426 rocker arm ratio
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Topic: 426 rocker arm ratio
Posted By: NEVER green
Subject: 426 rocker arm ratio
Date Posted: 22 Mar 2015 at 9:56am
Any body know the rocker arm ratio for the 426? Heard the 301 are the same?
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2-8050 1-7080 6080 D-19 modelE & A 7040 R50
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Replies:
Posted By: injpumpEd
Date Posted: 22 Mar 2015 at 3:01pm
301's are the same, at 1.5:1 I think. I put Murphy's roller Rockers on last year that are 1.75:1, which got me around .075" more lift. But, better pay close attention to piston to valve clearance with stock pistons. Mine had deep enough reliefs.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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Posted By: NEVER green
Date Posted: 23 Mar 2015 at 5:49pm
Thanks Ed, I also bought a set of Murphy's and called them and they were clueless on stock ratio, little odd I thought. Say Ed, you could save me a lot of grief if you were to mention how deep your reliefs are cut?????
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2-8050 1-7080 6080 D-19 modelE & A 7040 R50
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Posted By: injpumpEd
Date Posted: 24 Mar 2015 at 7:33am
I think they are .200" deep. But, I also have a grouind cam, and a stroked crank. Stroking the crank increases compression ratio. When I assembled mine, I calculated(computer program in old laptop)comp ratio, and even with the stroked crank, the reliefs dropped the comp a full point from 15.5 to 14.5 if I remember right. So unless you're stroking the crank, I wouldn't cut them any deeper than needed, or you'll lose the lugging with too low a comp ratio.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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Posted By: Big Orange
Date Posted: 24 Mar 2015 at 4:11pm
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The service manual shows the rocker arm ratio to be 1.45 : 1 , it also shows the compression of a 7020 to be 16:1 & the 6080 to be 14:1 even though the combustion chambers measure the same CCs of volume, & have the same # on the pistons, go figure. So check it for yourself, & you will know for sure.
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Posted By: DrAllis
Date Posted: 24 Mar 2015 at 4:26pm
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200-7000-7010-7020 engines were always 15 to 1 compression (book info was in error)and have the same cc's in the bowl of a 180-190-190XT's do and they are 16 to 1. The difference is the 15 to 1's have .030" diameter (.015" meat) removed above the top ring to keep the piston head from swelling and dragging on the sleeve. The early 6060-6080's were truly 14 to 1 and their bowl cc's were more. Later on they were 15 to 1 to improve starting and when overhauled were probably 15 to 1.
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Posted By: NEVER green
Date Posted: 25 Mar 2015 at 7:28pm
Hey Ed, me again, did you have to shave .250 off the entire top of the piston for the added stroke?
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2-8050 1-7080 6080 D-19 modelE & A 7040 R50
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Posted By: injpumpEd
Date Posted: 25 Mar 2015 at 8:11pm
well, mine I cheated, and bought all the stuff used. lol! Now when we built Matt's a couple years ago, I had my machinist buddy shorten the top of the piston down the .250" in his cnc lathe. The bottom of the bowl as well. I had him pretty much maintain the original shape, except we kept the top of the bowl slightly rounded, instead of the sharp edge. He then cut the valve reliefs in his cnc mill.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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