I went through Dayton the other day with a friend in his gmc. We drove right past the GM assembly plant in Moraine where the diesels are put together. This particular truck I was riding in has 303k original miles on it. It's had some switches replaced in the transmission and that's it. Nothing else major has been done to it. The guy that owns the truck now bought it from a friend of his when it had 167k on it. The engine has had Shell Rotella T oil in it the entire time.

303K! What year is your friend's truck? What sort of driving does he do?

I'm going to turn 200k on mine soon, and I'm shooting for 300k. But my problem is that I dont' know what happend the first 165k of the life of this motor.

Guess we'll wait and see.

I should say that both guys that have owned this truck are retired truck drivers and their maintenance is obsessive. The truck is about a 94, it has the old style dash wich was updated for the 95 model year. It has an auto tranny. The truck has been used primarily as a tow vehicle. It has pulled a camper across the country many times. The guy that ownes it now has a small sawmill and it makes deliveries and pulls a fair amount of trailers. The trip to Dayton the other day was to deliver 65 bundles of Kindling to a garden center. 65 bundles @ 50lbs/each is 3250lbs.

Friend asked me what the stock hp rating on that truck is, what is it? I guessed 200, wasn't sure.

Everyone wants to bash the General for the 6.2 and 6.5 diesels. My experience has been very good. My dad had a 89 2500hd with a 6.2 and 400 turbo tranny. We absolutely pulled the crap outta that thing. It was not uncommon to pull two 350 bushel farm wagons at about 10 ton a piece. That truck got a tranny rebuild at 190k and a head gasket and valve job at 200k.

If im not mistaken the stock hp rateing was 185 and it had 375 Ft/Lbs. If I am wrong somebody chime in, I have been able to achieve about 270 at the motor on prob 500.00 worth of mods!

Countrycoach - it could be helpful if you would post the dyno runs indicating 270hp\engine and 220hp\rw, with horsepower rpm and torque rpm for reference.
Gives all the guys just beginning their upgrades something to shoot for.

See ronniejoe's posted dyno runs in the FAQ section, with a 'prepped' truck including charge-air cooler and hi-flow hi-pop 'marine' injectors for comparison\reference.

Then check out Turbine Doc's FAQ post as to complete method required to achieve that level of power.

And, yes - my truck has '95 OBD-1 EFI PCM with identical electrical\mechanical upgrades to the 'stock' 21.1:1cr engine as theirs.
TD and I run Heath's v2.0 upgrade, ronniejoe runs Kennedy.

Yea sorry about that, my truck made 220hp at around 4,000 rpms! :ro) Yes that is right I turned my truck 4 grand and made max power at the rear tires, which is about 260 or 270 at the flywheel. I don't know the tq right now because the dyno I went to didn't have the stuff to read tq on a diesel! If any body doing upgrades has some questions just let me know. I did all the work my self and it has made for a very nice driving rig! My next mods are going to be the intercooler, HO injectors, SSdieselsupply cold air intake, and I am going to have my turbo sent off to be modified! Then I will post some new numbers hopefully w/ tq readings! :ro)

PCM rev limiter didn't shut you back aT ~35-3700rpm?

No my truck will pull all the way to 4500 rpms! That is where that dotted redline, turns into a solid red line! :D

that is the first i have seen the cold air intake on ssdieselsupply. i wonder why it wont work on a 97 or newer?

My red line starts @ 3500, goes full red @ 4000 rpm, i'm only able to achieve about 3300 rpm before it shifts.

that is the first i have seen the cold air intake on ssdieselsupply. i wonder why it wont work on a 97 or newer?


Thats because the newer trucks use a MAF (mass air flow) sensor. IIRC it senses the amount of air coming through the filter, to much and it will give an error code (I think ):h ) but then again, I thought only 1500's use this sensor and not 2500 and 3500's? The real experts have to answer this one:)

PCM control is off the crank sensor - digital, non-variable.
Rev-limiter is off the crank position sensor.

Tach is off the alternator, and accuracy(?) is dependent on alternator pulley size and belt slippage.

None of these EFI engines will run crankshaft 4500rpm, and those shadings on the tachometer are merely sales ploy.

I think 75 bucks would be well spent at a local GM dealer, taking digital data with a Tech-II, for a realistic reference.

Your tach can vary depending on charging loading, where the belt is slipping, so it is not a good reference if flogging these low-rpm engines.

