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426 Hemi Minimum Valve Clearances #1706775
12/05/14 04:08 AM 12/05/14 04:08 AM
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USA
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SSAAHemiFan Offline OP
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I have to bore notch a OEM block and increase the radial clearance for the intake valve in the piston

What would be the acceptable minimum valve to bore clearance (seated and open)? and what would be the minimum valve radial clearance in the piston notch ?

It's a street engine - 4.27 bore - 2.30 intake valve - hyd cam .551/.533 and approx .235@50

The larger intake valve is making everything pretty cozy... I have found varying recommendations in the MP books and some generic recommendations on engine forums - some say the older recommendations were "generous and possibly outdated today"

Bottom line - I wan't to make 100% sure it lives but I don't have enough room to go overboard on the specs either.

Hoping I don't end up with some more expensive mistakes


Thanks

Re: 426 Hemi Minimum Valve Clearances [Re: SSAAHemiFan] #1706776
12/05/14 07:57 AM 12/05/14 07:57 AM
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Northern MN
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cedarmachine Offline
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I like to see .080” on the intake and .100" on the exhaust, in line. I would say no less than .060" radially, at the closest rocking point.
Between piston rock and valve flex, error on the side of caution. Those big valves with small stems are like pendulums at high rpm.

Last edited by cedarmachine; 12/05/14 07:58 AM.
Re: 426 Hemi Minimum Valve Clearances [Re: cedarmachine] #1706777
12/05/14 02:28 PM 12/05/14 02:28 PM
Joined: Jan 2012
Posts: 2,645
Stuttgart, Arkansas
rickseeman Offline
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rickseeman  Offline
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Using the stock head gasket as a template, if you take the Sunnen AN-980 chamfering cone and put a radius on the cylinder for the intake valve you will have plenty of radial clearance. And I can't believe a cam of that lift is going to hit anything.

2011 Drag Pak Challenger
Re: 426 Hemi Minimum Valve Clearances [Re: SSAAHemiFan] #1706778
12/05/14 05:01 PM 12/05/14 05:01 PM
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Bend,OR USA
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Cab_Burge Offline
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I would use light springs on the valves, all eight cylinders, to check the piston to valve clearances and then use clay on the piston valve notches to check the side clearance from the piston notches and valve edges first before making any decisions on adding any more clearances

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: 426 Hemi Minimum Valve Clearances [Re: Cab_Burge] #1706779
12/06/14 04:48 AM 12/06/14 04:48 AM
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SSAAHemiFan Offline OP
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The checking springs and clay are this weekends fun.

Rick thanks for the tip on using the cone for the bore relief - looks alot easier and faster than trying a die grinder and a carbide.

Right now I only have .003 to the bore so I already new I would be cutting

Re: 426 Hemi Minimum Valve Clearances [Re: SSAAHemiFan] #1706780
12/06/14 05:50 PM 12/06/14 05:50 PM
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SSAAHemiFan Offline OP
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SSAAHemiFan  Offline OP
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I found this today (Edelbrock Hemi Victor Instructions)

"Valve-to-bore clearance should also be checked, and the top of the bore notched for clearance, if necessary (Min Clearance 0.030”)
Re: 426 Hemi Minimum Valve Clearances [Re: SSAAHemiFan] #1706781
12/06/14 06:22 PM 12/06/14 06:22 PM
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Bend,OR USA
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Cab_Burge Offline
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Quote:

I found this today (Edelbrock Hemi Victor Instructions)

"Valve-to-bore clearance should also be checked, and the top of the bore notched for clearance, if necessary (Min Clearance 0.030”)



All the stock Mopar OEM blocks come with the cylinder walls notched for intake valve clearances, you can check the intake valve to block clearances by leaving the rod and piston out and spin the crank and cam with the head and valve train in place and measure from the bottom of the cylinders. Another reason I call them motors Hemiroids Better to be safe than sorry If you where using a bigger duration cam at .050 I would mention the valve to valve clearance issues in the ovrelap time at TDC but your not so I won't, dang them Hemiroids motors anyways

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: 426 Hemi Minimum Valve Clearances [Re: Cab_Burge] #1706782
12/06/14 11:58 PM 12/06/14 11:58 PM
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Posts: 2,431
USA
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SSAAHemiFan Offline OP
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SSAAHemiFan  Offline OP
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Posts: 2,431
USA
[


If you where using a bigger duration cam at .050 I would mention the valve to valve clearance issues in the ovrelap time at TDC but your not so I won't



YES - Thankfully that is the ONE problem I am not having

I have saved and collected these parts for over 14 years and it has been a dream since I was 13.

No reason to rush things now and make a mistake, I want to do it right

Re: 426 Hemi Minimum Valve Clearances [Re: Cab_Burge] #1706783
12/07/14 05:57 PM 12/07/14 05:57 PM
Joined: Jan 2012
Posts: 2,645
Stuttgart, Arkansas
rickseeman Offline
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rickseeman  Offline
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Joined: Jan 2012
Posts: 2,645
Stuttgart, Arkansas
Quote:

Quote:

I found this today (Edelbrock Hemi Victor Instructions)

"Valve-to-bore clearance should also be checked, and the top of the bore notched for clearance, if necessary (Min Clearance 0.030”)



All the stock Mopar OEM blocks come with the cylinder walls notched for intake valve clearances, you can check the intake valve to block clearances by leaving the rod and piston out and spin the crank and cam with the head and valve train in place and measure from the bottom of the cylinders. Another reason I call them motors Hemiroids Better to be safe than sorry If you where using a bigger duration cam at .050 I would mention the valve to valve clearance issues in the ovrelap time at TDC but your not so I won't, dang them Hemiroids motors anyways



I believe the Edelbrock exhaust valve is canted 1.5 degrees so a larger duration cam shouldn't be a problem like the old days anyway.

2011 Drag Pak Challenger

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