Topic: cylinder head airflow figures

[johno]

Hi Guys,
Im hoping someone out there can help me with my engine performance software, in mid 70s  I used have a specialist porting business where I tried lots of weird and wonderfull port shapes including a raised inlet port but that was before I purchased a flow bench, after the flow bench became my life I never got round to flowing any of the racing cb 750 honda ports I done as I had moved onto automotive racing chasing the dollars.  Now I'm an old fart and have long since sold my flow bench and dyno but still own my 72 K2 i purchased knew but looking at a late life crisis by having a go at the 900cc class salt lake racing in Australia.
Naturally I have targeted the softest class and am fooling around with some of my old engine performance software trying to work out how it might pan out.
What I'm hoping for is some flow rates from those of you lucky enough to have had a play with some decent heads on a flow bench. The fastest Honda engine I built had a raised port with some carbies from TZ yammy 750  so unless someone out there says otherwise will probably go down that path again.
Help, sling me some flow rates to enter into my software.

Cheers Johno senior

[Elan]

MRieck here on the forum is the porting Guru. He'd be able to chime in I'm sure. Unless it's his trick of the trade

[turboguzzi]

mrieck might have some specific numbers for you, but in my years in sohc4 never saw anybody giving actual CFM's at X inches of water and all that stuff.

In kzrider forum, there is a pro tuner called larry caravan (larryC) who often gives away some of his CFM numbers. as big zeds are two valvers too, some of that data could serve you as reference.

But if you really want to talk with the pros (other than mike ), you should register to the speedtalk.com forum, plenty of people who build their own flow meters and experiment in there.   

TG

[scottly]

Here is an article I found a few years ago. In case you can't read the numbers at the top of the chart, it's 12" H2O, 29.92 barometric, 70 degree temp corrected.
http://draftcycleworks.blogspot.com/2010/09/porting-honda-head.html

[NitroHunter]

In kzrider forum, there is a pro tuner called larry caravan (larryC) who often gives away some of his CFM numbers. as big zeds are two valvers too, some of that data could serve you as reference.

I think you mean Larry Cavanaugh. He does some very nice work.
 
I saw flow/lift figures on one ported F2 head, it flowed 78cfm @ .375 lift - but I don't remember at how much pressure.  More lift didn't increase the flow any on that particular head.

[johno]

Thank you gents , made my day waking up to a good dose of sohc info. Makes an old man smile.
So the bench mark numbers for cb 750 cylinder flow so far are;
Larry Caravan oops Cavanah  ..................... 78 cfm @ .375
Jerry Branch ( wonder if he is still kicking) ....75cfm @ .400

Very similiar hey !  so lets say they are the numbers for a good old fashioned port job. My next challenge is to compare to a raised port  so I can decide which way to go with my head. A lot hinges on the head port choice for me as it means the stock framed class i,m looking at I will have to cut the horizontal frame tubes to fit in the raised carbs if its a high port and I'll have to buy new carbs. I have a few old RC Eng bits from the 70,s still in the shed and the carbs I have are a RC Eng set of Webber DCOE 40 with 32 venturis  ( too big physically for raised ports ) so for me the choice of head format will make me decide which carbs I can use.
I am kind of hoping that there wont be much difference in the flow rates between the style of ports because it will save me a lot of work making  another high port and wont have to buy another set of  down draft style carbs.

Some good news also is that I have managed to contact a friend of a friend today that has the Honda cb 750 engine I modified in the mid 70,s with the raised inlet ports. It is in a road racing sidecar that hasnt been used for over 25 years so I am trying to convince him that I will come out of retirement and freshen up his motor if he lets me get the head flow tested, fingers crossed.

One of the reply comments was that some of the head gurus might have trade secrets but I,m sure anyone who is in the know would realise the cfm figures are just a number without other relevant information, big numbers are easy to get, just takes bigger valves and bigger ports. The real difference between the men and boys is getting required numbers with the smallest ports. For me big holes is for horsepower ( if lucky) and small ports is for torque and my favourite saying is a play on words.

Horsepower is for the bar and torque is for the track, maybe the opposite to what one may expect.

