how much engine do I need?
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Forum Name: Pulling Forum
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=99019
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Topic: how much engine do I need?
Posted By: JM
Subject: how much engine do I need?
Date Posted: 14 Dec 2014 at 8:40pm
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I have a wc I want to run in div.2, 3-4 mph class up to 4500lb class. I want to run 15.5 38s top cuts, how many cubes do I need to turn these in ohio clay?
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Replies:
Posted By: DrAllis
Date Posted: 14 Dec 2014 at 8:58pm
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There is a huge difference between 3 MPH (low gear) and 4 MPH (second gear)....what do you currently have ??
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Posted By: patrickmull
Date Posted: 14 Dec 2014 at 9:14pm
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I run 15.5-38 tires mine runs 4 mph in low gear
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Posted By: JM
Date Posted: 14 Dec 2014 at 9:29pm
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Most clubs run 3, one of them runs 4. Thing is, right now I have 14.9-28 @1600 rpm my wc runs 5mph in 1st, 9 in 2nd, 13 in 3rd and 20 road gear. This is using a gps cell phone that I have checked against car speedo and is correct. 38s are aprrox 15% bigger, so all those speeds go up 15%. I figure 1st should cover either speed limit. My tires measure 52 inches now. So in first how much to spin the 38s out at 4500lb.? I have been told by one guy 4 and 1/8 and offset grind the crank to 2 inch is in the 260 CI range and that is enough. I think he said use buda rods. What do you guys think, is that enough or just stroke it to 5 inch with allis rods? Thanks
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Posted By: DrAllis
Date Posted: 14 Dec 2014 at 9:47pm
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Something is waaaaay outta synch here. A WC low gear is 2 1/2 MPH at 1600 RPM....how does a 14.9 X 28 tire make it 5 MPH ???? and worse yet 20 MPH in 4th gear ?????
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Posted By: JM
Date Posted: 14 Dec 2014 at 9:55pm
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I don't know why so fast, 20 mph with hand brakes is scary. I wonder if the tac I am using is off. Maybe I running a lot more rpm than I think, I will check with another tac.
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Posted By: Zaddison
Date Posted: 14 Dec 2014 at 11:49pm
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May wc does 21 mph in road gear at 2100rpm. I've seen 5mph pullin a sled in first gear running 12.4/38s. So I'd say your running more rpms then 1600.
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Posted By: bigcountry48
Date Posted: 15 Dec 2014 at 2:42pm
I used a wd45 crank with regular wd45 rods and a 170 engine kit including a Berry's cam as 170 carb. It gives out about 70 hp and 241 cubic inches I think. That is a lot of power for not a lot of money. That motor is bullet proof too, seeing how its almost a stock allis engine it should last me another 50 years, with loads of power for pulling. Just my 2 cent!
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1950 B, 1952 pulling wd, and 1954 wd45
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Posted By: DrAllis
Date Posted: 15 Dec 2014 at 6:32pm
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Whatever you do with pistons and connecting rods and crank stroke, you have to have correct compression when you get done. The last engine I built for myself was Buda rods with 4 1/8" pistons and to get the 12 to 1 compression I was seeking, I had to stroke the WD-45 crank to 5 3/8" stroke. You cannot just grab a set of pistons and sleeves and throw a set of different rods and crank together without a plan.....you might be really disappointed when you're done.
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