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I-AM-JD

Apprentice
Jan 7, 2020
65
15
8
Sacramento CA
Mechanic called and told me my #4 cylinder is at 40% compression and engine teardown is recommended. Wondering if his advice is correct and what should it cost me? 1980 3.8 regal
 

L92 OLDS

Comic Book Super Hero
Mar 30, 2012
2,872
3,050
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West Michigan
Mechanic called and told me my #4 cylinder is at 40% compression and engine teardown is recommended. Wondering if his advice is correct and what should it cost me? 1980 3.8 regal
You could try using Seafoam to restore compression. The problem could be as simple as too much carbon build up on the rings. Mystery marvel oil also works. I’ve used it with good results on oil burning Saturns. The process is called the MMO soak and you leave it in the cylinders overnight.


 
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DSPbuilt

G-Body Guru
Jan 7, 2016
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Honestly I would go to harbor freight and pick a gauge or autozone might even do a loner one. Tests are very simple to do.
 

rogue_ryder

Master Mechanic
Oct 27, 2017
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Colorado
About a 16hr Drive along I-80 & $600

If you want to check compression yourself buy the tool at Autozone for $30 or if they loan it you can go that route too. Get the motor hot, disconnect the power wire to the HEI (so the car doesn't start) and do a cranking compression with the car at Wide Open Throttle. The PSI isn't super important, if you see one of the cylinders significantly lower than the others your mechanic wasn't lying.
 
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I-AM-JD

Apprentice
Jan 7, 2020
65
15
8
Sacramento CA
About a 16hr Drive along I-80 & $600

If you want to check compression yourself buy the tool at Autozone for $30 or if they loan it you can go that route too. Get the motor hot, disconnect the power wire to the HEI (so the car doesn't start) and do a cranking compression with the car at Wide Open Throttle. The PSI isn't super important, if you see one of the cylinders significantly lower than the others your mechanic wasn't lying.
I did he was right. All cylinders were between 160-167 #4 was 45. Would you recommend engine teardown or look for another engine?
 

I-AM-JD

Apprentice
Jan 7, 2020
65
15
8
Sacramento CA
You could try using Seafoam to restore compression. The problem could be as simple as too much carbon build up on the rings. Mystery marvel oil also works. I’ve used it with good results on oil burning Saturns. The process is called the MMO soak and you leave it in the cylinders overnight.


Thanks for the video! Definitely going to try that this evening.
 

ck80

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Feb 18, 2014
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Either a) any coolant in engine oil, or b) oil in radiator coolant?

Whats the spark plug for that cylinder look like?
 

I-AM-JD

Apprentice
Jan 7, 2020
65
15
8
Sacramento CA
Either a) any coolant in engine oil, or b) oil in radiator coolant?

Whats the spark plug for that cylinder look like?
So there's neither (a) or (b) now the plug which I switched out two days ago with wires also it's carbon fouled and I haven't even driven the car just let it idle for about 20 minutes and it already has black deposit on it. Also I'm having gas squirt from the carburetor with small backfires coming from the carburetor also. When I step on the gas when it's running it sounds like sputtering hollow pops.
 
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