Wow....
Took some compression and leak down readings before I started my top end rebuild. For those of you just tuning in, I am restoring a 1974 Merc 440 Max, with a KEC 440/22 reed valve engine. On to the details...
Compression readings...
Cylinder 1 185 psi
Cylinder 2 185 psi
Is this normal for this engine??? I was expecting something in the neighborhood of 120 or so. Is wondering if this engine might not have shaved heads and / or cylinders. Anybody have any compression number that they can share? Boy, looking at the heads, there is damn little "squish" area there. I hope to have some "cc" values for the heads in the next few days to share with everyone. Anybody have a good idea what to expect for a number there? Unfortunately, I did not check the piston to head clearance before I tore the engine apart, so that will have to wait until I get it back together.
Leakdown wasn't so good, but I expected it...
Cylinder 1 10% leakdown
Cylinder 2 19% leakdown
Tearing the top end apart verified #2 as having some damage to both the piston and rings. Looks like #2 was having either a timing issue or a lean A/F issue. Top of piston two is most definitely burnt, almost through, and I am suspecting it was the PTO seal leaking that caused it (common on this engine), but could be timing...worth checking timing anyway after its together. #1 looks as if its main leakdown issue was due to worn rings, with the endgap being excessive. Of note is that the compression test didnt reveal any issues, but the leakdown test did. That in itself turned a few heads from the guys here. If anyone cares for pictures, I can supply them.
Spent my Memorial Day taking cylinder measurements and piston measurements. Looks like I'll be going 0.010 over to be safe.
So, having said all that, what SHOULD I expect for typical compression readings on this engine?
Dave
440 Max Engine Compression
After a lot of research and measurements, I figured out why the compression was so high. The main reason was the wrong head gasket being installed. I have no idea what head gasket it was for, but it wasn't for a 440/22. Just measuring where it was obviously compressed showed it to be sticking into the bore by 1.7mm. The bore of the wrong head gasket was just a tad over 64mm. So whatever Kioritz engine with a 64mm bore is likely what this head gasket was for.
I hadn't noticed this when I tore the engine apart because the head gasket came off with the head. The only clue I had something was "up" was when the correct gasket set came in and I started the rebuild. The rebuild went really well. No major surprises...just lots of measurements and readings to take.
I measured and decided that 0.010 over pistons were needed. Got those in, and had the cylinders bored at Central Snow. I also ended up putting a brand new crank in it to make sure that the big bearings and seals were perfect. After all was said, I ended up taking some measurements and recording volumes of the cylinder and head volumes including spark plug volumes so I have what is as accurate of a compression ratio readings as I can record. So for those keeping track, these are the values that I recorded during the rebuild and the calculations I made.
Bore: 66.24mm (0.25mm overbore)
Stroke: 64.00mm
Cylinder Displacement 220.5cc (x2 = 441.0cc)
Head Volume + Spark plug volume (flat plexiglas cc method): 19.75cc
Head Gasket ID: 68.8mm
Head Gasket Volume: 3.72cc
Deck Height: 0.45mm
Deck Height Volume: 1.55cc
Piston Dome Volume: -3.00cc
"Total Volume" above piston at TDC: 22.04cc
Uncorrected Compression Ratio: (220.5+22.04)/22.04= 11.0:1
Exhaust Port Timing: 36.39mm
Corrected Cylinder Volume: 125.4cc
Corrected Compression Ratio: (125.4+22.04)/22.04 = 6.7:1
Estimated Static Compression: 149 psi
Based off of these measurements, the minimum octane fuel should be 89 minimum. I'll run 91 minimum to be on the safe side. Ran the engine at various throttle settings for 10 minutes to seat the rings and let things warm up, then took these readings.
Actual Static Compression:
Cylinder 1: 145 psi
Cylinder 2: 145 psi
Cylinder 1 Leakdown: 1.25%
Cylinder 2 Leakdown: 1.25%
I would imagine that the leakdown numbers should improve as the engine gets broken in within its first couple of tanks of fuel.
Now on to the other projects on this well ridden 440 Max. Hopefully this will help someone with their rebuild, or questions about their Kioritz 440/22 engine.
Dave
'74 440 Max
I hadn't noticed this when I tore the engine apart because the head gasket came off with the head. The only clue I had something was "up" was when the correct gasket set came in and I started the rebuild. The rebuild went really well. No major surprises...just lots of measurements and readings to take.
I measured and decided that 0.010 over pistons were needed. Got those in, and had the cylinders bored at Central Snow. I also ended up putting a brand new crank in it to make sure that the big bearings and seals were perfect. After all was said, I ended up taking some measurements and recording volumes of the cylinder and head volumes including spark plug volumes so I have what is as accurate of a compression ratio readings as I can record. So for those keeping track, these are the values that I recorded during the rebuild and the calculations I made.
Bore: 66.24mm (0.25mm overbore)
Stroke: 64.00mm
Cylinder Displacement 220.5cc (x2 = 441.0cc)
Head Volume + Spark plug volume (flat plexiglas cc method): 19.75cc
Head Gasket ID: 68.8mm
Head Gasket Volume: 3.72cc
Deck Height: 0.45mm
Deck Height Volume: 1.55cc
Piston Dome Volume: -3.00cc
"Total Volume" above piston at TDC: 22.04cc
Uncorrected Compression Ratio: (220.5+22.04)/22.04= 11.0:1
Exhaust Port Timing: 36.39mm
Corrected Cylinder Volume: 125.4cc
Corrected Compression Ratio: (125.4+22.04)/22.04 = 6.7:1
Estimated Static Compression: 149 psi
Based off of these measurements, the minimum octane fuel should be 89 minimum. I'll run 91 minimum to be on the safe side. Ran the engine at various throttle settings for 10 minutes to seat the rings and let things warm up, then took these readings.
Actual Static Compression:
Cylinder 1: 145 psi
Cylinder 2: 145 psi
Cylinder 1 Leakdown: 1.25%
Cylinder 2 Leakdown: 1.25%
I would imagine that the leakdown numbers should improve as the engine gets broken in within its first couple of tanks of fuel.
Now on to the other projects on this well ridden 440 Max. Hopefully this will help someone with their rebuild, or questions about their Kioritz 440/22 engine.
Dave
'74 440 Max