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Old 02-08-2015, 02:46 PM
scottdolsen scottdolsen is offline
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Default cracked head

One of my Edlebrock heads cracked between the hard seats. Is it necessary to weld the head and replace the seats? Has anyone had the seats fall out? Is it legal to use larger seats that overlap each other?

Thanks, Scott Olsen
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Old 02-08-2015, 08:17 PM
scottdolsen scottdolsen is offline
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Upon closer inspection, with my reading glasses on this time, the crack appears to be erosion. Does this need to be repaired?
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Old 02-09-2015, 01:29 PM
fastandyracing fastandyracing is offline
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Scott,

Had the same problem with mine, this is apparently very common on the Ford heads, not sure if it affects the chevy ones also.

The seats are quite deep, so there is no real risk of them falling out unless the erosion gets really severe. However, mine started to leak a higher percentage than I was comfortable with (teens, sometimes low 20's), and after taking the heads off to inspect, it appears as if over time the exhaust seat "sags" away from the valve (due to heat I suppose) and into the void between the seats. This not visible, but when I lapped the valves you could see where the exhaust valve was not properly seating in the area where the erosion was. I was in a rush and just lapped the valves some more and got most of the seat back, but long term I will have to deal with it. Heads are coming off soon to see how bad it has gotten.

I have talk to a local shop and they think they can do an interlocking seat and eliminate the problem. The heads will be coming off pretty soon, if I get any more info I will put it up.

Andy
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Old 02-09-2015, 06:13 PM
kbsmith1 kbsmith1 is offline
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Scott, my Chevy edelbrock heads had the exact same problem that I first
noticed when going through the engine prior to the runoffs. John
Rissberger's heads also had this same problem, I am running mine as is
for the time being. I have heard the the "fix" is to install slightly larger seats
that will interlock with each other so that there isn't a small bit of aluminum
between them to be subject to erosion.
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  #5  
Old 02-09-2015, 08:20 PM
scottdolsen scottdolsen is offline
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Are larger interlocking seats legal?
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Old 02-10-2015, 01:22 AM
MarkMuddiman MarkMuddiman is offline
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Legality depends on if the Edelbrock heads are policed the same way as Holley carbs.
Our rules don't specify part numbers or dimensions for original components for the "spec" heads, or for service replacements.
Does Edelbrock have documentation of the part numbers or dimensions & material properties used in the SCCA heads (or the Performer RPM series on which they are based)?
The only documentation I could find for these heads is written for the Performer RPMs, and lists the incorrect valve sizes (2.02/1.60 and 1.90/1.60).

But never fear - if the Tech Inspectors think you're illegal, you still get a chance for the appeals board to decide if rules are rules, or just guidelines.
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Old 02-10-2015, 10:49 AM
jimwheeler jimwheeler is offline
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There is a very clear diagram of the "Cylinder Head Repair Zone" on page 716 of the current GCR. This area may be repaired. It does not show interlocking valve seats.

As to the CoA. With the current court, expect that if the Tech person finds it non-compliant and the Chief of Tech finds it non-compliant, and the Tech Steward finds it non-compliant, the CoA will not overturn those findings unless there was some procedural error. Say it was not filed in a timely manner, etc.

I don't think you will see the CoA overriding the experts on a technical issue.
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Old 02-10-2015, 11:13 AM
scottdolsen scottdolsen is offline
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Is there any support for a rule change to allow interlocking seats, considering this is not an isolated case and appears to be a factory defect?
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Old 02-10-2015, 11:15 AM
jimwheeler jimwheeler is offline
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I don't recall anyone ever bringing it up. There is no letter in the system about this.
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  #10  
Old 02-10-2015, 02:18 PM
andy mcdermid andy mcdermid is offline
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The repair, that is on page 716 of the GCR,was been approved a few years ago. We have had a lot of heads do this and the repair works well. It wasn't
that much money either, oddly enough !

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