I'm back: Engine ID questions for oil pan replacement

[MassMan]

It has been a while, but I'm back for more! My hunk of junk is finally running well and moving under its own power thanks to all the help I got here.

Recently, after a full day of pulling logs and brush, I noticed oil running off the bottom of the pan. The starter was soaked and oil was burning off the passenger side exhaust. After replacing my valve cover gaskets I finally tracked it down to a rust hole in the oil pan right next to the starter motor.

After looking at replacement oil pans I have a few questions. It looks like I need to know if my engine is a 1 or 2 piece seal, whatever that means. When I bought the truck I was told it had a relatively new, dealer installed, GM Goodwrench 350 (it replaced the original 305). Now, I just scraped off enough grime to see the casting number and it reads 3970014, which was supposedly made anywhere from 1968 to 79 and could have a 2 or 4 bolt main (whatever that means). Is there any way to tell what type seal I have? Is there anything else I should know when shopping for oil pans? Is my engine really a rebuilt block from the 70's? I wish I knew a thing or two about engines, but that's why I have my membership here. So many questions, so little time...

 

[onetonbb74]

That casting number indicates a 2 piece rear main seal, as far as the mains go, 2 or 4 bolt were offered and you won't know until you pull the pan. There will be 5 main caps that hold the crankshaft to the block. The 3 in the middle will either have 2 bolts holding in on, or 4 bolts holding it on. Hope that helps.

 

[MassMan]

Thanks! That should be enough to order a new oil pan. Does anyone know how I can tell when the block was cast? I'd like to know if this really is a crate motor or not.

 

[MassMan]

Shoot. I know that 86+ used the 1-piece seal, but what's the difference between 55-79 and 80-85 oil pans?

 

[63chevyll]

If dipstick is on drivers side, then always a 2 piece seal.

If pass side it could be either 1 or 2 piece

 

[MassMan]

Definitely driver's side. That was easy!

 

[63chevyll]

Cool, the pass side dip stick needs a little more proof to determine. The pass dip sticks were only used for a few years in early 80's

 

[80' 427]

If you can find one get a MD truck one for a little more oil capacity. Otherwise stock should be easy

 

[MassMan]

MD for medium duty?

Still not sure if I should go with the 55-79 style pan or the newer 80-85. I'm going by the available parts on ebay at the moment.

 

[80' 427]

drivers side dip stick, 55-79. Pass side dipstick 80-85. If you have a good wrench yours is actually both but you can by the one that matches your dip stick and be OK. Yes Medium Duty. I tend to drive up and down steep stuff so I worry about oil around the pickup

 

[MassMan]

Well, that's easy. I'll order one with a new gasket today.

Anyone care to weigh in on the durability of the aluminum pans? I assume they wouldn't hold up as well to an off-road life. They wouldn't rust like my current one though.

 

[diesel4me]

I'd steer clear of an aluminum oil pan,my brother had a Mr.Gasket ribbed one on a 305 in his '69 Camaro some years ago,and the baffles in it broke off from vibration and ended up taking part of a piston skirt off!!...they crack easy too,if they make contact with anything hard..the fact they cant rust is about the only advantage IMO--but I've seen aluminum turn white and pasty after getting road salted too....................................................................................................I used J-B Waterweld putty on my diesels rotted oil pan,its been on it for over 3 years,its now starting to ooze oil from under the putty,I think the pan rusted more under the putty...it didn't leak at all till this summer--it'll get you by till you can fix the pan or replace it...I tried using solder and tinners flux to seal the scabby areas where it leaked first,then wire brushed it with a drill and used brake cleaner to wash it off good,after draining the oil,then I put the putty on,and this was in the dead of winter on a 20 degree day,so I put a droplight with a 100 wat bulb next to it for 2 hours to harden the putty...it was like a rock by then,and I put the oil back in and got away with not changing the pan yet...

 

[63chevyll]

My best recommendation is ft a perma dry felpro gaskets and a stock steel pan.

 

[MassMan]

Good to know. I'm going with the FelPro 1-piece gasket and a summit racing stock pan.

Anything else I should do, inspect, or replace while I have the pan off?

 

[MassMan]

Luckily I don't need a quick fix. I don't have the $$ to get this hunk of junk on the road so she's stuck hauling logs around the yard. Maybe I'll fork over the cash once I replace the front lift blocks with a proper lift all around...

 

[phreddei166]

Good to know. I'm going with the FelPro 1-piece gasket and a summit racing stock pan.

Anything else I should do, inspect, or replace while I have the pan off?

The old " might as well " do an oil pump while your there. $ 30 cheap insurance.

 

[diesel4me]

X2!..and I'd ditch that nylon oil pump drive sleeve too,its only about 5 bucks for a steel one...I put a oil pump in a 305 about 3 years ago in one of my trucks and Auto-Zone had the melling stock oil pump for 12.99!..the drive sleeve was about 5 bucks,and the new screen was less than 10 bucks...I did the timing chain & gears at the same time,the 3 peice Cloyes stock setup with metal cam gear was only 20 bucks,the one peice rubber oil pan gasket costed more!...Steve,thanks again for the gas tank and delivery!..much apprciated,now I can get to work on stopping at least one of my trucks expensive leaks!.....