Pulling Forum - M & W Piston

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M & W Piston

Printed From: Unofficial Allis
Category: Other Topics
Forum Name: Pulling Forum
Forum Description: Forum dedicated to Tractor and Garden Pulling
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=71390
Printed Date: 23 Nov 2024 at 5:06pm
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Topic: M & W Piston

Posted By: HasNat
Subject: M & W Piston
Date Posted: 05 Jun 2013 at 12:32pm

I am trying to find out what the CC is on a M & W Piston. the dished out part?
Does anybody know what the cc is on the dished out part an the power crater piston to. both 4 1/8 inch. also, how much compression can I run on a wd45 motor? with stock connecting rods.
Is there other connecting rods I can use that are stronger. somebody was saying there are some out there off of a Pontiac. but I don't know what motor.
thanks

Replies:

Posted By: wi50
Date Posted: 05 Jun 2013 at 1:38pm

both M&W pistons the AP-46 and AP-49 for the Allis have the same piston casting, they just vary the wrist pin height depending on the WC-WD or the WD-45 and D-17 piston. You can see the flashing in the casting for the other pin height on some of them.

I've measured the bowl volume to be right close to 70cc. They are thick enough and can be trimmed out more should you want to vary things some.

I don't know what the power crater piston volume is.

Stock rods will take quite a bit of compression, it's going to depend on when and how hard you light the cylinder, keeping good gas in and late timeing they will take a lot at least a 12 to 1 ratio and there's many of them running much higher. Though poor gas and advanced timeing would destroy them at 9 to 1 compression. It also depends on the rod angle, if you have a stroked crank and the shorter rod, they just bend easier when put at more of an angle. Simple physics.

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"see what happens when you have no practical experience doing something...... you end up playing with calculators and looking stupid on the internet"

Posted By: mlpankey
Date Posted: 05 Jun 2013 at 8:41pm

yeap a short rod will bend easier cause it will make more power. Its basic trig. piston speed is the highest when the crank and rod is at right angle. the tangent of the angle atdc is twice the rod ratio for the engine. According to Dimitri Elgin (sourced) you add 2 to 3 degrees to that for the signal to reach the intake valve at the speed of sound and its effect on the airflow . the shorter the rod the quicker piston acceleration peeks usually around 70 degrees atdc . the longer the rod the latter piston acceleration peaks occurring as late as 80 degrees atdc.

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people if they don't already know it you can't tell them. quote yogi berra