Miss Fire!!

B

Buck

Junior Member
I have a B engine in my 30 speedster that was running like a top. Was in the 4th of July parade and ran out of water. Got hot and it stopped! Had to tow it home. The block was cracked, externally! With the help of J/B weld and block seal did the trick. As it was down I adjusted the valves. So far everything is going smooth RIGHT? WRONG!! It started right up. Running a little rough. Let idle a few minutes. Checked the wires to be sure they were on right, they were. #4 is missing. Checked the points, Put in new plugs change the wires, cap, rotor,check the comp. 65 lbs in all Cyl . #4 cyl. is dead What is wrong?? Any help Please!!!!!!
 
Are you sure when you adjusted the valves you didn't mess one up on No 4 so that it is now not closing?
B blocks are renowned for cracking. Once you get it going again, keep a close eye on the water for oil. If it cracked badly enough that it was visible on the outside, I suspect serious damage lurks within.:eek:
 
Synchro909 said:
Are you sure when you adjusted the valves you didn't mess one up on No 4 so that it is now not closing?
B blocks are renowned for cracking. Once you get it going again, keep a close eye on the water for oil. If it cracked badly enough that it was visible on the outside, I suspect serious damage lurks within.:eek:
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I have Run the valves Adj. twice just make sure Their OK What's left?
 
No bubbles showing up in the rad coolant? How's the number 4 plug look like after running the engine? Is it just flooded with gas or is it wet with coolant also?
 
Make sure your getting good spark to that cylinder.
Spray around the intake gasket to see if you have a vacuum leak
Do a leak down test on #4 cyl
 
heneste said:
No bubbles showing up in the rad coolant? How's the number 4 plug look like after running the engine? Is it just flooded with gas or is it wet with coolant also?
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I've checked all of the plugs and they all look the same. I called my Brother and he said change the valve springs as they gotten hot and have lost their tension. Therefore they flout Wont close at a higher RPM. That is my next step! In despration I took the head off everything looks OK. The head gasket isn't blown. When it was running last and at a higher RPM water did gush out the over flow. I'll get the springs change this morn. Tks ford barn: :)
 
I doubt weak valve springs are going to cause a low engine speed mis-fire.
If all holes have good compression then that cylinder seems to be in good condition.
As mentioned, I too would recommend making sure there is good fire and no vacuum leak. I wouldn't assume anything.

I read the OP has having good compression on all holes.
 
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Compression tells a story. Cylinder No. 4 has none. Points to consider:
> As No. 3 has good compression, the head gasket does not have the classic burnout between Nos. 3 & 4;
> You adjusted the valves, but made no comment about the valves in No. 4, so I am guessing you were able to successfully adjust the clearances. So the loss of compression may be due to one or both the valves leaking at their seats. A crack into either of the valve seats and or burned valves may be the culprits;
> Another possibility is a crack in the block allowing compression gas to leak past the rings, or escape into the cooling system. Bubbles seen in the coolant at the top tank of radiator are not a good indicator of compression leakage into the cooling system of a Model A Ford.

My recommendation is to remove the cylinder head and do a thorough inspection of the combustion chamber of No. 4.
 
says #65 lbs in all cylinders.... i am thinking number 4 also.... states #4 is dead i am thinking dead in not firing
 
I've seen a couple distributor bodies have crossfire between 3 and 4 and cause a miss. Try the easy things first, like another distributor body. An engine scope would show what's up with plugs firing.

If you have a slow to close valve, then you can have good compression at cranking speed, but not at running speed. Connect a vacuum gauge and see if it remains steady during the miss.
 
Not to overstate the obvious, but this is a reminder that our A's are not like our modern cars, which are almost maintenance-free. We should adopt habits of checking oil, water, and tires (at least) every time before we take the car out.
 
my thoughts would go to the point's cam in the distributor and on number 4 the points may not be opening the same as the rest of the cyl.
just a guess because it sounds like you covered all other possible's
good luck

terry
 
First you need to see if you have a nice blue spark to that cylinder. If you do I would say you cracked the block on number 4 by the valves. Number 4 gets hotter than 1,2. If it is cracked you will get water on the plug which will stop it from firing. Because you said it ran ok until it got hot, it most likely has some thing to do with getting real hot. It won't be the valve springs.
 
George Miller said:
First you need to see if you have a nice blue spark to that cylinder. If you do I would say you cracked the block on number 4 by the valves. Number 4 gets hotter than 1,2. If it is cracked you will get water on the plug which will stop it from firing. Because you said it ran ok until it got hot, it most likely has some thing to do with getting real hot. It won't be the valve springs.
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#4 has 65 lbs. just like the rest of them. No water on the plug. I have taken the plug out and ran the engine and the plug fires there is good spark put the plug back in and that cyl. does not fire!! With the motor running, I stuck the comp. gage into the hole and have good compression. It is running on 3 cyl.!!!! Am at witts end!!!!! Any other ideas========= PLEASE!!!!










#
 
Switch that plug around and see if it changes the miss. I'll bet that plug has a cracked insulator that is not visible. The Cap may have internal carbon tracking grounding out #4 post.
 
in the original post he switched the plugs did a full tune -up

but he can try switching the new plugs from cyl to cyl for shits and giggles you never know maybe a new one is bad
 
Tom Wesenberg said:
I've seen a couple distributor bodies have crossfire between 3 and 4 and cause a miss. Try the easy things first, like another distributor body. An engine scope would show what's up with plugs firing.

If you have a slow to close valve, then you can have good compression at cranking speed, but not at running speed. Connect a vacuum gauge and see if it remains steady during the miss.
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One way to check for a slow to close valve (and I've seen such-dealing with one on my '40 now) is to hold a shop rag next to the tailpipe with the engine idling. If the exhaust valve is hanging open, the reverse pulse will actually suck the rag into the pipe. If it's an intake, it will show up on a vacuum gauge. Again, compression at cranking speeds will be normal.
 
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