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Adjusting valve on a dodge flat head

48
1
8
Location
Cape Girardeau,MO
I'm one of those guys who know a little about engines but can't remember what the process of checking valve clearance. I'm near the end of the process of rebuilding the engine and wanted to check the valve clearances.

I thing I remember that you need to turn the engine over on each cylinder to the power stoke of that cylinder and then you check the valve clearances.

If that correct? It's the dodge 6 cyl
 

NAM VET

Member
40
2
8
Location
Rock Hill, SC
and if you set them cold per above, with the engine on a stand, without all the manifolds and such, it is much easier. I just checked mine over and over, and now have no ticks or other noise.

NAM VET
 
48
1
8
Location
Cape Girardeau,MO
I understand the use of the feeler gauge and hot and cold adjustment.

My question is do you rotate the engine to each cylinder power stoke to check the valve clearance when both valves are closed.

I had a reply that said to check when the right intake just start to open do exhaust and exhaust just start to close do intake this is different and makes me more unclear about the adjustment procedure.

Thanks
 

just me

Member
322
10
18
Location
phoenix,az
I adjusted each valve with the tappet on the heel of its cam lobe. Since it is on a stand and out of the truck, you can more easily see it as you rotate the engine.
 

NAM VET

Member
40
2
8
Location
Rock Hill, SC
just be sure you have your valves at whatever position gives the maximum tappet clearance. When the piston is at TDC & about about to start its downward power stroke, its valves will be closed with maximum clearances. You need tappet wrenches to do this.

NV
 

mdainsd

Member
198
25
18
Location
San Diego, CA
I find it less hassle to just remove the entire passenger fender, and take off that tire. Its still a royal pain in the rear and messy, trying to adjust those while its running and not burn yourself.
 

NAM VET

Member
40
2
8
Location
Rock Hill, SC
wow, those are loose clearances!! I set mine per Charles Talbert's cold settings. Quiet, no tapping, and great power. But the military has their own reasons for specs.

NV
 

Bill W

Well-known member
1,985
42
48
Location
Brooks,Ga
wow, those are loose clearances!! I set mine per Charles Talbert's cold settings. Quiet, no tapping, and great power. But the military has their own reasons for specs.

NV
I reset mine from the OLD settings to the updated ones and the flutter I had on my vacuum gauge went away. I also had no tapping and more power As I have read, the military went to the new clearances after getting a lot of vehicles with burnt valves.
 

NAM VET

Member
40
2
8
Location
Rock Hill, SC
I am not here to say which valve clearance is best, or safest, or appropriate. But Having spent 30 years in the army, from '69 on, I have some awareness of the military having to "work with what they have" in personnel. I am pretty sure the American trooper of today is surely far more educated than the "average" soldier of those days. In my infantry platoon in '69, the education level of my troops ranged from 10th grade draftee to college graduates. Back in those days, the inductee who could type and handle office responsibilities were "siphoned-off" before they got down to a leg infantry unit. And while our company mechanics were talented and experienced, they too had to work with troops and drivers pulling first echelon maintenance, and trying to repair our M113's. M37's were leaving the active army when I started my own career, so I had no experience with them.

But if he army was experiencing burned valves because of the difficulty and hazards of adjusting hot side valve engines, and hence went to "change-1" for a substantially greater clearance, perhaps part of the reason was due to inexperienced troops trying to accomplish a complex and hazardous task under sometimes arduous conditions with demanding commanders who wanted as many vehicles duty ready, with limited access to the proper tools. So maybe better too much clearance than too little.

In other words, the reason for the larger clearance may not have been strictly for longer, more efficient engine life. If an engine runs better with a larger or smaller tappet clearance, it may be due to the unique characteristics of each motor.

I found it time consuming to precisely set my own clearances with my motor turned on its side on an engine stand. I can't imagine trying to it with the motor in the truck, much less hot and running.

all the best..

