Need clarification on bottom cut

Moparteacher · 05-31-2008, 10:09 PM

I have just dropped off my heads at the machine shop with instructions on the legal valve job for stock heads, but I suspect I have given the wrong instructions. So I need clarification and proffessional opinion.
Chrysler 383, 906 head.

The updated rules, posted on the NHRA site, state: "In third from last sentence delete “bottom cut may not extend more than .250 inch below seat angle”.

So am I to understand the bottom (throat) cut MAY extend deep into the port, thus removing additional material from the bowl? Legal?

Can I cut at any angle? 75 degrees? 80 degrees? etc. reguardless of the original bottom angle? Legal?

If a 75 or 80 degree throat cut opens the bowl, what happens to this valve job when NHRA comes out with the maximum runner CC's for stock heads?

What about the top cut? How far out can the top cut extend? It wouldn't be hard to utilize the top cut to unshroud the valve. Legal?

Could someone please clarify what exactly is legal and what is not.

Thank You
Gary Weaver

Tom Turner · 05-31-2008, 11:30 PM

Gary; The new valve job rule was designed to take NHRA out of the "scrutiny" business and give the a legally defensable club with which to beat you about the head and shoulders. There is no spec for the bottom or the top cut (although the rule still states "no chamber mods" grey area?)) I think the idea is to pour enough heads to "legally prove" that someone got carried away.....so dont. I talked with Bruce Bachelder about this (at length) and he was a little hesitant to divulge when the list of volumes was going to be published; or if it was ever to be published but that is what they will use as a criterea for judgement. I know that they have been pouring and gathering data for quite some time now and the guys with "port enhancement" may be in for a surprise; time will tell.

Woodro Josey · 06-01-2008, 10:37 AM

Just to add to what Tom has said, as i was told,,,,ANY VALVE JOB!

Moparteacher · 06-01-2008, 01:24 PM

So where does the valve job end and the unmodified port start?
I can't cut thses heads on a wnk and a nudge, yet I also don't want to leave HP on the shelf because it's unclear.

Bub Whitaker · 06-01-2008, 01:55 PM

Quote:

Originally Posted by Moparteacher

So where does the valve job end and the unmodified port start?
I can't cut thses heads on a wnk and a nudge, yet I also don't want to leave HP on the shelf because it's unclear.

You end the valve job/ bottom cut where you want... that's where the unmodified port starts. What Woody said... any valve job permited...

Moparteacher · 06-01-2008, 02:04 PM

Thank you for the replys.

05-31-2008, 10:09 PM	#1
Moparteacher Junior Member Join Date: Nov 2007 Location: Boise Posts: 49 Likes: 0 Liked 0 Times in 0 Posts	Need clarification on bottom cut I have just dropped off my heads at the machine shop with instructions on the legal valve job for stock heads, but I suspect I have given the wrong instructions. So I need clarification and proffessional opinion. Chrysler 383, 906 head. The updated rules, posted on the NHRA site, state: "In third from last sentence delete “bottom cut may not extend more than .250 inch below seat angle”. So am I to understand the bottom (throat) cut MAY extend deep into the port, thus removing additional material from the bowl? Legal? Can I cut at any angle? 75 degrees? 80 degrees? etc. reguardless of the original bottom angle? Legal? If a 75 or 80 degree throat cut opens the bowl, what happens to this valve job when NHRA comes out with the maximum runner CC's for stock heads? What about the top cut? How far out can the top cut extend? It wouldn't be hard to utilize the top cut to unshroud the valve. Legal? Could someone please clarify what exactly is legal and what is not. Thank You Gary Weaver __________________ Gary Weaver Moparteacher@yahoo.com

05-31-2008, 11:30 PM	#2
Tom Turner Member Join Date: Jan 2005 Location: Lake Tapps, Washington Posts: 137 Likes: 0 Liked 0 Times in 0 Posts	Re: Need clarification on bottom cut Gary; The new valve job rule was designed to take NHRA out of the "scrutiny" business and give the a legally defensable club with which to beat you about the head and shoulders. There is no spec for the bottom or the top cut (although the rule still states "no chamber mods" grey area?)) I think the idea is to pour enough heads to "legally prove" that someone got carried away.....so dont. I talked with Bruce Bachelder about this (at length) and he was a little hesitant to divulge when the list of volumes was going to be published; or if it was ever to be published but that is what they will use as a criterea for judgement. I know that they have been pouring and gathering data for quite some time now and the guys with "port enhancement" may be in for a surprise; time will tell.

06-01-2008, 10:37 AM	#3
Woodro Josey Senior Member Join Date: Jul 2007 Posts: 805 Likes: 0 Liked 3 Times in 1 Post	Re: Need clarification on bottom cut Just to add to what Tom has said, as i was told,,,,ANY VALVE JOB! __________________ Woodro Josey 2002 STK

06-01-2008, 01:24 PM	#4
Moparteacher Junior Member Join Date: Nov 2007 Location: Boise Posts: 49 Likes: 0 Liked 0 Times in 0 Posts	Re: Need clarification on bottom cut So where does the valve job end and the unmodified port start? I can't cut thses heads on a wnk and a nudge, yet I also don't want to leave HP on the shelf because it's unclear. __________________ Gary Weaver Moparteacher@yahoo.com Last edited by Moparteacher; 06-01-2008 at 01:29 PM.

06-01-2008, 02:04 PM	#6
Moparteacher Junior Member Join Date: Nov 2007 Location: Boise Posts: 49 Likes: 0 Liked 0 Times in 0 Posts	Re: Need clarification on bottom cut Thank you for the replys. __________________ Gary Weaver Moparteacher@yahoo.com