Thread: Certainly not what I expected.

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My curiosity got the best of me this weekend and I decided to pull the drivers side head on my T to see why it has zero compression on number 7. With all the compression immediately going into the pan I felt there had to be a sizable hole in the piston.

When I got the head off I set it down and looked at that cylinder's combustion chamber to see if there was anything there. Everything looked fine, a bit of carbon throughout every chamber, but I knew the car was running way rich due to a lack of pressure regulator. Then I looked into number 7 everything looked pretty normal, a lot of carbon but no hole! I took some WD40 and a rag and cleaned up the top of the piston and the cylinder walls, still no evidence of a crack or anything.

So, I have two theories:

1) There is still a crack in the piston land or somewhere that I can't see until I get that piston out, or.....

2) All that gas going into the engine washed that cylinder in particular because it sits lower than the rest, and the rings have lost their seal.

All the other cylinder walls on that bank look ok except number 3 has some scuffing on the one side, vertically going up and down the wall. I put this engine together on a budget because that was when I was trying for the $3K limit on this build. I cleaned up the old pistons, reringed them and had my machine shop hone the walls. It ran good for 2 years, so I guess I got my moneys worth.

Obviously, I have to pull the pan and get that cylinder out to see what I can see. I plan on running a cylinder hone down the bore to break any glaze that might be there, replace the piston and rings, and put it back together.

Do any of you who know engines see anything I am missing or have any opinions?

Don

What does the cylinder look like Don? If that looks good with little or no ridge, I would guess the you'll find a problem in the ring lands.

It looks pretty good Mike. No scoring and some of the crosshatch is still there. No ridge at the top at all.

Don

I'm no expert, but I agree, must have a stuck ring. I had a similar problem, not a severe, but all the ring gaps got lined up and that cylinder had low compression. the other thing I was thinking was if that cylinder ever got real hot and killed the rings. I think you have said many times that your car ran cool, so that probably isn't it. No oil smoke, huh?
Ken

Ken, no if anything it runs cold. That might contribute to the incomplete burning of gas, doesn't get warm enough maybe.

Denny, I will try that. After that next step is to pull the pan and examine the piston. I have never had a cracked ring or broken land in anything I know of, so this is new to me.

There was one funny thing that happened today. When I pulled the left valve cover there was the smallest frog I have ever seen hanging on to one of the 4 valve cover studs that Vortecs have. I have no idea how he got in there or how long he has been there, but he was in no hurry to leave. I finally took him across the parking lot to the drainage ditch and released him. Guess I need to start using my car more..........critters have taken it over.

Don

I know your getting old Don, did you have the compression gauge screwed in tight...LOL
Bradc

I assume you checked valve lash before you tore it down?

Its real hard to tell from pic. ,but the ring gap looks to be excessive.

Brad, I think so, but you know my memory isn't what it once was.

dbradley: Yep, I even backed off the rockers all the way and it made no difference. These are brand new 305 Vortec heads, so the chances of something there being wrong are probably slim. When I looked at them today all the valves seem seated well.

sg4356, I kinda thought so too. I was able to take my fingers and rock the piston a little in the cylinder. Not a lot, but noticeable. In the next couple of days I am going to get that one out of it's hole and should know more then.

Don

Today I dropped the pan and pulled number 7 piston out..........more confused than before.............everything looks normal. No holes, no broken piston lands, no cracked rings, etc........looks just like a piston should except the top is very carboned up from my overly rich condition.

The rings look good and have nice tension to them. I removed the two top rings and checked the end gap by putting them down in the hole, it was right at 20 thousandths, well within specs. So I started looking at the combustion chamber and valves in that cylinder. I removed both the exhaust and intake valves and they are definitely carboned up, but I don't know if that would be enough to drop the compression to zero. It might make it low, but to lose all the compression seems a stretch.

I cleaned up the heads of both valves on the wire wheel and then used a rotary wheel to clean up the chamber and valve seats, and reinstalled those 2 valves. The only thing I see left to do is put new rings on that piston and button it back up with new gaskets. For sure I have to cure my too high fuel pressure and am ordering a pressure regulator this week.

To get the engine decarbonized once I have the fuel pressure in line, I am going to run a heavy dose of a product we sell at work. It is made by Yamaha Marine for their 4 stroke engines and is called "Ring Free." As the name implies it is designed to remove carbon and glazing from cylinder walls. Our techs swear by it and run a shock treatment dose on engines we are having trouble with sometimes. Even the Honda and Suzuki reps say "I'm not supposed to say this, but put some Ring Free in our motors that are gummed up too." It is that good of a product.

Finally, one indicator that this thing is just dumping gas down the cylinders is the condition of the oil pan when I pulled it. The entire bottom was sludge, and I use Rotella T oil and change it often. I have got to get that fuel pressure problem under control. Here are some pictures of what I found today.

Anyone have any suggestions of a better way to decarbonize the entire engine?

Don

Don, I went back and re read the post. Are you sure the compression was going into the pan when you did your check?
Ken

i would grind the valves and the seats. if you do not have any valve equipment so lapping will do. if you hit the seats with a wire wheel . if the intake is that black valves were not seating or push rod pop out of cup held the valve off seat ? your going to hear some compression past the rings in the pan. rings would have to be stuck in the ring s lands closed up to pass all compression walls could be glazed up abit from to rich but that s not going to get you O. its in your upper end. compression out the ex would be a ex valve .compression pass the intake valve would come out intake . can be check with putting air in that hole .i know you know this but it may help some one

Yeah Ken, the dipstick was continually being pushed out of the tube about an inch or so. I would push it down in and then later on find it up again after running the engine. In the beginning I thought it was vibrating out but then I realized it was being blown out by compression.

Pat, you are right, I think I'll pull the other head since I am this far along and remove all the valves and clean up the chambers and valve faces. I think I have a combination of things going on. I think perhaps all the rings were leaking a little due to the cylinders being washed, and that might have been the compression in the pan. Then I think the worst part of the compression loss was through the valves in that cylinder. I was just assuming there was some major break in the piston because I thought all the compression was going down the rings. But I bet that the valves were my real culprits.

I don't want to get into having a valve job done on these heads right now as I want to keep concentrating on the Ford engine I'm building. I just want to get the T back drivable and try to get a few more miles out of it before I do a proper rebuild or maybe build a different engine altogether for it. I think if I clean up the valves and run a shock treatment of Ring Free through it for a few tanks of gas, plus lean down my fuel mixture, I might be able to accomplish that.

Don

HI I had the same thing happen on a 351 clevland no compressing but did a leak down and had only 4% leakage. Findly saw cam was broken and no intake valve open so no compressing on up stroke and vacum on down stroke. Put new cam and lifters and v8 again.

That was the very first thing I thought had happened, or maybe a lobe went away. But I pulled the valve covers and watched all of them going up and down equally when I cranked it.

Don