|
|
|
Compression |
Post Reply 
|
Page <123> |
| Author | |
Bruce W 
Member 
Joined: 29 July 2005 Location: Northeast Colorado Status: Offline Points: 8825 |
 Post Options
 Thanks(0)
 Quote Reply
 Posted: 28 Jan. 2023 at 2:40pm |
|
I found a chart that shows how much elevation will affect your compression readings. Your profile shows Seattle, so Im
ASSuming sea level, which makes it easier. I can’t get the chart copied here, but here’s what it says: At 8,000 ft, the Thirsty Dirt Ranch, compression readings will be .7860 of what you have at sea level. That means your 75 lbs will be less than 59 lbs. No bueno? You betcha. My home, the Crescent 🌙 Ranch, is just under 5,000 ft. Upstairs in my house is over 5,000. Here, your 75 lbs would be 64.2 lbs (.8617). I dont think I would leave here for FCT with an engine with less than 65 lbs of compression. A poorly performing jeep is not just an inconvenience for the driver, it affects everyone on the tour. Last year we had one tour that included 35 of the 50 jeeps present. The problems of leading a group that size is the reason for the FCT being limited to 50 jeeps. One problem jeep can slow or stop the entire group. People who don’t have problems soon grow irritated at those who repeatedly have trouble or can’t keep up. That’s why we urge everyone to make sure their jeep is ready. You say that it’s been two years since your compression test, so I wont ask you when was the last time you adjusted the valves. Maybe that’s all your engine needs. Run another compression test, dry and wet, adjust the valves and see if that helps (or adjust them first, it sure won’t hurt), and let us know what you find. Good luck, and good luck in the draw, I hope to see you at FCT! BW
|
|
|
It is NOT a Jeep Willys! It is a Willys jeep.
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You! We Have Miles to Jeep, Before We Sleep. |
|
 |
|
|
oldtime
Member 
Joined: 12 Sep. 2009 Location: Missouri Status: Offline Points: 3647 |
Post Options
Thanks(0)
Quote Reply
Posted: 28 Jan. 2023 at 4:14pm |
|
Exactly as Andy and Bruce suggest.
Find out the real problem first. Upping the CR by head shaving is merely a last ditch effort to gain anything you can get. In general any change done to a Jeep will be unnoticeable unless it is at the very least a 5% change. A 10% change of any sort whether the change be the tire diameter or the compression ratio; know that a 10% change will certainly be noticeable. That suggests you will feel the effects of CR change of .65 yielding a 10 psi increase or decrease from standard. Std L head should be 6.48 CR or 100 lb ft. Someone correct me if I’m wrong but a supersonic head would be 7.0 CR up to 110 lb ft psi. The std F head is at 6.9/1 CR. Or 125 lb ft. I run a 5000’ head on mine (7.4/1 CR) plus the head and deck were shaved so it’s up to near same as the factory 10’000 foot head at 7.8/1 CR. Your never going to get CR that high with an L head. Best I can recall my CR numbers were all even up about 135 to maybe 140 lb.ft. on all 4. Fresh like new engine rebuilt with 100% OEM NOS parts that were saved up from way back. Bottom line is it’s not the CR that gets you there it’s the actual compression readings. Edited by oldtime - 28 Jan. 2023 at 5:02pm |
|
|
Currently building my final F-134 powered 3B .
T98-A Rock Crawler using exclusive factory parts and Approved Special Equipment from the Willys Motors era (1953-1963) Zero aftermarket parts |
|
|
|
|
Beach Bum
Member
Joined: 21 Sep. 2019 Location: Seattle Status: Offline Points: 322 |
Post Options
Thanks(0)
Quote Reply
Posted: 28 Jan. 2023 at 4:35pm |
|
I will do as y’all suggest next week (I did adjust the valves and it didn’t help)
|
|
|
|
|
Oldpappy
Member
Joined: 09 Apr. 2018 Location: East Tennessee Status: Offline Points: 3490 |
Post Options
Thanks(0)
Quote Reply
Posted: 28 Jan. 2023 at 6:08pm |
|
If you will describe the steps you took to adjust the valves we may have a clue to something.
|
|
|
If you can't get there in a Jeep you don't need to be there
|
|
|
|
|
Mark W.
