compression question

[captain2207]

My 84 200s is giving me a real hard time to start.I've checked rechecked valves and timing.I put a compression gauge on it and it read 120-125 lbs.would those numbers not let it fire off?.thanks all

[Ghostv2]

The 200s is suppose to have 142-170 psi. So im guessing yes.

[El Camexican]

Keep in mind compression ratings are dramatically affected altitude. I can’t see 120psi not lighting up your fuel even if it is a little low.

[captain2207]

I figured it would at least fire off at 120-5 lbs.I guess I need to do a leak down test?any home made leak down tester posts?thanks all

[6speedthumper]

That compression reading should be adequate to start and run that engine. 120 is USUALLY the bare minimum GOOD compression reading. But, did you do this test with the throttle held wide open? Because it needs to be.

[captain2207]

6speed I did wot.it may have been full choke since I was trying to start it couple days before compression test.

[6speedthumper]

Well, if you are sure that your timing, valve lash, ignition system, and fuel system are working properly; compression is the last thing left on the table. I've seen engines with less comp then what yours is telling you, and they started and ran fairly quickly. But, all engines are different, and it could just be that yours is nearing it's limits. Have you tried to squirt a LITTLE oil in the cylinder, then try to start it?

[El Camexican]

How many times did you pull it to get a reading? Should be as many as it takes to get the highest reading, not just a couple.

[captain2207]

6speed I have not ied oil in cylinder,how much do I put in?I probably pulled it 8-10 times.the gauge had stopped about 5pulles but I did a few more.when it did run absolutey no smoke,so maybe base/head gasket time?

[oscarmayer]

when you pulled the readin, did you turn off the fuel and hold the throttle open? if not you will get false low readings. the thrttle needs to be open in order for correct amoutn fo air to be sucked down the cylinder. also you need to keep kicking, turning over the motor tillo needle stops climbing. that coudl be 7-10 kics or as early as 3-4 each engine is different, but again make sure the throttle was open.