Check it out - may save your engine.

OBD_II 1500 and some LD 2500 trucks have MAF sensor.
HD2500 and 3500 do not.

All have that 90deg hook-back duct out of the air-box.

My truck is a '94 also. My tach shows dotted red from 3500 up to 4500 where it goes full red. On flat ground unloaded, standing on the load pedal, it'll shift 3700~3800. Going up the inclined ramp to get on the expressway unloaded, it'll wind up to ~4300


The '94 models used a different injector pump than all the others. That might have something to do with these winding up higher.

220 at the rear wheels? With only an ECM, Exhaust, & Boost Controller?

Gimme a Break...



On Edit: That must be one Helluva Correction Factor...

I was trying to say it nicely, Billman......;)

You guys should really have your tachs checked against a Tech-I or -II.
Replacement alternators seldom - read, never - have the correct diameter pulley.

Or do the rear wheel dia\rotation\mile vs rpm calculation for sanity check.

Sorry...

This is becoming a habit of mine. Not being nice.

Where are these numbers corrected to? 3000' below sea level? That's what NHRA ProStockers call 'Mineshaft Conditions'.

I had asked about his numbers a few weeks ago, but it must have gone unoticed.

JD - Does anyone else have a hard time believing this?

country coach claims he dynoed at 260 hp. Ruben claimed 275 with heaths chip 303 with propane. I'd like to see my numbers after I'm done adding parts.

Ok first of all I have alot more than just a chip and a boost controller, if you look closely at my signature you will see what all I have done. Like I have removed the webbing from underneath the intake and chanferd the intake manifold and several other things. It dynoed 220 at the rear tires, witch is around 260 or so hp at the motor. And that is uncorrected on prob a 40 degree night. If you don't believe it I will be at muncie and yall can pay for me to put the truck on the dyno! Maybe yalls is just slower than mine! ):h And if it is that important I will print out the sheet that says my truck made 220 at the rear tires at 4,250 rpms! But yall will have to send me a check to dyno it again cause we didn't print the sheet since it didn't give me torque! Now that I am done being an ass to those who were trying to be one towards me, if you have any questions on things I have done then feel free to ask. Maybe another reason mine makes more power is because where I live. I am about middle state NC. Prob alot closer to see level then some of you! And for those who were talking about their autos' shifting at low rpms mine is a manual so that is why I can turn it harder, and that might be another reason to explain the higher hp figures!! Go figure!

Sure looks like it.....

And, on the same note - a 303cuin engine running 7700rpm pumps ~697cfm, na.

(6.5L engine running 3000rpm pumps ~347cfm, n\a, btw)

How is it possible that the 303" engine can make 700hp thru a 390cfm carb?

In petrochem industry, if the physical thru-put cannot be increased, input pressure can be increased for more volume thru that design limitation.

Relative to engines, that pysical thru-put would be bore, stroke, rpm, or any combination thereof, as you know.

So - 697cfm-displaced 7700rpm flow rate restricted by 390cfm carb.

I remember putting a new 390cfm Holley 4bbl on a 215hp 3.5L aluminum V8, which was sitting mid-ships in a '75 VW Scirocco driving thru a 914-6 transaxle, and thought it was a pretty bad combo, when working the 5-speed thru 2500 to 6000rpm.
Local VW dealer took a bunch of pictures to send back to Wolfsburg.
(Didn't impress his daughter, much, tho ;)).

Meaning - I pretty much got a handle on 390cfm at Barometric pressure performance.
So, what is it - the new math, or something?

I got my intro to ram-air tuning and the very narrow rpm bandwidth with the cross-ram induction system on the 413\426 Mopar wedges back in the early '60s, which GM successfully countered with hi-rise open-plenum intakes on the 396\427\454 and all the small-blocks.

Man - one rpm either side of the sweet-spot, and you may as well have parked it, painted it wood-grain, and planted flowers in it.
(Sorry, DLandy ;) )

And, of course, I understand 'restrictor plates', but - a restrictor carb?

And, is that a 390cfm 4bbl or the 390cfm 2bbl?

All silliness aside, what's your take on that?