Member
Sponsor Member Joined: 09 Nov. 2014 Location: Silverton, OR Status: Offline Points: 7447 |
Post Options
Thanks(0)
Quote Reply
Posted: 28 Jan. 2023 at 8:46pm |
|
If your lack of compression is due to worn rings increasing the compression ratio will have very little effect. Because the reduction in compression is due to the fact the rings aren't or can't hold more without allowing some of it to pass. If the cylinder starts out with a higher pressure due to a higher compression ratio that will not cause the rings to hold more of it. It will likely just increase the blow by. And Oldtime you are correct the Kaiser Head results in a 7-1 static compression ratio.
|
|
|
Chug A Lug
1948 2A Body Customized 1949 3A W/S 1957 CJ5 Frame Modified Late 50's 134L 9.25"clutch T90A D18 (1.25") D44/30 flanged E-Locker D25 5.38 Since 1962 |
|
|
|
|
Beach Bum
Member
Joined: 21 Sep. 2019 Location: Seattle Status: Offline Points: 322 |
Post Options
Thanks(0)
Quote Reply
Posted: 29 Jan. 2023 at 1:08pm |
|
I thank you all for the advice. At the moment I am 200 miles from my Jeep but will be there next week and will do a compression test as directed. My memory is not quite as good as it once was and I can’t be certain if I did all those things 2 years ago. I also adjusted the valves at that time “by the book” but it didn’t help. I will report back sometime next week. At this time I think that I probably have to concede that although this motor meets all my usual needs it is not up to the FCT requirements so I am anticipating having to do something about it.
|
|
|
|
|
Beach Bum
Member
Joined: 21 Sep. 2019 Location: Seattle Status: Offline Points: 322 |
Post Options
Thanks(0)
Quote Reply
Posted: 05 Feb. 2023 at 1:14pm |
|
Well I think that the verdict is in, compression test has been done and the results are less than encouraging tests results are as follows first number is for warm engine, WOT, all plugs out. Second number is with oil added to the cylinders 75/75, 75/70 (don’t understand that one), 80/85, 90/90. As I said before this motor has done everything that I have wanted/needed it to do until now but it looks like if I want to be running around at altitude I will have to do something.
|
|
|
|
|
Bruce W
Member
Joined: 29 July 2005 Location: Northeast Colorado Status: Offline Points: 8825 |
Post Options
Thanks(0)
Quote Reply
Posted: 05 Feb. 2023 at 4:29pm |
|
I dont know whether it’s been asked, have the valves been adjusted recently? Your compression test results indicate a valve problem. Stil pretty even, cylinder-to-cylinder. There’s more than the recommended 10% max variation, but no drastic amount.
BW
Edited by Bruce W - 05 Feb. 2023 at 4:31pm |
|
|
It is NOT a Jeep Willys! It is a Willys jeep.
Happy Trails! Good-bye, Good Luck, and May the Good Lord Take a Likin' to You! We Have Miles to Jeep, Before We Sleep. |
|
|
|
|
Beach Bum
Member
Joined: 21 Sep. 2019 Location: Seattle Status: Offline Points: 322 |
Post Options
Thanks(0)
Quote Reply
Posted: 06 Feb. 2023 at 11:36am |
|
I did a valve adjustment (by the book) 500-1,000 miles ago. I had high hopes that I would see some improvement but nada (I did not add oil to the cylinders that time around). From driving it you would never know (at least at sea level which is where I use it) that it had a problem, it starts easy, uses very little oil, has minimal blow by (after it’s warmed up), no unpleasant knock or other noises. I do not know what a 2A will do with a good motor but have had mine (with hard top installed) over 50 mph on level ground. It would have gone more than that but not with me driving it (and with my wife on board too) (maybe when I was 16 LoL). I am no expert on vacuum gauge diagnostics but vacuum gauge appears to indicate bad valve guides (needle bounces 2-3” all the time except maybe under hard acceleration). I would be happy to not do anything about it except I hope to do some high altitude driving in the future.