I'l give you an example ( one of many I can assure you)

In the mid 70,s I was hooked on Hondas and had customers who had state and a national record at two local drag strips  in south Australia and feeling confident I was getting things done right.. One of them a mafiosa kind of guy, Mark Skehan went over to the USA near the end of their drag season and after the last race approached the boys from the RC Eng pro stock bike of Vance and Hines  Kwaka 900 and purchased as it returned to the pits on the proviso it was his as is and he could take it right then and there.

He shipped it back to South Oz and I still remember just staring at it in awe, it also gave goose bumps when we started it up and done a test run up the strip. It was the best in the world and was simply a credit to those 3 guys who put it together. I though hell I,m behind the times here I and need to find a benchmark for my headwork so I ordered a heap of go fast bits for my shop and two cyl heads race ported from RC  to see what the best guys in the world could do.  Now before I offend anyone I must qualify what I,m going to say is I learnt from buying those heads the difference between a special race job and a run of the mill  job, and I got an important lesson in retailing. The heads i purchased had big momma shiny holes nothing like what I had been doing and so I couldnt wait to build an engine with them and pick up all that extra horsepower.   Well the lesson was learned, big holes and flow rates didnt work for me as I thrashed around changing timing , cams carbies , etc eventually give the head a flick and put on a" jerry Branch style head for a good result.

Anyway just an old bloke remanissing about the fun I used to have, I'll keep you gents posted on the raised port numbers. Cheers all

[754]

 Jerry Branch, far as I know still around..was at Bonneville in 09. (& probably since). doesnt work in the shop from what I hear.

 I think sometimes a specific head works better with a specific  "combination"..start sustituting..results change..

 The road to "Worked Well", is littered with pieces  of "Did Not Work as Well"

[NitroHunter]

  The road to "Worked Well", is littered with pieces of "Did Not Work as Well"

+ 100         

[754]

 The road to "Worked way too well "is littered with pieces of stock CB750 pistons.......snicker..lol..

 Nitrohunter knows what I mean...

[scottly]

I have are a RC Eng set of Webber DCOE 40 with 32 venturis  ( too big physically for raised ports ) so for me the choice of head format will make me decide which carbs I can use.

The choice is clear to me: screw the raised ports, and run the Webers!!!

[Retro Rocket]

Welcome Johno, RC's son is a member here, he's in the middle of restoring the triple Honda engined drag bike Russ raced in the 70's...

http://forums.sohc4.net/index.php?topic=99452.0

Its a long thread but well worth a look.....

[johno]

Thanks for making me feel welcome guys, its not easy dealing with these super hi tech things called computers.  I noticed you folks a pretty pic to help ID you, its cool I have been putting some thought into it today so I,m hoping to be able to load it on tonight.

Scottly re carbs yeh tempting, especially after you see my pretty pic ID.

Just to make you blokes envious I will attach some info re the salt lake record and class regs I am looking at.
The reason for your envy will be in the softest class I can find the 900 modified Gas or Fuel  Gas has no record at all and the fuel record is only 103mph I think, so dont pack your bike and come to OZ and cut my lunch.
But if you do plan to let me know and I would welcome you and make the journey easier, accommo, travel,  etc

The big attraction is it should be a chance for the greatest motor ever built in 1969 SOHC engine grab a record in the year 2012 or 2013, wouldnt that be cool.

Link is google ... Dry Lake Racers Australia..... select   "about the DLRA " ....then select DLRA rule book and down load, read pages 47 to52.

Then for the records.. page 60 the 900 cc class.

What do you reckon guys , think the SOHC can do the job ?
I,m prefering gas as its easier to deal with .
I,m excited fellow Honda enthusiasts.

Also if Jerry Branch is still out and about its amazing, he was a really really old fart when I was young, must be the calming effect of constant grinding keeping him going, especially the Honda heads.
cheers gents.

[bear]

The big attraction is it should be a chance for the greatest motor ever built in 1969 SOHC engine grab a record in the year 2012 or 2013, wouldnt that be cool.

Link is google ... Dry Lake Racers Australia..... select   "about the DLRA " ....then select DLRA rule book and down load, read pages 47 to52.

