newbie needs 4d55 advice.

[84spx]

Hey there,
My name's toby and I've recently (monday 4/12/10) purchased a 1984 spx 4x4 with the 4d55. it seems to make full power down the highway, but smokes black when into the turbo, also doesn't seem to rev up very fast when starting out. Taking off from a stop on a slight incline is do-able but seems like it should have more power down low. also, mileage at 70-75mph for long periods of time (6hrs) only netted 17.5mpg. What I have observed is what I believe to be an exhaust manifold leak at the cylinder head. would this explain the poor mileage? vehicle only has 114k on it. any ideas would be greatly appreciated. I'm new to diesels but I'm an old hat at gassers. I'll tell ya though, I already think I'm becoming a convert! something about this truck just speaks to me. I have zero post-purchase remorse and I'm looking forward to dialing in my new baby.
thx in advance for any tips/advice/theories sent my way.
toby in flagstaff

[wrngwae]

you may have a bad turbo seal or Leakey valve guides. but it really dosen't have a lot of low end like you would think at a stop. they make the most at about 4000 rpm.......that smoke too could be some old injectors too...

[mikewarme]

Shush you redneck! 4000rpm....... Mine cruises at 3000 at about 68 mph. Look 2 things... Bad injectors, just pull em off and inspect the tips. If they are not flat on the bottom and have a dish etched into the bottom than their junk. $50 a piece to rebuild and they are good as new. Also at 114,000 thats all you get out of those pumps. We had lots of sulfur in the fuel before and that killed them. So rebuild pump and new injectors. You could try timing the pump, but I doubt it will help. I changed my transmission in my 4wd to the 85 model which has a lower 1st gear and it helped alot starting at the bottom of a driveway. Also, I know its not cheap but listen to me. CENTERFORCE clutch. The diesel OEM clutches suck! They slip so much! Get a centerforce clutch. I have one. It made a major diffrence. Anyways if you want good info hit us up. We also have all the parts for repair and restoration to these trucks. Weatherstripping etc. Parts are hard to find

[84spx]

Thanks guys you rock.
Let me give you one more piece to the puzzle that I forgot to add earlier. The temp gauge never gets to the middle. if the engine is cruising down the highway, it'll read just above the minimum mark. then, if you're coasting off an exit ramp, it drops to the bottom of the scale. if you're flyin' and giving full throttle at 3000 rpms going up a hill at 70ish, the needle will climb to almost normal but only stays there for the duration of the hill. I ordered a 179.5 degree thermostat through checker and was suprised to see that they also had a 170 degree thermostat. I've already downloaded the 4d55 service manual in it's entirety and that's where the 179.5 came from. and then there's that crappy gas mileage. 15 gallons is giving me 230 miles. any more ideas? thx again you guys seem like you've been into these for a while and know the ins and outs. I'm so glad I found this site!
toby

[wrngwae]

mike it makes the best hp and torque at 4000. i wouldn't hold it there.....lol......California tree hugger. but your mileage is greatly affected by your fuel pump timing and your injector spray. once you get those knocked out you should be at least in the 20's.

[84spx]

all sounds like good advice thank you. I'm going to go after the exhaust gaskets, find that one or more that's leaking, check the injectors, adjust the valves (why not eh?) and then go from there. the very first step though is to put a proper thermostat in and see if that helps the needle get to the middle of the scale. seems like it's running too cold.
oh and btw I'm looking for two front fenders if anyone has any. mine are rusted pretty bad at the bottoms and I live in arizona and can't be havin' that.