427-425hp w/GM 401 heads

dahkahuna · 12-06-2012, 01:22 AM

I see in the NHRA blueprint specs that when you use the 401 the 1.84 exhaust valve is the legal valve to use ........Ruler you were right , thanks

RULER · 12-06-2012, 05:19 AM

The iron head uses the 1.72 exh. and the 401 alum. uses the 1.84 exh and also you run at 435hp. with the alum. head 425hp with the iron head. Thanks

Pedigo Perf · 12-06-2012, 10:02 AM

I think the 401 alum head has a standard spec for all combinations it can be used on.

2195/1845 with a 103.3 chamber volume.

Again, check the guide as always.

RULER · 12-06-2012, 11:55 PM

The 401 head can be used on the 1969 427/430 ZL1 or L88 with 2.195 1.885 valve and 114.8cc camber also.there is a different HP. rating for the ZL1 and the L88, The ZL1 gets a bigger cam. If you use an original head casting (aliuminum) then there is a HP reduction.

dahkahuna · 12-07-2012, 01:32 AM

Is there a horsepower penalty on the 396=375hp aluminum head engine if you use the original # 842 aluminum casting cylinder head or is the factored hp # for the 401 only ?

RULER · 12-07-2012, 02:30 AM

All the info you are asking for is in the classification guide. I don't think there is any difference on the 396 aluminum heads (new or old) but i could be wrong, just be careful if you call it a 402 that changes alot of small stuff.

Alan Roehrich · 12-09-2012, 01:46 AM

We have a 427/425 with 401 heads. I would not build another one. If I get the chance, we'll be going to a set of 840 iron heads.

It is a good choice for a ZL-1, an L-88, or a Super Stock engine, and probably for a 396-375 or 402-375 in Stock.

Don Morris · 12-12-2012, 03:09 AM

I come from the land of Mopar where things seem a bit easier. That being said, I have to ask a few questions: How did NHRA wind up allowing the "401" aluminum head as a replacement head for the 427/425 iron head combo when it has a 1.845 exhaust valve? Didn't this combo originally come in only one version and that being a 1.725" valve in an iron head? There is also the question about how did NHRA arrive at the smaller chamber volume with the 401 head?

I would gladly stand corrected if any of my information is wrong. Inquiring minds would like to know.

12-06-2012, 01:22 AM	#1
dahkahuna Member Join Date: Jul 2006 Location: san dimas , calif Posts: 128 Likes: 0 Liked 5 Times in 3 Posts	Re: 427-425hp w/GM 401 heads I see in the NHRA blueprint specs that when you use the 401 the 1.84 exhaust valve is the legal valve to use ........Ruler you were right , thanks

12-06-2012, 05:19 AM	#2
RULER Member Join Date: Jan 2006 Posts: 222 Likes: 15 Liked 58 Times in 18 Posts	Re: 427-425hp w/GM 401 heads The iron head uses the 1.72 exh. and the 401 alum. uses the 1.84 exh and also you run at 435hp. with the alum. head 425hp with the iron head. Thanks

12-06-2012, 10:02 AM	#3
Pedigo Perf Member Join Date: Feb 2008 Location: Wichita Ks Posts: 383 Likes: 70 Liked 30 Times in 17 Posts	Re: 427-425hp w/GM 401 heads I think the 401 alum head has a standard spec for all combinations it can be used on. 2195/1845 with a 103.3 chamber volume. Again, check the guide as always.

12-06-2012, 11:55 PM	#4
RULER Member Join Date: Jan 2006 Posts: 222 Likes: 15 Liked 58 Times in 18 Posts	Re: 427-425hp w/GM 401 heads The 401 head can be used on the 1969 427/430 ZL1 or L88 with 2.195 1.885 valve and 114.8cc camber also.there is a different HP. rating for the ZL1 and the L88, The ZL1 gets a bigger cam. If you use an original head casting (aliuminum) then there is a HP reduction.

12-07-2012, 01:32 AM	#5
dahkahuna Member Join Date: Jul 2006 Location: san dimas , calif Posts: 128 Likes: 0 Liked 5 Times in 3 Posts	Re: 427-425hp w/GM 401 heads Is there a horsepower penalty on the 396=375hp aluminum head engine if you use the original # 842 aluminum casting cylinder head or is the factored hp # for the 401 only ?

12-07-2012, 02:30 AM	#6
RULER Member Join Date: Jan 2006 Posts: 222 Likes: 15 Liked 58 Times in 18 Posts	Re: 427-425hp w/GM 401 heads All the info you are asking for is in the classification guide. I don't think there is any difference on the 396 aluminum heads (new or old) but i could be wrong, just be careful if you call it a 402 that changes alot of small stuff.

12-09-2012, 01:46 AM	#7
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,118 Likes: 1,573 Liked 1,837 Times in 417 Posts	Re: 427-425hp w/GM 401 heads We have a 427/425 with 401 heads. I would not build another one. If I get the chance, we'll be going to a set of 840 iron heads. It is a good choice for a ZL-1, an L-88, or a Super Stock engine, and probably for a 396-375 or 402-375 in Stock. __________________ Alan Roehrich 212A G/S

12-12-2012, 03:09 AM	#8
Don Morris Junior Member Join Date: Dec 2009 Posts: 39 Likes: 5 Liked 69 Times in 9 Posts	Re: 427-425hp w/GM 401 heads I come from the land of Mopar where things seem a bit easier. That being said, I have to ask a few questions: How did NHRA wind up allowing the "401" aluminum head as a replacement head for the 427/425 iron head combo when it has a 1.845 exhaust valve? Didn't this combo originally come in only one version and that being a 1.725" valve in an iron head? There is also the question about how did NHRA arrive at the smaller chamber volume with the 401 head? I would gladly stand corrected if any of my information is wrong. Inquiring minds would like to know.