Swap Done... It's A "Pooch"

[painthorsman]

Well... The engine swap from 454 to freshly rebuilt 6.2 is done. All the little pitfalls with the glow plug system are fixed.. thanks to all the DP members who posted tips on here
The engine starts instantly, idles smoothly with the normal GM diesel clatter (sounds wonderful!) BUT!! It is a DOG! on the bottom end! It doesnt seem to come alive till you get it wound up pretty good and then the "power band" is pretty narrow and it could really use a Gear Vendor overdrive. I had a 67 dodge power wagon with a 225cid slant six with a one barrel and the same 4 speed tranny and gear ratio (4.56), that would outperform this truck in every aspect except fuel economy! What gives? I must be too used to overhauling and driving/operating "real" diesels made by international harvester and cummins etc...
I have done about everything... new timing chain, pump advanced about 1/16th to 1/8th towards drivers side, new filters, electric boost pump between the tank and the OEM pump. Pump and injectors are supposed to be less than one year old on rebuild. If you mat it from a stand still in second gear it does ok.. third gear shift is a dog until the rpms come up a little and fourth is about the same. It will smoke black some at lower rpms and when it starts getting into that "power band" range with the throttle held down... it smokes pretty good and seems to pull pretty decent... but up till it gets to that "magic spot" it is a SLED!
Anyone have any ideas to help it out.. short of turboing it? That is part of the long range plan but the chips are lean right now.
Exhaust is a Flowmaster set up with the 2" pipes coming from the manifolds and Y'ing into a single 3 inch pipe from the transmission area to behind the right rear wheel.
All comments would be welcome.

[britannic]

That powerband is worrying. Have you timed the engine with a meter @ 1400-2000rpm to see what the timing is really doing?

Have you confirmed the cam timing is correctly set?

Do you have an EGT gauge to let us know how much fuel is getting into the engine?

FYI: before I swapped out my badly stretched timing chain for gears and got the pump timing locked in, I had a fierce powerband above 2500-3500rpm, but very little torque below that.

[britannic]

Just a thought, but if your engine clatters like a Cummins, it may be too advanced. Try setting the IP pump timing with the marks lined up, since you have a new timing chain.

Let us know if it has less power after this or more - it'll help with benchmarking it, if you don't have a timing meter (strongly recommended).

[painthorsman]

Its not really a "power band" so to speak... its just that it doesnt have much guts on the bottom end, under 1800 to 2000 then at about midrange to upper rpms... pulls pretty good.
The cam timing is correct ( built the motor myself) compression is between 425 and 450 on all cylinders (cold) If cam timing was out much it wouldnt run... or would run rough. It starts intantly when warm and within 1-2 seconds on 35 degree mornings. It runs very smoothly, great idle!
I don't have a lumi meter to check "actual" injection timing. I set timing with pump/gear marks aligned and harmonic balancer mark at TDC. After engine was finished and test fired, I re adjusted pump so mark was about 1/16th to 1/8th towards drivers side.
I dont have a Pyro installed yet... not sure where to put the probe in a NA engine.
I'm tempted to advance the pump a little more or turn the fuel screw a little... something needs to happen. For example in fourth gear under 35 mph it has 0 guts when you floor it... keep in mind that this truck has 4.56 gears and would act like a jack rabbit and haul a _ _ with a gas burner in it... doing the same exact test. With the 6.2 it just mildly accelerates up to about 40 mph and then it starts to come "alive" ... all the way to the govenor limit... I'd say under 1800 rpm, its about "helpless" especially if I was towing anything or going up a hill.With that gear ratio, I should be able to pull the world apart with a "coffee grinder" I have yet to hook my 5th wheel camper to it, to see if it will pull it more than 40 or 50 mph.... at this rate I have my doubts.

[britannic]

FYI and not wishing to infer that you didn't set your cam timing correctly, but my cam was very retarded due to the wildly stretched chain and starting was still excellent, but there wasn't much torque down below 1500-1600rpm.

If you're already seeing black smoke, don't add any more fuel, it'll just get worse and the EGTs will climb.

Assuming the cam timing to be spot on: too much advanced or retarded IP timing can cause black smoke, so will not enough air, either through retarded cam or restricted air intake/exhaust.

Did you actually drive the vehicle with the timing marks aligned?

With the timing gears installed, I had my IP aligned on the marks and got black smoke; turns out that the timing was too advanced when set to the factory's marks and I had to retard it to 1/16" to passenger side of the line.

A new timing chain does have a little stretch from new, so the factory marks should normally be about right.

Before you add any more fuel, do get the timing checked out with a meter so you have a benchmark to work from.

[painthorsman]

Hi Britannic,
I will re set the timing marks on the IP to aligned and see what happens today. It doesnt clatter bad at idle and is quieter than a cummins or powerstroke. Throttle response is good but the pullout is somewhat sluggish till I get close to the halfway point in each gear... then it does pretty good, though not quite as good as the 6.9 in my old 83 F350 dually
Where can I get a timing meter for these diesels? I'm assuming you are using a luminosity probe in the #1 glow plug hole to get exact point of injection?

[britannic]

I got my meter off of eBay; it's actually a Ford Rotunda lumy/mag timing meter for timing the 6.9L/7.3L mech. pump engines, but they share the same glowplugs with our engines and it works fine.

