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compression test results


easywind's Avatar
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05-27-02, 01:14 PM   #1  
compression test results

Today I did a compression test on my 85 Dodge B150 with a 318 I had the engine warmed up, pulled the plugs and on the 3rd and subsequent 3 cylinders I go zero reading so knowing the truck was running I went and got another compression tester. It took me an hour and the van was rather cold when I took the readings. on the first crank the readings were 150, 120, 112, 113, 117, 120, 140, 140 after 4 cranks the readings are 185,, 165, 145, 124, 150, 155, 165, 165. I have limited auto knowledge but from the readings I would guess I have a carbon build up in the head. If this diagnosis is correct is there anything other than a valve job, maybe a chemical that will break up some of the deposits. thanks

 
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05-27-02, 02:27 PM   #2  
Joe_F
What symptoms/problems are you having? If everything's fine, leave it alone and drive it until it drops. Not worth fixing an old Chrysler heap like that with extensive repairs.

 
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05-27-02, 02:52 PM   #3  
compression test results

Joe, I'll probably be keeping the van forever, I park on the streets of Manhattan and drive to Mexico every year and it's a campervan. That being said, the symptoms are white smoke on startup and a general lack of power. I'm going for a retest on emissions tomorrow and tuned it up and changed the oil so it would run cleaner. I also put in a bottle of something that said I'd be guaranteed to pass emissions and I had more power for the tankful. I like the van a lot, money is not a problem. I also like to involve myself in doing whatever is necessary to the van. I also have much more money in it than it's worth but it's worth it to me.

 
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05-27-02, 04:25 PM   #4  
A 318 is worth a rebuild.

Why don't you just rebuild or have someone rebuild your 318 for you? That will let you pass the emmisions test and with todays oil, get another 150,000 miles out of it.

The parts like Gasket kits, and rings & bearings are not that costly & will give your engine a new lease on life.


Juat a thought Marturo

 
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05-27-02, 04:48 PM   #5  
Marturo, I most probably will rebuild, what I'd like to know in the meanwhile is what the problem is. I've very rarely heard of compression numbers that high.

 
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05-27-02, 04:49 PM   #6  
Joe_F
Puffing on startup in many cars is valve stem seals. Chryslers are pretty decent about burning oil though...I'd be surprised if your truck has an oil problem. It sounds a bit tired though.

Squirt some oil in the cylinders when you do the second compression test. Does it improve? If so, bad rings.

 
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05-27-02, 05:44 PM   #7  
Compression test pressures.

Hi easywind


185,, 165, 145, 124, 150, 155, 165, 165. I have limited auto knowledge but from the readings I would guess I have a carbon build up in the head.

Now all of my readings on my 350 Chevy are around 185-180 psi, so I dont think you are in the exsesive range.

I once did a comp check on a 1984, 305 in a four wheel drive Chevy they were all around 195 psi. It had a little over 100,000 miles, and we did a head job on it. Other than a black soot all over it had no carbon build up. I talked him into doing the bottom end also and he has a sweet runing 305 today with 40,000 miles.

We don't have the sniffer test yet around here yet so I wonder if they are looking for unburnt petrodistilates. Anway I would not think looking at your cold & hot readings that you have a over compression problem at all.

I will tell you this, when I take a compression test I am looking for less than ten lbs difference between cylinders. Like 150, 145, 140, 150, 147, 145, 150, 145, all the way up to the 190s I want to see damn near the same pressure in each cylinder.

All things right in the system, this means that you will have a very smooth balenced runing engine. So based on your readings I would do a rebuild and get that 318 purring again. Squirt a little oil into that cly with 124 psi, & if it comes up let's say 20 to 30 psi your rings on that cylinder are worn out, if not it is a leaky valve.

Take my word for it those readings are not to high, besides we don't have the biggest carbon builder anymore Leaded gas Ye Ha, best thing that ever happened to fuel. Get the lead out, some of us remember our Dads running a tankful of Ammaco white Gas back in the 60s and 70s to get the carbon out. I don't know if it was the gas or the 90 MPH ride down the Hiway that blew the carbon out LOL Who cares we were going 90 MPH and that was fun!

 
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