Need advice on whether to rebuild motor

My 77/74 has a 304 with 60,000 miles on it. I've been researching performance upgrades and decided on a fuel injection kit. I though I had cleared the biggest hurdle when the wife gave me the green light for the Edelbrock multiport kit based on nothing more than a promise to liquidate some golf equipment in the future.

An Edelbrock tech rep told me a motor rebuild would not be necessary on a 60,000 mile motor as long as cranking compression was over 125 pounds. The cranking compression test performed today showed all cylinders above 150 pounds. The bad news was one cylinder was burning oil.

The tech that did the compression testing said he would "probably" do an engine rebuild before putting the money and effort into installing the EFI, but he did not sound very confident in his opinion.

Any opinions from those that know engines would be greatly appreciated.

 

The one cylinder that your Mechanic referred to as "burning oil.... was the compression valid on all eight? Also, the cylinder that is in question... what pressure did it hold in relation to other seven? Has pan been pulled and journals checked? Visual of cylinder walls from below... results? as to any scoring, etc.

Having one cylinder be reported as "burning oil" and then being told that all eight cylinders check very good with a compression test... Well.... Have personally rebuilt everything from four cam, twin distributor Mercedes V8 (119 family) and V12's (120 family) though most of the GM and Ford Power Plant products... I would say a second opinion would be in order Sir. Your Mechanic may have good intentions.... but his interpretation of your 60K Power-Plant would carry a stronger analysis if a thorough investigation were carried out. Dropping an oil pan is a minor task to possibly find there are a lot of trail miles left in your 304. Take your investigation through another mechanic... even two more if necessary for comparison of results...

One other thing.... DO NOT SHARE the previous Mechanic thoughts or findings.

I bet there are a few others on here that will agree as well... even if you spend a few dollars for comparison inspections... the results will be interesting and hopefully put you back on the trails faster and with less expenditure! Get that second opinion before making a decision!

Good luck and Semper Fi!

Gunner

 

A leakdown test would help you figure things out.

 

If the compression checked out as you indicated, and further checks show no real issues, I'd run the FI. If you have to rebuild it later on, do so. But I don't think I'd do it now.

 

150 psi on all cylinders is good. The mechanic should have given you the reading from each cylinder. The difference between the cylinders is very important, as important as the average reading. Did they show you the actual numbers? If not, why not? A compression test will not tell you if a cylinder is burning oil. Maybe the mechanic looked at the spark plugs and one was oily ... but the compression test itself tells you nothing about oil consumption. 60K is very low mileage for a modern engine - there's no realistic expectation of a rebuild due to normal wear at that mileage. Is the engine consuming oil between oil changes? Is there blue oily smoke coming out the exhaust?

My advice - if you can install the Edelbrock MPI kit, you can check compression and look at the spark plugs. I'd advise you do both.

JMO - it's very difficult to own an old car if you can't do your own diagnosis and service. Most repair shops won't want to work on older cars. Look around the shop and see what kind of vehicles they are working on. Listen carefully, ask lots of educated questions, and be skeptical of everything they tell you. I'd think it'd be hard to find a shop to work on an old car that's both competent, will look out for your interests, and is not some kind of 'boutique' old car specialty shop ($$).

 

The mechanic that did the compression test gave me the actual numbers:

150 160
155 150
150 155
150 155
[radiator]

The cylinder that read 160 showed a very oily spark plug, which was the basis for the "burning oil" diagnosis. He put in a new plug and told me to check it in a month. When we drove the jeep through the mountains this summer I did get some small puffs of blue smoke going uphill when shifting from second to third.

The motor runs very good and starts like it is new; I'm reluctant to mess with a good thing even though I am itching to try the fuel injection. Maybe I'd be better off to look around for another 304, take my time and rebuild it (which would be a good refresher course for me) then put the EFI on the "new" 304 and swap them out.

 

With compression numbers like that I would look at replacing the valve seal on top. They age due to the heat they are exposed to.

Valve spring compression tool, and a spark plug/air compressor adapter.Pressurize the cylinder, take keepers off, remove spring, remove old seal, install in reverse order.

Jay

 

The oil burning could be worn valve guides and not related to the piston rings/compression issues.

 

NOW YER TALKING!!!! ​

THAT IS WHAT I LIKE TO HEAR! LESS WORK on THAT ENGINE and more miles on the trails!
I have a 350 hanging on an engine stand and T18's with it..... tinker with it from time to time.... but a bad day in my Jeep is better than any other day!

HELL, Maintain, Drive till she stops, fix her and keep on going! Less work and more play... life is too short!
​

Gunner

 

If the wet plug (not oily since that's subjective as well) is truly from oil, and you have deposits, they could be raising the compression on that cylinder. As a couple have said, check the valve guides and seals.

Do your EFI swap, you'll love it.

 

If you have the cash, do the fuel injection. If it was your daily driver I might address some top end seals and guides. But for an 30+ engine and good numbers go for it.

If you have $$$$, grab up a 401 and bolt it in.

 

Drive it and save the money on an overhaul.

I also wanted to share that a few years ago, I had a jeep that had a smoking habit. An older mechanic friend suggested I pull the spark plugs and pour in some Marvel Mystery oil in each spark plug hole and let soak for a few days. He said I probably had a stuck ring that was not flexing. I tried it and it worked. A three dollar can of MMO fixed my problem.

 

So what if it burns a little oil in one cylinder. It probably leaks more than it burns. Put a high energy electronic distributor in it along with the injection and forget it.