Cylinder #1 no compression

-
D

Dustin The PcP

Well-Known Member
Joined
Oct 30, 2010
Messages
321
Reaction score
1
Location
Sugar Land, Tx
Well this isn't a fun situation to be in, but here I am. Cylinder #1 has no compression at all during a compression check, not even a little bump in the gauge, After adding oil to the cylinder still nothing. Cylinder #3 and all other cylinders compression is fine, so I ruled out head gasket, which is new anyways. The heads are J heads with new valves and springs, no cracks in the heads either. I removed the valve cover and watched the rockers go up and down, smooth, so I know it is not a wiped cam lobe. With the engine running you can hear the compression leaking out somewhere. Before I tear anything apart I am trying to diagnose and pinpoint the problem.

I am going to do a leak down test when I can, I do not have the tools right now, but any direction, input, or advice is welcomed.
 
1968FormulaS340 said:
You can't "leak down" what isn't there. Time to pull the head off.
Click to expand...

x2

if you cant get it to show any compression than there will be no compression to "leak down".....sounds like its evacuating just as quick as it builds.

rings,hole in the piston,junk cylinder wall,cracked cylinder,valve not seating,tipped valve,head gasket,cracked head....the list goes on of possible things it could be.

your only TRUE bet to find out was is wrong is to pop the head off and see if anything stands out at you.
 
I am going to hook air up to a fitting and screw it into the spark plug hole, and find out where the air is coming from.
 
Give it a shot....but odds are you will find that what ever the cause you will probably have to remove the head to remedy it.
 
Any noises or anything before this happened? If you have zero compression that would lead me to believe either you dumped a valve or a piston. Most other failures would at least still give slight compression readings.
 
DusterDude72 said:
Give it a shot....but odds are you will find that what ever the cause you will probably have to remove the head to remedy it.
Click to expand...

I am sure that I will, I just want to find out exactly what it is with diagnosing it, in case it is not obvious.


And no there was no odd noises or anything. I just reassembled the engine and it has less than 100 miles on it. I couldn't get what I thought was the carb tuned right and it kept back firing and so it turns out it is not the carb at all.
 
1968FormulaS340 said:
You can't "leak down" what isn't there. Time to pull the head off.
Click to expand...

leak down gauge is not looking for compression...it is looking for where it is leaking...

it will show if it is leaking pass the rings or valve...intake or exhaust...
 
is it back firing out the intake or out the exhaust? Whichever it is its a good bet that is the valve that is the issue. Another good quick test for zero compression is to watch your oil pressure gauge or crankcase breather it will show the piston/wall related problems.
 
The air is escaping from one of three places. Back up through the intake through the carb, through the exhaust or into the crankcase. Just remove the oil fill fap with it running. If you got a ton of blow by, you probably gotta hole in number one piston.
 
It turned out to be a bent exhaust valve, it actually hit the piston what looks like three times just a little. None of the other pistons have marks and all other valves are fine. I will be doing a little investigating to figure out what the cause was.

Thank you everyone for your input and advice!
 
Are you using an hydraulic cam and did you pump up the lifters before installing them. Also plan on replaceing the valve guide on the bent valve location could be cracked now.
 
demon seed said:
Are you using an hydraulic cam and did you pump up the lifters before installing them. Also plan on replaceing the valve guide on the bent valve location could be cracked now.
Click to expand...

Yes it is a hydraulic cam, no I did not pump the lifters up before installing them. And thank you for the tip on the possible valve guide. I will check it out and take a look at it, now that you say that though I will probably replace it anyways.

I will take pictures of the valve, the head, and the piston and put them up.
 
Ouch.....

I think that was one of the things I mentioned earlier that could be a possible cause.

now the question is.....WHY?

did you have the heads milled or block decked or anything?

any other machine work done?

did you clay the pistons the see what your clearances were?

hopefully it was a fluke and a tiny pebble or something fell down the intake and got caught between the valve and piston.

have you accidentally dropped any nuts or bolts down the intake (maybe a jealous friend was over and while you were not paying attention dropped a few tiny rocks down the carb all the while mummbeling to himself ( MWHOOOHAHAHAHA this will put a wrench in the gears) LOL......ya never know lol.

also ,check to see if all the screws are in place on the butterflies on the bottom the the carb..... sometimes people rebuild a carb and ruin those screws and end up drilling and tapping the shaft and using a regular screw.....or sometimes you may find that one of those screws were not flattened on the shaft to stop them from backing out.

