Compression tests.

#1 150 psi
#2 155 psi
#3 125 psi
#4 120 psi
#5 130 psi Doesn't look too bad, does it???
#6 92 psi :eek: :eek: :eek:
#7 135 psi
#8 110 psi :eek: :eek: :eek:

How much of this do you suppose is due to the 214K miles? Camshaft wear? If anybody paid attention, it was the number six lobe on Discochef's truck that was wiped out.

I'm trying to make arrangements to swap the tranny and transfer case. Once that job is done, swapping the 4.2 I got from Slade should be an easy question to answer.

I have done a coupla engine swaps, but never swapped a non-serpentine engine into a serpentine engine compartment. I'm assuming that using a spacer between the crank sprocket and the dampener will be necessary-anybody got any insight for me? I'll call Pendy on the way to work tomorrow and maybe ask some of the techs at work what they think. Worst case, I haven't talked with Robinson in a couple of months-won't he be surprised to find I've crossed to the dark side. Where's Luke when I need him to draw me back?:flipoff2:

Looks like my work is laid out for me, eh?

Peace,
PT

stop winning get er done damit :p :p

Where are the wet compression test reading?Also do a leakdown before you condemn it.Cams have to be pretty wiped out to drop compression that low,usually you can see the lack of motion in the rocker arm when they're that bad.Camwear also shows up on running compression tests before cranking tests.

BTW,most dealership mechanics only know straight part installation,not what you can swap around to make work:shaking: (not to discredit dealership mechanics,they usually know the current model technology very well,they just can't waste time hacking things together)(:flipoff2:)

afirover,did you pick a diagnostic platform yet? You can run down here and check ours out anytime.

Dunno man, I've done plenty of short to long snout crankshaft conversions, with the spacer going over the end of the crankshaft. What you are talking about is going the other way, long to short, right? Not sure about that as the crankshaft is much shorter. You'd need a really long bolt and I'm not sure the dampener would be properly supported. OR is the serpentine engine in question the '95 3.9 that has a short snout crank ( an odd one that I've had to deal with that stumps a lot of people) which will look like it should work, but the keyway on the crankshaft is longer than regular short snout cranks (fawk). Meaning youd have to extend the keyway on the 4.2 as the short keyway will drive the oil pump but only just engage the serpentine dampener (PITA but can be done) assuming the 4.2 is a short snout. I have no idea what the end of the 4.2 crankshaft looks like. It's the only one I don't have in my collection of engine fronts....arranged in chronological order across the back of a bench.

Matt Browne
Overland Engineering

PT,

I thought those numbers were for the motor I gave you! You'd better check it before you decide you want to put it in your Disco.

I hope my engine measures up! :worried:

You need to use a spacer on the lower crank pulley... I have found that an old lower timing gear works nicely... Just grind off the teeth....

PT,

I thought those numbers were for the motor I gave you! You'd better check it before you decide you want to put it in your Disco.

I hope my engine measures up! :worried:

Nope, these are the numbers for the existing 3.9 I'm gonna shoot some oil into the cylinder and repeat the test.

Matt-it is the '95 3.9. I'm gonna have to tear it apart someday to find out what I have to deal with here. Cobbling keyways won't be that big of a deal, especially if the key is supported in a robust fashion for the majority of its length.

Leakdown is nigh impossible as I don't have an air compressor available where the truck is right now and as it sits, it can't be driven to the store. The consensus of the guys at the store is camshaft. The fact that the rear-most cylinders have such low compression kinda supports the contention it might be the cam (I'm really hoping it is the cam so I can just throw a cheap cam at it and drive it until I get a 4.2 together. There are so damned many trails and folks inviting me to go it's driving me nuts (granted that isn't a very far ride:flipoff2: )

PEace,
PT

Do you have a dial indicator handy to check lift at the valve? You wouldn't need to know the spec,just if the suspected cylinders have less lift than the good ones.

Years ago I made a vacuum waveform tester to test for worn cams and burnt valves that consisted of a GM map sensor and a 5 volt power source,hooked it to a lab scope that was triggered off of #1 cylinder,adjusted the time scale to put all 8 pulses on the screen and you could easily see valvetrain problems in the waveform. Most modern engine analyzers now have some sort of vacuum waveform patterns built in.

