Robert Smith Posted July 31, 2012 Report Posted July 31, 2012 Hey guys, I had a compression test done today on the Dodge. The mechanic had a shop manual for a '40 Plymouth handy, and I figured it would be the same for the Dodge... Well, I checked under Engine and it was saying something about the compression should be 90 and over. Well, my motor tested like so: Cylinders: Compression 1. 80 2. 90 3. 90 4. 90 5. 100 6. 105 A friend just told me now that a 1940 Chilton's manual states 140psi is ideal compression for that model car. Is it just me or does that sound right? I'm not really sold that that's correct. That sounds high for a flat head 6 of this vintage... Then again, I could be wrong. What sayest thou? =R
RobertKB Posted July 31, 2012 Report Posted July 31, 2012 Drive it and don't worry. The 80 psi could be a bit of carbon or it just needs a really good run to loosen the rings up. I would drive it lots and check it again later. 140psi sound very high to me also.
greg g Posted July 31, 2012 Report Posted July 31, 2012 I believe stock for 40 was about 110, which would pretty much be in line with an engine with a 6.5 to one compression ratio. Number one seems a bit low but the rest are in a range that would be acceptable for an "experienced" engine. You don't mention whether this was a dry test or a wet test. but I see no cause for alarm there. According to the spec sheet I am looking at the Plymouth of that year was 6.7 to 1 so given the Plymouth's smaller displacement the over all PSI numbers would have been pretty close.
Don Coatney Posted July 31, 2012 Report Posted July 31, 2012 This might or might not help. But to find out you first must read it.
Robert Smith Posted July 31, 2012 Author Report Posted July 31, 2012 Excuse my ignorance in these mechanical types of things. I can't recall what the difference is between a dry or wet compression test. We had the plugs off the head, we fallowed the directions in the Plymouth manual, to hold the throttle wide open as I cranked over the starter motor 4 revolutions. Also, I'm not sure as to how long the spark plugs have been in use on this motor, they could have been in there several years or more. But, there was very little carbon build up on them, and no signs of oil on the plugs. So, this is a good sign. I'm thinking a valve job would help things get back up some. Also a tune up this motor can stand as well. Who knows when the last tune up was performed on this motor. PS: Thanks for your input gents, I appreciate the continued assistance! :-)
Plymouthy Adams Posted July 31, 2012 Report Posted July 31, 2012 for a car that has sat for a long time and not run or second sceneario a car that has been difficult to start and may have the oil washed from the cylinders and rings by gas..squirting the oil in the cylinder wi show increase and point to specific problems, ie valves and gaskets over blow by..do read the page in its entirety that Don posted..causes and effects are explained
fortunateson Posted July 31, 2012 Report Posted July 31, 2012 Perhaps a leak down test is in order if you are having any serious problems. better than a compression test as it points you to the specific area where the problem is.
55 Fargo Posted July 31, 2012 Report Posted July 31, 2012 Run this engine, change oil, and drive it for a while, then run tests again, sounds like a leaky valve or 2. Possibly as others have mentioned, been sitting relaxed fora while, time to run this engine a bit, get her running at temp for some miles....
pflaming Posted August 1, 2012 Report Posted August 1, 2012 " . . . a leak down test. . ." Please explain, what it is and how it is done. Thank you.
Plymouthy Adams Posted August 1, 2012 Report Posted August 1, 2012 the actual leak down test is really deep and require a bit of set up and special fixture to perform...the best thing to do here would be google HOW TO DO A LEAK DOWN TEST..many site there to explain and actually show images of the set up and how to read the results..
Rusty O'Toole Posted August 1, 2012 Report Posted August 1, 2012 Dry test = normal compression test, turn over on starter, throttle open. Wet test = repeat after squirting some oil into the cylinders with an oil can. Compression should come up a little, if it comes up a lot the rings are not sealing, if it does not come up at all the valve is burned ( or, more rarely, a hole in the piston) This is done to diagnose cylinders with low compression. Leak down test involves putting a compressed air fitting in the spark plug and seeing how long it takes for compression to leak down. By listening at the oil filler, carburetor and tail pipe you can tell if the leakage is rings, intake valve or exhaust valve.
