GT_80 New Member 1991 GMC K1500 SLE Z71

[GT_80]

HI, I think I have been a member on here for a couple years, not sure I ever posted...

I just bought one truck that I have always liked, and never tried to own...

1991 GMC Sierra 1500 4x4 SLE stepside. It was a 1 owner truck with only 91,000 miles, bought off the showroom floor. It had Ziebart coating in the whole body, factory undercoated, and it is in pretty good shape even for being in New England it's whole life. Has a 350 TBI motor that was blown up when I got it. Came with Dee Zee tube steps, Lund Moonvisor, Lund Racerback, flowmaster single in dual out exhaust, bedliner, and otherwise was just a clean truck- power windows and locks work, everything else was pretty well kept. I had to change out the rear spring hangers and shackles, one cab mount needs to be rebuilt on the frame, one bed mount needs some work on the frame... BY and by, all in decent shape-

I yanked the factory 350, and inside was a horror show - 1 shattered connecting rod (#8), the #7 connecting rod had a chunk missing and one nut was almost all the way unscrewed, the bottom of cyliner #8 had a chunk gone, the cam was in 5 pieces, rear freeze plug behind cam had popped out, and the oil pan had tons of metal in it... The guy said it has a bad connecting rod bearing, and he only drove it 3 miles after it started knocking, and he heard a clunk when he shut it off... I also got the impression that this guy was a bit of a lush and may have been too drunk to know what the noises were making...

SO I ended up buying a complete 1985 Corvette motor with all pulleys and TPI setup, pulled the TPI off, pulled the heads (crappy 468824 heads), cleaned it really well, cleaned my 193 heads off the TBI motor, installed those, new oil pump, water pump, all new gaskets, and I dropped that in this weekend. It should be running this weekend maybe...

The exhaust is a High Flow front Y pipe (not a crappy stock one), to 3" pipe, into a flowmaster 40 series, with dual 2 1/2" pipes.

My plan for the truck is to fix the rust, make it a reliable daily driver, and sell my avalanche so I can get rid of a monthly payment.

The Sierra needs tires, a rear ebrake cable, trailer hitch, and some other odds and ends (many of which I have already purchased)


so what do you guys think?

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[twomanymontes]

Nice truck! Welcome aboard!

 

[mistaake]

Nice! I see you like dark red/maroon/burgundy color trucks Anyway that's insanely clean for the year so IMO a good find!

 

[GT_80]

I got it registered and insured yesterday, drove it to work, about 75 miles round trip- It drives amazingly well for being 24 years old! It is smoother than my avalanche both acceleration, and just cruising, transmission shifts about like I remember a 700R4 shifting... But I put a big 9x15" with 1/2" tubes trans cooler on it in place of the factory crappy plastic tank one on the radiator to keep that trans cool. The cruise control doesn't work currently, but I think I may have unplugged it to get something out of the way while working on it, I have to double check again.

The front of the oil pan, under the timing cover is dripping oil a bit though... Not a ton, but it is concerning- I think the "dry" install of the oil pan gasket as suggested by fel pro, may still have needed some sealant on the timing cover as it's chrome. Chrome stuff always seems to leak- so I will make sure the lip of the gasket is still in place correctly, then clean it all with lacquer thinner or non-residue solvent, and slather RTV all over the cover, gasket, and pan to get rid of the leaks. it won't look that great because I like using the copper RTV as it seems to adhere better, but again, the motor in this one just has to run nice, not look nice.

There was a bit of a lope at idle when I was running it, and at first I thought i might have been because I retarded the cam 2 degrees when I installed it - I really don't know why, but I think now it may have had a sticky lifter because after driving it on the highway, the lope went away and it runs perfect. There was no pinging, no hesitation, it sounds healthy, drives great, so I think for now I am just going to drive it, gauge my MPG and if it seems ok, I am not going to worry about the chip.

I'll get a video soon, and post some more pics.

 

[jkeaton]

Nice truck!

 

[GT_80]

I found the leak- It wasn't the timing cover as I thought... Well, not the major leak anyway- that it weeping a tiny bit, but there are about 5 pinholes rusted through the pan where the deep part of the sump starts on the bottom in the front of the pan- most likely it is where the pan was touching the ground from sitting for years. The pinholes are very tiny, and I thought about JB weld or similar, but since I plan on keeping this truck, I think my better option is to pull the pan, weld it, and then rtv the "Smile" and bolt it all back together. I drained the oil last night (glad I used Walmart oil for the first change now!) and I attempted to clean the pinholes, but they kept weeping so I gave up for the night.

Besides welding, does anyone have any "permanent" fixes? I am positive the rest of the pan has no rot, because I cleaned it inside and out before assembling it. I didn't see any holes at all, just these looked like bubbly paint. Although, now that I think of it, the holes were under the splash tray so I couldn't see them anyway... I would swap the pan out, but the Vette pan is shallower than the truck pan, and has a different splash tray in it since the motor has an additional splash tray bolted to the main studs on the bottom of the crank. I have to see how much the shallow oil pan would be.

Now my avalanche started misfiring, multiple random misfires, and it's running in half limp mode, getting about 6 MPG so I need to get my new truck fixed asap. I hate problems like this...

 

[thz71]

Best fix would be a used pan imo

 

[badazzbulldog]

i would do a new pan they cost under $75 dorman brand you can get one thru auto zone and the part numbers are the same vette or truck motor

 

[thz71]

I used one would probably be around $10 and I've never seen on rot out

 

[GT_80]

I realized how much work is involved it getting the pan out last night... Starter off, trans inspection cover off, support from motor mount to inspection cover off, oil filter adapter off, y pipe unbolted, and I cannot slide the pan off as I thought - I think the correct pan may slide out, but after 2 hours of messing with it last night, I decided 3 things:

1) I'm never not replacing a part like this on another build unless I triple inspect it
2) I am unbolting the motor mounts and jacking up the motor to get the pan off
3) I am replacing the pan- I found the correct truck one at advance auto with a coupon is was like $36 - if I have to take the windage tray off the motor to make the pan fit, so be it.

this job sucks enough to make me never want to do it again- And the straight axle trucks are much easier to work on.