been tinker on my car this weekend and last night it had a bad miss under high RPM. i suspected that it was the fact i am running the stock ignition i'm running on my combo.
i pulled all the plugs to close to gap up to see if that would help etc so i figured i would run a compression test while its easy....
engine was cold.... i cut off fuel, spark and hooked up the compression gauge to each hole and here are my results
cyl 4- 160 psi cyl 8- 170
cyl 3- 178 cyl 7- 180
cyl 2- 172 cyl 6- 175
cyl 1- 172 cyl 5- 175
all look to be good except for cyl 4 making 160, not a bad number just considerably lower than the rest.
i hooked up an air compressor to that cyl to see if could get some bubbling out the radiator if i had a bad head gasket, no bubbles.
the only thing i can think off that it might be.
when i had the engine apart all my lifters were pumped up TIGHT, when i tried to adjust my rockers it would just hold the valves open and would compress the lifter plunger. so i took them to work and make a little tool to compress the lifters with an arbor press so get all the oil out of them so they were free again.
when i did this i made the mistake of leaving one lifter at home and never smashed the oil out of it. i ended up assembling the engine anyways.
engine ran fine, less than a week later i had the engine apart again and i went to adjust rockers again and i notice the same lifter that i never bled out was still pumped up TIGHT, it never compressed after running the engine.
i went ahead and adjusted the rockers and that one lifter pushed the valve open a bit instead of preloading the lifter, i was hoping it would compress after a few heat cycles.
and this lifter is in the same cyl that i got the lower compression readings? but if the valve was still being help open i doubt it would even make that much pressure on during the test.. i put .030 preload on the lifters so if the valve was still being held open it would be .030 open, about 1/32 of and inch.
just looking for ideas... the engine runs smooth and all. should i be too worried about that one cyl being a tad lower than the rest...? i mean i can pull the VCs and see if the lifter still is pumped up to tight...
they say to have them within 10% of each other, highest was 180 and lowest was 160 so thats 12%, not much more....
i pulled all the plugs to close to gap up to see if that would help etc so i figured i would run a compression test while its easy....
engine was cold.... i cut off fuel, spark and hooked up the compression gauge to each hole and here are my results
cyl 4- 160 psi cyl 8- 170
cyl 3- 178 cyl 7- 180
cyl 2- 172 cyl 6- 175
cyl 1- 172 cyl 5- 175
all look to be good except for cyl 4 making 160, not a bad number just considerably lower than the rest.
i hooked up an air compressor to that cyl to see if could get some bubbling out the radiator if i had a bad head gasket, no bubbles.
the only thing i can think off that it might be.
when i had the engine apart all my lifters were pumped up TIGHT, when i tried to adjust my rockers it would just hold the valves open and would compress the lifter plunger. so i took them to work and make a little tool to compress the lifters with an arbor press so get all the oil out of them so they were free again.
when i did this i made the mistake of leaving one lifter at home and never smashed the oil out of it. i ended up assembling the engine anyways.
engine ran fine, less than a week later i had the engine apart again and i went to adjust rockers again and i notice the same lifter that i never bled out was still pumped up TIGHT, it never compressed after running the engine.
i went ahead and adjusted the rockers and that one lifter pushed the valve open a bit instead of preloading the lifter, i was hoping it would compress after a few heat cycles.
and this lifter is in the same cyl that i got the lower compression readings? but if the valve was still being help open i doubt it would even make that much pressure on during the test.. i put .030 preload on the lifters so if the valve was still being held open it would be .030 open, about 1/32 of and inch.
just looking for ideas... the engine runs smooth and all. should i be too worried about that one cyl being a tad lower than the rest...? i mean i can pull the VCs and see if the lifter still is pumped up to tight...
they say to have them within 10% of each other, highest was 180 and lowest was 160 so thats 12%, not much more....
