396/375 Replacement cyl head

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"...

07-23-2009, 07:30 PM	#1
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,315 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	#2
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	#3
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	#4
Rich Biebel VIP Member Join Date: Jun 2007 Location: Northern New Jersey suburbs Posts: 2,315 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	#5
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"...