The B TDC on a cylinder
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Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=162410
Printed Date: 06 Jun 2025 at 4:29pm
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Topic: The B TDC on a cylinder
Posted By: 2011dandd
Subject: The B TDC on a cylinder
Date Posted: 02 Jul 2019 at 1:55am
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Hi guys I had some trouble with hot starting the b then starting it at all so I have had the magneto rebuilt. Only thing is I forgot to check which cylinder the rotor arm was on when I took the mag off. So I’m asking for a fool proof way of knowing that number one cylinder is at tdc and not 180 degrees out, without taking the bonnet and rocker cover off. Cheers guys |
Replies:
Posted By: HoughMade
Date Posted: 02 Jul 2019 at 5:49am
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#1 piston at the top, and the word “center” visible through the inspection hole on the left side of the bell housing. If you want to be super extra sure, take the valve cover off and both rocker arms on cylinder #1 should have some free play, in ther words, not pressing n the valve stem. ------------- 1951 B |
Posted By: Jim.ME
Date Posted: 02 Jul 2019 at 6:31am
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#4 will be at the top the same time as #1, so you can't go by the mark alone, you need to be sure #1 is at the top of the compression stroke. #4 should be just completing its exhaust stroke at that time. If #4 is on its compression stroke you will be 180 out. Remove all 4 spark plugs. You (or a helper) can hold a finger or thumb over the #1 sparkplug hole but if you have or can borrow a screw-in compression tester it will be easier to watch while you crank the engine over. Install the tester in #1 cylinder. Crank the engine over and watch the gauge. It should show pressure building as #1 comes up getting ready to fire. Once you see the pressure building watch, in the timing window, for the TDC/CENTER mark on the flywheel. When the mark is centered in the window you should be in the correct location. My thoughts, others may do it differently. |
Posted By: Joe(TX)
Date Posted: 02 Jul 2019 at 12:11pm
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It has to be TDC on the compression stroke a Jim said. ------------- 1970 190XT, 1973 200, 1962 D-19 Diesel, 1979 7010, 1957 WD45, 1950 WD, 1961 D17, Speed Patrol, D14, All crop 66 big bin, 180 diesel, 1970 170 diesel, FP80 forklift. Gleaner A |
Posted By: Gerald J.
Date Posted: 02 Jul 2019 at 12:41pm
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There might be some help in the shop manual: http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf" rel="nofollow - http://geraldj.networkiowa.com/Trees/Allis-Chalmers-G-B-C-CA-Service.pdf Gerald J. |
Posted By: 2011dandd
Date Posted: 02 Jul 2019 at 1:48pm
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Cheers guys. I was being lazy I think I will be much better off taking the bonnet and rocker cover off and getting the valve position right to get tdc. Cheers Dan |
Posted By: CTuckerNWIL
Date Posted: 03 Jul 2019 at 6:32am
That's a complete waste of time, when you can get TDC of the compression stroke by removing number 1 plug and feeling for compression as you turn it over. Unless you are in need of replacing the valve cover gasket that is! ------------- http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF |
2011dandd wrote:Posted By: WF owner
Date Posted: 03 Jul 2019 at 9:18pm
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This link may help: http://dueyschutter.freeservers.com/photo6.html%20" rel="nofollow - http://dueyschutter.freeservers.com/photo6.html
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Posted By: chaskaduo
Date Posted: 04 Jul 2019 at 2:13am
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http://dueyschutter.freeservers.com/photo4.html" rel="nofollow - http://dueyschutter.freeservers.com/photo4.html ------------- 1938 B, 79 Dynamark 11/36 6spd, 95 Weed-Eater 16hp, 2010 Bolens 14hp |
Posted By: DaveKamp
Date Posted: 05 Jul 2019 at 12:33am
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Leave the bonnet on, Dan- finger over the plug hole takes but 20 seconds... ------------- Ten Amendments, Ten Commandments, and one Golden Rule solve most every problem. Citrus hand-cleaner with Pumice does the rest. |
Posted By: 2011dandd
Date Posted: 05 Jul 2019 at 3:31am
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Sorted I did take it all off Not a waste of time in my opinion. At least that way I can watch the valves and know when I’m on tdc and correspond it to the fly wheel fire mark. By taking the plug out and feeling the build up of pressure/air I can’t be sure on what stroke I’m at Anyway it’s sorted now Cheers guys |
Posted By: Unit3
Date Posted: 05 Jul 2019 at 9:34am
------------- 2-8070FWA PS/8050PS/7080/7045PS/200/D15-II/2-WD45/WD/3-WC/UC/C |
Posted By: CTuckerNWIL
Date Posted: 06 Jul 2019 at 9:57am
When your exhaust valve is open on the upstroke, there is no pressure building up like when the compression stroke comes up with both valves closed. ------------- http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF |
Posted By: 2011dandd
Date Posted: 06 Jul 2019 at 1:55pm
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Of course that makes complete bloody sense. Any way folks for the moment it’s running sound and starts up lovely |
Posted By: Sugarmaker
Date Posted: 06 Jul 2019 at 6:14pm
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2011dandd, Awesome! Sometimes it nice to know how things work too. Regards, Chris ------------- D17 1958 (NFE), WD45 1954 (NFE), WD 1952 (NFE), WD 1950 (WFE), Allis F-40 forklift, Allis CA, Allis D14, Ford Jubilee, Many IH Cub Cadets, 32 Ford Dump, 65 Comet. |