I bought a GMC jimmy a few years ago that had a knocking engine and was over heating and puffing white smoke ..... The guy I got it from had just had an intake gasket done on the jimmy....afterwords it developed all the problems I just mentioned.

I tore the engine down and it turned out to be that the mechanic he had install the intake gasket dropped one of the TINY screws that hold the distributor cap to the distributor base and it fell down the intake.

when he started the engine that tiny screw smacked the bottom of the head when the piston got to TDC and it ruined a rod bearing and it tipped the piston and cracked the cylinder wall and was allowing coolant to flow into the combustion chamber (causing the over heating and white smoke).

so make sure to inspect it well for any piston and cylinder damage aswell.

good luck!
 
After you have the head fixed. I would use some modeling clay on top of your piston, reinstall the head, install the push rods and rockers and turn it over by hand to measure how much valve to piston clearance you have. I do this without head gaskets and then add the comp. gasket thickness to your figures to see where your at clearance wise. You want at least .080 intake .100 on the exhaust.
 
hopefully it was a fluke and a tiny pebble or something fell down the intake and got caught between the valve and piston.
Click to expand...

Good way to get shot ........ Some asswipe "friend" who had a thing for my girlfriend poured sugar into my 413....... Made a mess of the mains and rods too.
 
Here are a few pictures I just took.

100_0071.jpg


100_0070.jpg


100_0072.jpg


100_0074.jpg


100_0073.jpg


100_0077.jpg


100_0078-1.jpg
 
I ruled out head gasket, which is new anyways. The heads are J heads with new valves and springs, no cracks in the heads either.
Click to expand...

how long a go was this done?

you may have other tight valves, just waiting, for a repeat performance :scratch:
 
It is very possible a small rock got into the engine. I usually work on the car at my work, which is a mile long gravel road to get to, and about a mile of open gravel all around it. I have had to have the intake, heads, and carb off multiple times up there.
 
No nuts or bolts dropped down in it, and the heads were milled .020". I did not clay the pistons, but rather did it out in an equation of math to figure out my clearances and they were fine.
DusterDude72 said:
Ouch.....

I think that was one of the things I mentioned earlier that could be a possible cause.

now the question is.....WHY?

did you have the heads milled or block decked or anything?

any other machine work done?

did you clay the pistons the see what your clearances were?

hopefully it was a fluke and a tiny pebble or something fell down the intake and got caught between the valve and piston.

have you accidentally dropped any nuts or bolts down the intake (maybe a jealous friend was over and while you were not paying attention dropped a few tiny rocks down the carb all the while mummbeling to himself ( MWHOOOHAHAHAHA this will put a wrench in the gears) LOL......ya never know lol.

also ,check to see if all the screws are in place on the butterflies on the bottom the the carb..... sometimes people rebuild a carb and ruin those screws and end up drilling and tapping the shaft and using a regular screw.....or sometimes you may find that one of those screws were not flattened on the shaft to stop them from backing out.

I bought a GMC jimmy a few years ago that had a knocking engine and was over heating and puffing white smoke ..... The guy I got it from had just had an intake gasket done on the jimmy....afterwords it developed all the problems I just mentioned.

I tore the engine down and it turned out to be that the mechanic he had install the intake gasket dropped one of the TINY screws that hold the distributor cap to the distributor base and it fell down the intake.

when he started the engine that tiny screw smacked the bottom of the head when the piston got to TDC and it ruined a rod bearing and it tipped the piston and cracked the cylinder wall and was allowing coolant to flow into the combustion chamber (causing the over heating and white smoke).

so make sure to inspect it well for any piston and cylinder damage aswell.

good luck!
Click to expand...
 
You must log in or register to reply here.
-

Back
Top