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Discussion Starter #1
9.315 deck 3.875 stroke 4.185bore 6.25 rod in a dragster. 5800-6000stall bbc cam journals. motor will run on alcohol with rons injection. 15.5-1 compression. and i plan on crossing the line at 8000-8200rpms. heads are 15* brodix-12's 1.65/1.6 rockers.
flow around337 at700. if the flow sheet even belongs to these heads. planning on getting them ported down the road.
whats it take to get 800+ outa this combo.
 

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9.315 deck 3.875 stroke 4.185bore 6.25 rod in a dragster. 5800-6000stall bbc cam journals. motor will run on alcohol with rons injection. 15.5-1 compression. and i plan on crossing the line at 8000-8200rpms. heads are 15* brodix-12's 1.65/1.6 rockers.
flow around337 at700. if the flow sheet even belongs to these heads. planning on getting them ported down the road.
whats it take to get 800+ outa this combo.
A BMEP of just about 200 psi at 7500. That is going to depend on who's "down the road" and if he thinks he can fix/help the -12s.

Given the right folks doing the heads, intake and valvetrain, I think that BMEP is doable, but I would ask my "down the road" guy. Cam is the last step after the good head work is done.

My $.02

Jon
 

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whats bmep stand for.
Brake Mean Effective Pressure.

That is "torque per cubic inch" measured at the flywheel, converted to psi. The engine actually produces torque, but does it at various rpms which calculates to hp.

BMEP (torque/cube) is the great equalizer when comparing any engines. If you can do 200 psi BMEP or 1.33 lb-ft per cubic inch at horsepower peak rpm you are doing quite well on an NA engine. In the case of a 427 @ 7500, that's (427 x 1.33) x 7500/5252 or 811 hp. Now if your 427 made 811 hp @8000 instead of 7500, the BMEP would only be 188 psi. It's more difficult to get BMEP at higher rpm because there is more fricton, windage, etc. reducing the Indicated (actual in-cylinder) torque/cube before it gets to the flywheel (Brake measurement).

A 358 cube Cup engine that produces 850 hp @9000 has a BMEP (@9000) of 209 psi. A 2.4L (146.4 cube) F1 engie that produces 750 hp @17,500 rpm has a BMEP (@17500) of 232 psi. A Pro Stock 500 cube engine that makes 1450 hp @9500 rpm has a BMEP(@9500) of 242 psi. I find those examples very interesting, becaue many folks try to compare hp/cubic inch without factoring in rpm (aka RicerMath).

In the above examples:

Your 427 = =1.90 hp/cube 200 psi BMEP
Cup engine = 2.374 hp/cube 209 psi BMEP
F1 engine = 5.123 hp/cube 232 psi BMEP
PS engine = 2.90 hp/cube 242 psi BMEP

I am most impressed by the PS engine due to it's high BMEP.


I hope this isn't thoroughly confusing.

Jon
 

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Just curious, but what does any of that have to do with helping a guy choose a camshaft? :confused: I think what he meant by "down the road" is later on in the future, and not literally "the guy down the road". Yes, I would have the heads done by a reputable porter to get the most from the combination. As I explianed in our PM's. Chooseing a camshaft now for an unported head will need a different one when the heads are ported and you will net the best results this way, even if it takes a little longer to get it together. Haveing to know what BMEP on paper does nothing with what you are trying to do. That info and a dollar still won't buy you a cup of coffee at the local gas 'n sip, and will only confuse most people to the point of getting the "confused dog" look when all they wanted to know is what cam profile to run. The money in the heads will be well spent and is where you will get your power and rpm potential, camshaft should be chosen after this. The camshaft I suggested to you was meant for a ported cylinder head with the correct runner design. Once that is achieved, the rpm you are looking for will follow.
 

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9.315 deck 3.875 stroke 4.185bore 6.25 rod in a dragster. 5800-6000stall bbc cam journals. motor will run on alcohol with rons injection. 15.5-1 compression. and i plan on crossing the line at 8000-8200rpms. heads are 15* brodix-12's 1.65/1.6 rockers.
flow around337 at700. if the flow sheet even belongs to these heads. planning on getting them ported down the road.
whats it take to get 800+ outa this combo.
Contact Chris at:
www.straubtechnologies.com
 

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Actually if you want a good camshaft for that thing someone needs to see the heads first. -12's can either be junk or awesome, and my rule on head porters is, the guy either kicks EVERYONES ass all the time and is expensive (CFE, Slawko), kicks NOBODYs ass and is well known.... (just look around) or kicks ass and doesn't want ANYONE to know who he is. (these are the guys I like)

If the heads are RIGHT and the cam guy knows this for sure you can make something rock..... the heads need to move much more than that.

The BMEP plays right into this actually.... the right camshaft with the right heads will get you the BMEP to make this kind of power and the old man is right on with how you analyize that. I just got home from a racetrack where the guys who build all the motors that came in behind us (they all were) and they all have no clue what BMEP is, or most likely what a thrust curve for a car is and we are so far off on the car setup being dead nuts it's not funny... well the funny thing is the ass kicking and being like that. Knowledge is directly related to power and results.

Worry about the heads first and throw a cam at it... then get the whole setup done and you will get what you are looking for. Otherwise you are just wasting money worring about a cam now when the heads are the BIG issue.

