cyl. pressure psi ?

Posted By: earthmover

cyl. pressure psi ? - 08/14/10 09:20 PM

Hay guys I ran a comp. Check on the old 340 and I got some diff. Reading and want your thoughts on what I got. I got 1 cyl at 160 the lowest and few at 175 and everything else on 185 is that to bad to keep running or is it time to spend

Posted By: emarine01

Re: cyl. pressure psi ? - 08/14/10 09:28 PM

If you post more info like what the testing order was and haw you did the test, all plugs out with engine hot .... ect, sometimes the cranking speed will effect the #s, a leak down test might be next

Posted By: earthmover

Re: cyl. pressure psi ? - 08/14/10 09:35 PM

Ok sorry I had motor at 180 temp. All plugs out carb open and turn motor same #s of turns. I tried 1 cyl on leak down but never did it before so I stopped.how is it done thanks mike

Posted By: emarine01

Re: cyl. pressure psi ? - 08/14/10 10:11 PM

Were you charging the batt during the test? Some times the last few cyls will read low on compression as the batt fades, What type of leak down tester are u using

Posted By: MR_P_BODY

Re: cyl. pressure psi ? - 08/14/10 10:12 PM

Quote:

Ok sorry I had motor at 180 temp. All plugs out carb open and turn motor same #s of turns. I tried 1 cyl on leak down but never did it before so I stopped.how is it done thanks mike

Next thing to do is squirt some oil in each cyl and
re test the compression to see if its valves or rings
(have a battery charger on it)... the one cyl is low
in relation to the highest... 10% is suppose to be the
max difference

Posted By: earthmover

Re: cyl. pressure psi ? - 08/14/10 11:22 PM

Thanks guys yea I had the batt charger on and the lowest 1 is the 1st to be checked #1

but could the val. Lash have a affect on this cause I did it last time and never did it before

so I'm gonna check all that as well. Car has been a best of 7.44 in the 1/8 mile last night was a best of 7.70 with 1.70 short times and 90 mph people told me the car pick the wheels up a little and went bout 5ft with them

but something is going on here I changed jets cause lean cond. And the front got worst

don't know how but did. Just trying to get this thing back where it was or close. I made some changes since it ran the best in this order I moved muff. Back 18 inch from coll. Got fuel system up to par adv cam 4 deg and moved timing to 34 from 38 so help please

I will shoot oil in and report back thanks mike

Posted By: emarine01

Re: cyl. pressure psi ? - 08/14/10 11:31 PM

The valve lash being too tight can drop cyl pressure, valve not sealing, Your #s spread is showing some things up, If its a ring seal issue I would just wait till winter and over haul

Posted By: earthmover

Re: cyl. pressure psi ? - 08/15/10 12:03 AM

Yea. I don't want to rebuild right now plan to build something new next year so want to get by but man . Anyway could adv. The cam make this happen where I lost 3ths with all the mods I did

would have thought that I help with the verta at lease buyt dunno

Posted By: MR_P_BODY

Re: cyl. pressure psi ? - 08/15/10 12:23 AM

Quote:

Yea. I don't want to rebuild right now plan to build something new next year so want to get by but man . Anyway could adv. The cam make this happen where I lost 3ths with all the mods I did would have thought that I help with the verta at lease buyt dunno

Have you checked to see if you have a lobe on the
cam going south(check the cyl that is low)

Posted By: earthmover

Re: cyl. pressure psi ? - 08/15/10 12:33 AM

Ill check that mr.p never thought bout that good to know