NV
 

NAM VET

Member
40
2
8
Location
Rock Hill, SC
Bill, I just had a glass of wine with dinner, and got to wondering if the civilian Power Wagon maintenance specs also changed to the larger clearances. I think I will try to find something about it. Your picture above shows a handsome motor. I think I have finally fixed my oil leak, it was the 90 degree NPT/flare fitting where the oil returns to the oil pressure relief valve. It was tricky in such a confined space, but I took my Dremel to a socket to get a grip on the fitting, which was not snug, then I could get a stubby open end on it and turned it 360 degrees to be tight. Driving today shows it to be bone dry!

I hope to have my 1919 30cal MG in the truck in a few weeks.

NV
 

mdainsd

Member
198
25
18
Location
San Diego, CA
Curiosity question: What do you guys see on a vacuum gage? After hot adjusting (running) to the old numbers I get 19 inches, jiggling back and forth to 18 inches. I assumed that would be called a steady reading, now I wonder. Its a new motor with compression lowest cylinder 119Psi and highest cylinder 120Psi.
 

Bill W

Well-known member
1,985
42
48
Location
Brooks,Ga
17-21 inches is the range a engine vacuum should be in.
I got a steady 20inches vacuum ( at sea level ) after re-setting tappets and adjusting carb idle/air screw. I also adjusted my timing with a vacuum gauge which ended up being about 3-4 degrees BTDC ( again sea level ). One of the Change Orders also calls for resetting the timing from 2 degrees ATDC to 2 degrees BTDC that alone made a big difference on the vacuum needle flutter. This set up worked great on my M37 and my WC21.
 

just me

Member
322
10
18
Location
phoenix,az
Just a rule of thumb about valve adjustments. Loose is good for idle and low speed operation at the expense of high rpm performance. Tighter is better for high rpm performance at the expense of low RPM torque and idle. Since these 230's aren't exactly high revving, the wider gaps work well.
 

NAM VET

Member
40
2
8
Location
Rock Hill, SC
I was thinking more about this topic today, when I was out driving my newly rebuilt 230 engined M37. Which seems to run fine. As for Just Me above, I can see where a little more or less lift of a valve can have some effect on power and torque, ie with valve lift and duration. But we are talking about 3-4 thousands of an inch here. The essential thing is that the tappet screw setting allows the valve to close completely when hot. So after allowing for length expansion of the valve, could not an absolutely precise setting of say just a thousand of an inch be perfect? Is the spec of 10-15 thousands mostly to allow for the vagaries and complexity and even difficulty of accurately setting a safe tolerance, and perhaps cam wear, or cam shift/flutter, tappet/screw wear, or other valve train variables to ensure the valve always closes on its seat? If all the variables could be held to zero, could one safely set the clearance to as little to 0.001 inch?

Are the specs for these old motors stated to avoid the worst scenario, that being burnt valves and seats?

Your thoughts?

I am no SAE engineer, but for most of my life, being an auto enthusiast, I have tried to understand why this and that is so.

NV
 

just me

Member
322
10
18
Location
phoenix,az
The reason for adjusting these HOT on the flathead sixes is to avoid the vagaries. Since the wear on the valve stem and the tappet screw will affect the accuracy of a cold reading, adjusting them hot with everything grown to its operating conditions makes for a more accurate adjustment.
In these low compression, low speed engines, the clearance change isn't that big of an issue. In my 9,500 rpm motors, large percentage differences can be measured in lap times or dyno readings. On a long, wide open track, we tune for top end as the engine will be there for longer periods. For short twisty tracks, we tune for the bottom to get better launch from the corners. (An aside: 1/4, 1/2, 3/4 full race cams were oval track length designations. A 1/4 race cam move the torque down compared to a 3/4 cam that put the peak at the top of the curve)
For our engines, just having them the SAME at each valve at operating temperature is the best. Holding very close clearances would work only in engines that ran at a constant temperature. The engine is constantly changing temp due to load and expanding and contracting. Thus changing the tappet clearance.
Modern materials and designs allow us to hold much tighter tolerances than these old, barely oiled, random material, partial water jacket motors.
 
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