I use #3 glowplug for the lumy probe with 99.5 degrees offset, because #1 is 9.5 degrees offset at the mag probe and doesn't give enough time for the two probes to provide an accurate reading.

Here's another thought:

If the IP timing is too advanced, then the engine will be fighting itself until the auto advance systems cancel above 2000rpm, after which there will be a point that the timing becomes close enough, that the piston will be just @ TDC as the injected charge starts burning - this would give a powerband.

During my testing, I had similar symptoms to the ones you described and found my timing was at 3-5 degrees BTDC @ 1400rpm. This much advance will shock the piston's crown as it's hammered the wrong way on the compression stroke. Eventually, the glowplug tips may melt and possibly the piston crowns will start to thin just before they crack/melt under heavy load.

However, all of this may be moot and your timing could well be fine (too much advance will definitely give very loud clatter at 1400-2000rpm) - sometimes it's the IP itself that can be out of whack.

[painthorsman]

Sorry I'm so late in getting back to this... I set the pump marks at aligned and the thing really became a sled!!! So I put them at about the thickness of the line itself towards the drivers side and it did quite a bit better.. better than when it was at about 1/8th or a little more towards the drivers side. Its still not Great! but then I'm used to driving powerstrokes and turbo cummins engines... my other truck is a 99 powerstroke dually rated at 250 hp! I guess I'll have to get used to it accelerating at nearly about the same speed as the 350 cummins in the three axle dump truck I drive at work ( loaded with 20 tons of rock ) :( I'm not sure what to do at this point to improve it...unless it is to trash the intake breather for something better... what a joke! huge breather with a intake hole you cant shove a tennis ball through! Someone at GM musta been picking their nose and reading Mad Magazine when that thing was laid out on the drafting table. The breather on the old 6.9 Ford that I had, had about the same filter area but the actual intake (snorkle) area is nearly twice as big... not to mention that ford used the 4911 series DB-2 IP... Other than being slow as hell... its reliable... starts right up every time and runs smoothly all the way from idle to near gov limit.My only other gripe is that the heater won't put out but about 1/2 the heat that it did when it had the big block gas engine in it... It gets warm... in about 20 minutes! and thats all..no more scorching hot air coming from the heat ducts.

[britannic]

If you don't have the dough for a turbo just now, you could implement Doc Lee's double air cleaner setup and let that engine breath some more. I reckon you'll need to get your torque back by replacing the timing chain (timing gears preferably if you're going to keep it) as well.

My wife just got back from driving my milspec (her first drive since I installed the timing gears) and reckons it's as quick as her Duramax to 60mph now :D !

BTW, I can out accelerate my friends' 7.3L Ford PSD and 2002 Dodge Cummins - they've both driven my truck and can't believe it's as quick as it is. In fact both of them had to get the trucks chipped and air upgrades, 'coz it didn't feel right to be passed by an old 1985 military truck :D !!!

[Lothar]

Doc lee's double air cleaner setup?? where can i learn more?

[painthorsman]

Get the torque back? This engine is a total fresh rebuild,from bottom to top/front to rear... including timing chain... it has plenty of torque... just not much pizazz until you get it wound up to about 1800 to 2000 rpm... just guessing by the sound of it... its a shame no one ever came up with a reliable factory type tach for this engine... you'd think one of the "brains" at GM would have done it considering that a factory tach was an option on gas burners from 73 to 87, taking the normal gas gauge spot and installing a large tach and putting a small gas gauge in one of the little gauge pokets on the left side of the dash.

[britannic]

I glued 4 rare earth magnets onto the back of the harmonic balancer using Loctite 330. Installed an Isspro magnetic pickup and wired that directly into a gasser tach and gauge cluster from a Suburban or similar that matches the 1985 setup I already had.

Works great and looks completely original.

Someone else on this forum had done a beautiful job of installing a tach into the fuel gauge in their cluster - sadly, the recent forum thread deletion catastrophe has lost who and how forever...

Dr. Lee wrote this article: Tachometer Alternatives (http://www.thedieselpage.com/members/features/swangertach.htm) detailing how to build a an electronic tachometer drive.

You can also use the R terminal on the alternator to drive a tachmeter; Dakota Digital makes a convertor that will help calibrate the output to match the tach. and alt. pulley ratio.

[ 10-27-2003, 07:51 PM: Message edited by: britannic ]

[painthorsman]

Hey Britannic,
Can you post directions and or photos on how to do the magnet/harmonic balancer/isspro pickup to factory GM tach? Particularly what wire goes where and does what... If you'd like you could e mail it to me at pnthorse@nalu.net ... you may still have my email address from when you sent me that IP cable clip... by the way THANKS MUCH ! Had to get a new cable though... couldnt find the bushing for the IP end of the cable...

[britannic]

I don't have pictures I'm afraid, but the good news is that it doesn't matter which wire you use from the magnetic pickup. I just followed the IssPro instructions and it worked.

It's very important that the magnets are installed with the correct polarity side out. The ones I got from Isspro were painted blue on one side to make it easier. If I remember right they are set to repulse the magnetic pickup. In any case, I placed the magnets on a tank cutter mounted in my drill and spun them in front of the mag. pickup to test the tach. before installing everything.