Understanding cylinder heads
Thread Starter
Racer
Joined: Mar 2006
Posts: 291
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From: Guantanamo Bay, Cuba (home in Colorado Springs)
Understanding cylinder heads
After browsing Summit for a set of aluminum cylinder heads, I have discovered way too many choices.
56,62,64,70 &72 cc combustion chambers. Why so many and which do I want?
170 up to 215 cc intake runner volumes. Oh my!
Intake valve sizes up to 2.08!
Port shapes? What does mine have now I wonder?
What does it all mean? What combo and balance of sizes should I seek?
Can someone please provide me some intel on what I may want for a DD application? I just want to cut some weight off my '80 with an engine aluminum top end. More power is always a good thing, but I don't need a track dragster.
Thanks!
56,62,64,70 &72 cc combustion chambers. Why so many and which do I want?
170 up to 215 cc intake runner volumes. Oh my!
Intake valve sizes up to 2.08!
Port shapes? What does mine have now I wonder?
What does it all mean? What combo and balance of sizes should I seek?
Can someone please provide me some intel on what I may want for a DD application? I just want to cut some weight off my '80 with an engine aluminum top end. More power is always a good thing, but I don't need a track dragster.
Thanks!
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
The chamber size is used to attain the desired compression ratio. For example, if a 76cc head gives you 8.5:1, and you want to bump your compression ratio up, one way to do it would be to go to a 64cc head. The smaller chamber size, the higher the compression ratio.
The runner volumes are used to determine what type of use you will use the engine for. A smaller runner size (170) would be good for a smaller displacement engine, such as a 350. A 200cc runner would be used for a stout 350, a 383, or a mild 396. A 215 would be a stout 383 or larger. The bigger the runner, the more airflow, hence a higher RPM operating range.
The port shapes are different for different heads. The old cast iron heads were not very good at optimizing combustion. Most modern heads today have a port shape that is superior to the old cast iron heads. The port shape determines the burn pattern of the combustion and directs the flow of fuel and gases. The easier the fuel and gases can get in and out of the chamber, the better.
If everything else stays stock, a nice set of L98 style aluminum heads would work well for your setup. They are 58cc size. This would give you a higher compression ratio and give you pretty nice power down low. A cam swap would also be in your future.
The runner volumes are used to determine what type of use you will use the engine for. A smaller runner size (170) would be good for a smaller displacement engine, such as a 350. A 200cc runner would be used for a stout 350, a 383, or a mild 396. A 215 would be a stout 383 or larger. The bigger the runner, the more airflow, hence a higher RPM operating range.
The port shapes are different for different heads. The old cast iron heads were not very good at optimizing combustion. Most modern heads today have a port shape that is superior to the old cast iron heads. The port shape determines the burn pattern of the combustion and directs the flow of fuel and gases. The easier the fuel and gases can get in and out of the chamber, the better.
If everything else stays stock, a nice set of L98 style aluminum heads would work well for your setup. They are 58cc size. This would give you a higher compression ratio and give you pretty nice power down low. A cam swap would also be in your future.
Thread Starter
Racer
Joined: Mar 2006
Posts: 291
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From: Guantanamo Bay, Cuba (home in Colorado Springs)
Good info there, thanks.
Yes, I'll need a cam too, but that's another post.
How big are the valves and runners in the L98 heads mentioned?
Also, I live out in Colorado, above 6000 feet. What factors should I consider for head considerations for my given altitude?
Anyone know of an engine build calculator?
Endless thanks to all...
Yes, I'll need a cam too, but that's another post.
How big are the valves and runners in the L98 heads mentioned?
Also, I live out in Colorado, above 6000 feet. What factors should I consider for head considerations for my given altitude?
Anyone know of an engine build calculator?
Endless thanks to all...
Abby Normal
Joined: Dec 2001
Posts: 53,466
Likes: 92
From: Press "2" for English
while there is a great deal of personal experience and good advice on this forum, the best advice you can use would be to contact your cam maker of choice (comp, crane, etc) and let them suggest a combo that's going to give you what you want. the altitude thing is kind of a big deal considering how extreme it is.
