Head CFM vs. HP per c.i.?

[thumper 823]

To relax the heads for the long haul
There are some tricks I use and no secret.
  A man that does not know much will not share much.
I may miss a step as reflex habit abound here.
One, , always drill out the guide as much as you can to make it an EZ pull.
use a threaded puller rather than a driver.
Heat the head first B4 the extraction.
This way you do not need to OS the guide ..usually
I like dry ice and to hear the guides scream.
Literally.
try it.
Cryogenics is nothing new. A very tight guide to head fit helps cool the valve better.
You want the tightest fit posable without hurting the head.
Two,-
Next, you want to heat the head in the oven and install the cryogenic guide of your choice.
Dont use a beater to install them. Use a push or pull method.
Let cool, and heat a few times.
I do it six times with banging the heads on wood blocks as they cool.
I feel this makes everyone comfy for the long haul, plus we do this on out 911  engines.
It will not hurt anything and I am sure it helps.
We don't want the guide to move at all after it has been fitted for the valve, so it is all an insurance policy.
If it does it no longer will seat and be a leaker.
I would like to know how you guys do this also.

[1workinman]

To relax the heads for the long haul
There are some tricks I use and no secret.
  A man that does not know much will not share much.
I may miss a step as reflex habit abound here.
One, , always drill out the guide as much as you can to make it an EZ pull.
use a threaded puller rather than a driver.
Heat the head first B4 the extraction.
This way you do not need to OS the guide ..usually
I like dry ice and to hear the guides scream.
Literally.
try it.
Cryogenics is nothing new. A very tight guide to head fit helps cool the valve better.
You want the tightest fit posable without hurting the head.
Two,-
Next, you want to heat the head in the oven and install the cryogenic guide of your choice.
Dont use a beater to install them. Use a push or pull method.
Let cool, and heat a few times.
I do it six times with banging the heads on wood blocks as they cool.
I feel this makes everyone comfy for the long haul, plus we do this on out 911  engines.
It will not hurt anything and I am sure it helps.
We don't want the guide to move at all after it has been fitted for the valve, so it is all an insurance policy.
If it does it no longer will seat and be a leaker.
I would like to know how you guys do this also.

apples to pears I guess but I was watching a fellow on u tube go into some head work where he stated that some of the guys built a new engine ran in on the dyno for a while then pulled the heads down and reworked the heads as now the head have heat cycled and the valve seats would be concentric with the guides or I believe that is correct

[thumper 823]

That seems more OCD then needed...but to each their own...

[kd]

It sounds like that was a symptom of poor fitting (as in maybe worn) valve grinding tools or guides being changed and no follow up seat work?     There always will be some valve shake due to stem to guide fit tolerance so I don't really see what is to be gained if the initial work was done accurately.

[Don D]

What does this have to do with head flow and horsepower

[1workinman]

What does this have to do with head flow and horsepower

None I guess as I have not seen any suggestions on for example what is needed to make 150 hp in a 124 inch engine . I have an idea but only that 

[thumper 823]

What does this have to do with head flow and horsepower

None I guess as I have not seen any suggestions on for example what is needed to make 150 hp in a 124 inch engine . I have an idea but only that

Cyanide, suicide, and being cynical have the same results.
Tort comments for a thread that meanders is not  not such a bad thing.
There is a lot of merits and a whole bunch to be gleaned here.
For instance -you just aske about 150 Hp from a 124-inch engine.
That should be EZ as all you are asking for is 1.25 HP per cube.
That's pretty conservative in the big picture of things.
Crotch rockets and hitech engines produce way more  (@ a way higher RPM )
The devil is always in the details, and that part is the confluence of some math and some luck.
The tight guide to head assembly just talked about is a detail,
and a very good stem fit will help keep the hell created in there cool.
A proper cam, a fuel map generated and spark advance to follow it and the RPM up the scale should net you the results.
Once past the basics,  HP in most arenas cost 100 bucks per, its just a matter how much you want to spend.
With good heads ETC , 10.5/1 CR,  I am pretty sure you would be there.

[TJAH]

Is there a standard of how much HP you should be able to achieve given the amount of CFM your heads flow? Meaning, if your head flows 300CFM you can achieve (x) hp ci.

