Kilgore47 Posted May 9, 2022 Report Share Posted May 9, 2022 The 47 P15 is in my shop for a few projects. Valve adjustment, replace the intake manifold and replace the rear main seal. Got the valves adjusted and the intake replaced but I think I will hold off on the rear main. Not sure what type rear seal this engine has but I don't want to dig that deep right now. So I'll do that later. Adjusting the valves has made a huge difference in how it runs. They were way off - probably haven't been adjusted since that engine was put in the car in 1974. The engine used to spit and spudder a little at idle. Now it purrs. Some of the exhaust was as high as 18 thousandths and the intake was up to 16. Made a lot of noise - now it's smooth and quiet. After the valves were adjusted I decided to do a compression check before the spark plugs were put back in. Grabbed the HF compression check kit and went for it. First cylinder came up at 60 pounds. My heart sank. Could I have adjusted the valves wrong? Is there a burnt valve? It could happen. So I went to #2. It came up 60 pounds also. OK one cylinder going bad is possible but two going bad with the same low pressure is not likely. So I dug around in my old tools and found the old compression tester. The one with the rubber tip that you have to stand on top of to get a good reading. Turns out the compression is good and the almost new HF kit has gone bad. Time for a new tool. Going to look into getting a lift for the shop. Rolling around under the car on a creeper is getting harder as I get older. But I really enjoy working on this old car so I'll keep trying. I'll consider doing the rear main if I get a lift. 2 Quote Link to comment Share on other sites More sharing options...
Dodgeb4ya Posted May 9, 2022 Report Share Posted May 9, 2022 Chinese junk tools...seems like. 1 Quote Link to comment Share on other sites More sharing options...
Plymouthy Adams Posted May 9, 2022 Report Share Posted May 9, 2022 (edited) with the cost of metal as it is and continuing to rise.....lifts have jumped to well over 1000.00 in the past year for you basic 8K 4 poster. Don't look to it getting any better soon either....I am afraid to say it but those were the good ole days. I just came from the metal shop....bought misc stuff for a project and came out at 54 lbs of metal. I'm very happy to not be forced to buying full stick like most retailer SOP is for metal Edited May 9, 2022 by Plymouthy Adams Quote Link to comment Share on other sites More sharing options...
Los_Control Posted May 9, 2022 Report Share Posted May 9, 2022 I had same issue with my compression tester last time I used it. And have only used it to check all 6 cylinders 4 or 5 times while monitoring the compression ... watching it rise after several heat cycles. With mine the 0-ring was torn, possibly me over tightening it & my fault. Still I have a option to remove the adapter and check it that way, it still showed low compression but the tool is not really meant to be used like that so I dunno. I bought a new 0-ring for it but not yet checked to see if that fixes it. The way the engine starts and runs I know it has more compression then the 20-60 the gauge was showing. Just not convinced my gauge is any better then the HF gauge you have. Quote Link to comment Share on other sites More sharing options...
keithb7 Posted May 9, 2022 Report Share Posted May 9, 2022 (edited) I have had a K&D Tools compressor for 30 years. Works quite well. I am curious what you measured for good verified compression? My recently rebuilt 237 engine has about 300 miles on it. 100 psi, dry test, across all. I am at about 2000 ft above sea level. Edited May 9, 2022 by keithb7 Quote Link to comment Share on other sites More sharing options...
Kilgore47 Posted May 9, 2022 Author Report Share Posted May 9, 2022 The pressure I have now is about 95 pounds in each cylinder. I'm at about 400 feet above sea level, That's not bad for a 48 year old engine. The guy I bought the car from said this engine probably only had 10 to 15 thousand miles on it. That was his guess because the speedo didn't work when I got the car. Quote Link to comment Share on other sites More sharing options...
