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Engine Woes

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Pythias

Pythias

Jedi Knight
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Took the red thing out for a drive today. All was going well until
all of the sudden it started to miss, acting like it's running on
two or three cylinders. I checked the cap and rotor and it all looks
good. Checked the plugs and plug wire connections, again all good.
It has a Crane so it's not the points or condensor. I got it stared
up again and it still misses.. I pulled the air cleaner and watched.
Both pistons rise the same amount at the same time,

BUT.... MIST would blows back out of #2 carb. Puff, Puff, Puff....

Have I burned a valve?
 
When you checked the plugs, where they dark, light, dry or wet? How many the same and not the same?
 
I checked the plugs.. believe it or not, they all looked not bad.. the puff was from the rear, but the worst plugs were 1 and 2....

I swopped out the plug wires one at a time, .. no difference
swapped out the dizzy cap, no difference..

No way to check compression that I know of here, as I don't have a gauge. ..

Well, let me look.....

[5 minutes pass]..

Nope no pressure gauge here...
 
You can pull the valve cover and check valve clearances, Bill. When did you last set the valves?? I would first expect tightened up valves then burned valve. May be leaking head gasket as well. Really need to check compression.


Kurt.
 
The chain parts stores like O'Reilly's or Autozone will lend tools like compression testers. Unplug the coil and block the throttle open and remove all plugs when you test.
 
Valves last set about 3500 miles ago, give or take. I had the valve cover off before the tow home but didn't SEE anything out of whack when I turned the engine over. I'll check clearances...
 
Sounds like a head gasket......It has happened to my 1275 3 times. I don't think the torque rating advised for the head is tight enough....42 lbs. It scares me to go more but I've gone 52-56 lbs and been sucessful.[no broken bolts] Check out your oil in the oil pan too. There may be water there as a result of a bad gasket. Has anyone else 'gone over' on the head torque? If so, how much?
 
With a prior engine I had in a Mini, it was the head-gasket. This may also explain the puffing you had. Of course, there are lots of ways for a gasket to fail (to outside, to inside, to coolant). I'm going to presume that the water in your radiator isn't creamy brown... and go with the possiBILLity :yesnod: of what happened to me: a leak between two cylinders. I popped off the head, swapped the gasket and all was well. I went from major loss of power to back to normal. Of course if you're going to go to the trouble of pulling the head, you might consider some work on it (as you may be able or it may need).
 
Bill,

One other thing I would check is whether your spark is finding another path to ground on one of your leads, I recently tracked down a miss on a Morris Minor, attributed to the spark jumping to nearly heater hose. The hose had a tiny leak so the moisture exacerbated the problem.

Regarding speculation of the head gasket as the cause, this is possible too. I had a Midget here recently with a completely fresh engine that would develop a miss after about 500 miles. I replaced the (3rd) head gasket with a good Payen head gasket, thinking gasket quality was the issue. I even replaced all the studs with ARP fasteners and gradually torqued to about 55 or 60 lbs.The problem still came back. The head was checked and I think even surfaced one more time thinking it might be a little warped. After two more tries at head gaskets, it was determined that the head was warping just enough when warmed up to breach between #2 and #3 cylinder. The problem was finally solved by milling the head AFTER it was heated in an oven. Apparently, though rare, some heads have been know to do this. The problem went away after this last solution.
 
I just happen to have a brand new SHINY 12G295 head just sittin' around (thanx to Bill M.). My plan is to have it flow benched, hardened valve seats, nothing radical, just "breathed on" a little. I've been going to have it done for 6 or 8 months, but now my hand is forced. When it comes back I'll just change heads and if I find a holed piston I'll pull the engine and go from there.

It is a 1098, not a 1275, but I have a flywheel for a 1275 that has already been modified by Paul A. for the Datsun 5 speed that's in the car. If it's a holed piston I'll probably swap the lump...
 
I'm betting head gasket as well, Bill.

Always a good idea to check the block and head with a straight edge to make sure they are flat.

Also, I've had three gasket failures on different engines all with the copper/steel sandwitch gaskets so recommend the standard Payen head gasket.

Kurt.
 
I just had a head gasket failure on my 1275 (6000 miles since the rebuild). Mine blew between 3 and 4. I very carefully checked both the head and block for flatness using a machinist's square. Everything checked out. I was in a bit of a rush to get the car to get the car back together so I installed another Black Payen Composite head gasket. Many people told me to recheck my timing to be sure it wasn't over advanced. So I double checked that (all the way out to 4000 rpm).
If it fails again I may try one of the Cometic MLS head gaskets.

Good luck and keep us posted.
 
I don't know if this is related or not, but most likely IS..

I had trouble keeping the engine from pinging. I use Chevron Supreme at all times, so it's not the gas. I had the Dizzy redone by Jeff at Advanced. He recommended 10 to 14 degrees at idle. PING PING, etc. I've been dialing it back for a month or so every time I drive. Last check was about 5 degrees advance. It was running fine-no trace of ping- then all started pinging more and more just before it blew.

Head gasket?
 
Sounds like you have many possible start points to explore. At this juncture it could be internal engine issues, dizzy, vacuum (you didn't say if was mechanical or vac advance, carbs, or other electrical issues. Take a deep breath and start from the beginning.
 
It's not the dizzy vacuum. I have less than 1000 miles on a dizzy rebuilt by Jeff. It's not electrical, as its a CRANE unit, and I swapped out the cap, rotor and wires.. It's not carb, they both rise and fall at the same time and same amount when it runs... it's mechanical, whether head gasket, (no oil in the water, or water in oil that I can detect) or sucked valve, or burned piston. I had valve guides that needed replacing anyway, so I get a head built and go from there.
 
Pythias said:
It's not the dizzy vacuum. I have less than 1000 miles on a dizzy rebuilt by Jeff. It's not electrical, as its a CRANE unit, and I swapped out the cap, rotor and wires.. It's not carb, they both rise and fall at the same time and same amount when it runs... it's mechanical, whether head gasket, (no oil in the water, or water in oil that I can detect) or sucked valve, or burned piston. I had valve guides that needed replacing anyway, so I get a head built and go from there.
Click to expand...

Then I'm DEFINITELY voting a head gasket where there is a leak between two cylinders. You could still acquire a pressure gauge and test. I have one but am a hour south of you.

Good luck!
 
Doubt that it would be related, Bill, but just because both pistons rise and fall alike would not necessarily mean the mixture is the same. You mentioned the front 2 plugs looked different than the back and that could mean the back 2 are lean. Course the current problem probably is the cause for that.

Kurt.
 
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