This was(?) Superflows formula. I could not find the document anymore from their site, https://www.superflow.com/

Potential hp = [0.256 x cfm @ 28 in. water] x no. of cylinders , at the crank.

I'm not saying that this is the whole truth, but should give you a ball park figure.
Propably the headporters here disagree, because none of the Superflow operators did bring this up ?

[N-gin]

There are some combos here that I've seen have 300 CFM put out 115 hp while others that top out at 270 CFM and lay down 170hp.

Like others say it is the whole picture, Dyno included.

Way too many variables.

[Don D]

 

[Barrett]

There are some combos here that I've seen have 300 CFM put out 115 hp while others that top out at 270 CFM and lay down 170hp.

Like others say it is the whole picture, Dyno included.

Way too many variables.

I do understand it's the whole package but I doubt 270CFM will get you 170HP.... Unless, it's a very happy dyno..

[rigidthumper]

Or a hair dryer attached to the intake

[build it]

To relax the heads for the long haul
There are some tricks I use and no secret.
  A man that does not know much will not share much.
I may miss a step as reflex habit abound here.
One, , always drill out the guide as much as you can to make it an EZ pull.
use a threaded puller rather than a driver.
Heat the head first B4 the extraction.
This way you do not need to OS the guide ..usually
I like dry ice and to hear the guides scream.
Literally.
try it.
Cryogenics is nothing new. A very tight guide to head fit helps cool the valve better.
You want the tightest fit posable without hurting the head.
Two,-
Next, you want to heat the head in the oven and install the cryogenic guide of your choice.
Dont use a beater to install them. Use a push or pull method.
Let cool, and heat a few times.
I do it six times with banging the heads on wood blocks as they cool.
I feel this makes everyone comfy for the long haul, plus we do this on out 911  engines.
It will not hurt anything and I am sure it helps.
We don't want the guide to move at all after it has been fitted for the valve, so it is all an insurance policy.
If it does it no longer will seat and be a leaker.
I would like to know how you guys do this also.

Good practices Thumper. I'll only install guides and seats with liquid nitrogen in my own stuff. I have 3 sets of moldstar 90 seats for some raw b2s thatre just itching to get touched, 2.300" intakes, 1.700" exhaust valves. I wanted to run a 2.350" or bigger intake, and a 1.600 or smaller exhaust but someone I know personally with a lot of experience with UPM heads didn't like it at all; I respect this guy, he's a mentor and a friend.

OHC or block machine aside, where a torque plate is necessary for most procedures, and unbolting the plate, letting the work return to room temp and retorquing at each successive step is absolutely necessary; I'm not seeing much "binding" necessitating a "relaxing" process. That includes extreme duty max effort two valve applications.

Now, if serious welding is part of the program, particularly around the seats or guides, I have a different opinion. In that case, first, I machine shy of where I want to end up, and expect it to run like "Potty mouth". I might even use a single angle cutter for a seat to come in and leave all else alone (talking about seats only). I'd run the engine for 500-1000 miles and tear it down for inspection. The goal here would be adequate heat cycles for the probable but not inevitable movement to take place. Then I'd tear everything down, inspect, measure, final machine, and measure again.

If you keep pushing I think you'll achieve a level of performance higher than you expect.

[thumper 823]

Hay !
I am glad someone agrees with a way to do this! LOL
After studying Metallurgy for a whilst  (welding school about 40 years ago ) LOL
One quickly learns there is much to be learned.
There is no end.
There is no end, to the little details that make the difference between satisfactory and excellent.
I have not ever tried welding up my heads ..yet.
You have me there.
Raised ports are looking like another interesting project.

[build it]

Hay !
I am glad someone agrees with a way to do this! LOL
After studying Metallurgy for a whilst  (welding school about 40 years ago ) LOL
One quickly learns there is much to be learned.
There is no end.
There is no end, to the little details that make the difference between satisfactory and excellent.
I have not ever tried welding up my heads ..yet.
You have me there.
Raised ports are looking like another interesting project.

There're some very interesting things you can do with welded heads, flow, spring, chamber, valve train wise, and still fit in an OE frame. No one will like it though because it's based on efficiency and not that atypical bulk cube approach.

