396/375 Replacement cyl head

demps45 · 07-22-2009, 06:21 PM

As an old racer thinking about getting my 69 chevelle back on the track - is the 401 alum cyl head acceptable on "all" 375 HP engines?

Alan Roehrich · 07-22-2009, 08:45 PM

It's legal for the 69 396-375. Of course, you should check the guides for the factored HP, the weight, and the specs. All of it is online now at the NHRA site.

demps45 · 07-23-2009, 10:28 AM

Thanks Alan, I have checked all the NHRA specs, factored Hp and such, but was a little confused regarding the 401 alum head use on my Chevelle. At one point in the specs, it mentions the alum head for the Nova and Camaro only, but I have since learned it is also legal on my can. Thanks again for your help.

mannymen · 07-23-2009, 01:47 PM

Question? Isn't the 401 replacement head an open chamber head at 118 + - CC's? The 396/375 combo is a closed chamber 106 or so CC head. Can someone explain whether one is allowed to modify the chamber or to decrease the CC's on the head to run stock or even SS? Can you run it as an open chamber and are you then allowed to use the open chamber piston that fits the combustion chamber better. Confused on how this works. I thought I saw an SS camaro racer running an alum head 427, but claim the 445hp instead of the 476hp for the L88 open chamber headed motor.

demps45 · 07-23-2009, 02:29 PM

Mannymen - According to the NHRA specs, the stock cast iron head is listed as 104+cc, and the 401 alum head is at 103+cc. Also, the alum head motor is factored at 405HP and the cast iron head motor is at 390.

Rich Biebel · 07-23-2009, 07:30 PM

The LS-6 454 SS engine combination has used the open chamber heads at the closed chamber CC for years and years. I machined a number of sets so I know how they got from 119 cc's down to the legal CC number.....

I just had a friend ask me about doing an engine using the 401 heads and wondered the same thing...How did these heads become acceptable for an engine that used CC heads. I am assuming the arguement that the legal iron CC heads are getting harder to find and more expensive is how these aluminum heads came into the picture...... '840's and '291's There are also aluminum CC stock GM versions..... A friend has a set....

mannymen · 07-23-2009, 09:51 PM

Ed and Rich,
So you guys are saying that they modify or aluminum fill the 118 CC open chamber 401 head to get it down to the 103 or 104 CC closed chamber spec in both Stock and in Superstock?

sorry for my ignorance

Bryan Broaddus · 07-26-2009, 07:45 PM

I have run the 1971 425 HP LS6 with the 401 alloy heads for several years. You can angle mill the heads to get the chambers down to 104 cc's. Same thing on the Iron heads. You have to cut .100 off the plug side and 0 on the manifold side, then correct the intake manifold face.

Rich Biebel · 07-27-2009, 05:23 AM

I didn't want to be the first one to say how I made them the right CC's......I angle milled the iron open chamber "990 heads......zero to .125" than flat milled them the rest of the way. corrected the intake side and faced the head bolt bosses to make them for an LS-6....I did not realize the 401 heads were being used for that engine as well.....

bsa633 · 07-27-2009, 06:45 AM

when you angle mill a head you change the valve-angle..another of those "grey areas" i guess..while many makes doesn't get a replacement head at all..some others can just "make heads fit"...

07-22-2009, 06:21 PM	#1
demps45 Junior Member Join Date: Jul 2009 Location: Lockport, NY Posts: 7 Likes: 0 Liked 0 Times in 0 Posts	396/375 Replacement cyl head As an old racer thinking about getting my 69 chevelle back on the track - is the 401 alum cyl head acceptable on "all" 375 HP engines? __________________ Fred Dempsey G/S, H/S, I/S, D/SA

07-22-2009, 08:45 PM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,105 Likes: 1,564 Liked 1,789 Times in 408 Posts	Re: 396/375 Replacement cyl head It's legal for the 69 396-375. Of course, you should check the guides for the factored HP, the weight, and the specs. All of it is online now at the NHRA site. __________________ Alan Roehrich 212A G/S

