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Old 08-20-2022, 03:48 PM   #1
Lugnutz65
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What’s wrong with this 1964 230ci?

1964 Chevy 230ci inline six that’s been rebuilt about 10K miles ago by a machine shop. RV cam. I bought it from the original owner because he did a V8 swap so he could tow a trailer.
I recently removed it from my 1965 C10. I was never very happy with how it drove. Just didn’t have much power at highway speeds. I remember doing a compression test on it right after I bought it and things were fine and oil pressure was good too.

Update. I put the 230ci on my engine run stand so that I could show it running and sell the engine for a fair price. Oil pressure checked out great. Starts right up. Cylinder compression check is 130 psi in all cylinders.

Today I ran a cylinder leak down test on this engine. Disappointing results. I didn’t bother testing all of the cylinders because cylinders #3, #4, #5, and #6 all had leak down numbers of at least 50%.
To run the test I loosened all of the rockers so the valves were all closed. At first I thought I had terrific numbers but realized that the hose I was using still had a Schrader valve in it. Haha, joke is on me. After I removed the Schrader valve, I was shocked to see 50% leak down. I tested all of the cylinders listed above. My heart sank. No air out the exhaust or from the carburetor.

So I have concluded that the air is getting past the rings. I had been using this engine in my 1965 C10, but was never impressed with how it ran. Maybe this is why.
I put new valve seals on the exhaust valves #5 and #6. I had those springs off to check for sloppy valve guides, but they were fine. Absolutely no wobble.
I rotated the crank to find the base circle on the cam for each cylinder and reset the lash properly for each valve. The engine starts and runs.
I tested my leak down tool by hooking up 100 psi from my compressor without connecting it to the engine. Both sides show 100 psi as you see in the picture. I think my leak down tool is working properly.
Does anyone think my conclusions are wrong?
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Old 08-20-2022, 05:23 PM   #2
AussieinNC
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Re: What’s wrong with this 1964 230ci?

You are most likely correct of excessive blow by on the rings....

You should also realize that a 230 in a 1965 C 10 will never be a super performer on the highway, given the weight of the truck and the original design use of the engine...

You could do a rebuild on the 230 reasonably cheaply, dont be surprised if the rings in those cylinders you mentioned come out either broken or with super wide gaps....I have seen engines bored oversize and standard rings put on the pistons !

Anyways, thats my 2 cents worth....

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Old 08-20-2022, 05:26 PM   #3
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Re: What’s wrong with this 1964 230ci?

Saw this article on leak-down test:

https://www.motortrend.com/how-to/cy...akdown-tester/
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Old 08-20-2022, 06:26 PM   #4
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Re: What’s wrong with this 1964 230ci?

Quote:
Originally Posted by AussieinNC View Post
You are most likely correct of excessive blow by on the rings....

You should also realize that a 230 in a 1965 C 10 will never be a super performer on the highway, given the weight of the truck and the original design use of the engine...

You could do a rebuild on the 230 reasonably cheaply, dont be surprised if the rings in those cylinders you mentioned come out either broken or with super wide gaps....I have seen engines bored oversize and standard rings put on the pistons !

Anyways, thats my 2 cents worth....

I would do another compression test just to confirm...I agree with Aussie dude
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Old 08-20-2022, 08:42 PM   #5
Lugnutz65
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Re: What’s wrong with this 1964 230ci?

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Originally Posted by AussieinNC View Post
You should also realize that a 230 in a 1965 C 10 will never be a super performer on the highway, given the weight of the truck and the original design use of the engine.

A story if you have time.

It’s funny sometimes how we learn stuff. I had a 250ci in this1965 C10 but it had low oil pressure. I bought this 1964 inline 230 to replace it. Swapped it one weekend and started driving it. Then a minor accident took it off the road for a while.

Bought a 1963 C10 and it had a 250 in it that ran good but cylinder #6 had 90 psi compression while others had 125 psi. It ran better than my 1964 230, but I just figured it was because it had 30 more cubic inches.

Then I bought a bunch of parts from a local man. Included in the pile of parts was a used 1963 in line 230ci engine. It was a package deal. I never heard the engine run, but he said it ran fine. I figured I might rebuild it one day and put it in the 1963 C10.

One rainy weekend I put that 1963 in line 230ci on my run stand and it seemed to run very well. Engine compression was great in all cylinders. It had good oil pressure too. I did not own a cylinder leak down tool, but I decided the engine was in good enough shape to swap it out for the in-line 250ci that was in the 1963 C10.

I distinctly remember my first drive down the road with the 1963 in line 230ci. It had LOTS of power and I immediately realized that the 1964 in line 230ci in my other truck was not nearly as powerful as this one was. I didn’t know a 230 could perform better than what I had because I had never driven a C10 with a decent 230ci.

