Slow Restoration, Starting With Engine - Options?

I have a 79 CJ7 Golden Eagle that is stock, with a 258 3 speed. I've owned it since the mid-1980s and it was my daily driver until I retired 7 years ago. Until a couple of weeks ago, I had decided to sell it rather than restore it. I got it out of the barn and cleaned it up with the idea of taking it to a local jeep show with a for sale sign on it. But then I drove it to town to get gas. I realized that I miss driving it and that I want to restore it, not sell it. It needs a new tub and fenders, clutch, upholstery, and an engine overhaul or swap (low oil pressure).

I am just starting a restoration on my 47 CJ2a. So the CJ7 is going to be done as I have time and money. It is very drive-able as is, but I would like to cure the low oil pressure problem as a start. After reading here and on other forums, I don't think a high output oil pump will solve the problem. So I'm looking at options and would like to hear the collective wisdom of this group.

I won't have the time (and if I'm honest the skills) to do an overhaul myself. Money is a concern and I am assuming this would be the cheapest route. I don't know of a local shop that could/would do the rebuild. so I am assuming my other option is to buy an engine. Here things get a little fuzzy for me.

I would appreciate any advice you might have from what you would do, to vendor recommendations.

Thanks,

 

304 swap

 

Look around for a shop. Evaluate the engine that you have. Check the oil pressure at hot idle and cruise with a quality mechanical gauge. You want 10 psi for every 1000 RPM. Measure the compression, wet and dry. Measure the bearing clearances.

Another used engine? Pre-81 258s are sought after for their crankshafts, so you're more likely to find an '81 or newer 258. A 232 will bolt in. A 4.0L engine can also be used. They are all fuel injected, but they can be converted to a carburetor if you were so inclined.

You're pretty much asking us to write a book for you ... if you want to save money, you need to research your options. A 258 is a very ordinary cast iron inline six, and any competent shop can handle machining or rebuilding. Your local auto parts store can get you a long block or a short block, quite easily. Rebuilding a 258 would be easy in comparative terms. A patch-up job is harder, because you must make the judgement of what to fix and what to leave alone.

 

JMO - you could go 304, but I would not. There are not a lot of them out there; there are more 360s available than 304s. A 360 is too strong for a T150, IMO. You may not be able to buy a rebuilt 304 without a core to exchange. If I wanted a V8, I would go modern small block Chevy and an automatic, like a 700R4 or TH350 ... but the OP is trying to keep the cost down. A CJ-7 is long enough for the Chevy overdrive automatics. With some searching you might find a 304/TF999/D300 combo from an '80-up CJ-7... they were built that way, but not plentiful.

I predict a 4.0L HO swap would be cheaper than V8 swap, and would have a lot of power compared to the 258. Plus it comes with the excellent Mopar multiport fuel injection.

 

What is the viscosity of the engine oil. Is the oil possibly too thin (gas contamination) from choke starting and not driving enough to evaporate the gas in the oil? Leaking fuel pump diaphragm contaminating the oil? Do a little trouble-shooting before you condemn the engine.

 

Thanks for all the replies. A couple of years ago, I worked on the low oil pressure issue. Installed a mechanical gauge, changed oil type and filter. Came to the conclusion that the bearings were worn (mainly from reading a bunch of posts on the subject). It was at that time I decided I didn't want to do a restoration, so purchased the 77 pictured in my aviator. It is a V8 with QuadraTrac. I'm just not enjoying it as much, so plan to sell it when I finish the 79. So I don't want a V8, although I might be tempted by a 4.0 with fuel injection. However, I've had really good performance with a Weber swap on the 258. So again, thinking of staying stock.

I think I will call my regular mechanic and see if he will check it out and give me some advice.

 

How many miles on the 258? They have plenty of bearing surface, and the pre-81 crank has 12 (!) counterweights, making for a very smooth-running engine. '81 up engines have 4 counterweights. I would measure the rod bearing clearance with Plastigage. The long stroke of the 258 makes the rod velocity quite high when you bring the engine speed up, so the connecting rod bearings are what to look at first. Generally 258s do not have a problem with oil pressure until they are really worn out. Have you checked the compression?