TodFitch Posted August 1, 2012 Report Posted August 1, 2012 Dry test = normal compression test' date=' turn over on starter, throttle open.Wet test = repeat after squirting some oil into the cylinders with an oil can. Compression should come up a little, if it comes up a lot the rings are not sealing, if it does not come up at all the valve is burned ( or, more rarely, a hole in the piston) This is done to diagnose cylinders with low compression. Leak down test involves putting a compressed air fitting in the spark plug and seeing how long it takes for compression to leak down. By listening at the oil filler, carburetor and tail pipe you can tell if the leakage is rings, intake valve or exhaust valve.[/quote'] Or bubbles in the radiator indicating bad head gasket or cracked block or head. Or adjacent spark plug holes indicating bad head gasket... There might be more but those two came to mind quickly.
Don Coatney Posted August 1, 2012 Report Posted August 1, 2012 Excuse my ignorance in these mechanical types of things. I can't recall what the difference is between a dry or wet compression test. We had the plugs off the head, we fallowed the directions in the Plymouth manual, to hold the throttle wide open as I cranked over the starter motor 4 revolutions. Dry test = normal compression test' date=' turn over on starter, throttle open.[/quote'] Makes me wonder why I bother to post instructions such as I did above. Nobody bothers to read them let alone apply what they have or have not learned.
greg g Posted August 2, 2012 Report Posted August 2, 2012 Ya mean like all the information in post #4???
Don Coatney Posted August 3, 2012 Report Posted August 3, 2012 **** you. Might I ask to whom this remark is directed to?
Plymouthy Adams Posted August 3, 2012 Report Posted August 3, 2012 that is a question that GTK may need to address..
55 Fargo Posted August 3, 2012 Report Posted August 3, 2012 Where's the popcorn, gonna be an entertaining thread.
Tom Skinner Posted August 3, 2012 Report Posted August 3, 2012 Wooooo hoooo here we go again. Hey guys - go pour a drink. Chill. I like Crown Royal Reserve straight up in a heavy tumbler. A Chesterfield cigarette helps it taste better - smooth - full tasting - enjoyable - thats life. We are just here to help people, God Bless us everyone. I think the World of Don, and Rusty, two of the best guys we have on this Forum, and I think the rest of us do too. Tom Skinner Huntersville, North Carolina you'all come down and visit sometime.
55 Fargo Posted August 3, 2012 Report Posted August 3, 2012 Cheers to you Tom, gotta love this place, enjoyed your post
Plymouthy Adams Posted August 4, 2012 Report Posted August 4, 2012 Wooooo hoooo here we go again. Hey guys - go pour a drink. Chill. I like Crown Royal Reserve straight up in a heavy tumbler. A Chesterfield cigarette helps it taste better - smooth - full tasting - enjoyable - thats life.We are just here to help people, God Bless us everyone. I think the World of Don, and Rusty, two of the best guys we have on this Forum, and I think the rest of us do too. Tom Skinner Huntersville, North Carolina you'all come down and visit sometime. Really..can you still find Chesterfield cigarettes..I thought that brand died long ago..but of course I have not bought a cigarette since 1974
james curl Posted August 4, 2012 Report Posted August 4, 2012 What does a pack cost now days in North Carolina? I bought my last pack when they went to 35 cents a pack in the machine at work. Just refused to pay that ridicules a price for something to burn up in an ash tray on my drawing board.
55 Fargo Posted August 4, 2012 Report Posted August 4, 2012 What does a pack cost now days in North Carolina? I bought my last pack when they went to 35 cents a pack in the machine at work. Just refused to pay that ridicules a price for something to burn up in an ash tray on my drawing board. In Manitoba $10.00 for cheap brands, $14.00 for goodname brands, this is for packs of 25 cigs. I do not smoke, the Wife still does, infact She is standing outside in the rain,having 1 now, well under the front overhang of the house.
Young Ed Posted August 4, 2012 Report Posted August 4, 2012 What does a pack cost now days in North Carolina? I bought my last pack when they went to 35 cents a pack in the machine at work. Just refused to pay that ridicules a price for something to burn up in an ash tray on my drawing board. I don't know which dates the time you quit more the cheap price or the fact you bought them from a vending machine.
james curl Posted August 4, 2012 Report Posted August 4, 2012 About 1967/68 time period, I would light one up take a couple of drags and the engineer that I worked for was on his way back to my drawing board to see if something was wrong, all they wanted to see was rear ends and elbows with the head down when they looked out of the window in their office. So it went into the ash tray to burn up.
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