I don't want to rain on anyone's parade, but, when the diesel page built their 300 hp, 18:1 penninsular diesel 6.5, it only dynoed 205 hp at the wheels, about the same as a lot of stock powerstrokes. It ran, runs very well and it is very quick but for real world numbers a diesel needs to be run on a dyno with other diesels that there is a reference for. For instance it is a pretty well known fact that a Duramax in stock trim puts out about 240 hp to the ground. A stock 6.5, about 155, with an automatic. Replace the auto with a manual and you will put down some better numbers. The main thing is that all dyno's are not equal, so in order to be fair to all concerned it is best to go to a dyno day and put down your best numbers while others are doing the same and you will see a pattern. Most diesels will duplicate hp numbers on the same type of dyno (mustangs are a good example) with the same type of mods and will be repeatable. I am highly sceptical of 260 rwhp with stock compression and a stock injection pump. I had a highly modified 6.5 with a mechanical pump that was wide open on the fuel setting and running 20 psi of boost with 18:1 compression and a .030 over bore and on a good day with low ambient temps(which really helps hp) it might have made an honest 230 hp at the wheels and it hauled ass for a 6.5, but as much as I liked that set up, it didn't come close to the 350 rwhp I have now and man can you feel the difference!:D

I agree with you D.!!!! I have never seen another diesel run on this dyno. My buddy has an svo mustang that was on the dyno before I was and put out some lower numbers than he expected. Now whether or not my trucks reading was accurate or not I am just going by what the dyno told me. I would be glad to put my truck on the dyno against other diesel trucks and see what it does and it wouldn't hurt my feelings one bit if it didn't put out the same numbers cause I too was shocked at the results. But what I don't like is people on here accusing me of lieing! But I do know on my dyno run the truck didn't hit its max boost of 16psi!!! I don't think the rollers had enough load to get it to. Now I don't know if that means I got a higher reading than I should or a lower, that is for you dyno "experts" to decide. But what I do know, on an in ground dyno jet my truck made 220 hp at the rear wheels!! For those who don't believe it then sorry I guess I just got a special truck, or for some strange reason the dyno didn't read correctly. But I did three pulls, 1st= 200, 2nd=220, and the 3rd at normall temps did about 210. Guess I will take it to another dyno here locally so I can get a print out and some torque numbers to post on here before I run my mouth more and come to muncie and get my feelings hurt. All im saying is offer some more possibilitys to the high output like D. did before you tell me I am crazy or that I did some off the wall crazy correction factor!

OK. You're not lying. You are only the messenger.

The Dyno/Operater is lying to you.

Anything can be made to look good. Location means nothing.

You don't have enough mods/fuel to make that HP claim judging from what I've read.

Ok, I will try to make arrangements this weekend to take it to a diff dyno. I will try to get a print out of what the truck does so I can take a picture of it and put it on here. That is perviding I have the extra cash to do so.

Sorry...

This is becoming a habit of mine. Not being nice.

Where are these numbers corrected to? 3000' below sea level? That's what NHRA ProStockers call 'Mineshaft Conditions'.

I had asked about his numbers a few weeks ago, but it must have gone unoticed.

JD - Does anyone else have a hard time believing this?
I tend to take people here at their word JUST like I do you Billman, and when GMTD starts talking bout his 390cfm carb thingy back up there a few post. I, too would like to see that dyno pull if nothing else biut to say WOW and nice job. I wished we could somehow all get together and have a dyno test and tune weekend or two across the country. I know most of ya ex-perts make more power than I can afford or even put to ground down here in southern OK, but It would be cool to see the changes with different trucks and different tuning.
BUT THATS JUST ME.
BTW Any of ya believe I pulled over 125,000 pounds last night? Just checking

See if you can entice someone else to go with you with a different vehicle or ask the dyno operator what some other diesels have put down for numbers. One other thing, ambient temp. has a major effect on hp. The numbers that any diesel engine will put down at 20f will be considerably higher than same engine at 90f. That is why our trucks will really run good at cold temps due to the higher oxygen saturation in the colder denser air. Torque numbers are also what it is really all about with a diesel any way. Torque is power and the flatter your torque curve is the longer you can hold a gear towing a load.:D

Yea I know all about the temps! It was a pretty cold night, prob 40 degrees. I am currently trying to find another dyno, but if all else fails I will go back to that one and get the actuall print out and post it just so you know that is what I read. I will try and get something this weekend or next week and post it on here for you guys to bash some more!

Bowtie

I'm not exactly sure what your saying. Are you buying 220 RWHP? It sounds like you are. If so, then this is the thread for you.

