New issue...again

[72Hardtop]

It was a burned valve on #4. From the looks of it, it appears that during the previous valve job the builder did not gap the rings correctly on the pistons. There was literally no gap at all ! Seems I will bring this up to him when I visit him in a few days with a cylinder/piston in hand along with my receipt to show he was the last to have had the engine apart.

I requested him during the valve job to go ahead and hone the cylinders and re-ring the pistons. All the cylinders were the same. It's very likely he just assembled as is without checking the gap measurement on the rings. I know damn well they wouldn't have changed with time...impossible!

[Amskeptic]

it appears that during the previous valve job the builder did not gap the rings correctly on the pistons. There was literally no gap at all likely he just assembled as is without checking the gap measurement on the rings. I know damn well they wouldn't have changed with time...impossible!

The goal is to have no ring gap! Nobody likes blow-by.
The gap is only to allow for expansion as the engine heats up. If there is an insufficient gap, you generally seize the engine in just a few minutes after the first start.
Now go buy the guy a beer.
Colin

[Sylvester]

it appears that during the previous valve job the builder did not gap the rings correctly on the pistons. There was literally no gap at all likely he just assembled as is without checking the gap measurement on the rings. I know damn well they wouldn't have changed with time...impossible!

The goal is to have no ring gap! Nobody likes blow-by.
The gap is only to allow for expansion as the engine heats up. If there is an insufficient gap, you generally seize the engine in just a few minutes after the first start.
Now go buy the guy a beer.
Colin

Can you explain what all this means in laymans terms? Having a basic idea of ring placement but never having done so, make statements like this hard to follow.

[72Hardtop]

it appears that during the previous valve job the builder did not gap the rings correctly on the pistons. There was literally no gap at all likely he just assembled as is without checking the gap measurement on the rings. I know damn well they wouldn't have changed with time...impossible!

The goal is to have no ring gap! Nobody likes blow-by.
The gap is only to allow for expansion as the engine heats up. If there is an insufficient gap, you generally seize the engine in just a few minutes after the first start.
Now go buy the guy a beer.
Colin

Goal being: during the compression stroke. There must be a certain gap amount for the gases to build up and press the rings against the wall of the cylinder.

My rings had no gap at all if you were to look down from the top of the cylinder with the ring/s inserted level in the cylinder.

[RSorak 71Westy]

Then they should have seized when the engine got hot. If they didn't then they have enough gap.

[72Hardtop]

Then they should have seized when the engine got hot. If they didn't then they have enough gap.

With the ring in the cylinder without the piston there was literally no clearance. Cylinders had excess carbon build up.

[Amskeptic]

it appears that during the previous valve job the builder did not gap the rings correctly on the pistons. There was literally no gap at all likely he just assembled as is without checking the gap measurement on the rings. I know damn well they wouldn't have changed with time...impossible!

The goal is to have no ring gap! Nobody likes blow-by.
The gap is only to allow for expansion as the engine heats up. If there is an insufficient gap, you generally seize the engine in just a few minutes after the first start.
Now go buy the guy a beer.
Colin

Goal being: during the compression stroke. There must be a certain gap amount for the gases to build up and press the rings against the wall of the cylinder.

My rings had no gap at all if you were to look down from the top of the cylinder with the ring/s inserted level in the cylinder.

I think the "gap" you are thinking of is the space between the piston lands and the flat surfaces of the rings. An insufficient gap here would prevent the rings from being able to move enough to press against the cylinder walls. You would know this at assembly time as you tried to rotate the rings to stagger the end gaps.
Or you would have what happened to me with the Road Warrior. A loose valve guide (thanks, LeRoy Engine Machining) caused the top of the piston to develop such a head of carbon that it contacted the head. This punched the crown of the piston down enough to trap the upper ring. Sounded like a poorly adjusted valve. Began to smoke when cold.
Colin

Only the upper ring has that inner "bevel" to allow combustion gases to help press the ring outward throughout its circumference. The end gaps are nothing more than necessary evils ...
Colin

[72Hardtop]

With regards to the bevel...which way would it be? I believe its down. If I remember correctly. The gap I was referring to was each end of the ring itself. When placed in the cylinder I was not able to get a feeler gauge in at all. I've got my new AA p/c's and they check out good. Using Hastings rings. Also new heads from Headflow Masters (42x36mm) reworked AMC's.

[Bleyseng]

yes, there is a "ring gap" spec and its in the Bentley book.. if its too small or no gap the ring just doesn't have room to expand properly to seal or seizes the engine. I dunno the spec off hand.

[SlowLane]

For the 2.0L 94mm pistons, Bentley says 0.016-0.028" end gap for new compression rings, wear limit is 0.035".

Ring side clearance in the piston grooves should be 0.002-0.003".

[72Hardtop]

Just to update:

I've installed the P/C's and heads and am now putting on the freshly cleaned/painted tins and shroud. Should have it ready to run by early next week. Will put some photos up when I get a chance.

Also replaced oil pressure switch, gasket for oil filter mount, alt. boot, oil press. switch boot, alt grommets, new frt. & rear seal, pilot bearing, clutch disk etc...

[SlowLane]

I see you're using an 009 with a Pertronix. Have you considered using this instead of the Pertronix: http://www.compu-tronix.com/DIS4009.htm

[72Hardtop]

Anyone using one? Feedback? Price is higher than a set of P/C's. Damn... What would I open the plug gap to? Perhaps .035???

Priced anywhere cheaper? Any similar alternatives?

How's it compare (performance wise) to a German 009 w/high output coil? Or how about towards an SVDA?

[RSorak 71Westy]

That distributor system is complete overkill unless you're too rich or attempting to set a land speed record. The pertronix is fine upgrade for a stock type engine.

[SlowLane]

Sorry, I probably shouldn't have dangled that particular carrot. But the OP seems to have quite a bit invested in his engine already, so I thought I'd point out another toy.

I'll agree that it's probably overkill, but I really like the idea of eliminating that 19th century revolving spark delivery system under the distributor cap.

The concept behind the Computronix DIS systems is simple and elegant. It uses the advance mechanism of the 009 (or other mech-advance) distributor to define the spark advance, but mates it to a distributorless wasted-spark coil pack so that the spark is delivered directly to the plugs without any messy air-gap in the way. It also controls the charging duty cycle of the coils in a dynamic way that no fixed "dwell-angle" could hope to match, thus ensuring optimal spark output at all RPMs.

I've never seen one in action, but I'd bet dollars to doughnuts that it would blow a Pertronix system out of the water in terms of delivering highly consistent ignition.

Keep in mind that this type of system, because it's reference is the body of the distributor, will only work with the centrifugal-advance portion of a distributor, so it's intended only for an 009 or other pure mech-advance dizzy. It's conceivable that one could figure out how to bolt it onto an SVDA, but then the vacuum advance mechanism would have no effect whatsoever on the timing.

Given the proclivities of the folks over on the ShopTalkForums, I wouldn't be surprised if someone over there hasn't used one of these and rendered his opinion.

Cheers