 

The engine was a replacement when I purchased the jeep 20 years ago, but assume over 100K. So not sure of the engine manufacture date. I have an appointment with my shop next week. I asked them to evaluate the low oil pressure. I said I was looking at rebuilding or replacing options. I know that is pretty vague, so what would you recommend I asked them to do? I'm assuming they will check the compression. Should I ask them to drop the oil pan and check all the bearings? Is that, along with the compression test, the best way to determine if the engine is really worn out?

I trust the shop. They aren't cheap, but fair. If the compression is OK (the engine runs fine except for the low oil pressure) and the bearings are worn, should I have them replace the bearings, or is that just delaying a total rebuild? IE, if the bearings are worn, is it a sign that the rest of the engine is or soon will be worn too?

I'm sorry about my lack of knowledge here. I do appreciate your advice.

 

Typically a worn engine will have low oil pressure and low compression. Really worn out will give you low and variable compression on all cylinders, because the rings are worn out. A 258 with 100K on a rebuild should not be this worn. Really worn rings will oil-foul the plugs. Inspect the spark plug condition. It's a lot of labor to look at the bearing condition - probably not practical to ask the shop to do it. If you were spending your own effort, you could drop the pan and look under the bearing caps. You could measure the rod clearance with Plastigage. As I mentioned, the 258 has a long stroke, and if you run it fast it will have a high rod velocity. This could lead to premature rod bearing wear, which would be evident as low oil pressure. The 12-counterweight engine is very well balanced, so I would not expect the mains to be significantly worn unless it was run out of oil or subjected to some other catastrophe.

For the shop, it will be much more cost-effective for them to install a rebuilt engine. Realize that this is the best option for them, if you will go along. The major cost will be removal and replacement of the engine, which is comparatively fast and low risk. They offload the engine risk onto the rebuilder, and will get the cost of their time back from the rebuilder if they have a warranty issue.

An old-fashioned overhaul replaces the rod bearings and rings, hones the bores and grinds the valves. This was done a lot back at mid-century, when cars had forged steel cranks. Not so much today, when cars have cast iron cranks (which wear out with the bearings) and shops can get factory-built remans at a competitive price.

 

Thanks! I may just cancel the appointment for now, unless you think they might be able to address the low oil pressure without too much expense. I don't want to waste money. I'm going to need a new clutch too and I wouldn't want them to replace the engine without doing that.

 

Your decision. They might have some insight. Just tell them what you want and how much you can spend. Could be something strange that they would spot. If you're a good customer you'll get some free advice about what they can do and how much it would cost.

You can measure the compression and inspect the spark plugs yourself. Easy. That would tell you a lot.

 

On the flip side, how many miles do you drive it and how long do you plan to be driving it? I have seen many a motor run an incredible time with low oil pressure.

 

I think talking to the shop is the best approach for me right now.

Again, really appreciate the help and advice here. Will let you know what they find.

 

Jeep is back from the shop. They measured 35lb at 2K oil pressure. Next step is to get a mechanical gauge. Gauge recommendations? Would like to keep the stock look.

Thanks,

 

Ok!

I like this gauge - not stock looking though.

https://www.summitracing.com/parts/sww-82322/overview/

 

Ordered! Thanks.

 

Installed the gauge and getting the same numbers as the shop! It does drop off at idle (engine hot) to below 10PSI, but assume that is OK on this engine.

Since I had changed both the sending unit and the gauge, I'm assuming the second sending unit might have been defective too. Can't believe I worried about this for 2 years.

Thanks again for the help.

 

A mechanical gauge pipes the pressure directly to the gauge. There is no sender as such.

Presume you got an installation kit with the gauge. The gauge I showed will tell you the pressure all the way to zero. Theoretically you should be fine with 7 psi at 700 RPM.

 

Yes, I did buy the installation kit with the gauge you recommended. I think the only negative review of the SW gauge was that it didn't come with the installation hardware, so that alerted me to the fact I need to purchase that too. On a side note, I received the gauge next day from Summit. That was good service.

Both the sending unit and the electrical gauge unit I removed looked brand new, because they were.

Idle after a drive to heat up the engine was right at 9/10PSI. Saw 50PSI during warm-up high idle.