This place has broken my BS-meter on a number of occasions.

Just for the record, again. I'm not claiming high HP numbers. I never have. But I will say that I can make 15+ boost, run ambient intake temps all day long, and not see a hint of smoke out of my tailpipe.

But I would be surprised(read: shocked) to see more than 190 at the wheels.

Once I get another chance to dyno my truck, it it turns out to be bs, then I will be the first to admit it. But you can't blame me for sharing what I made on this particular dyno with the group. It may well be a boguss run, but then again maybe my truck just makes power! It would be great to confirm the 220 rwhp, but wether or not the next dyno run proves me or not, there will be those of you who will still call bs on it. But just for my ego and knowledge I will spend the money and make a few more passes and get a print out to try and post on here for all of you to read. And if it turns out I am only making 180 at the rear wheels or worse I will still post it so yall will no I am not telling a lie. Only the next dyno run will tell! ):h If it turns another 220 rwhp run, then maybe all you non believers should go buy a 94 2 wheel drive 5spd dually and talk to Mr. Bill heath so then you can claim my numbers. But if it doesn't, no biggie, because I garuntee by the time I go to muncie it will make atleast 220! :ro) Either way instead of bashing my truck, maybe you should be asking in more detail of what I have done!?!?!?

Well put Bowtie, and just to give yall some food for thought till I get a chance to prove my self, at a quarter mile dragstrip my truck went 17.8's leaving the line at idle. Now I know those hp calculators on the net aren't exactly right, but if you plug that elapsed time in with even an 8,000 pound truck (wich is prob lighter than mine) it shows a net hp of 280 wich would be at the motor. But I have no way to prove my time so I guess that doesn't do much good either! But I do know that on that run I outran a 97 powerstroke reg. cab long bed 4x4 w/ a 5spd and a few mods. And that is all that counts right guys?

In countrycoach's favor is the 40deg ambient temps, same as in Canadian Rigger's favor.
At CR's current stage of development, this summer will be a real killer, based on established, proven data.

I'm at work, now - more later, but re-read D.Camilleri's post, above, for relative info, incl results from a prepped 18:1 truck.

Thankyou bowtie, that is all I ask. I am trying franticly to find a dyno that is open this weekend and has an open spot for my truck! But it is supposed to snow down here in the south saturday and you know how us southerners act when the white stuff starts falling! haha But as soon as possible I will make another dyno run and get the print out so I can prove my self wrong! lol or vise versa of course! I don't know about some, but I look forward to meeting some of you at muncie and admireing your rigs! Maybe by then I can put a hurtin on a stock power choke on the dyno! ;-)

Munice, Munice where?? when ?? who invited ??? what we doing there ??? Dyno'ing ???? can I bring my "COP" car too???):h ):h ):h

Hey i see a reference to my truck in this post, well at least i'm not forgotten. Anyways it seems my truck is making 0 - 60 times closer to 12 seconds now and i can't figure out whats changed to make it do that.

I'm in the pondering proccess of trying to figure out how to get an IC in front of the radiator and think i can do it but i will have to get a custom rad built along with a custom IC. If things go as i think they should, i will be cutting down my rad by 3" on the passenger side to allow for IC tubes to be run.

Firstly though i would like to do some fabrication to the battery box and route my intake air from beneath it and behind the signal light, i should get good ram air from there, i'm planning on removing the lights completely and putting some kind of bug mesh in its place. Then i just need to find some small lights to mount elsewhere and all should be peachy.

Hey CR, on another post about a 6.5L builup there's some links to a $500 spearco slim bar and plate Ic that will fit in front if you move the condenser core over toward the radiator, It's only 3" wide x 18" long x 8" tall or something like that.

I read something about that, i thought it went under the truck??

You could put it there, at an angle or you could put it in the direct airstream for maximum effect.

To countrycoach - I want to reassue you, in light of other responses, that neither I or Billman are indicating that you are lying.
Nor would I do so, unless I was on-site and had seen the numbers, and knew that you were inflating them, as is the male wont.

See - that's why women don't make good engineers. Guys keep tellin' 'em, ' naw, babe - that really is X number of inches, believe me!' ;)

I question the numbers in one manner, Billman in another - sort of good-cop\bad-cop scenario. ;)
(Personally, I enjoy his responses).

