427 heads on my 396?

chuckphillips · 12-01-2007, 05:48 PM

I assume some of you guys know I am restoring a 1969 CST/10 with a 396. I just took the covers off to check the heads to see if they are correct. Not too my suprise, they are not! the casting is 3935401, both are the same with a date of F24 8. I know the block casting is 3935440 which is a mid 68 casting and was used for 68 and 69 so it correct.

I wonder... would they 427 heads put on for performance reasons?

Something else to keep in mind.. they have "M Truck" casted on the inside of the heads. Mortec.com shows the casting is used for 427's, I wonder if they used them for the 69 truck as well...

75K30 · 12-01-2007, 08:42 PM

There were service trucks that used the 427. This was not like the 427 corvette engine, but closer to the 366 truck engine.
It is my guess that these heads currently on the truck are not the original ones that came on the engine. These are open chamber oval port heads that really do not flow great numbers, so while the idea that these could be used for performance reasons is a good one, but probably not the pot of gold that we might hope. After all of the years that have past, and the fact that it is a truck and not an LS6, chances are that the thing got hot and cracked a head, and these babies were what they replaced the originalls with. Maybe.....
You had asked about making some extra power, and this is a good time to yank those things off and find some real performance units. You can still keep those for your restoration needs, and build up some closed chamber units from a car, and make some decent power.
Worth a look. I will see if I can find some flow numbers for those heads. Might be tough, since they do not get kept for performance stuff..

chuckphillips · 12-02-2007, 05:29 AM

Good morning Ed...

I don't know what heads would work best, from what engine and what years.... Would my Chevy by the numbers book help? Should I look for a heads that went to a certain year and motor size that was rated the Highest HP and as long as it was a Chevy BB it should work on mine?

As far as keeping what is on it, HECK no... If they are for a truck and Low HP, they are anchors as far as I can tell..... I will just clean them up and throw them on E-bay for someone shooting to make a numbers matching motor. They obviously don't go with mine anyways.

Thanks for all your help and time... It sure is appreciated. If you lived near by, I would take you to this place downtown Pittsburgh where you grab a bite to eat, and drink some beer and look through this big glass window and watch them brew some beer!

Chuck

tjzz4 · 12-02-2007, 06:09 AM

eBay Motors: big block chevy aluminum cylinder head bbc heads boetie (item 300177813509 end time Dec-09-07 15:32:51 PST)

chuckphillips · 12-02-2007, 07:00 AM

Sounds like I would pay more for those than I did the Whole truck! But wow.... Sure look nice.

75K30 · 12-02-2007, 07:59 AM

Quote:

Originally Posted by chuckphillips

Good morning Ed...

I don't know what heads would work best, from what engine and what years.... Would my Chevy by the numbers book help? Should I look for a heads that went to a certain year and motor size that was rated the Highest HP and as long as it was a Chevy BB it should work on mine?

As far as keeping what is on it, HECK no... If they are for a truck and Low HP, they are anchors as far as I can tell..... I will just clean them up and throw them on E-bay for someone shooting to make a numbers matching motor. They obviously don't go with mine anyways.

Thanks for all your help and time... It sure is appreciated. If you lived near by, I would take you to this place downtown Pittsburgh where you grab a bite to eat, and drink some beer and look through this big glass window and watch them brew some beer!

Chuck

Chuck:

That sounds like it would be woth the trip anyway.
As far as the heads being boat anchors, well they are still reasonable heads, and can be capable of making some power, just not in stock form. The Combustion chambers are also too large to even bump the compression ratio high enough to even consider making real power.
At any rate, usually with BBC heads the limiting factor for power is the design of the CC itself. What I mean by this is that you can find a nce set of closed chamber heads (oval port) but the closed chamber (while increasing compression) does shroud the valves, and hinder a little flow. But the sacrifice in flow far outweighs the benifits of additional compression.
The fix:
A little bit of bowl blending and relief of the CC. This is a process where you will cut the CC back some and open up the area that is problematic with BBC factory heads.
Aluminum heads were mentioned above, and are very nice pieces, but I doubt that with this smaller big block that you would be obtaining the full potential of the heads. A decent set of closed chamber "Pass Hi-Perf" heads would be a start. I would not limit myself to someotherwise rare heads like the higher performance "425 HP Chevelle" heads. Remamber tha these made additional power with aggressive cam profiles and solid lifters combined with the heads to produce this power, and your current combo may not support this, or have similar results.
Even later model heads can produce decent numbers, and would open up the possibilities withpuut killing the bank.
Should keep Mrs chuckphillips happy. lol.
I have a couple of suggestions regarding decent heads that i will PM to you. You can seperate it into a "wish list", and more reasonable "this will work list", and you can go shopping. Being able to seperate the have to have and settle for differences can be the difference between finishing a project on time with reasonable results, and having one sit around collecting dust.
Ask me how I know.......

