compression
01-03-2009, 02:58 PM
#4
Mopar Lover
i think, think, if it is stock compression, it should be somewhere around 150
but im not sure
but, the readings that you get should be within 10 of each other
but im not sure
but, the readings that you get should be within 10 of each other
01-03-2009, 03:20 PM
#5
Admin
Those numbers seem a little low. How many times did you turn the engine over? you should turn it over til the gauge stops moving, which should be in 5 full rotations.
01-04-2009, 05:59 AM
#9
Mopar Lover
Good rule of thumb... sea level mean atmospheric pressure is 15 psi. 10-1 compression should give you 150 lbs, or thereabout, even if you're not at sea level. Lower ratios, lower levels, for instance, 8-1, 8 times 15 = 120 lbs. When you check your compression, you really shouldn't have much more than 10% difference between the highest compression and the lowest. More than that, you should be seeing what problem you have with your motor.
01-04-2009, 08:39 AM
#11
Admin
How far did the guage go down? The guage should stay the same when you are done turning the motor over.
01-04-2009, 09:50 AM
#12
Guest
Posts: n/a
With your compression going all over the place it's not a good sign. But, give us more history?
1.) What vintage is the engine?
2.) Has it ever been rebuilt before?
3.) Has it been driven exclusively in town?
Part of what could be happening is just carbon build up which can be removed.
Dating myself but in the old days we would throw in a quart of ATF, top off the tank with high test gasoline and take it down the highway at a 100 miles per hour for at least 5 - 7 miles and then back to 60 -70 miles per hour for one hour.
Return to shop and retest all cylinders. This being said there are modern day combustion chamber cleaners that you run through the carb but I would suggest dropping the oil afterwards and replacing the oil filter.
MM
Last edited by 69 Mopar Maniac; 01-04-2009 at 11:48 AM.
01-04-2009, 09:53 AM
#13
Guest
Posts: n/a
ill check again later let you all know.ripped a finger nail plum off taking spark plugs out.the finger was one i had all ready chopped end off when i was a kid lucky i even had a nail any ways pretty sore today might be a few weeks before i can wrench again.thanks
01-04-2009, 11:16 AM
#14
Guest
Posts: n/a
motor is a 69 model.dont know history probly rode hard and put away wet.does have a cam with a lop.and has been running richh.trying to solve this problem 2 different carbs same prob.thinking dist.have had car for 10 years but only been drivable last 2 years and drove very little.had the car checked out supposably ,starting to doubt the person.they said cam was to big and had blow by.im checking compression then going to pull valve covers off and see how oily,had off few years ago and was super clean [like its been rebuilt]so im going to check again and see .and go from there.
01-04-2009, 11:51 AM
#15
Guest
Posts: n/a
Sometimes when you think it's running rich it is really just a needle valve under the fload that is either dirty or has an obstruction.
Take off the top and check it out. Another common issue is the case top of the carb may have loose screws which allows air to be drawn it causing a similar problem.
Maybe tighten them up first and see what happens.
MM
Take off the top and check it out. Another common issue is the case top of the carb may have loose screws which allows air to be drawn it causing a similar problem.
Maybe tighten them up first and see what happens.
MM
01-19-2009, 03:58 AM
#17
Mopar Lover
also if you have a large duration cam with over lap you won't get a true reading at turning over speed . was told that just the other day so i may have more comp than i thought .
02-03-2009, 09:23 PM
#21
Mopar Lover
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