Do you have a dial indicator handy to check lift at the valve? You wouldn't need to know the spec,just if the suspected cylinders have less lift than the good ones.

Years ago I made a vacuum waveform tester to test for worn cams and burnt valves that consisted of a GM map sensor and a 5 volt power source,hooked it to a lab scope that was triggered off of #1 cylinder,adjusted the time scale to put all 8 pulses on the screen and you could easily see valvetrain problems in the waveform. Most modern engine analyzers now have some sort of vacuum waveform patterns built in.

I have a handful of indicators, just to try to find them where they are stored.

My vantage meter is back home for the time being, otherwise, I'd be cobbling up a waveform viewer like you described :flipoff2:

I'm gonna go shoot some oil into the cylinder and see what I find.

PT

OK, shot some WD-40 down the two worst cylinders. They both came up to about 135 psi.

Now I'm wondering if I followed good experimental practice by ensuring the adapter was screwed home securely, did I crank each cylinder the same number of times, etc.

Either way, I'm very pleased at the apparent condition of the inside of my high-miles engine. Perhaps a cheap cam/lifters and a new set of heads with good manifold bolt hole threads and a set of headers might not be all I need after I get the tranny/t-case swapped out. Oh yeah, somewhere, I have a set of new five-o motorsports injectors.

Thoughts?

PT

OK, shot some WD-40 down the two worst cylinders. They both came up to about 135 psi.

Now I'm wondering if I followed good experimental practice by ensuring the adapter was screwed home securely, did I crank each cylinder the same number of times, etc.

Either way, I'm very pleased at the apparent condition of the inside of my high-miles engine. Perhaps a cheap cam/lifters and a new set of heads with good manifold bolt hole threads and a set of headers might not be all I need after I get the tranny/t-case swapped out. Oh yeah, somewhere, I have a set of new five-o motorsports injectors.

Thoughts?

PT



Looks like it's time to re-ring to me then,camwear won't show a bump in compression during a wet test,only leakage past piston rings will.I'd repeat the compression test on all cylinders wet and dry,trying to be as scientific about it as possible.Make sure the battery is fully charged,hold the throttle wide open,count the number of revolutions as you do the test.I know your working conditions aren't ideal,just try to do the testing like you were working on a customers truck.Use a ruler to check valve lift,like I said,lift has to drop dramatically to affect compression during cranking due to the time it has to fill the cylinders.Once running there is significantly less time to get the air in and out so you should get a misfire under load before it'd ever show up on a compression test.
I would borrow a air compressor and rig up some sort of leakdown test,even without a leakdown tester,just to verify where the compression was escaping.take the rocker shafts completely off to eliminate having to find top dead center of the compression stroke.With both valves completely closed you can hold the crank so that you could check the leakage past the rings at different positions of the piston in the bore.(hold tight,best to block the breaker bar with something)
I know you know all this,it's just easy to fumblefvck around when trying to mess with you own crap in less than ideal situations:beer:

BTW,trade that vantage in on a vantage pro,lots of rover info,even has pinouts for the engine processors and much better display,plus BIG rechargable battery.Unfortunately for me it doesn't have SLABS,gotta DII in my bay,ABS/TC/HDC! lamps on,no codes,scan data locks up the moment you start driving.You can read the wheel speed sensors turning the wheels on the lift so it ain't them(didn't think it was,TC/HDC! come back on immeadiately after bulb check):confused: I'll figure it out but haveta do regular parts installer work on Jappers before I have time to mess with it.

Yeah PT,the 4.2 will have to have the keyway on the crankshaft lengthened. You will not need a spacer for the dampener though.

Boy do I feel dumb. 'Round here a waveform veiwer is a "fat cat used to be a hippie in the '60's leaning over the hood of his Lexus watching the waves, wishing he had the balls to get out there......." ha....and if they do get out, old MB tools by and sets the alarm off with his exhaust.:flipoff2:

Matt Browne
Overland Engineering