tjzz4 · 12-02-2007, 08:46 PM

Yeah but for a little more investment the heads in the link are 110cc combustion chambers with oval ports.. A little porting work would really make a nice set.
edit... sorry..says in the link they are 119cc heads. Also says though they are the same as part# 12363399 which are the same as the heads used on the 502/502.... THOSE are for sure 110cc

chuckphillips · 12-03-2007, 04:33 AM

Thanks for the information. I am taking the family (14) on a vacation, starting Friday, after the Holidays I might consider spending a few bucks on heads, but I guess I don't know enough about them to know if what I get for the money.... How much hp will I gain over the ones I have and will the ones I get work with my set-up or do I need to change the Cam?

chuckphillips · 12-03-2007, 04:43 AM

Is 119CC the way to go, or what CC should I get and why? Do I want OPEN or CLOSED CHAMBER and why? Do I want OVAL or SQUARE PORT HEADS and why? Sorry for asking so many questions, just the kind of guy that likes to know how things work and why I should go one way or the other.... Thanks!!! Chuck

75K30 · 12-03-2007, 11:36 AM

On a 396 CI engine, I do not see were this thig could make any compression at all. An open chamber, or chamber of over 110 cc's can't make any compression in a small displacement BBC. Gotta get those bad boys down under 100.
Early high perf closed chamber heads like 201's are being cut down to obtain around 90 cc's and being used on 454's with flat tops.
We would never consider this size chamber in a SBC 400 right? Absolutely not, So why would we consider this in a small displacement BBC? We would not.
Oval port would be the way to go, simply because a rectangle port has a larger port and will stall the air entering the cylinder. This larger port will be too large for a small displacement engine.
Oval port is a wise choice, and your combustion chamber will dictate your compression ratio. Now I am assuming a .040 head gasket and a flat top piston with valve reliefs. Domes, zero deck heigth, and a thinner head gasket will all contribute to greater compression.
Since you are gonna run this on pump gas, you will need to keep a reasonable ratio, but I get away with over 10.5:1 on a big, big block chevy on pump gas and 32* of timing.
FWIW, I run a 540 CI BBC with AFR 357 heads and these have a 119 cc combustion chamber.

12-01-2007, 05:48 PM	#1
chuckphillips Senior Member Join Date: Oct 2007 Posts: 136	427 heads on my 396? I assume some of you guys know I am restoring a 1969 CST/10 with a 396. I just took the covers off to check the heads to see if they are correct. Not too my suprise, they are not! the casting is 3935401, both are the same with a date of F24 8. I know the block casting is 3935440 which is a mid 68 casting and was used for 68 and 69 so it correct. I wonder... would they 427 heads put on for performance reasons? Something else to keep in mind.. they have "M Truck" casted on the inside of the heads. Mortec.com shows the casting is used for 427's, I wonder if they used them for the 69 truck as well...

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12-01-2007, 08:42 PM	#2
75K30 Senior Member Join Date: Jul 2006 Posts: 2,960	There were service trucks that used the 427. This was not like the 427 corvette engine, but closer to the 366 truck engine. It is my guess that these heads currently on the truck are not the original ones that came on the engine. These are open chamber oval port heads that really do not flow great numbers, so while the idea that these could be used for performance reasons is a good one, but probably not the pot of gold that we might hope. After all of the years that have past, and the fact that it is a truck and not an LS6, chances are that the thing got hot and cracked a head, and these babies were what they replaced the originalls with. Maybe..... You had asked about making some extra power, and this is a good time to yank those things off and find some real performance units. You can still keep those for your restoration needs, and build up some closed chamber units from a car, and make some decent power. Worth a look. I will see if I can find some flow numbers for those heads. Might be tough, since they do not get kept for performance stuff..

