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Low Compression on Cylinder 5

Posted By lostdogcustoms 8 Years Ago
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lostdogcustoms
Posted 8 Years Ago
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Hello all,

   I am new to the y block, but I put my first one in a 27 roadster I just got on the road.  It seems the people that know these engines really know them.  I finally got it going and it ran great...except for a little miss on the driver side.    So here is my situation.

  I have an eck 292. That I got out of a "running" car, the car was in a restored Thunderbird a guy was putting a 289 in...dont ask me why...  it had been sitting in the shop for some time but he said it ran great.
When I started going over it I noticed it has been apart and I am pretty sure it has 272 heads on it but i can  no longer find the casting number that I think is under the he headers now (i think it was ecg-d??...)
   I got it going recently and it seemed to be doing really well but it had a miss that I started to track down.   I adjusted the valves and my vacuum gauge was still wobbling between 15ish and 21 ish.   It still had a miss.   I tracked it down to cylinder 5.  It was only reading about 60 psi on a compression test.  So I put that cylinder at top dead center  on the compression stroke and hooked it up to my air compressor.  I did not get anything out of the carbs or exhaust.   But air was getting out from under the valley pan near the push rods and the fill tube.   I then realized that the head gasket on that side is on upside down (according to assembly errors websites) because the corner is sticking out towards the rear of the car. I am wondering now if these two things are related, or if I have two problems concurrently like, a stuck ring and a bad head gasket.  I want to make sure I do not forget to check something when I pull the head.  Also if I do have the 272 heads which head gasket would be correct?  Thanks for reading this.
Ryan
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charliemccraney
Posted 8 Years Ago
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Wow, it looks like it probably is a T-bird motor.  Many Y-blocks become T-bird motors when they are for sale.  Yours actually has T-bird parts.  The mismatched heads are not really a concern.  The motor is going on 60 years old.  It could have anything on it at this point.

Re the low compression, you just can't know until you take a look.  The head must come off to correct the gasket issue.  You'll have a good opportunity to look when you do that.

Unless you really like having the t bird components, you should get rid of the water pump spacer.  It does no good for cooling.  You can fit a spacer under the pulley to realign the belt or if you have room, get rid of the T-bird generator brackets and damper and get a set of more common car/truck brackets and damper which will line up without additional spacers.  Then just put a spacer between the pulley and fan.  Sell the T-bird parts to a T-bird guy.

I see that the crankcase vent is blocked off.  Is there any kind of tube or vent in the back of the valley cover?  You need to make sure you have proper crankcase ventilation. 

I also notice that the vacuum canister of the distributor does not seem to be connected.  That's not necessarily a problem.  Does the distributor have mechanical advance?



Lawrenceville, GA
lostdogcustoms
Posted 8 Years Ago
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I was there when the guy pulled it out of the Thunderbird....I got the 3 speed overdrive and floor shifter with it (the three speed overdrive is in the car) .  wild huh.

I do kind of like the t bird stuff.  I am not sure what removing the spacer on the water pump would do with the strange t bird crank pulley set up.   But at this point I have it all together and happy....except for that miss. 

I am not sure what crank case vent is blocked off, but the filler has a breather on it and I modified the road draft spot on the valley pan to take a pcv valve.  


The distributor is a 57 and I do not have the a correct ported source for it so I am running it with mechanical advance only.   It seems the advance curve is pretty good. 

As for the compression i know i need to pull the head.   I would still like suggestions in looking for trouble spots that could cause this... places they crack , valve guides...whatever is yblock

charliemccraney
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There isn't really a trouble spot.  You just need to pull it apart and see what's going on.  It could be the gasket, it could be rings, oh, try squirting some oil in the cylinder and then do the compression test again.  If the compression comes up, then that suggests it is the rings.  Since the heads seem to have been changed, it could be a problem with the deck of the head or maybe even the block.

For the vacuum advance, you could try manifold vacuum.  That works great for some of us.  You'll have to readjust the idle tune but that's about it.



Lawrenceville, GA
charliemccraney
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I thought of a trouble spot.  The head bolts, the longer ones, under the valve cover were different lengths on most later Y blocks.  There will be either 5 same length bolts or 2 which are about 1/4" longer than the rest.  If you have the two longer bolts, they should be installed at the ends of the head.  If they are in one of the the center positions, they can bottom out and do not clamp the head gasket properly.  I'd expect a compression drop in the two neighboring cylinders in this case, though.



Lawrenceville, GA
Talkwrench
Posted 8 Years Ago
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Well if you have to yank the head[s] you can do it easy  ; o P 

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Ted
Posted 8 Years Ago
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Based on your air test, it does sound like a piston or piston ring problem.  The only way to resolve this is to simply remove the piston and see exactly what is going on.  The problem with continuing to drive the engine without addressing the problem is additional cylinder wall damage depending upon what kind of damage has taken place.  If caught early enough, there's a good chance that the engine will not have to be completely torn down.



Lorena, Texas (South of Waco)


lostdogcustoms
Posted 8 Years Ago
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Thanks for the advice so far, I am going to pull the head as soon as I can and take a look.  I need to fix the gasket anyway.  I will try to post the results.  It may have to wait about a week while I finish wiring the shop, but it is getting to be great weather for a  roadster  and I do not want to miss out.  

Unfortunatly i do not know how long it has been run like this.   I think the engine sat for many years in the car as it was getting restored.   I guess will see
MoonShadow
Posted 8 Years Ago
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As long  as you are going to have the head off you may be able to soak the piston and cylinder with a solvent. Not as good as pulling the piston but can help free up rings. Chuck



Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire


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