Head porting on 426
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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=158033
Printed Date: 02 May 2024 at 5:31am
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Topic: Head porting on 426
Posted By: Operation chaos
Subject: Head porting on 426
Date Posted: 09 Feb 2019 at 7:59pm
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Got a 426ci with 4-.024 injectors,s300 turbo, stock cam advanced 9 degrees and Murphy’s rockers Limited to 3000 rpm. Did the standard pocket port cleanup under the valve. is there much to gain taking 1/8” out along the right side of runner on the exhaust port. Seem to me it would lessen the curve on that side and not be as restrictive or would it lose to much velocity
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Replies:
Posted By: DrAllis
Date Posted: 10 Feb 2019 at 6:48am
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The very best thing you can do for the exhaust is graft an IH 1066 exhaust manifold on it. I've done it and it works.
You have cut valve pockets in the pistons, right ??
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Posted By: Operation chaos
Date Posted: 10 Feb 2019 at 9:26am
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Pistons are cut. The manifold on it now is a 210 center dump. Would it gain noticeably with a IH manifold yet? Also would a reground cam be much help?
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Posted By: NEVER green
Date Posted: 10 Feb 2019 at 9:54am
I did that on my head, flowed 254cfm, at that flow you wont loose velocity. Regrind the cam the exhaust has poor lift and duration. Hogged out my manifold the runners are smaller then the ex ports.
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2-8050 1-7080 6080 D-19 modelE & A 7040 R50
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Posted By: DrAllis
Date Posted: 10 Feb 2019 at 10:02am
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There will be nothing negative to your performance using the IH exhaust manifold. It only has one turn out of the cylinder head, where the A-C turns the exhaust flow twice before sending it down the runner. I'm guessing this tractor will be in a "no-speed-limit" class ?? with a 3 inch turbo inlet size ?? If the Murphy rocker arms are the standard ratio, my money would have been spent on a better grind on the camshaft instead. I'm ignorant to advancing the cam timing 9 degrees with a stock grind. I hope this is a proven change.
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Posted By: NEVER green
Date Posted: 10 Feb 2019 at 10:46am
The IH manifold already has the dividing plate at the turbo flange, worth 1oo horse on a 1200 hp engine on the dyno.
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2-8050 1-7080 6080 D-19 modelE & A 7040 R50
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Posted By: Operation chaos
Date Posted: 10 Feb 2019 at 1:11pm
Run in farm stock 12000#,12 mph.
Murphy rocker 1.7 ratio , s300 turbo with 2.3/8” inlet. Anyone run without valve seats in the 3000rpm limit
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Posted By: DrAllis
Date Posted: 10 Feb 2019 at 1:35pm
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OK. So we aren't necessarily, looking for 1200 HP with a 12 mph speed limit. You are looking for an engine that will put that tractor down the track at 12 MPH at about 2200-2400 RPM and be able to throttle it up to 3,000 RPM as you go. What chassis?? and what gear ?? are you thinking? Not sure you need the IH manifold just yet. What injection pump?? You didn't say, so I'm guessing a RoosaMaster?? When I had my 220 I ran a 10 MPH/12,000 lb class like that with 20.8 x 38 BFG radials.... .450 Roosa with 4 x .020" nozzles......HX50 Holset……..220 exhaust manifold...…..7060 intercooler...….stock camshaft and rocker arms and stock pistons/sleeves/crankshaft...….6th gear and that was a near perfect gear ratio for 10 MPH. What I really needed was more fuel as the competition pretty much had all gone to P-pumps. More fuel was first and then I would have looked into a different camshaft, etc. Over the Winter months the 10 MPH speed was raised and I sold the tractor.
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