"A.G..... I've found that
"A.G..... I've found that many of the later model high horsepower engines have a difference in the compression reading between the port and starboard bank, but never as great a difference as you've stated (25 lbs). Usually (what I've encountered) it was a difference of approximately 5 lbs and even on the bank cylinders ie starboard bank 125 lbs, port bank 120 lbs, with the starboard bank always being the higher reading.
I've asked a couple factory reps about this and had something rambled off to me about the design of the crankshaft throws being responsible.
I'm wondering if possibly the engine was in a tilted position and leaning on the high reading side (starboard ??). If so, it might be possible that an excess of the fuel/oil mixture was diverted to that bank. However, if the engine was in a normal upright position, or had been running shortly before the compression check, that scenario would be canceled out.
I'd suggest the following. Make sure that the fuel primer solenoid has its red lever in the automatic position (facing straight back towards the back of that solenoid). Have the throttle set at a dead idle so as not to draw any excessive fuel. Remove the s/plugs and crank the engine over for 10 seconds to blow out any excess fuel/oil mixture. Take another compression reading.
If the readings on both banks have now dropped to the same reading, or have closed the gap to a lower difference of 5 to 10 lbs, the port bank (cyls #2 & #4) being the lower, I wouldn't be concerned about that. However, if you still have a 25 lb difference, I'd suggest that you remove the affected banks cylinder head to inspect the gasket, sealing surfaces, pistons, etc.
Joe
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