|
|
|
|
|
cpt logger
Member
Joined: 23 Sep. 2012 Location: Western Colorad Status: Offline Points: 2748 |
Post Options
Thanks(0)
Quote Reply
Posted: 06 Feb. 2023 at 12:31pm |
|
I would drive it up Mt Rainier as far as the road goes. That will tell you what it will do at altitude. Its an easy test. Disclaimer: I do have to admit to using any excuse to drive my rigs though.
|
|
|
|
|
Beach Bum
Member
Joined: 21 Sep. 2019 Location: Seattle Status: Offline Points: 322 |
Post Options
Thanks(0)
Quote Reply
Posted: 06 Feb. 2023 at 4:37pm |
|
That’s a really good idea (we would probably do Mt. Hood because of where we are)!
|
|
|
|
|
Tom in RI
Member
Joined: 07 May 2009 Location: RI Status: Offline Points: 968 |
Post Options
Thanks(0)
Quote Reply
Posted: 06 Feb. 2023 at 6:08pm |
|
#1 enjoy the drive up Mt. Hood and take time for the view.
#2 consider a leak down test. This might give more insight relating to valves, head, rings.
|
|
|
|
|
Agas46cj
Member
Joined: 09 July 2022 Location: 17569 Status: Offline Points: 187 |
Post Options
Thanks(0)
Quote Reply
Posted: 06 Feb. 2023 at 7:20pm |
|
I just read through this again. I just rebuilt my supersonic because it had compression numbers like you posted. It was basically undrivable over 30-35mph. Not enough power. I haven’t seen what you’re using for a compression tester. I admittedly have a cheap one. It has a connector hose that goes in the spark plug hole and a short metal tube with a rubber end I have to hold down with much force by hand. I had about 20psi different readings between the small metal tube and the 10” hose. If it’s driving well like you say I really suspect your tester based on how bad mine was behaving with those low numbers. I have 115 to 120 now with a fresh rebuild on the same short tube and 95-100 with the hose. Try the mountain drive and if you can try a different tester. I hope it goes well in the mountain drive. Hopefully this summer mine will be all back together and I can go in mountain drives too this fall.
|
|
|
|
|
Beach Bum
Member
Joined: 21 Sep. 2019 Location: Seattle Status: Offline Points: 322 |
Post Options
Thanks(0)
Quote Reply
Posted: 07 Feb. 2023 at 2:00pm |
|
I used the old style (the first one you mentioned) the first time I did the test (about a year ago). This past week I used the Harbor Frieght version of the tester with the hose. If I had had the old style comp tester available this time I would have used both but I didn’t so these results are using the hose type.
|
|
|
|
|
Oldpappy
Member
Joined: 09 Apr. 2018 Location: East Tennessee Status: Offline Points: 3490 |
Post Options
Thanks(0)
Quote Reply
Posted: 07 Feb. 2023 at 3:54pm |
|
Wish one of you two would change your avatar so I don't keep getting confused.
|
|
|
If you can't get there in a Jeep you don't need to be there
|
|
|
|
|
mbullism
Member
Sponsor Member x 4 Joined: 29 May 2015 Location: MA Status: Offline Points: 4459 |
Post Options
Thanks(1)
Quote Reply
Posted: 07 Feb. 2023 at 5:10pm |
Late to the party, but I think the term you're looking for ^ is "valve shrouding"... basically you get the top of the combustion chamber so close it affects the air stream trying to get into the valve opening by restricting the space. The following, if memory serves, I found over on the G some time ago. I believe it was posted by Jim Allen so any credit is his, and if found to be wrong I'll take the blame, lol. I just think it goes towards what I see is previous discussion regarding CR and elevation, and how much you can (aka might be able to) take off a head before physical contact- "I did this research for my "Classic Mode" column in the now defunct J-Rations Magazine. Rather than have it languish and never be seen, I though I'd post it into a place where it might do some good. The high compression head for the flathead Willys (part # 640035) was a standard head with an extra 0.035-inch milled off. It was stamped “7.0” on the front of the thermostat housing and delivered a 7:1 compression ratio, the same as the Kaiser Supersonic engine, a rebadged Willys engine used in the Kaiser Henry-J. The Henry-J made 68 hp at sea level, five more ponies than the Willys. At 6K feet, 7:1 should gives back most of what you lose at that altitude. In milling the head, you increase the compression ratio by