It is, hopefully, to get the most correct data.

Your upgrades indicate a particular power level, but your posted figures are much greater than a fully prepped 18:1cr engine will produce.

Therefore- the resulting questions.

You do not indicate a charge-air cooler, which would result in the PCM pulling power as Intake Air Temperature climbed over 240deg, a temperature level which 15psi sustained Boost would easily achieve.

D.Cam and I both remarked on the 40deg ambients - that would improve your chances of keeping IAT lower, particularly by also lowering turbo inlet temps.
Reducing inlet temps by 10deg lowers compressed temps by ~10deg.
Lower temps, greater density, more oxygen per cubic foot, more power.

To understand Bill Heath's, or any other vendor's, stated data, you must inquire as to the circumstances of that data - charge-air cooler, hi-flow injectors, advanced timing, etc.
What is involved to achieve his 60hp stated increase?

I referred you to ronniejoe's posted data, including dyno charts, with a prepped - all available options installed - 21:1 engine, for reference.
That is the absolute maximum, without liberal application of snake oil, that you - specifically, and collectively - could hope for, without nitrous or propane.
Final drive ratio can alter the torque readings.

Conceptual understanding prompted the questions, hopefully without intimidation.
When numbers are presented, far in excess of established data, it tends to raise questions, honest questions.

My truck? I can guarantee you that, with all the improvements, it makes an honest sustainable 195hp, with no apologies.

ronniejoe's and Turbine Doc's trucks - well........they will pull the earwax outta your ears from zero to over 90mph. At which point, I was sincerely urging a cessation of the test.....

Awsome ride.............

To countrycoach - I want to reassue you, in light of other responses, that neither I or Billman are indicating that you are lying.
Nor would I do so, unless I was on-site and had seen the numbers, and knew that you were inflating them, as is the male wont.

See - that's why women don't make good engineers. Guys keep tellin' 'em, ' naw, babe - that really is X number of inches, believe me!' ;)

I question the numbers in one manner, Billman in another - sort of good-cop\bad-cop scenario. ;)
(Personally, I enjoy his responses).

It is, hopefully, to get the most correct data.

Your upgrades indicate a particular power level, but your posted figures are much greater than a fully prepped 18:1cr engine will produce.

Therefore- the resulting questions.

You do not indicate a charge-air cooler, which would result in the PCM pulling power as Intake Air Temperature climbed over 240deg, a temperature level which 15psi sustained Boost would easily achieve.

D.Cam and I both remarked on the 40deg ambients - that would improve your chances of keeping IAT lower, particularly by also lowering turbo inlet temps.
Reducing inlet temps by 10deg lowers compressed temps by ~10deg.
Lower temps, greater density, more oxygen per cubic foot, more power.

To understand Bill Heath's, or any other vendor's, stated data, you must inquire as to the circumstances of that data - charge-air cooler, hi-flow injectors, advanced timing, etc.
What is involved to achieve his 60hp stated increase?

I referred you to ronniejoe's posted data, including dyno charts, with a prepped - all available options installed - 21:1 engine, for reference.
That is the absolute maximum, without liberal application of snake oil, that you - specifically, and collectively - could hope for, without nitrous or propane.
Final drive ratio can alter the torque readings.

Conceptual understanding prompted the questions, hopefully without intimidation.
When numbers are presented, far in excess of established data, it tends to raise questions, honest questions.

My truck? I can guarantee you that, with all the improvements, it makes an honest sustainable 195hp, with no apologies.

ronniejoe's and Turbine Doc's trucks - well........they will pull the earwax outta your ears from zero to over 90mph. At which point, I was sincerely urging a cessation of the test.....

Awsome ride.............VERY NICE POST gmctd

Guys I pulled some of the posts were straying way off topic, it's getting long also Lets start a new thread and try to keep to the topic, I have been away the last week or would have commented earlier.

CC, Bowtie the intent is not to jump on any individual it happens sometimes inadvertantly, use the PM feature to the member you feel wronged by, text message boards hard to infer ones tone with, there is no facial or verbal reference to determine message originators tone. Hopefully I'll get a chance next weekend in Milton Fl to do another dyno run myself, put some numbers out better than my last run.

Type of dyno will have big impact on numbers observed, also for 6.5 you also need to make sure the torque converter remains locked up, you need a Tech 2 for this or lock up control like Ronnie Joe has.