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Old 01-03-2019, 08:20 PM   #1
Praxiss454
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Oil Pan Question - how straight is enough?

I'm in the middle of rebuilding the 230 in my 65 GMC. I just went through and tried to straighten out the bolt holes around the oil pan, and they individually look okay now -- more flat than before -- but when I set the pan on my flat workbench, it only makes contact at the 4 corners of the pan near the larger 4 bolt holes. I can see some light along the entire edge down to the other end.

So my questions are
1. How straight is straight enough?
2. If this is not straight enough, how do I straighten it further?

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Old 01-03-2019, 08:27 PM   #2
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Re: Oil Pan Question - how straight is enough?

My opinion is that you buy an aluminum pan for the better heat dissipation if you can, and throw away that one.

I thought about it, and maybe that bowed out part is where you put the bolts into first, to pull the bowing out of the pan, to kind of help seal it.

Last edited by kazoocruiser; 01-03-2019 at 08:31 PM. Reason: Asking why an oil pan is bowed.
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Old 01-03-2019, 08:33 PM   #3
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Re: Oil Pan Question - how straight is enough?

Quote:
Originally Posted by kazoocruiser View Post
My opinion is that you buy an aluminum pan for the better heat dissipation if you can, and throw away that one.

I thought about it, and maybe that bowed out part is where you put the bolts into first, to pull the bowing out of the pan, to kind of help seal it.
I do believe you are supposed to fasten from the middle outward, which would have that effect. But I don't know if they are supposed to be flat or bowed.

Regarding the "throw this one away" thing, if you can find me a repop pan for a Chevy 230 linear 6 truck, I might just do that. But in all my searching, they do not exist.
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Old 01-03-2019, 08:45 PM   #4
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Re: Oil Pan Question - how straight is enough?

Straiter is better, IMO.....if you have a flat steel surface like an old table saw, lay it upside down and put a piece of 2" strait steel in the groove and clamp it down. Paper under the corners to give a little extra. Hope that helps, may depend on what kind of clamps and hardware you have around.
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Old 01-05-2019, 01:31 PM   #5
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Re: Oil Pan Question - how straight is enough?

It's metal, you can make it into whatever shape you need to. Keep straightening.
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Old 01-05-2019, 10:29 PM   #6
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Re: Oil Pan Question - how straight is enough?

Is there a chance that pan stiffeners were supposed to be used and they got lost in the past?
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Old 01-06-2019, 12:30 AM   #7
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Re: Oil Pan Question - how straight is enough?

If it bolts up & doesn't leak, that is straight enough.

Perfectionism is masochism.
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Old 01-06-2019, 01:00 AM   #8
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Re: Oil Pan Question - how straight is enough?

It's often the bolt holes that get bent from over-tightening that make it not flat.

Use a deep socket as large as can fit between the side of the pan and the outer edge of the pan rail. Set the deep socket standing up on the edge of your work bench and use a hammer (often I use the ball-peen end) to persuade the raised area back down.

Alternatively,

Support the pan rail with a piece of plywood just thick enough to fit, and persuade the offending area(s) flat with a hammer.

Always hammer _on_ something, like a block of wood, a socket, a piece of metal, something.
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Old 01-06-2019, 04:40 AM   #9
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Re: Oil Pan Question - how straight is enough?

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Originally Posted by Blue666(2) View Post
If it bolts up & doesn't leak, that is straight enough.

Perfectionism is masochism.
Before I pulled the engine, it leaked like a mother, but primarily from the rear seal area. I just dont want to get it all buttoned back up and installed in the truck only to find another leak. Maybe I will try to work it a little flatter/straighter for peace of mind.
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Old 01-06-2019, 09:51 AM   #10
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Re: Oil Pan Question - how straight is enough?

Looks like it's stretched from the straightening process ,rather than work it any more place some 1/8 thick washers under the pan ,between the pan and block loosely install the 4 corner bolts (NO GASKET ) then start all the rest of the bolts using the largest washer that will fit in the oil pan rail ,Starting from the center slowly work out going from side to side to evenly tighten down the pan to it's mating surface , this should bring it back to a usable pan once gasket is installed . Try it it works .
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Old 01-06-2019, 01:00 PM   #11
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Re: Oil Pan Question - how straight is enough?

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Originally Posted by Grumpy old man View Post
Looks like it's stretched from the straightening process ,rather than work it any more place some 1/8 thick washers under the pan ,between the pan and block loosely install the 4 corner bolts (NO GASKET ) then start all the rest of the bolts using the largest washer that will fit in the oil pan rail ,Starting from the center slowly work out going from side to side to evenly tighten down the pan to it's mating surface , this should bring it back to a usable pan once gasket is installed . Try it it works .

If your engine is still in the truck, the above method should get it pretty close. You should probably aim to get it even within the thickness of a gasket.

Leaks from the rear main are a completely different beast. You will need to check your crankshaft to see if a groove has worn in. If so apply either a sleeve or remove & repair/replace the crankshaft. Getting the new seal in place while under the truck can be tedious. I have had to repeat the job three times in a month until I got it right.
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Old 01-06-2019, 01:14 PM   #12
kazoocruiser
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Re: Oil Pan Question - how straight is enough?

[QUOTE=Praxiss454;8419463

Regarding the "throw this one away" thing, if you can find me a repop pan for a Chevy 230 linear 6 truck, I might just do that. But in all my searching, they do not exist.[/QUOTE]

If you can find a part number for the original, you might find something that will help you with your repair.

http://www.gmpartswiki.com/browse
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Old 01-06-2019, 01:21 PM   #13
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Re: Oil Pan Question - how straight is enough?

Quote:
Originally Posted by Blue666(2) View Post
If your engine is still in the truck, the above method should get it pretty close. You should probably aim to get it even within the thickness of a gasket.

Leaks from the rear main are a completely different beast. You will need to check your crankshaft to see if a groove has worn in. If so apply either a sleeve or remove & repair/replace the crankshaft. Getting the new seal in place while under the truck can be tedious. I have had to repeat the job three times in a month until I got it right.
Yeah the old crankshaft was wrecked. Somehow (worn thrust bearing? I still don't know) it was getting pushed forward and wearing against the caps. The engine is on a stand in my garage while I rebuild it
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Old 01-06-2019, 02:26 PM   #14
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Re: Oil Pan Question - how straight is enough?

Here's a trick I learned for valve covers and oil pans. If you're willing to use a cork gasket. Get the pan surface as straight as possible, then use the "right stuff" gasket maker and apply to the gasket and pan until tacky. Then set them both, gasket side down on the flattest surface you have (I personally use a 5/16" steel welding table). Put something heavy on top and leave it overnight. The gasket maker is thick and will allow some variances while curing. Your gasket surface will be as flat as the surface you placed it on, same as an engine block or cylinder heads. Works REALLY well for thin valve covers.

OR, get straight as possible and see if you can find the thick rubber Felpro gasket, they are also forgiving. As for straightening, don't be afraid to use a heavy dead blow hammer to tweak the whole thing from the top, or flange pliers to move the edge, whatever it takes that won't score the gasket surface badly. It's just metal, make it your b**ch.
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