Safety Car
Joined: Oct 2005
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From: Algonac Michigan
Drifting
Joined: Jun 2007
Posts: 1,404
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From: Ansonia/NYC CT
Go to autozone, and buy their book on rebuilding the 350s. They have two, one specifically for aftermarket/extreme building, and one for a milder engine. BOTH, however, will answer ALL of your questions. I bought it, and I love it, and it also makes awesome toilette reader. Leave it on the bowl, that way, anyone who uses your bathroom knows that a REAL man lives there.
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Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
Dgruenke gave a great overall summary;a few comments:
Chamber size is chosen to provide a desired CR with a particular piston. Since we're just looking at a top-end replacement, it's critically important to know your existing CR before making a recommendation.
Runner volumes also determine driveability - generally, the smallest runner volume that will deliver the flow that you determine appropriate for the build will deliver the best driveability. Good rules of thumb on CID/build level/runner size - but each build is different.
Additionally, you should pick the cam before you pick the heads - usage drives the cam, cam drives the heads. IMHO, swapping to aluminum heads just to lose some weight isn't worth the effort - and you won't see significant gain on a stock engine with the stock intake/exhaust/cam. If you're going to top it, then TOP IT with a well-designed plan.
At that altitude, maybe a supercharger is your best bet ;-)
Chamber size is chosen to provide a desired CR with a particular piston. Since we're just looking at a top-end replacement, it's critically important to know your existing CR before making a recommendation.
Runner volumes also determine driveability - generally, the smallest runner volume that will deliver the flow that you determine appropriate for the build will deliver the best driveability. Good rules of thumb on CID/build level/runner size - but each build is different.
Additionally, you should pick the cam before you pick the heads - usage drives the cam, cam drives the heads. IMHO, swapping to aluminum heads just to lose some weight isn't worth the effort - and you won't see significant gain on a stock engine with the stock intake/exhaust/cam. If you're going to top it, then TOP IT with a well-designed plan.
At that altitude, maybe a supercharger is your best bet ;-)
Tech Contributor
Joined: Jun 2004
Posts: 20,914
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Thread Starter
Racer
Joined: Mar 2006
Posts: 291
Likes: 0
From: Guantanamo Bay, Cuba (home in Colorado Springs)
The C3's are porkers at 3600+ pounds. Any weight reduction is cost effective for me. The stock '80 350 motor put out an optimistic 195 chipmunk power...Oh yea, baby; I need a supercharger! But I need to fit it all under a stock hood. We loose about 30% at this altitude, and a drive up to the top of Pikes peak or Mt. Evans (above 14,000 ft) is hard breathing even for my motorcycle.
What about spark plug angle? Straigh or Angle? I hear the angle are difficult to work with if you use headers and are typically for "hardcore" racing applications.
My cam research will require another spreadsheet to crunch the numbers.
What about spark plug angle? Straigh or Angle? I hear the angle are difficult to work with if you use headers and are typically for "hardcore" racing applications.
My cam research will require another spreadsheet to crunch the numbers.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
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From: Seattle WA
St. Jude Donor '14
60# isn't trivial, but unless you're going the full route of a lightening program and taking it to the track, I challenge you to objectively demonstrate difference on the skidpad/slalom...or SOTP on the street.
No argument that if you're going to top, top with aluminum - but do it for performance and benefit from the weight difference; doing it just for weight with little or no performance enhancement makes no sense to me at all.
Spark plug angle is more about header choice - either what you have or what you're planning. If you're sticking with stock manifolds then the choice is easier
Head selection without cam selection first is going to cost you money and/or breadth of cam options - why buy a brand new head and then find out that the springs won't work with your cam choice, or aren't well-suited to what you ultimately select for a cam and so force a compromise there?
Tech Contributor
Joined: Jun 2004
Posts: 20,914
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Always nice to start the new year with a negative crack about a poster vs. rational arguement. Crack?? Okay, lets do numbers. 60-70 pounds (sb or bb) is roughly two percent of the car's total weight. And again, it's up front and up high. And remember, F=mA. At a 50% efficient use of this weight reduction, you're looking at a free second per lap reduction on a lot of road courses. Drag racing? Okay. Same horsepower pushing 98% of the weight ought to be measureably quicker ETs.