Then for the records.. page 60 the 900 cc class.

What do you reckon guys , think the SOHC can do the job ?
I,m prefering gas as its easier to deal with .
I,m excited fellow Honda enthusiasts.

Good luck with that Johno.
The way Lake Gardner's shaping up it may not dry up till 2020.

Cheers,
Brian

[BLUE71TURBO]

Welcome Johno, RC's son is a member here, he's in the middle of restoring the triple Honda engined drag bike Russ raced in the 70's...

http://forums.sohc4.net/index.php?topic=99452.0

Its a long thread but well worth a look.....

               
                      Hey Rocket Man,  Don't forget Russ Jr is also restoring the Sorcerer double engine dragbike also.      

[Retro Rocket]

Welcome Johno, RC's son is a member here, he's in the middle of restoring the triple Honda engined drag bike Russ raced in the 70's...

http://forums.sohc4.net/index.php?topic=99452.0

Its a long thread but well worth a look.....

               
                      Hey Rocket Man,  Don't forget Russ Jr is also restoring the Sorcerer double engine dragbike also.      

Gday bud, no i hadn't forgotten , just didn't want an information overload....

[johno]

Hi Gents,
The old honda engine with the hi ports arrived today, a flash from the past, not sure what the year was, mid 70s be near enough.  My plan is to spec the engine on the weekend , cam profile, comp ratio, clearances etc the the best bit will be flowing the head during the week.

Dont worry Scottly it wont be log before we find out if the webbers get the nod or retired.

I tried to down load some pics but they stall badly and I think they are too big or pixels or something, says Johno the technosaurus.  How do you dumb down these pics from 3.6 mb to forums max side 1,000 kb ?

Cheers all

[LesterPiglet]

I tried to down load some pics but they stall badly and I think they are too big or pixels or something, says Johno the technosaurus.  How do you dumb down these pics from 3.6 mb to forums max side 1,000 kb ?

Cheers all

Open a free photobucket account  www.photobucket.com and upload pics there. From there you can post to anywhere.

[754]

 just notch frame/tank..get them Webers on there..

 A member on here is furiuosly searching for his flow info that came with his Branch sohc head..

[johno]

Thanks Lester who and 754.
I spent a few hours last night trying to down load the pics of the engine, I hope I can work it out as I think you will find them interesting.
Lester I uploaded th pics to bucket do da then got lost but ended up downloading them back to me at smaller kb thingsy, I wil try send tonight.
Cheers
Johno

[trueblue]

If you manage to get them onto your photobucket account, copy the IMG code from the thumbnail in your album, it looks like this
 [IMG.]http://i1096.photobucket.com/albums/g339/a_z862/P2150047.jpg[/img]
copy that where you want the picture in your post and it will look like this

[mick7504]

G'day johno and welcome mate.
Being an ex Port Pirie boy myself, your not that far away from the Sulphur City with the BHAS lead smelter back in the day.

Berri holds a lot of fond memories from when we were kids.
We spent quite a bit of time there and also other places around the Murray water skiing/fishing etc and doing the general tourist bit way back in the 60's & 70's.
The old man and his mates used to have ski boats with the old flat head Ford motors or a marinised 308 donk if you had the bucks to afford one  back then.

An old mate of mine comes from Berri originally and lives on a farm up near Pirie these days. (Telowie)
You may know him, Ricky Ireland (Riverboat Rick as we call him) and we all had a bit of Whyalla in us from the early 70's when we were all hairy arsed apprentices. 
Anyway, it's good to have you here with us mate.