Bret
 

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Just curious, but what does any of that have to do with helping a guy choose a camshaft? :confused: I think what he meant by "down the road" is later on in the future, and not literally "the guy down the road". Yes, I would have the heads done by a reputable porter to get the most from the combination. As I explianed in our PM's. Chooseing a camshaft now for an unported head will need a different one when the heads are ported and you will net the best results this way, even if it takes a little longer to get it together. Haveing to know what BMEP on paper does nothing with what you are trying to do. That info and a dollar still won't buy you a cup of coffee at the local gas 'n sip, and will only confuse most people to the point of getting the "confused dog" look when all they wanted to know is what cam profile to run. The money in the heads will be well spent and is where you will get your power and rpm potential, camshaft should be chosen after this. The camshaft I suggested to you was meant for a ported cylinder head with the correct runner design. Once that is achieved, the rpm you are looking for will follow.
Kris,

I took the OP's question to be what would he have to do to the parts he has to make 800+ . My intent was to say that I don't think he can get there from where he is with just a cam. I probably should have said it that bluntly. I hate to make such a statement without explaning the background logic, hence the BMEP explanation. I would hate it even more to see him misled into thinking that just a cam wolud give him 800+ in the higher 7000s.

No offense, but if you really don't know what the heads do and the intake manifold lengths, cross section, etc. how can you chose valve events ("suggest a cam") that will produce 800+ (200 psi BMEP)?

IMO, way too many cams are sold on unsubstantiated promises.


"I hate it when that happens." ...Goose



Jon
 

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Kris,

I took the OP's question to be what would he have to do to the parts he has to make 800+ . My intent was to say that I don't think he can get there from where he is with just a cam. I probably should have said it that bluntly. I hate to make such a statement without explaning the background logic, hence the BMEP explanation. I would hate it even more to see him misled into thinking that just a cam wolud give him 800+ in the higher 7000s.

No offense, but if you really don't know what the heads do and the intake manifold lengths, cross section, etc. how can you chose valve events ("suggest a cam") that will produce 800+ (200 psi BMEP)?

IMO, way too many cams are sold on unsubstantiated promises.


"I hate it when that happens." ...Goose



Jon

Jon-
Don't get me wrong I do agree, I would recommend the cylinder heads being done first. He knows that as we have been talking in PM's discussing this. His budget is the main factor, and he knows that by camming it the way the heads are, he will be down on power and rpm. I did advize him however, that theengine will want a different cam profile for the heads untouched, and once they are ported, and what he should look for in a port to make the power/rpm that he is trying to achieve.
No offense taken here. It's all good. I am just more of a realist, and talking numbers like this can confuse alot of people just looking for basic answers. What engines SHOULD do is always different than what they WILL do, especially going from paper to actual performance. That's just me, everyone has their own way and I'm not knocking how anyone else goes about it.
 

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Jon-
Don't get me wrong I do agree, I would recommend the cylinder heads being done first. He knows that as we have been talking in PM's discussing this. His budget is the main factor, and he knows that by camming it the way the heads are, he will be down on power and rpm. I did advize him however, that theengine will want a different cam profile for the heads untouched, and once they are ported, and what he should look for in a port to make the power/rpm that he is trying to achieve.
No offense taken here. It's all good. I am just more of a realist, and talking numbers like this can confuse alot of people just looking for basic answers. What engines SHOULD do is always different than what they WILL do, especially going from paper to actual performance. That's just me, everyone has their own way and I'm not knocking how anyone else goes about it.
Kris,

Do you think a cam alone will make 800 fwhp on the OP's existing combo?

If not, what will it make? Please explain how you arrived at your number. Perhaps you have a lot more information on the engine than the OP posted.

How would you fix the -12s to get 800 hp (200+ BMEP)?

I'm not convinced that people are confused by numerical explanations of what makes power. Sometimes explaning thrust curves even helps folks understand how their car will accelerate with the new cam/heads/etc. It isn't just hype if one does it correctly and honestly and gives a customer credit for his ability to understand.

Just my take on the world.

Jon
 

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Discussion Starter #11
thanks for the info.
the csa on the heads is too small for what i wana do. gona get a cam that is used (not the recommended specs) put the motor together n go from there. use the track as my dyno n go from there.
no sense in buying a new cam when the heads are not where they need to be in the first place.
even though some of the things mentioned may be confusing , the more you ask the more you learn and someone else might get some insight into there project as well.
thanks for the info guys.
 

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Kris,

Do you think a cam alone will make 800 fwhp on the OP's existing combo?

If not, what will it make? Please explain how you arrived at your number. Perhaps you have a lot more information on the engine than the OP posted.

How would you fix the -12s to get 800 hp (200+ BMEP)?

I'm not convinced that people are confused by numerical explanations of what makes power. Sometimes explaning thrust curves even helps folks understand how their car will accelerate with the new cam/heads/etc. It isn't just hype if one does it correctly and honestly and gives a customer credit for his ability to understand.

Just my take on the world.

Jon

Do I think he will make 800hp with box stock -12's with just a camshaft? Absolutely not, and he knows that, as per our conversations. We are mapping out a program that will work for him with his budget, spending the money wisely, as to not have to do it twice.
He knows he won't make the power and rpm he is trying to accomplish without the heads properly done, but he wil only make the power his budget tells him he can make. I still feel he will make 750hp+ with compression, cubic inch, and the fact he has a decent head on it, even with a smaller camshaft. However, he can run more camshaft than what he thinks as small heads on a big inch engine usually require more camshaft to help move air through them to overcompensate, he just won't have the rpm.
How I arrived at it is from actual experience building them. Our real small 23* 434 engines make 750hp and need alot of camshaft to compensate for the lack of cyl head. Once the cylinder head was added, rpm and hp followed. We have made more with the 23* stuff on the grudge versions but requires a ton of money..which he don't have.
How I would fix them? I don't know about fixing them so to speak, but putting the right port in it, as well as chamber work and valve sizing all goes a long way, which we all know. It is the entire combination I take into consideration, and from experience and dyno testing and track testing that is what I base my advice on. Some guys do it differently...:cool:
 
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