Los_Control Posted May 9, 2022 Report Share Posted May 9, 2022 Curious how much altitude will play a part in compression test? Having lived in Albuquerque 15 years at over 5300 ft above sea level, travel to Sante Fe at over 7100 ft. Is very difficult driving a carburetad vehicle. Cooking beans or potatoes takes a longer time because of altitude. I never paid attention to tire pressure, just kept them what they should be. Today in Texas I am 650' above sea level, my truck coming straight out of a 15-20 year slumber in a field, 2 cylinders had 110 psi compression, others were lower but after running a few times all but 2 were over 100, they were around 90 psi ... but improving. So a freshly rebuilt engine with 100 psi, I wonder what the difference would be from 650' to 2k' .... Altitude could be the reason? Or is it just possible the old school new rings just have not fully seated yet? Quote Link to comment Share on other sites More sharing options...
keithb7 Posted May 9, 2022 Report Share Posted May 9, 2022 (edited) I believe elevation makes a difference. How much? I don’t know. The density of air is higher at sea level. Pushing down so to speak. A layer of air that is 2000 feet thicker than up here at my elevation. It makes sense to me more air could be packed into the cylinder at sea level. Sort of a natural boost. I also agree my rings are likely not fully seated yet. 300-ish miles so far. Edited May 9, 2022 by keithb7 Quote Link to comment Share on other sites More sharing options...
Los_Control Posted May 9, 2022 Report Share Posted May 9, 2022 I know older rings because of the material they were made out of, they took longer to fully seat ... up to 1k miles. Now modern vehicles better material it does not take as long ... thinking this may play a part in older cars rings sticking from sitting ... I have no clue if a modern rebuilt flathead rings uses material the same as the modern vehicles .... I kinda suspect they use the same old rings to match the Iron the block is made out of? Really does not explain the poor quality of tools we have today, not what was built 30 years ago. Quote Link to comment Share on other sites More sharing options...
Bryan Posted May 9, 2022 Report Share Posted May 9, 2022 30 minutes ago, Los_Control said: I know older rings because of the material they were made out of, they took longer to fully seat ... up to 1k miles. Now modern vehicles better material it does not take as long ... thinking this may play a part in older cars rings sticking from sitting ... I have no clue if a modern rebuilt flathead rings uses material the same as the modern vehicles .... I kinda suspect they use the same old rings to match the Iron the block is made out of? Really does not explain the poor quality of tools we have today, not what was built 30 years ago. Quote Link to comment Share on other sites More sharing options...
Los_Control Posted May 9, 2022 Report Share Posted May 9, 2022 (edited) Yeah thinking it was the old chrome molly rings that took longer to seat. Same time I have no idea what modern rings for a old flathead are made of. I actually should check my compression gauge with the new 0-ring & see if lisle is a good product. Or if it is the actual gauge head that needs replaced ...... Sigh been 3 days now I was going to change the oil on my daily driver .... once that is completed will check the Dodge. In fairness is the first days of summer temps over 100 the last few days, we kinda need to acclimate to it. Edited May 9, 2022 by Los_Control Quote Link to comment Share on other sites More sharing options...
Sniper Posted May 10, 2022 Report Share Posted May 10, 2022 3 hours ago, Los_Control said: In fairness is the first days of summer temps over 100 the last few days, we kinda need to acclimate to it. Tell me about it, I was out in Sprayberry starting up some units today and they hadn't got their HVAC up yet, new construction natural gas plant control center. I lost 9lbs in sweat today. Not uncommon for me. It was 110 the day before yesterday, you know that movie No Country for Old Men was filmed in this area for a reason, lol. 2 Quote Link to comment Share on other sites More sharing options...
LazyK Posted May 10, 2022 Report Share Posted May 10, 2022 mark me surprised seems altitude does affect compression https://www.tw200forum.com/threads/altitude-correction-factor-table-for-compression-testing.61426/ For example: Specified compression = 150psi, Altitude = 2000ft, (150 x .943 = 141.5psi expected@2000ft) Quote Link to comment Share on other sites More sharing options...
keithb7 Posted May 10, 2022 Report Share Posted May 10, 2022 (edited) Cool info. Thanks for finding it LazyK. So about 106 psi at sea level, nets me 100 psi at my home at 2000 ft. Altitude (ft) Correction Factor Altitude (ft) Correction Factor 500 .987 3500 .907 1000 .971 4000 .888 1500 .960 4500 .880 2000 .943 5000 .862 2500 .933 5500 .853 3000 .915 6000 .836 Edited May 10, 2022 by keithb7 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.