Stant and I had temp swings, the AC works much better.
 
i didnt know about the acdelco t stat but ill most likely replace it just got off the phone with the guyi i traded vehicles with and he said it has new injectors in it he paid 1200 to get them replaced and installed.
 
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