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Old 09-03-2009, 10:18 AM
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Push rod pinch

Can any of you guys help me, I need to know what is the area of the push rod pinch on a head that will support 400hp.
Thanks in advance
Clive W.

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Old 09-03-2009, 11:01 AM
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Originally Posted by klx650sm2002
Can any of you guys help me, I need to know what is the area of the push rod pinch on a head that will support 400hp.
Thanks in advance
Clive W.
no easy answer, it depends on your engine, RPM, rod, etc. I recomend getting a copy of Pipe Max from Larry Meaux, its only like $40, and is EXTREEMLY useful and accurate.
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Old 09-03-2009, 12:52 PM
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Originally Posted by klx650sm2002
Can any of you guys help me, I need to know what is the area of the push rod pinch on a head that will support 400hp.
Thanks in advance
Clive W.
Any factory or aftermarket head intended for the SBC 350/400 CID engine can support mixture flow for 400 horespower thru the pushrod pinch area of the ports. The amount of restriction this area offers to mixture flow is highly over-rated and isn't a problem till the revs and power are getting up around 6500 RPM and 500 horse or more. The big issue is in the valve pockets of pre Vortec heads. This is an area in these older heads that resonds greatly to clean up of the walls and streamlining of the guides. Get your hands on this book: How to Build & Modify Chevrolet Small-Block V-8 Cylinder Heads
by David Vizard


Bogie
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Old 09-04-2009, 04:16 AM
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Re:- Push rod pinch

The reason I am asking about port area is I'm looking to get 50 hp out of my 652cc single. My carb is 42mm at inlet and exit and 41mm at the venturi, inlet port is round and 42mm diameter leading to two 37mm valves, Exhaust valves are 2x32mm, the pipe is 41.3 i.d. leading into a big glasspack approx 2" i.d.
With a dynojet kit with std filter, carb and pipe she was making 40.5 hp the needle in the std 40mm CV carb and the 41mm slide carb I have now are about the same but the CV had a 4.3mm thick butterfly spindle which has to be a major restriction also silencer exit is now 39mm was 19mm.
Any comments welcome.
Clive W
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Old 09-04-2009, 05:53 AM
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Just curious- what's the make of this 4-valve pushrod thumper.

Generally speaking, 100 HP/L is achievable w/anything approaching a "modern" design, although it may be at the cost of some low end.

What's the deal- bike, trike, ATV, a one-off lightweight Morgan?
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Old 09-04-2009, 06:34 AM
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4V single

My 4 valve motor is DOHC not push rod, it's a Kawasaki KLX650 with a custom pipe and a Keihin FCR 41 carb with a one off bellmouth with 270* roll back. She also has 17" wheels front + back and EBC discs and pads f+r.
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