60# isn't trivial, but unless you're going the full route of a lightening program and taking it to the track, I challenge you to objectively demonstrate difference on the skidpad/slalom...See above. or SOTP on the street. My experience is SOTP measurements on the street is too subjective to be useful for most things.
No argument that if you're going to top, top with aluminum - but do it for performance and benefit from the weight difference; doing it just for weight with little or no performance enhancement makes no sense to me at all....................
Crack?? Okay, lets do numbers. 60-70 pounds (sb or bb) is roughly two percent of the car's total weight. And again, it's up front and up high. And remember, F=mA. At a 50% efficient use of this weight reduction, you're looking at a free second per lap reduction on a lot of road courses. Drag racing? Okay. Same horsepower pushing 98% of the weight ought to be measureably quicker ETs. 60# isn't trivial, but unless you're going the full route of a lightening program and taking it to the track, I challenge you to objectively demonstrate difference on the skidpad/slalom...See above. or SOTP on the street. My experience is SOTP measurements on the street is too subjective to be useful for most things.
No argument that if you're going to top, top with aluminum - but do it for performance and benefit from the weight difference; doing it just for weight with little or no performance enhancement makes no sense to me at all....................
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Performance is more than just straightline acceleration. It's braking (negative acceleration) and cornering (lateral acceleration) too. As I indicated in my first post, your definition of performance is extremely limited in scope. These are Corvettes (ie: sports cars), not Chevelles.
And of course...not completely applicable to a daily driver that's carrying a few hundred pounds in carpet, heavy A-arms, copper radiator, etc.I don't see where I defined performance or noted I was a Chevelle drag racer (you seem to really enjoy telling me what you think I don't know and repeating what I don't say), but my observation was (and is) that saving 60# in and of itself is not going to make an appreciable difference in handling for a daily driven street car, and is not worth the $2K+ expense SOLELY for the weight improvement.
Benefitting from the weight gain as part of a well-planned top swap that adds power - all good. That's the "A" part of that formula you noted.
I suggest we let the thread snap back back to the poster's interest in finding the right set of heads for his application.
Thread Starter
Racer
Joined: Mar 2006
Posts: 291
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From: Guantanamo Bay, Cuba (home in Colorado Springs)
I suggest we let the thread snap back back to the poster's interest in finding the right set of heads for his application. [/QUOTE]
I fully realize that cam, intake, carb, piston & head all play symbiotic relations in the internal working of engine operation & performance. Cylinder head design was where I lacked the most experience.
As a pilot and engineer, I have seen the performance variances with even a few pounds of weight and thrust on aircraft.
Not wanting to get a second mortgage on my house to pay for a roller cam, I have been surfing Summit today.
Thoughts on this conventional flat tappet hyd cam, please?
RPM range duration lift sep PN#
1000 5500 213 219 0.454 0.468 112 LUN-60101LK
[/QUOTE] I fully realize that cam, intake, carb, piston & head all play symbiotic relations in the internal working of engine operation & performance. Cylinder head design was where I lacked the most experience.
As a pilot and engineer, I have seen the performance variances with even a few pounds of weight and thrust on aircraft.
Not wanting to get a second mortgage on my house to pay for a roller cam, I have been surfing Summit today.
Thoughts on this conventional flat tappet hyd cam, please?
RPM range duration lift sep PN#
1000 5500 213 219 0.454 0.468 112 LUN-60101LK
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
I fully realize that cam, intake, carb, piston & head all play symbiotic relations in the internal working of engine operation & performance. Cylinder head design was where I lacked the most experience.
As a pilot and engineer, I have seen the performance variances with even a few pounds of weight and thrust on aircraft.
Not wanting to get a second mortgage on my house to pay for a roller cam, I have been surfing Summit today.
Thoughts on this conventional flat tappet hyd cam, please?
RPM range duration lift sep PN#
1000 5500 213 219 0.454 0.468 112 LUN-60101LK
As a pilot and engineer, I have seen the performance variances with even a few pounds of weight and thrust on aircraft.
Not wanting to get a second mortgage on my house to pay for a roller cam, I have been surfing Summit today.
Thoughts on this conventional flat tappet hyd cam, please?