I suspect that the rings on this 1964 engine have been a problem for quite some time. Maybe since I purchased it.
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Old 08-22-2022, 02:44 PM   #6
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Re: What’s wrong with this 1964 230ci?

Lugnutz:

Your leakdown tester has a small orifice between the two pressure gauges. In most automotive gauges, it is .040" diameter. When you hook your leakdown tester to your engine, it basically compares the leak of the engine against the .040" orifice in the gauge. Leave the output to the gauge open and you get 100% leak (the output gauge reads 0 psi), close it and you get 0% leak (the output gauge reads the same as the input gauge). As a sanity check, put a .040" orifice on the output of the gauge and you should read some kind of sensible leak. Apparently the theory is a little complicated to come up with an exact answer and the detailed flow characteristics of the hole also come into play. Really good leakdown testers come with a calibrated orifice that can be placed at the output of the leakdown tester.

Another alternative is to run a leakdown on a known good motor for a yardstick.

If it is the rings, you should be able to hear the crankcase getting pressurized. You could even seal the crankcase (the best you can) and place a small opening, maybe at the PCV outlet, and be able to feel or hear air coming out.

Another quick test is to run the leakdown, get a number, and then squirt oil into the cylinder, and run it again. A dramatically improved number suggests ring wear.

As you probably know, you don't have to undo the rockers to run the test, just get the cylinder to be tested at TDC on the compression stroke. Also beware, at 100 psi, the piston might actually move with the pressure.

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Old 08-23-2022, 09:23 AM   #7
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Re: What’s wrong with this 1964 230ci?

Pressure escaping past the rings enters the crankcase and escapes the crankcase through a leak through the valve cover or oil pan seal, the PCV, or the oil dipstick tube. The small diameter of the dipstick tube makes it easy to feel and hear air flow. That’s assuming air is not escaping through the valves.
I will do the wet test next using some 90 weight oil in the cylinder.
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Old 08-23-2022, 03:23 PM   #8
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Re: What’s wrong with this 1964 230ci?

Lugnutz:

I recently had to check a 292 inline 6 for overall health. It passed a cranking compression test fine, but the leak down was a little suspect on a couple of cylinders. I ended up pulling the head and then making a sealing plate that mounted in the head bolt locations. This allowed me to pressurize each cylinder and use my leak down tester. The cylinders were fine. I then flipped the plate over and used it to seal the head and tested for leaks. I found a couple of exhaust valves leaking (easy to tell by sound). That was easily cured by lapping the offending valves. My problem was mostly carbon build up.

This particular 292 was a GM replacement engine from the late 80's so its overall condition was pretty good.

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Old 08-23-2022, 06:09 PM   #9
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Re: What’s wrong with this 1964 230ci?

^^now that's working smart^^
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Old 08-27-2022, 11:46 AM   #10
Lugnutz65
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Re: What’s wrong with this 1964 230ci?

Final testing was done today. I brought the engine temp to 195*. Then I did a dry and wet leak-down test on #4, #5 and #6 with the piston a few degrees past TDC. I used 75-90 gear oil to wet the rings.
I think the numbers confirm that I’m losing compression at the top of the cylinder from cylinder wall taper.
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Old 08-27-2022, 11:47 AM   #11
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Re: What’s wrong with this 1964 230ci?

Cylinder #6.
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Old 08-29-2022, 12:48 PM   #12
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Re: What’s wrong with this 1964 230ci?

Lugnutz:

Number 6 looks like it is closing on unacceptable. In the aviation industry, they say anything under 60 psi with an 80 psi input is failing. (That's about 25%.)

BTW, your T5 transmission info and steering column info has been a great help to me. Appreciate you documenting all of that stuff!

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Old 08-29-2022, 01:02 PM   #13
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Re: What’s wrong with this 1964 230ci?

Quote:
Originally Posted by Cris View Post
Lugnutz:

Number 6 looks like it is closing on unacceptable. In the aviation industry, they say anything under 60 psi with an 80 psi input is failing. (That's about 25%.)

BTW, your T5 transmission info and steering column info has been a great help to me. Appreciate you documenting all of that stuff!

Cris
The engine runs and has great oil pressure. Unfortunately the cylinders seem worn. I have a buyer and have given full disclosure to the buyer about the condition of the engine.

I’m glad to hear you got some useful info from my steering column and T5 pages.
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Old 08-29-2022, 05:51 PM   #14
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Re: What’s wrong with this 1964 230ci?

Before I put in the 292, I had the original 230. I never leaked checked it, but it had a couple of weak cylinders even in a cranking compression test. I drove that all over the place. It wouldn't pull a hill in 5th, but otherwise had adequate power. It was well tuned with HEI and a reconditioned monojet.
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