Firing Order Seems Strange

[Mr.Big346]

Hey y’all. My Farmall SA is being fixed righ now and while cranking the engine over with the head removed, the cylinders move 1+4 and 2+3 not 1342. Is something wrong or is where the tractor fires the next cylinder right before it reaches TDC?

 

[BarnyardEngineering]

Remember that it takes TWO full revolutions to go through the firing order so all the angles are doubled. The four cylinders are 180 degrees out from each other, not 90 degrees. That's why they move in pairs.

 

[Jim.ME]

Spark normally occurs before TDC on the compression stroke for all cylinders. How far before TDC depends on the engine, rpm, and any advance method designed into the distributor.

1 and 4 are companion cylinders when 1 is up on its compression stroke with both valves fully closed, about to go down on its power stroke. At the same time 4 is at the top end of its exhaust stroke with the exhaust valve just closing and its intake valve just opening for the intake stroke as the piston goes down. When the valves are at that point it is often called being "on the rock". On a four-stroke engine this is why people say be sure #1 is on the compression stroke as the timing marks line up ever rotation of an engine but the spark only occurs every other rotation. Checking to see that the #4 valves are "on the rock" is one way to confirm #1 is at the right TDC for spark. The same principle applies to the 2 and 3 cylinders; however, most engines do not have timing marks for those cylinders.

The 1342 firing order is controlled the position of the valves in relation to the pistons and by the location of the plug wires in the distributor cap. The distributor must have the rotor button pointed at the cap location for cylinder #1 when it is at TDC (may vary slightly depending on the specs for the engine) with both of its valves closed for static timing. Then the plug wires need to be placed in the distributor cap starting from #1 in the direction of distributor rotation and in the firing order for the engine.

That is a basic rundown, you can find a lot more detail online if you search on how four-stroke engines and multi-cylinder four-stroke engines work.

 

[Mr.Big346]

Thanks I thought that might be the case y’all have a blessed Christmas

 

[rustred]

Hey y’all. My Farmall SA is being fixed righ now and while cranking the engine over with the head removed, the cylinders move 1+4 and 2+3 not 1342. Is something wrong or is where the tractor fires the next cylinder right before it reaches TDC?

Hey y’all. My Farmall SA is being fixed righ now and while cranking the engine over with the head removed, the cylinders move 1+4 and 2+3 not 1342. Is something wrong or is where the tractor fires the next cylinder right before it reaches TDC?

There will be 2 pistons at TDC at the same time. 1 and 4, and 2and 3. These are called running mates. Say on an 8 cylinder engine firing order 18436572 you cut the numbers in half and put 6572 under 1843 and that shows you the running mates. 2 pistons at TDC. Firing order is determined by cam timing. Simple explanation.

 

[560Dennis]

Mr. Big , I took a look at your photos and around the head stubs your have excess crud that needs to be cleaned away to allowing head gasket to seal .
Got some impact mark on the flat top pistons 2 on left 3 on right but not on 1and 4 . Are the cyli wall scoring from ring issues ,suggest further checks , good luck with the project

 

[Mr.Big346]

Mr. Big , I took a look at your photos and around the head stubs your have excess crud that needs to be cleaned away to allowing head gasket to seal .
Got some impact mark on the flat top pistons 2 on left 3 on right but not on 1and 4 . Are the cyli wall scoring from ring issues ,suggest further checks , good luck with the project

Yea I had seen that. I’m fixin to pull the studs once I get them unstuck and clean the whole surface. Also gonna pull the cylinders to check rings, I reckon they need replacing but I’ll have to look into the walls closer. Where are you seeing the scoring on 2 and 3? Just wanna make sure I see that gets fixed. Thanks

 

[560Dennis]

Yea I had seen that. I’m fixin to pull the studs once I get them unstuck and clean the whole surface. Also gonna pull the cylinders to check rings, I reckon they need replacing but I’ll have to look into the walls closer. Where are you seeing the scoring on 2 and 3? Just wanna make sure I see that gets fixed.

high lites of the studs I had the most difficultly remove. your studs reminds me of my exp. You may need to be aware of this. Don’t get in a hurry and snap one of these cause it will make for a bad day ,take your time ,some heat from propane torch penetrating oil,, Propane heat, repat this may take two or three days of heating and cooling to get the penetrating oil t to penetrate.
I use double nuts , I also grip with radius vise grips tight as you can get it around the studs as close to the block as I can get it. I use a long box wrench to get maximum purchase .
Not recommend any extension on the wrench’s ,cause break one and it will very timely and costly And foul lang.
recc tapping all the block tapped holes to removes rust and oil crud to give false torque readings. Run taps thru all the head nuts also . Cleaning everything with brake cleaner the better the result , lube with 30 wt oil.
buy a good carbide scraper from napa ,to clean the scale off the block , use a lot brake cleaner, it will make for a much better headgasket seal ,
I number the studs with paint pens and put studs in the same holes they came out of . Also use the same nuts that came off the studs . I set the studs when replaced to same height .

circle my conconerns the deformation on pistons why only 2&3 and not the 1,4 ? Something in was doing beating on those area ?
hope this helps , can’t emphasize that do not get in a hurry or get discouraged.
ask if there’s more

 

[[email protected]]

Typically 4 cylinder firing orders are 1342 or 1243

 

[grandpa Love]

Hey y’all. My Farmall SA is being fixed righ now and while cranking the engine over with the head removed, the cylinders move 1+4 and 2+3 not 1342. Is something wrong or is where the tractor fires the next cylinder right before it reaches TDC?

If you are just doing rings I would NOT try to remove those head studs. Just asking for trouble . Just clean around them really good. We have replaced head gaskets on dozens of tractors. Why make life hard on yourself?. I would hold those sleeves in ,I use a short pipe,a washer and the head bolt nut. If the sleeve comes out you will need new o rings at the bottom of it. Not expensive,but a little annoying to replace. Maybe this picture is helpful