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Old Today, 10:33 AM   #1
68isgreat
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Join Date: Mar 2023
Location: Portland, OR
Posts: 53
Engine swap yes or no?

I've got a frame off 68 short stepper that I'm about halfway through the restoration. I've put in a 1990 350 tbi out of a Suburban that I was told only had about 90k miles on it. I have a 700r4 that isn't hooked up to it yet. I put a new Painless harness in it and a new distributor, plugs and wires and it runs well enough, but has a lopey idle. Both injectors seem to be working fine. The check engine light on the harness isn't on or flashing. I did a (cold) compression test and most of the cylinders are 125psi, and cylinders 3 and 5 (driver's side in the middle) are weak, around 100 and 110 psi). Plugs in 7 and 8 in the rear are also oily, and one or two others as well. It sat on its side for a while before I bought it, and there was water in the top of the left head under the valve cover from rain seeping in. I turned the engine upside down on a stand to get all the water out, but I wouldn't be surprised if the valves are a bit rusty. There is no water in the oil, so that's good. A couple of the push rods have a bit of surface rust on them. Very minor oil seepage at one spot at the rear of the intake manifold, which is common with these apparently. I'm not a mechanic, but it seems like it obviously needs a valve job (which maybe is causing the lopey idle?) and new intake sealant, and who knows if the rings are letting oil seep in.

Given all that, and the expense associated with head work, and the fact I would like to use this as a long term daily driver, would I be better off just spending another 2k for a stock crate long block, or just try to drive it as is for a while. I like reliability, and don't like tinkering with engines. I just want them to run well, out of sight and out of mind.

This is my first time doing this, so any advice is appreciated. Thanks!

Last edited by 68isgreat; Today at 10:42 AM.
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Old Today, 01:41 PM   #2
LT7A
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Join Date: Oct 2015
Location: PNW
Posts: 3,543
Re: Engine swap yes or no?

I'm not an engine expert, but if you're that far along, I'd drive it for a month and then check all of those things again. Much of what you're concerned about could be from the engine sitting and how it was stored. If you're not happy in a month or two then a crate engine might be the answer. Regarding the idle specifically, you will probably want to verify that it has the stock cam.
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