reducing combustion chamber volume. To get a 7:1 ratio, you want the volume of the dome in the head to be about 82 cc, as measured via “CC-ing” the head with the spark plug installed. The standard 6.48:1 head dome volume was about 90.5 cc. It’s important to know if your head has already been milled (for reasons I outline later) before you have it milled. You can tell by measuring the thickness of the head from the mating surface to one of the machined head stud bosses on the corner of the head. A standard head will be around 2.1406 inches (plus or minus a few thousanths). If you want to go for the 7:1, then you want the total thickness of the head to be around 2.109 in., which should not be exceeded unless you know what you are doing. The thickness of the head deck and combustion chamber roof is about a quarter-inch, so you have a little room to play, but don’t be careless. Verify the chamber volume by CC’ing. There are some dangers in removing too much material, strictly from the performance level. When you skim material from the head, it moves the roof of the combustion chamber closer to the valves. Taken to excess, that can create a situation called valve shrouding, which reduces airflow in and out of the combustion chamber. In some cases, you can gain from the CR boost and then lose what you gained due to shrouding. From what I can glean from very old magazine articles and tech manuals, where I got much of the information for this answer, that point may come around 8:1 for the Willys. For an engine with a stock cam at sea level, 7-7.5:1 may be the practical limit. Also remember there are two compression ratios to consider, static and effective. Static is the often quoted number calculated on the total volume of the air in the cylinder with the piston at the bottom of stroke compressed into the much smaller combustion chamber. The effective ratio takes into account the closing point of the intake valve. The compression stroke doesn’t truly start until the intake valve is fully closed, which happens at 20 degrees After Top Dead Center on the Go Devil. The effective ratio is always lower than the static. The rough effective ratio of a stock Willys flathead with a 6.48:1 static ratio is 5.17:1. With a 7:1 static ratio, the effective ratio is 5.57:1. How much compression an engine will tolerate is highly variable. The old-time Jeep “Hotrodding” info isn’t of too much use today, because the fuels have changed so much. The only people I could speak with directly have only gone to a verified 7:1 at sea level. Finally, if you removed too much head material (about 0.090-in) the valves will hit the roof of the combustion chamber when they open." |
|
|
1946 CJ2A #69750 - "Plowshare"
Bantam T3-C #8502 Bantam T3-C #9704 Bantam T3-C #15849 1969 Kaiser CJ5 (sold) If you have an L134, ESN on or about J71297, we should talk :) |
|
|
|
|
Mark W.
Member
Sponsor Member Joined: 09 Nov. 2014 Location: Silverton, OR Status: Offline Points: 7447 |
Post Options
Thanks(0)
Quote Reply
Posted: 07 Feb. 2023 at 5:47pm |
|
I completely agree with mbullism posted. I shaved .035" off my head (which had been uncut prior) I also removed .007" from the Deck. And when using the Fel-Pro gasket which when compressed was if I remember correctly .015" thick. CC'ing my combustion chambers and factoring in the .007" Decking. My engine ended up with a Static Compression Ratio of a tiny bit over 7.2-1 I figure to make up for any tiny mistake or inaccurate reading I would call it 7.2-1 I am sure I could have had another .005-.010" removed from the head but did not want to push it. I was just looking for that 8 HP bump. I run a NOS stock Willy's Cam.
|
|
|
Chug A Lug
1948 2A Body Customized 1949 3A W/S 1957 CJ5 Frame Modified Late 50's 134L 9.25"clutch T90A D18 (1.25") D44/30 flanged E-Locker D25 5.38 Since 1962 |
|
|
|
|
Beach Bum
Member
Joined: 21 Sep. 2019 Location: Seattle Status: Offline Points: 322 |
Post Options
Thanks(0)
Quote Reply
Posted: 08 Feb. 2023 at 12:04pm |
|
Thanks for the great info Guyz! I think that it is obvious to all that I am going to have to get into this motor. I think that when I do I will shave the head.
|
|
|
|
|
Post Reply
|
Page <123> |
| Tweet |
| Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |
Topic Options
Beach Bum wrote: