Tdc
 

Is any one else using this combination, a nu-rex timing strip and a Yapp small diameter pulley. I installed these yesterday, set 0 or TDC using the pin and my timing marks do not agree. The pully is premarked for 20 degrees retard and 30 degrees advanced. When the motor is at 0 by the pin, the 0 mark on the pulley is at 9 degrees retard on the nu-rex. Am I doing something wrong, or should I just remark 0 on the timing strip?

[ATTACH]Attachment 534716[/ATTACH]

Re: Tdc
 

I believe your timing pin is not in the dimple in this picture. The ones on the two cars I have owned move in further than yours is at TDC.

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I don't think the degree indicator will work with the smaller pulley.

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The pin method is usually very accurate, but Bob C may be right.

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What is the advantage of the small pully?

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It slows down the water pump, which can sometimes help alleviate radiator overflow if you don't want to pay to fix/replace the radiator.

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Interesting.

For me, if I changed mine I'd be inclined to opt for a harmonic balancer. I am on the fence about how much it helps engine life, and smoothness. I already have balanced flywheel, pressure plate, and counterweighted crankshaft.

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The flywheel and clutch have been balanced and it is a counter balanced crank with insert bearings, The #1 piston is at TDC and I rotated the crank and this is the only divot. The pulley size shouldn't matter. I can draw a line from the center of the crank through the degree marks and it is always at 9 degrees. The rad was completely serviced and flows just fine. The primary reason for using this pulley is the degee marks and yes to slow down the flow of water.
Warren

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You could just buy a new stick on timing tape, overlay the nurex tape aligning with your pulley zero mark or just make a new mark on your pulley to align with the nurex zero, notch or white paint then use the nurex zero with your timing light. Either way you get the same result.

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That's probably what I will do, but it bothers me that two very well sourced products are doing this unless I am missing something.
Warren

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Warren
The difference is that the nurses tag is made for the 5” pulley and you are comparing it to a 3” pulley
Both are calibrated correctly
Think of circumference of each and equally divided by 360

Simple mistake

John

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Wouldn't also slow done you generator/alternator.

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From Charlie Yapp:

ABOUT OUR PULLEYS

In the 1930’s George Riley, the famous race engine designer, discovered that stock Model "A" water pumps would spin too fast for the best rate of cooling at higher engine RPMs, like normal traffic today AND RACING.

Hi-speed Design Has A Reduced Diameter To 3-1/2".
Reduces Water Overflow & Foam/Mass Build up By Slowing Pump RPM Approximately 28%.
Best For Higher Road Speeds.
Precision Degree Timing Marks.
Use Our V-belt, Sized Slightly Shorter For A Neat Appearance.
Alternator: Normal Charging Occurs After A Quick Rev-up To 1500 Rpm.
Generator: The 3rd Brush Can Be Moved To Increase Charge.

Re: Tdc
 

To double check top dead center, remove the #1 plug and observe the piston. This is not rocket science. Usually the crank will turn very easy when the piston gets to the top. To be totally accurate note the degree markings when the piston is a set distance down, say 1 inch, on either side of TDC. Top dead center is half way between these two readings. Accurately measure the distance the piston is down. This is easier with head off.

Regarding the harmonic balancer: These are really dampeners. They dampen the torsional vibration in the crankshaft. If you normally run your stock Model A engine at 1,500 to 1,800 maximum rpm they are probably not needed. But if you run above that rpm then they can prevent crankshaft failure or excessive wear on the center main bearing. The crankshaft has torsional vibration at all rpm's but it can be excessive at the critical speed.

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More importantly, they free up horsepower due to the reduced draw required by the pump.

Yes they will also slow the generator or alternator, but that’s only an issue for the generator. An alternator will compensate for the slower rpm. You’d have to adjust the 3rd brush in the generator to do the same.

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A cut down version of the water pump impeller was introduced to solve this problem.

https://www.snydersantiqueauto.com/p...4033&cat=41793

Regards
Bill