[Don D]

There are some combos here that I've seen have 300 CFM put out 115 hp while others that top out at 270 CFM and lay down 170hp.

Like others say it is the whole picture, Dyno included.

Way too many variables.

I do understand it's the whole package but I doubt 270CFM will get you 170HP.... Unless, it's a very happy dyno..

Tounge in cheek.
Agree on that too a bit of an exaggerated statement but I get his point

[thumper 823]

Hay !
I am glad someone agrees with a way to do this! LOL
After studying Metallurgy for a whilst  (welding school about 40 years ago ) LOL
One quickly learns there is much to be learned.
There is no end.
There is no end, to the little details that make the difference between satisfactory and excellent.
I have not ever tried welding up my heads ..yet.
You have me there.
Raised ports are looking like another interesting project.

There're some very interesting things you can do with welded heads, flow, spring, chamber, valve train wise, and still fit in an OE frame. No one will like it though because it's based on efficiency and not that atypical bulk cube approach.

I would love to see some pics  of your work.!
I will warn you,
iI I like them I will steal your ideas! LOL
Like I said my heads are off right now ....Between Sturgis overhaul.

[build it]

Thumper, as I said earlier it will be a while before I can afford the welding. It could be a few months or more, but I'll gladly send some progress pics once I put chips on the floor. I'm just wrapping up an education in high performance, and looking for work in the field with either strong leadership or a low hourly rate and a lot of hours. FWIW, whatever I send will be backed up by cold hard data, nothing else.

[thumper 823]

I tried to PM you..
My Nephew tigs, we are both gearheads.
I know I can get him to fill what you want for nothing.
He just needs to know where and how much.

[build it]

I tried to PM you..
My Nephew tigs, we are both gearheads.
I know I can get him to fill what you want for nothing.
He just needs to know where and how much.

Thank you for the generous offer, but I have to pass. I've got enough scratch to get me where I need to go in 3 weeks, buy a tent, and get a storage unit. It's looking like Florida, Indy, or possibly Phoenix; I prefer the second two but originally planned on being further west or the Carolinas. Not many shops hiring, so we'll see how it turns out. I give you my word that I'll update you the second I make progress.

[N-gin]

There are some combos here that I've seen have 300 CFM put out 115 hp while others that top out at 270 CFM and lay down 170hp.

Like others say it is the whole picture, Dyno included.

Way too many variables.

I do understand it's the whole package but I doubt 270CFM will get you 170HP.... Unless, it's a very happy dyno..

sorry  150 hp!

http://harleytechtalk.com/htt/index.php?topic=91480.0

[thumper 823]

There ya go 1.36 per cube .
A very doable number,

[1FSTRK]

So we have an higher rpm, street strip 110 ci example of 1.36 HP/CI with .545 HP/CFM.

[Johnwesley]

Oops

Wrong thread

[1FSTRK]

There are some combos here that I've seen have 300 CFM put out 115 hp while others that top out at 270 CFM and lay down 170hp.

Like others say it is the whole picture, Dyno included.

Way too many variables.

I do understand it's the whole package but I doubt 270CFM will get you 170HP.... Unless, it's a very happy dyno..

sorry  150 hp!

http://harleytechtalk.com/htt/index.php?topic=91480.0

N-gin you get the concept. A 110 CI making 150hp is 1.36 HP/CI and the heads flow about 282cfm so we are at .531 HP/CFM
Once we have examples of what is possible we can look at what is going on with similar combos that do not produce as well. The happy dyno and flow bench BS is always brought up but really is just a diversion from the subject . If you gather large data samples (like we have here on HTT) you can always disregard the very top and very bottom numbers and still have plenty of usable data to draw from when looking for trends. You also can only draw so much from programs and info gathered from autos or any other types of engines because of the unique design of the HD V-twin engine. Your not going to get a formula that spits out the HP of an engine just by plugging in the cfm number of the head from a flow bench. What you can get is an idea of what should be possible from a given CI V-twin engine of the HD design with a head that flows X cfm and when the engine comes up short you know something is wrong and you need to find out what. This is the very basis for questioning the performance of the M-8's. They have flow but as a group the power is not on par with other HD engines when you compare similar stages of builds using the hp/cfm numbers.