D'OH! Compression Check question

[72_EB]

Hey, just borrowed my friend's tester to check out the engine.
I did have the motor warm but I forgot to wire the throttle open. D'OH! %)
Is this going to make a big difference? Choke was open though if it matters.
It's getting nippy out there and I really don't want to do it again. I think I know the answer here (Do it again, Sucker), but I'm asking anyway.

 

[ransil]

If you have all good readings then your done, if any are questionable then you may want to redo them.

 

[72_EB]

Didn't really like my readings :'( that's why I'm asking. Ugh!

 

[bronco-uno]

what kind of readings did you get?
were they too low?

 

[72_EB]

what kind of readings did you get?
were they too low?

CYL

1 - 100
2- 105
3- 120/125
4- 65! Added oil bumped up to 125
5- 85/90 Added oil bumped up to 125
6- 95
7- 100
8-105

Not pretty. That #4 and #5 would suggest lower engine and rings, huh?

Strange thing is the truck runs like a bat outta hE%^!
Was driving it yesterday and it runs very well! Doesn't blow any smoke (did valve seals and head gaskets last year?). Doesn't seem to be loosing much oil either!
It did have problems recently when I popped on a used, but rebuild Qjet. Couldn't get rid of an irratic idle. Popped the Holley 500 2 barrel back on. Runs smooth.
Plugs are all nice and gray. I might have the carb running a bit too rich though. What's going on?!

 

[73stallion]

the lowest cylinder needs to be within 10% of the highest. i've never opened the butterflies when i did a compression check.

 

[Jeepster]

If its running to your satifaction, not burning oil too badly, starts and runs.....dont sweat it...run the beast and be happy. Dont go looking for trouble my friend. ;D

 

[bronco-uno]

yeah jeepster is right....as long as it runs good and your oil control rings are good you can run it.

 

[72_EB]

The only thing I'm craving on it is a little more punch from a 4 barrel. I've had this 2 barrel on since I owned it. I could tell that Qjet would make the 302 FLYYYYY if I could get it right. But it bogged like a fat pig if I romped on it. Maybe Sanda will bring me a new one from Chuck or an Avenger and I can quite monkeying with these old ones. Gotta believe. ;D

 

[Blue71]

72,

I did a compression check on the '68 289 V8 that had been sitting for 14 years. I got two cylinders that were low. One was 75 and the other 90. I was worried. After getting it started and running it...it does really well. I say run it and don't worry to much about it.

Blue71

 

[Dr. Awsome]

I aggree with all everyone here. If the Rig runs to you stisfaction great run it. But just to say the proper way to do a compression test which i'm sure everyone probably eveyone here knows how to do. But just in case. You need the motor to nice and toasty the warmer the better. Then you need to remove all the plugs. And prop the throttle open as far as you possable can. One other thing that I just found out resintly is it's best to have the rig hooked up to a battery charger so the cranking rpms don't drop. It sounds like you did everything right but the propping the throttle and the battery charger. The only difference it will make it the results will be slightly higher. also what's the compression ratio of you motor. If it's about a 9:1 it should still be in great shape except for cyl. 4 and 5. They just need a ring job. If youre really wondering where the problems are you can do a leak down test. If you don't know how to do that onw I can explain it if you desire.

 

[mtkawboy]

Id do the test over hot and with the throttle open and all the plugs out and a fully charged battery. You dont say what the motor mileage is but Id be looking for a burnt exhaust valve on #4. If you have a way to put air into the cylinder listen for air out the exhaust from #4. A leak down tester would tell you a lot more then a compression tester if you can borrow or rent one

 

[72_EB]

Thanks for the tips. I'm going to just run it for now. Maybe go rent a leakdown when it warms up a bit. Getting too cold out there to mess with it! Still want to drop in a warmer tstat for winter, put on my wiper arms, and maybe looking into popping in block heater ;D. Anyone in the frigid north running one? How much should I expect to pay? Thanks again.

 

[mtkawboy]

A 195 degree thermostat makes a big difference here in Montana