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GMC pickup help....

Tamper84

Active User
Active Member
#1
Hey guys, I know that this isn't a mechanics forum, but the place feels like home to me and I figured I would ask. I have an 86 gmc 3/4 ton that has started a pretty big oil leak. It's either the rear main or coming from the back of intake. The problem is, I need help identifying the engine. The p.o. told me its a 283 out of a 69 Chevelle, but I do know they stopped making the 283 in 66 or 67. But considering the size I do believe it is a 283. (Before this truck I have been an all Ford guy) But is there any way to tell what engine I have so I get the right gaskets?

Thanks,
Chris
 

Tamper84

Active User
Active Member
#3
Randy thank you for the site. I will have to check it out.

Bill I will post a picture when I get home. Other then this oil leak it does run pretty good. And that's why I was thinking its not a 69 motor. I'm just hoping if it is the rear main, it still doesn't have the rope seal in it!!

Thanks,
Chris
 

Tamper84

Active User
Active Member
#6
Well if it is a ho engine it's sicker then I thought lol. This motor isn't a power house lol. But I'm at work right now posting from my iPhone :whistle: So I will post a picture when I get to the house. Probably around 3:30 or so.

Thanks,
Chris
 

Bill Gruby

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#7
Where is my head this morning. I shoud have said 2nd generation HO. But then everyone has there own opinion of the HO. 350-350 in a 70 Elcamino does weird things. :lmao::lmao:

"Billy G"
 

Bill Gruby

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#8
Hmmm -- Giving this some thought I went to the book and it seems the HO first went into Pontiacs in 1968. It just might be one. Some were good, some weren't acording to GM stats.

"Billy G" :thinking:
 

Tamper84

Active User
Active Member
#12
Hmmmm...now Im really thinking here..:thinking: Bad things may happen lol. Thank you Bill!!! It is appreciated. Now Im going to have to find casting numbers.........

Thanks,
Chris
 

Tamper84

Active User
Active Member
#13
I have through both web pages. But one question I still have before I head back out. Where are the casting numbers? Or are they stamped or cast into the block?

Thanks,
Chris
 

Bill Gruby

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#14
Chris -- I have never had to look for them but the last list I gave you says they are at the top of the block. Shouldn't be too hard to find.

"Billy G" :))
 

Tamper84

Active User
Active Member
#17
Thank you guys. I have found the casting number. 3896944 and according to the chart its a 283 made between 65-67. It is in a rough spot to get to. I had to use my fiancees mirror from a compact to see it! I have absolutely no clue why it doesn't look like your pics Bill. But it does have an aluminum Edelbrock intake on it. The valve covers, I have no idea...

j1w2t3, if those places are bad, would it leak a whole bunch of oil? Its a pretty bad leak. Although back there by the distributor is pretty wet along with the whole back of the motor. I'm about tempted to just buy a whole gasket kit and put it all in. I just hope it still doesn't have the rope seals in the mains. Maybe I will be lucky and be able to get the distributor back in the right spot the first time lol :lmao:

Thanks,
Chris
 

Bill Gruby

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Staff member
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#19
In the GM world of engines there are many aftermarket parts that change the configuration of an engine. The manifold probably masks the oil filler hole and it has 350 valve covers with the fill from there. Main thing is that you found what you are looking for. Also you found out this Forum has a place for everyone. Good Luck Chris, it was a pleasure.

"Billy G" :))

Forgot -- The oil sending unit is on top of the block behind the distributor. It will cause a leak like you first discribed. Oil will be all over the back of the engine and firewall.
 

Tamper84

Active User
Active Member
#20
Thank you guys! I hoping that's it. But knowing my luck lol. And thank you all for the help! I'm not a mechanic but I stayed at a holiday inn last night lol. It is really cramped in there to fix anything. I am seriously thinking of throwing a whole gasket kit in it. Just to be sure, I do know I got a leak on the valve cover.

Thanks,
Chris
 

Tony Wells

Former Vice President
Staff member
Administrator
#21
The sending unit is made up of a diaphragm and a linkage to a switch inside if it has an indicator light. If it has a gauge, it still has a diaphragm but the switch is a variable resistor. Point is, the diaphragm can split, crack, pinhole, etc., and it is under direct oil pressure. They are crimped closed at assembly, and not serviceable. But they can leak a lot of oil. Usually you can tell by looking at the crimp area, or where the stud/screw comes through the phenolic.

