Taylormade

Valve Clearance

8 posts in this topic

With the weather warming up I'm finally getting around to the initial valve adjustment on my 1932 Dodge Brothers DL sixI was going to do last month.  With the plug in the head removed (using a rod set on top of number six cylinder) and the timing mark on the flywheel, I have no problem finding top dead center and I can tell by the position of the valves that I'm on number one cylinder firing.  Since this is the first start up, I won't be setting the clearances hot.  My good friend Phil Kennedy found that his DL liked .014 exhaust and .012 intake settings.  He says there is a bit of valve noise, but he gets the best performance with these settings.  He drove from Connecticut to Michigan with no problems, so I'm going with his initial settings.  I have a crank, so it's easy for me to turn the crankshaft by hand, but the new rebuild is still stiff enough that turning the engine backwards is more of a chore (the crank doesn't work going backwards), so rocking it back and forth to accurately see when the valve stems are free is a problem, even with the plugs out.  So I was worried that I wouldn't be able to get the clearances set accurately due to not having the tappets totally clear of the cam lobes.  Doing some research on the web, I discovered this tech tip from the excellent P 15-D 24 site.  They say you can set the clearances with just two turns of the crank.  I know there are some differences in the later Chrysler Company flathead sixes, but the early engines are very similar and I'm hoping this approach may work.  This is directly from their tech page...

 

Turn the engine  over to Top Dead Center (TDC). Verify piston #1 is in firing position by checking the position of the distributor rotor. If should point around 7 o’clock. If it points to the 1 o’clock position, you have piston #6 in firing position. Manually turn the engine one full revolution and you are ready to start. Remove the valve covers and use the following sequence for the order of the valves to adjust.

Stage A, #1 and #6 at TDC, #1 in firing position
Stage B, #1 and #6 at TDC, #6 in firing position
To move from Stage A to B, manually turn the engine 1 revolution.

Stage A – Adjust #1 Both valves, #2 Inlet valve, #3 Exhaust Valve, #4 Inlet valve, #5 Both valves.
Stage B – Adjust #2 Both valves, #3 Inlet valve, #4 Exhaust valve, #5 Inlet valve, #6 Both valves.

 

Has anyone set clearances with this method?  It seems too simple to be true, not having to turn the crank trying to find when both tappets are clear.  On my engine, you have to use three wrenches - one to hold the tappet from turning, one to loosen the adjusting nut and one to adjust the clearance, plus using the feel gauge at the same time.  My seventy-year-old hands lack the dexterity to handle this, so my lovely bride of 48 plus years has offered to manipulate the two bottom wrenches while I do the actual adjustment.  We'll see if our previously successful marriage survives.

 

Any comments on the above would be most appreciated.

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The only comment I have about it is to NOT rotate the crank BACKWARDS. I have been under the impression that it is not the thing to do. I believe I have read it several times in several places.

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I too have heard that and the design of the crank, which was still with the car, makes it impossible to do - at least with the crank.

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I cant think of anything that could do damage by turning backwards. I do it all the time.

Ha, But I am sure that I don't read as much as Keiser.

So if the crank wont let you do it there must be some merit to that.

I commented on the valve adjust on another thread.

 

Just for grins I will tell a short story.

In Sprint car and other racing that use mechanical fuel injection, especially alcohol engines it is not uncommon to get puddling of fuel in the cylinders, especially on a very quick shut down as it a spin out or crash.

This can cause a hydraulic lock and the engine may not turn over and if it did and fired it could bend a rod.

This is why you will see the push trucks pull the car backwards for several feet before pushing off to get the thing started again.

Purging the fuel from the cylinders.

These old mechanical injections don't atomize the fuel, it simply dumps it on the intake valve as a liquid.

You will hear these guy shut the fuel off when they come to their pits. The engine will lean out (rev a bit) just before it dies when the fuel is shut off.

 

I guess it wasn't all that short.

 

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Just confirm that each one you do is on the baseline of the cam. This is how I use to do overhead cam engines, don't even need to know the order.

 

Very important that the cam and crank are timed/lined up correctly. Otherwise, everything you do is wrong.

 

And yes, like keiser31 said, don't turn the engine backwards. The slack in the timing chain will affect your setting.

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Posted (edited)

I've heard this business of setting the valves loose and I don't agree with it. The factory engineers based their recommendations on hundreds of thousands of miles of road tests, thousands of hours of dyno tests, and millions of miles of customer feedback. As far as I can see, all you will get is a noisy engine, reduced performance since the valves will not be opening fully, and increased wear as the valve train slowly pounds itself to oblivion. One of those engines in top shape should idle down to a walking pace as smooth and quiet as a Swiss watch then pull away to 80 without changing gear.

Edited by Rusty_OToole (see edit history)

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Yes, the method you describe in the first post will work.

 

As already stated, turning the crank back will allow the timing chain to slacken a little, wont damage anything but next time you turn it forward the slack will have to be taken up again, and, during this small amount of crank travel, the cam will remain stationary.

 

I`m with Rusty, why second guess what the engineers designed, set the clearances as per specs.

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Oddly enough I have never heard a trained mechanic or anyone with an engineering degree do this. They always stick strictly to factory specs. It's always hillbillies and people with very limited mechanical knowledge who think it clever.

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