Did a compression test today....not good.

1. 150 psi
2. 150
3. 153
4. 138
5. 136
6. 56.

I squirted some oil into #6 and got 60 psi the second time. This explains the pfft pfft out of the exhaust and why I've been chaising my tail trying to figure out the rough idle. I pulled the valve cover and checked the valves again...all in spec. So, I'm thinking a burnt valve or bad head gasket...but I'm leaning toward a valve since I don't have any bubbles in the coolent while the engine is running. Or is it? Strange thing is, is sometimes the engine runs smooth, and the exhaust has a nice, even brrrrr to it. Other times the miss is so pronounced I want to drive it off a cliff. Also, very little blow-by and no smoke out of the exhaust pipe. Thoughts?

My burnt valve had its gap tighten over time, but it took a while.

They make test kits to see if theres combustion gas in the coolant.

I vote for head gasket break between #4 and #5. 130's isn't the best but its not terrible either. Its the difference between it and 1/2/3 thats concerning, and since those two holes show essentially the same numbers...

Time to find a core head and build it up.

Who is they?

Eric,

What kind of miles are on this engine?

Could it be possible that 4,5 & 6 rings maybe plugged? If so, what oil do you use? Maybe it's time for a flush or a cup of xmission fluid in the oil.

When I used to work in a junkyard I would get old Darts and Valiants with this condition. I never touched the head other than a valve adjustment, just the flush like Dan describes or overtime a gentle flush of a cup of xmission fluid and the compression would come back. One year I got (6) SL6 cars back on the road with just the engine flush.

It maybe worth a try.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Here is some info on one. Its a generic tool that any decent autostore should stock.

Basically a contraption to draw gas out of the top of the radiator and pass it through a colored liquid - the liquid has a chemical in it that reacts with combustion gas and changes color to indicate any presence of it.

If you don't want to buy a Blok-Chek kit, head to your friendly local emission testing station with the radiator cap loosened to the first stop, and see if they'll put the test probe above the (open) radiator filler with the engine running. If there's any significant combustion gas in the cooling system, it'll show up on the test meter.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Here are my results from 2006:
Forum: Engine Posted: Sun Jul 30, 2006 5:31 pm Subject: Eric's once a year compression test #'s....
....What do you think?

1. 145
2. 142
3. 155
4. 154
5. 155
6. 151

Seems the forward 3 are about the same, the aft 3 a significant drop. Maybe it is just the head gasket....

My money is on that #6 exhaust valve.

Do you have a source of compressed air? Is the hose from your compression tester removable? Mine has a quick disconnect coupler that matches my air hose. I remove the check valve from the end of my compression tester hose and use it to put air into the cylinder. Of course for this test you'll need #6 on TDC with the valves closed (line up the timing marks with both valves closed) put air in the cylinder and check for air leaking at the tail pipe.

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Joshua

Can you measure intake manifold vacuum? If relatively high and steady at idle, then most likely a burnt exhaust valve seat. You can confirm by pressurizing cylinder with valves closed as described. Air out the tailpipe = exhaust seat.

Mitch

I blew between 4&5 and 5&6 across the narrowest point between cylinders. No combustion gases were going into the coolant.

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Cheers!
Al T

I am experiencing the same "pfft" syndrome from the tail pipe, albeit I call it "chuffing".

Haven't done a compression test, as I still average 24 MPG and my sparkplugs (which have 3 years and 35K miles on them) are clean as a whistle.

The car has been doing chuffing for at least 40K miles, so I continue to proceed with "business as usual".

The car under consideration is a '64 Valiant with 189K on the clock (almost broken in)...

Timmy
I think yours is just the valve train talking. At 24 MPG I certainly wouldnt change anything.
Frank

_________________
Scrapple: Because a mind is a terrible thing to waste.
73 Duster - Race Car
66 Dart Wagon - DD
178" FED
82 D150
All Slant powered

I found a head at a local wrecking yard, a '77 unit out of a truck. I'll pick it up later this week....hopefully its in good shape. I'll lap the valves, new gaskets and hope for the best. I'll keep the old head and replace the valves and mill the head. Wait, should I mill the "new" head too? I'll also check the clearence on the rings while the engine is apart. The really bad part is I won't get to do the work until the 4th of July weekend. This sucks...

I would chack the CC's of your old head vs. the new one... I've noticed the older drool tube heads can be slightly 'roomy' compared to the later peanut plug heads (so you might get lucky and find the '77 head is 52-53CC, and your old head is something more like 54-57CC).


-D.Idiot

Um, what do you mean D?