First time engine rebuild

I'm not sure I'll have to do it, but my engine is starting to burn oil and I'm pondering the thought of possibly having to do a rebuild if the rings are shot or something (yes, I know I need to do a compression & leak-down check before I jump into a rebuild). Just curious how hard it is to rebuild a 4 cyl engine for someone who's mechanical but has never rebuilt an engine before? Is it particularily hard or require lots of tools I likely won't have never having done it before? What is some advice you all have should I figure out I have to do it?

I've always wanted to rebuild an engine, but I always thought it'd be fun to do on a spare motor or project car rather than a vehicle I'll actually want to use come next summer. The thought of getting it done by the spring intimidates me a bit.

For what it's worth, it's an OMC 140 (GM 3.0L) 4 cyl.

Re: First time engine rebuild

A full and true rebuild is something I might be reluctant to tackle.

I don't know my motors all that well so what I say next may be a worthless comment. Sometimes burning oil is caused by burnt valves. Pulling the head, having the valves ground and adding a new head gasket cures all with minimal pain. That I have done and with the right tools I bet you can also.

Re: First time engine rebuild

Most times burning a little oil doesnt hurt anything, so how much oil is it burning? Burnt valves wouldnt generally cause oil burning, but bad valve seals could.

A complete rebulid would include, having the block bored and honed, and new pistons, and rings, besides the bearings, and all seals. Having the head completely gone through also. New timimng chain, crank checked, cam, lifters, ect.

Re: First time engine rebuild

I just did this to my 3.0L. Putting the engine back together is pretty simple, just follow torque charts and specs when you do it. Getting the engine out of the boat is the tricky part, unless you have a cherry picker or a huge oak tree. My machine shop did a block rebuild for about $1200 with a warranty on everything in it. Just as a ball park for you. This included a valve job, head mill, cylinder bore/hone, and re-assembly. I've seen small blocks go for 1400-2000 online, not including shipping.

I agree with etracer on the valves. If you're just burning a bit of oil it's not that big of a deal, I'd start at your valve seals. That's not a hard job. All you need is compressed air in the cylinder to keep the valves in place, and a spring compressor to take off the valve springs. Auto parts stored sells them for about $20. Unless you wanted to do the head gasket for insurance, then you just need the spring compressor. Good luck!

Re: First time engine rebuild

That engine doesn't have a timing chain -- it has timing gears. Just because the engine is burning oil does not mean it needs to be bored and new pistons installed. Although that is part of a total rebuild, if the pistons measure within tolerance and the bores are within spec (not tapered or out of round) you can simply deglaze the cylinders, clean up the pistons, install new rings. Have a valve job done by your local NAPA store or engine rebuilder (specify that you want "umbrella valve stem seals). Have the same shop inspect, check and resurface the crank if necessary. If resurfaced you will need undersize bearings. All of the specs and procedures for engine teardown, assembly and adjustment are in the service manual for your engine. DO NOT attempt this job without it or you will likely get to do some tasks twice (or more) and you may get the engine installed again only to find you screwed it up. You won't find a simpler engine to work on as a first attempt. The key to this is to "be smart". No guess-work here.

Re: First time engine rebuild

This summer I had to add 1qt of oil just before the last run of the season. It just started being a bit rough on idle when first started. Once it warms a bit it runs like a top. Is just doing the head hard? Is it still easy to get parts for the head portion (valve guides/seals, springs, gaskets, etc)? What about lifters, should those be addressed too if I'm in that far?

Are valve seals something that can be done without removing the head?

Re: First time engine rebuild

I rebuilt a 350 by myself having never done it before. It wasn't that bad. If you are good at following directions and good at looking stuff up and figuring stuff out I think you will be ok.

There are lots of videos on YouTube that will help.

Don't skimp on anything though. If your gonna do a full rebuild then do a full one. If you think something needs machine shop work then get it done.

Re: First time engine rebuild

superbenk said:

Are valve seals something that can be done without removing the head?

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Yes, you can replace the seals without removing the head.

Re: First time engine rebuild

If you added only one quart of oil all season that is certainly no reason to even begin thinking about a rebuild. If an engine consumed one drop of oil every rev it would consume gallons in an hour so I suggest you rethink this. 1) compression check. 2) Leakdown test. 3) Full tune up. Running rough is also not a symptom of the need for a rebuild. Yes - valve seals can be replaced without removing the head. NO! Umbrella seals cannot be installed with the valves in place unless the head was originally set up with them. No it is not hard to do a "head job" as you call it. But refurbishing a cylinder head is not necessary unless it needs it or unless you have the engine out for rebuilding or overhaul anyway. No you cannot install umbrella seals unless you have the special tool to cut the outer portion of the valve guide. If the engine was set up with them the machine work was already done.

Re: First time engine rebuild

Even if valve seals are leaking, generally that makes for a bit of smoke on initial startup but clears right up. Rope in a cylinder, bring it up to TDC by hand. Use a head mounted valve spring compressor ( Advance Auto/ Autozone will rent them ) and it can be done with relative ease. Rebuilding an engine is not real complex but it's not something I would do 'just because'. Need at the very least a set of snap gauges, micrometers to read them, and I would recommend a Dial bore gauge to find taper in the engine bores. Could just take the guesswork out, and see what it's current overbore is ( if any ). Have it punched .010-.030 depending on piston availability, then have the crank turned .010 and have rods resized accordingly. It would be brand new then, but that is a great expense. $20/hole for boring&fitting, consider the same total cost for having the crank turned, rods resized, and then the cost of the parts. A rebuild kit might cost $600 for that, and machine work could easily go to $600+, .. The shop manual for the engine is an absolute must have, but again, I would not even consider this unless the engine shows visible/audible signs of being worn out..

Re: First time engine rebuild

superbenk said:

Is just doing the head hard? Is it still easy to get parts for the head portion (valve guides/seals, springs, gaskets, etc)?

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Hey Ben, I can't answer most of your questions I can jump in on some. I had to do a head gasket on my '72 OMC this year (165 HP / Chevy 250 I6). I am not all that mechanical. It was really much easier than I expected on mine. I had the head and valves done together at a local shop (head cheap ... valves, not as cheap) and got it all put back together.

Not so bad.