The PCV valve is suspect for being stuck closed. The design is to recirculate crankcase vapors (smoke) from ring blowby back into the intake and be burned. If it is stuck closed, pressure builds up in the crankcase and can force oil out in weakly sealed areas, or sometimes even pop seals out of place. If there is a leaky seal, a small leak becomes a large leak because of the increased pressure.
 

xalky

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Director
#22
I'd start with the oil sending unit, it's a pretty easy fix, if it's not too hard to get to. Before anything, if it was mine, i would degrease the $h!t out of the motor and pressure wash the rear of it well, covering the distributor with a heavy plastic bag. Let it dry thoroughly, don't start it during that time. Once dry , get some light on it, start the motor and try to eyeball where the oil is coming from. It'll be easier to spot once the motor is cleaned and dry, because it'll shine if you can see it, or it'll be the only oil spot if you can feel it but not see it. Either way it'll be a lot more pleasant to work on when it's clean.
 

irishwoodsman

Active User
Active Member
#23
Chevy is one of the hardest to stop oil leaks, as a chevy owner and gmc i have banged my head against the wall many times, i think you will find it is the intake gasket in the back of the engine that is leaking, slite chance valve cover, if you do find out it is intake make sure you use threaded rods as dowl pins when reinstalling the intake, cause the slightest slip of the intake and wham oil leak, i have seen the small canister type oil sending units leak around the seam at bottom, thats why i always use the manuals oil pressure gage with the copper tubing even in my 2009 yukon, the 283 is one of chevys best engines made they have plenty of torque and with a nice shave of the heads will give you some eye opening adventure, good luck and more chevy power to you. lol
 

Tamper84

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Active Member
#24
Thanks guys!!! It is a big leak in the back. Smaller leaks I don't really care about, but when it looks like the Valdez out there after work I'm a little worried lol. I'm going after work to get some degreaser, idk what kind though. Should I spray it on when the motor is hot?

The valve covers do have a small leak to them also. I will probably change them as well. I'm just a little worried about getting it back in time. I'm going to have to look for the torque specs also. Are they any different since it is an aluminum intake?

I will check out the sending unit tonight. As soon as I find it lol. I'm telling you I was under that thing and even the transmission cooler lines are soaked. It's a mess!!

Thanks,
Chris
 

irishwoodsman

Active User
Active Member
#25
Thanks guys!!! It is a big leak in the back. Smaller leaks I don't really care about, but when it looks like the Valdez out there after work I'm a little worried lol. I'm going after work to get some degreaser, idk what kind though. Should I spray it on when the motor is hot?

The valve covers do have a small leak to them also. I will probably change them as well. I'm just a little worried about getting it back in time. I'm going to have to look for the torque specs also. Are they any different since it is an aluminum intake?

I will check out the sending unit tonight. As soon as I find it lol. I'm telling you I was under that thing and even the transmission cooler lines are soaked. It's a mess!!

Thanks,
Chris
Chris let the engine cool a tad 20 min. before degreasing dont want no flames poping up or castiron poping, and yes aluminum intakes take a different torque setting which can be got from your intake website . Mac:))
 

Tamper84

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Active Member
#26
Well I degreased it and still couldn't see anything. Oh well that's my luck lol. But I do believe I'm just going to put a new intake gasket, valve cover gasket, oil pressure sending unit and new gasket around the distributor. It will be like 40 bucks from Napa for it all. I couldn't see anything from the bottom of the motor. Now the fun begins.........

Thanks,
Chris
 

irishwoodsman

Active User
Active Member
#27
Well I degreased it and still couldn't see anything. Oh well that's my luck lol. But I do believe I'm just going to put a new intake gasket, valve cover gasket, oil pressure sending unit and new gasket around the distributor. It will be like 40 bucks from Napa for it all. I couldn't see anything from the bottom of the motor. Now the fun begins.........

Thanks,
Chris
Chris dont know how much mechanical experience you have, but when pulling the distributor make sure your harmonic balancer and pointer is lined up at top dead center then pop the distributor cap off and make sure the bug is pointing to number 1 plug wire if not rotate engine to make sure number 1 plug is correct with bug and pointer in top dead center, that way when you re install the distributor it will be in time, if any doubt pull number 1 plug piston will be up and pointer will be pointing at top dead center, if you have electronic ignition use the plug and pointer tecnique. Mac
:))
 

Tamper84

Active User
Active Member
#28
Thank you Mac. I hate pulling distributors, I would rather go to the dentist lol. But thank you!! I just hope it will go back together in time :rofl:

Thanks,
Chris