RPM range duration lift sep PN#
1000 5500 213 219 0.454 0.468 112 LUN-60101LK
Transmission type, rear-end gears and usage are needed for a cam recommendation. Agreed that roller cams are expensive - but as an aside they will virtually always make more power. Overall, that's a great "general purpose" cam...depending on the head
Dual-pattern cams generally (not always) produce more top-end power at the expense of some low- and min-range power. I'd get some recommendations here - and then call/email CompCams, Lunati, etc. and get their recommendations for balance.
Last edited by billla; Jan 1, 2008 at 03:57 PM.
Thread Starter
Racer
Joined: Mar 2006
Posts: 291
Likes: 0
From: Guantanamo Bay, Cuba (home in Colorado Springs)
Nice Navion. I've never had the opt to fly one. When I get back from my next tour "over there", I'm doing my ATP rating.
Yes, I'm calling Summit & Crain later this week to discuss technical specs on heads & cam. No one at work today/yesterday (except me).
Yes, I'm calling Summit & Crain later this week to discuss technical specs on heads & cam. No one at work today/yesterday (except me).
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
CompCams has a GREAT tech line as well - and they have an online form you can fill out today.
http://www.compcams.com/Information/CamForm/camform.asp
Tech Contributor
Joined: Jun 2004
Posts: 20,914
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
I'm extremely clear what Corvettes are, and I'm familiar with the math, but thanks for copying that formula out of your high-school Physics book. Don't have any HS physics books. Do have a few from college, though. Herb Adams' book might be a better reference for you, as theoretical physics doesn't always effectively model he real world. Got his book sitting right here. Looking at his data, he uses a weight reduction/speed improvement efficiency of about 85%. I used 50% for those of us who do this for fun, rather than a profession. If you're noting that 60# is worth 1 second a lap, I'd like to see the before and after track times...preferably yours Already got the lightweight heads on. No point in putting the heavy stuff back on for a short test. But, on common tracks with 100-130 second lap times, one second is less than one percent. Doable with a two percent weight reduction. And of course...not completely applicable to a daily driver that's carrying a few hundred pounds in carpet, heavy A-arms, copper radiator, etc. Wrong. There is no threshold level that nullifies performance improvements when reducing weight. Every less ounce or pound is an improvement.
I don't see where I defined performance In your previous post you stated that you do the heads "for performance and benefit from the weight difference". Weight reduction is performance. We want the whole car to perform, not just the engine. or noted I was a Chevelle drag racer (you seem to really enjoy telling me what you think I don't know and repeating what I don't say), I didn't say you were a Chevelle drag racer. I was trying to show by example the difference in philosophy when hopping up a Corvette rather than other familiar performance cars. but my observation was (and is) that saving 60# in and of itself is not going to make an appreciable difference in handling for a daily driven street car, and is not worth the $2K+ expense SOLELY for the weight improvement. The OP and I both disagree with you there.
Benefitting from the weight gain as part of a well-planned top swap that adds power - all good. That's the "A" part of that formula you noted.
I suggest we let the thread snap back back to the poster's interest in finding the right set of heads for his application.
Already got the lightweight heads on. No point in putting the heavy stuff back on for a short test. But, on common tracks with 100-130 second lap times, one second is less than one percent. Doable with a two percent weight reduction. And of course...not completely applicable to a daily driver that's carrying a few hundred pounds in carpet, heavy A-arms, copper radiator, etc. Wrong. There is no threshold level that nullifies performance improvements when reducing weight. Every less ounce or pound is an improvement. I don't see where I defined performance In your previous post you stated that you do the heads "for performance and benefit from the weight difference". Weight reduction is performance. We want the whole car to perform, not just the engine. or noted I was a Chevelle drag racer (you seem to really enjoy telling me what you think I don't know and repeating what I don't say), I didn't say you were a Chevelle drag racer. I was trying to show by example the difference in philosophy when hopping up a Corvette rather than other familiar performance cars. but my observation was (and is) that saving 60# in and of itself is not going to make an appreciable difference in handling for a daily driven street car, and is not worth the $2K+ expense SOLELY for the weight improvement. The OP and I both disagree with you there.
Benefitting from the weight gain as part of a well-planned top swap that adds power - all good. That's the "A" part of that formula you noted.
I suggest we let the thread snap back back to the poster's interest in finding the right set of heads for his application.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
Clear skies and tailwinds