07-23-2009, 10:28 AM	#3
demps45 Junior Member Join Date: Jul 2009 Location: Lockport, NY Posts: 7 Likes: 0 Liked 0 Times in 0 Posts	Re: 396/375 Replacement cyl head Thanks Alan, I have checked all the NHRA specs, factored Hp and such, but was a little confused regarding the 401 alum head use on my Chevelle. At one point in the specs, it mentions the alum head for the Nova and Camaro only, but I have since learned it is also legal on my can. Thanks again for your help. __________________ Fred Dempsey G/S, H/S, I/S, D/SA

07-23-2009, 01:47 PM	#4
mannymen Senior Member Join Date: Apr 2003 Posts: 728 Likes: 5 Liked 13 Times in 7 Posts	Re: 396/375 Replacement cyl head Question? Isn't the 401 replacement head an open chamber head at 118 + - CC's? The 396/375 combo is a closed chamber 106 or so CC head. Can someone explain whether one is allowed to modify the chamber or to decrease the CC's on the head to run stock or even SS? Can you run it as an open chamber and are you then allowed to use the open chamber piston that fits the combustion chamber better. Confused on how this works. I thought I saw an SS camaro racer running an alum head 427, but claim the 445hp instead of the 476hp for the L88 open chamber headed motor. __________________ N/A

07-23-2009, 02:29 PM	#5
demps45 Junior Member Join Date: Jul 2009 Location: Lockport, NY Posts: 7 Likes: 0 Liked 0 Times in 0 Posts	Re: 396/375 Replacement cyl head Mannymen - According to the NHRA specs, the stock cast iron head is listed as 104+cc, and the 401 alum head is at 103+cc. Also, the alum head motor is factored at 405HP and the cast iron head motor is at 390. __________________ Fred Dempsey G/S, H/S, I/S, D/SA

07-23-2009, 07:30 PM	#6
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: 396/375 Replacement cyl head The LS-6 454 SS engine combination has used the open chamber heads at the closed chamber CC for years and years. I machined a number of sets so I know how they got from 119 cc's down to the legal CC number..... I just had a friend ask me about doing an engine using the 401 heads and wondered the same thing...How did these heads become acceptable for an engine that used CC heads. I am assuming the arguement that the legal iron CC heads are getting harder to find and more expensive is how these aluminum heads came into the picture...... '840's and '291's There are also aluminum CC stock GM versions..... A friend has a set.... __________________ Rich Biebel S/C 1479 Stock 147R Last edited by Rich Biebel; 07-23-2009 at 07:35 PM.

07-23-2009, 09:51 PM	#7
mannymen Senior Member Join Date: Apr 2003 Posts: 728 Likes: 5 Liked 13 Times in 7 Posts	Re: 396/375 Replacement cyl head Ed and Rich, So you guys are saying that they modify or aluminum fill the 118 CC open chamber 401 head to get it down to the 103 or 104 CC closed chamber spec in both Stock and in Superstock? sorry for my ignorance __________________ N/A

07-26-2009, 07:45 PM	#8
Bryan Broaddus Member Join Date: Jun 2002 Posts: 104 Likes: 2 Liked 18 Times in 4 Posts	Re: 396/375 Replacement cyl head I have run the 1971 425 HP LS6 with the 401 alloy heads for several years. You can angle mill the heads to get the chambers down to 104 cc's. Same thing on the Iron heads. You have to cut .100 off the plug side and 0 on the manifold side, then correct the intake manifold face. __________________ Bryan Broaddus 7568 STK ,SS

07-27-2009, 05:23 AM	#9
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,314 Likes: 25 Liked 544 Times in 213 Posts	Re: 396/375 Replacement cyl head I didn't want to be the first one to say how I made them the right CC's......I angle milled the iron open chamber "990 heads......zero to .125" than flat milled them the rest of the way. corrected the intake side and faced the head bolt bosses to make them for an LS-6....I did not realize the 401 heads were being used for that engine as well..... __________________ Rich Biebel S/C 1479 Stock 147R

07-27-2009, 06:45 AM	#10
bsa633 Banned Join Date: Mar 2002 Posts: 310 Likes: 0 Liked 0 Times in 0 Posts	Re: 396/375 Replacement cyl head when you angle mill a head you change the valve-angle..another of those "grey areas" i guess..while many makes doesn't get a replacement head at all..some others can just "make heads fit"...