help with an oil leak

[ryan_289]

Ive got a problem with an oil leak and need some help. Saturday I purchased a 78 GMC 3/4 with a 350. This motor was "supposedly" rebuilt in 2000 and parked in 2002 when the old man passed until last year sometime. We drove it 65 miles on Saturday morning with no issues. On Sunday I made the 220 mile trek home in it. About 60 or so miles into the trip I sprung a leak and had to stop every 30 miles or so and put a quart in. Its leaking somewhere on the front right side of the engine. I cant tell where its coming from. There isnt much oil in the engine compartment. Its leaking down and then blowing all down the right side under the truck. Made a nice little smoke screen and got oil on the wifes car behind me. (she was happy about that!) Other than the oil leak, the truck made the trip just fine. Engine seems to run great other than the leak. Not sure how accurate the factory gauge is but oil pressure settles out just a tick above the 1/4 mark on the gauge.

Last night I took 3 cans of brake clean and sprayed the front of the motor down but I cant seem to find the leak point. Any suggestions?

 

[ryan_289]

Here are a couple pics.

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[74 Shortbed]

If it's leaking that bad it should leak at an idle, I'd take it to a car wash and wash the whole thing down real good, then fire it up and let it idle and watch for oil it should show up pretty quick.

 

[84c10Tony]

^^ what he said, last time I had one go like that, the rear of the valve cover cork gasket had dried up and cracked, cleaned it up and replaced with rubber, making sure the valve cover bolt holes were flat, added longer spreader bars with the valve cover bolts torqued correctly, and was it good for a long time.
When the bolt holes get bent from over torquing it tends to add to a leak.
Now, "first things first", you owe your wife a nice detail, and cook her some dinner...; )

 

[ryan_289]

Is there supposed to a bolt in these holes in front of the fuel pump?

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[CSFJ]

one of them should give access to the fuel pump pushrod. That one should definitely have a bolt in it. Not sure if the others are blind holes or not.

 

[HotRodPC]

I'm going to go with it's the fuel pump rod access hole spitting oil at high rpm, like on the freeway driving speed. Find a short bolt and put in it. Don't get one to long or you'll rub or seize the fuel pump rod.

 

[chengny]

I'm going to go with it's the fuel pump rod access hole spitting oil at high rpm, like on the freeway driving speed. Find a short bolt and put in it. Don't get one to long or you'll rub or seize the fuel pump rod.

X2 that for sure.

But it makes you wonder - why would anyone take the time and effort to pull that particular bolt? Unless it was never installed during the rebuild. If that were the case, the previous owner must have driven real slow and/or added a lot of oil.

 

[HotRodPC]

X2 that for sure.

But it makes you wonder - why would anyone take the time and effort to pull that particular bolt? Unless it was never installed during the rebuild. If that were the case, the previous owner must have driven real slow and/or added a lot of oil.

Which might be why they sold it. Maybe they actually did know it had an oil leak? Or, the bolt was loose and dropped out on the trip.

 

[ryan_289]

There was not oil all over under the truck when I went and looked at it. I also didn't notice any oil leaking or burning off on the initial 65 mile trip. Those speeds were around 45-50 mph. I didn't really notice it until I was consistently driving around 60 mph. Either that or a bolt was in it and it fell out.

How deep can I go there without causing problems? The shortest 3/8" bolt I had was 3/4" long. It threaded in there but I ran into resistance before it bottomed out. I used 4 washers to space it out. I estimate ive got somewhere between 1/4 and 1/2 threads in the block with permatex #2 on the threads.

 

[chengny]

The top bolt hole (the one that aligns with the fuel pump push rod) can accept up to a 3/4" bolt - without the bolt impacting the rod.

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Here's an SBC fun fact:

Some block assemblies are supplied from the factory with a 3/8" by 7/8" bolt with (2) thick washers under the head allowing the OEM bolt to be re-inserted without the washers to secure the rod in place. Once the (2) fuel pump mounting bolts are tightened, the bolt securing the push rod can be removed and re-inserted with the washers under the head thereby preventing contact with the rod but sealing the hole.

 

[AustinDube]

Check the valve cover gasket and if its not that how about the distributor holddown gasket

 

[vkh]

Isn't it pipe thread for the access hole? Or is it just big blocks that use pipe thread? Or am I just totally off here?

 

[CSFJ]

Isn't it pipe thread for the access hole? Or is it just big blocks that use pipe thread? Or am I just totally off here?

The sbc used a regular bolt thread for that hole. Allowed use of a longer bolt to hold the pushrod out of the way for fuel pump installation. Pull the over length bolt out, releases the pushrod, and install the short bolt with some sealant. Works pretty slick. Never knew the bbc used a pipe thread there. Seems almost odd. Are you sure it wasn't a p.o. modification?

 

[vkh]

The sbc used a regular bolt thread for that hole. Allowed use of a longer bolt to hold the pushrod out of the way for fuel pump installation. Pull the over length bolt out, releases the pushrod, and install the short bolt with some sealant. Works pretty slick. Never knew the bbc used a pipe thread there. Seems almost odd. Are you sure it wasn't a p.o. modification?

Don't believe it would be a modification, I blew my first block and have a different one now. I might be remembering wrong but I think it was a plug with a square end to remove it on both. When i did ny pumps I always had a to stick my finger i the hole to keep the rod up. I might have to go outside and take a peak for my sanities sake now.