Mick


 

[johno]

gday Mick,
Thanks for the hello, must have been ESP or something , I was just reading a whole lot of your comments on a 900 build thread.
Its a small world Mick. I done my crime and time at BHP in Whyalla, I would have been just finishing as you were starting.  For me it turned out a good opportunity as the training there was diverse and good compared to a couple of mates in a small garage that spent more time cleaning the floor and getting parts for the first couple of years. As a mechanic I got to spend time automotive, bikes , machine shop, boilermaking , jack of all trades master of none.   The best part was I done everything in my power to smooth into the engine and dyno rooms where I spent the last two years of my apprenticeship.   I started building racing 750 hondas for friends in 3rd year , hot street bikes, mostly drags and occaisonally speedway sidecars.  Built decent street cb 750 drag bike , silver colour, for a guy I worked with Mick Treloar, not you is it?  BHP would have kittens if they new the hours of machining that I put in on night shift.  They had some nice equipment.  I left whyalla and went to Europe for a while changing tyres and oil for F1 team that had the smallest budget at the time ( hence thats why I was working for them) and spent more time shooting rats with a slug gun filling in time between races than doing good engineering stuff. Come back and decided I just wanted to build race motors etc , great life , no money and enjoyed every minute of it

I feel at home with tools in my hand but this dam computer is driving me nuts,  3 days of trying to place some engine pics on the thread , good advice from a couple of blokes but still turning to #$%*.  At my age the smart money is tomorrow I,m gunna pay some IT genious to hit a few buttons and make it work.

Thanks for saying hello Mick, I look forward to some feedback from you when I get into full swing on this salt lake rocket.  Flowing the head next week to make some decisions, might be better if I just lease your engine for a couple of pretend dyno runs and not tell you where the dyno was.  I must say I have been really excited about this forum, feel like a kid in a candy store with all these interesting inputs, really good info , just generates so many flash backs for me.
cheers

[mick7504]

G'day johno

The Mick Treloar you built the drag bike for is a different Mick.
There are just so many names and faces from over the years that it is hard to remember everyone from years gone by.

Although from time to time, people will drop in for a visit up here in Darwin and say "you remember me?" and that could be going back from nearly 35 > 40 years ago.
They were magic days back then.
We were really only young fellas with no money and no fear back then but we had a ton of fun.

A mate up here in Darwin wants to have a crack at the LSR on a 1965 CD175 Honda when he gets it together.
That will be at Lake Eyre or Lake Gardiner.
His biggest challenge will be to get rid of his beer belly if he wants to be in with a chance. 

I hope that you get the Photobucket thing sorted out mate and get some pictures up here for us all.
It is quite straight forward to do once you see how it's done.
Looking forward to it.

Mick

[scottly]

johno, to the best of your memory, were the Webers with the 32mm chokes properly sorted out? I would like to know what jet sizes are in those carbs. Thank you in advance for adding to the knowledge pool!

[johno]

Hi Scottly,
I purchased them new in mid 70,s  from big Barry Taylor at Capalaba in Queensland who was importing RC stuff and the MTC distributer for OZ. Lovely bloke Barry and his wife twinkle toes if I remember. I drove up from Whyalla to pick up the goodies , a lazy 4,000 kilos.  I remember it well as their hospitality was amazing , bundled me into the back of a big chevy impala or something and we went out to the local "drive in theatre" and watched "blazing saddles", Big Bazz was trying to show the actors in the fart scene who had the most hot air.
Hell he done a good job.
 re the webbers I run them on two bikes I had, both I sorted out with an exhaust gas analyser strapped onto the bike and went for a blast out the road.
first a stock piston with ported head , mild cam, 4 to 1
Chokes 32mm
main jet 115
Emulsion tube F11
Idle jet 50 f 9
aircorrectors 200

second bike;  812, Yoshy bottom end , ported , valves, yoshy cam and springs, 4 to 1
chokes 32mm
main jet 120
emulsion tube F16
air corrector 150
idle jet 45 f 9

the acclerator pumps are big shooters, I remember one day in the workshop having water pistol type shootout with a customer after him showing how far they shoot. lucky we werent smoking hey.

Seriously take it easy on the throttles if starting , easy to flood.

I also fitted a couple of sets of Dellorto side draught carbs distributed by Lynx in OZ, the street guys liked them cos they had filters , good for the street but I had trouble getting a long term reliable seal on the bloody pulsating manifold rubber connectors.  The jetting from memory was similiar to the webbers except the idle jets and I cant remember.

On the webbers I used to run my Girl F stockings for rock stoppers, was a good excuse to get them off some days. Wonder if the modern panty hose types are as good as the old stockings.

Probably why I prefer webbers.

Hope this helps Scottly