12-02-2007, 05:29 AM	#3
chuckphillips Senior Member Join Date: Oct 2007 Posts: 136	Good morning Ed... I don't know what heads would work best, from what engine and what years.... Would my Chevy by the numbers book help? Should I look for a heads that went to a certain year and motor size that was rated the Highest HP and as long as it was a Chevy BB it should work on mine? As far as keeping what is on it, HECK no... If they are for a truck and Low HP, they are anchors as far as I can tell..... I will just clean them up and throw them on E-bay for someone shooting to make a numbers matching motor. They obviously don't go with mine anyways. Thanks for all your help and time... It sure is appreciated. If you lived near by, I would take you to this place downtown Pittsburgh where you grab a bite to eat, and drink some beer and look through this big glass window and watch them brew some beer! Chuck

12-02-2007, 06:09 AM	#4
tjzz4 Senior Member Join Date: Oct 2007 Posts: 266	eBay Motors: big block chevy aluminum cylinder head bbc heads boetie (item 300177813509 end time Dec-09-07 15:32:51 PST)

12-02-2007, 07:00 AM	#5
chuckphillips Senior Member Join Date: Oct 2007 Posts: 136	Sounds like I would pay more for those than I did the Whole truck! But wow.... Sure look nice.

12-02-2007, 08:46 PM	#7
tjzz4 Senior Member Join Date: Oct 2007 Posts: 266	Yeah but for a little more investment the heads in the link are 110cc combustion chambers with oval ports.. A little porting work would really make a nice set. edit... sorry..says in the link they are 119cc heads. Also says though they are the same as part# 12363399 which are the same as the heads used on the 502/502.... THOSE are for sure 110cc

12-03-2007, 04:33 AM	#8
chuckphillips Senior Member Join Date: Oct 2007 Posts: 136	Thanks for the information. I am taking the family (14) on a vacation, starting Friday, after the Holidays I might consider spending a few bucks on heads, but I guess I don't know enough about them to know if what I get for the money.... How much hp will I gain over the ones I have and will the ones I get work with my set-up or do I need to change the Cam?

12-03-2007, 04:43 AM	#9
chuckphillips Senior Member Join Date: Oct 2007 Posts: 136	Is 119CC the way to go, or what CC should I get and why? Do I want OPEN or CLOSED CHAMBER and why? Do I want OVAL or SQUARE PORT HEADS and why? Sorry for asking so many questions, just the kind of guy that likes to know how things work and why I should go one way or the other.... Thanks!!! Chuck

12-03-2007, 11:36 AM	#10
75K30 Senior Member Join Date: Jul 2006 Posts: 2,960	On a 396 CI engine, I do not see were this thig could make any compression at all. An open chamber, or chamber of over 110 cc's can't make any compression in a small displacement BBC. Gotta get those bad boys down under 100. Early high perf closed chamber heads like 201's are being cut down to obtain around 90 cc's and being used on 454's with flat tops. We would never consider this size chamber in a SBC 400 right? Absolutely not, So why would we consider this in a small displacement BBC? We would not. Oval port would be the way to go, simply because a rectangle port has a larger port and will stall the air entering the cylinder. This larger port will be too large for a small displacement engine. Oval port is a wise choice, and your combustion chamber will dictate your compression ratio. Now I am assuming a .040 head gasket and a flat top piston with valve reliefs. Domes, zero deck heigth, and a thinner head gasket will all contribute to greater compression. Since you are gonna run this on pump gas, you will need to keep a reasonable ratio, but I get away with over 10.5:1 on a big, big block chevy on pump gas and 32* of timing. FWIW, I run a 540 CI BBC with AFR 357 heads and these have a 119 cc combustion chamber.