Hey everyone I was hoping you could help me come to a decision; but first some background.

The Car: 1969 Plymouth Valiant I bought from a junk yard a few years ago. It has a 225 I upgraded to a Super Six with a 2 ¼ exhaust and a HEI. Still runs; I driven it most every day since the upgrades.

The Problem: The car starts fine, cold or hot, but lacks power and stalls if I give it too much gas from a stop. Now I can turn a wrench pretty good but I couldn’t diagnose my way out of a paper bag, so I finally broke down and took it to a mechanic someone recommended. Well the diagnosis is in; no compression on cylinders 1, 2 and 3; valve leakage and crank case leakage.

Questions
1. How much trouble am I in?
2. Could the trouble be in the block or might I get away with replacing the rings and rebuilding the head?
3. What else should I replace once I have it open?

Any advice would be helpful.

Without compression on three cylinders its good that it still runs! I think you can find a used motor in better shape for almost free.

I find it hard to believe it starts fine with no compression in 3 holes. That thing would sound like hell turning over on the starter and sound like a helicopter when running.

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Official Cookie and Mater Tormentor.

Absolute zero compression on one cylinder sounds horrible... Are we talking none as in 0 or just low?

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1976 Dart Sport
Currently under revision

Other threads on this forum talk about pressurizing a cylinder by doing a differential compression test, where you put a piston on top TDC and listen out the induction, exhaust, and oil fill cap to see where the leaking air is coming from. If it is out the oil fill cap hole, then you have a piston ring (or worse) problem. If out the intake or exhaust, it could be only valves- as in a valve job. Have you tried adjusting the valves to spec? Differential compression tester is used on aircraft engines, sold in aviation tool catalogs for about $70.00. Just my thoughts.

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"Louise", a 1976 Dart Custom project, (now sadly reverted to being just an "organ donor" to our other project Darts.)

Like slantzilla said, I also have a hard time believing there's no compression on 3 cylinders. The engine would sound so horrible that you wouldn't be on here just talking lack of power and stalling from too much gas. Do you have your own compression tester? They're pretty cheap but I have one if you need to use one.

Down on power and stalling from a dead stop are classic symptoms of a BBD with the throttle shaft bushings worn out.

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Official Cookie and Mater Tormentor.

I think that shop might be angling for some work. Get your own compression gauge ($30) and test cranking pressure yourself with engine hot. A friend of mine had a shop tell him comp was low and he did a head rebuild himself and it ran exactly the same. Problem was a $10 dist cap...

I second the carb idea from 'Zilla.

Lou

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Home of Slant6-powered fun machines since 1988

I set the valve lash over the summer; it was my first time doing it so i might have messed up, but it didn't seem to have any effect on performance.

I agree with many of you about having absolutely no compression on three cylinders; I have a tester and will check it myself this weekend.

This is what was on the paper work they gave me:
"Verify hesitation. Test fuel system. Found carb leaking fuel t fuel inlet. Test ignition system. Ok. Test condition of engine. Found cylinders 1,2 and 3 have no compressions. Leak test cylinders 1, 2 and 3. Found Intake Valve leakage. Exhaust Valve Leakage and Crank Case Leakage. Recommend Replace Long Block and Recheck."

[quote]Found cylinders 1,2 and 3 have no compressions. Leak test cylinders 1, 2 and 3. Found Intake Valve leakage. Exhaust Valve Leakage and Crank Case Leakage.[/quote]

One valve intake or exhaust valve leaking is sign of burnt valve or perhaps out of adjustment lash, but six valves in three cylinders…

If intake and exhaust valves were leaking on one, two, and three I would bet that the lash adjustment is too tight on those three intake and exhaust.

Have another go-round on adjusting lash. 0.010â€￾ intake & 0.020â€￾ exhaust is what factory lists for setting. One can run a bit looser by 0.002â€￾ in other words I= 0.012â€￾ & E =0.022â€￾

Be aware that the first three cylinders have E - I, E-I, E-I, and last three the switch starting with I-E, I-E, I-E as you go from cylinder one to six.

Just look at the exhaust and intake manifold as each valve is adjusted. EI,EI,EI,IE,IE,IE = 6-5-4-3-2-1 as you lean over passenger’s fender looking at engine.

After resetting lash, perform a compression test with all plugs removed, and carburetor throttle plate held open with a screw driver.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I don't think it would even run on 3 cylinders. Go to Auto Stoned and take advantage of their free tool rental. Do the compression test yourself and a cylinder leak down test. If you suspect a bad valve, take the lash out of those valves completely and test again.

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If it was easy, everybody would be doing it.

A Slant most certainly will run on 3. I did it when I put a set of plugs in my Duster and forgot to put the 4-5-6 wires back on. Took me a minute to figure out why it had to have so much throttle to idle.

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Official Cookie and Mater Tormentor.

I got busy over the weekend so I didn't get to check on anything till today. As soon as I got home from work I Pulled all the plugs and valve cover. I wanted to check the valve lash because I only did it once before and I was afraid I messed something up. The valves were all a little tight but not far off. I checked the compression and it was like the guy said: nothing on 1,2, &3. Cylinders 4, 5, & 6 all above 120 in/lb.

So whats most likely the problem Block, Head, or Rings?

Pull the head and look. Anything else is just a guess.

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Official Cookie and Mater Tormentor.

Usually if it's rings only you can bump up the compression by adding a little oil to the cylinder, so that probably isn't it. I agree, pulling the head is the only real way to know for sure what's going on in there. :shrug:

I did not know a slant could run on half the cylinders. That amazes me.

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If it was easy, everybody would be doing it.