Topic: Low Buck 750 Cylinder Head Project

[johno]

the ol play do makes life fast and easy for guide shapes

Hey johno, I prefer modeling clay to play-doh. 

Hey Scotty, mine is blue  and yours is pink     whats that saying 
johno

[Greg H]

I've been waiting for this bit  . How do you propose to establish whether your re-worked exhaust port will flow better than stock ?.

Flow bench should confirm that I guess.

A very good guess brother. That F2 exhaust doesn't need very much at all......a good size valve in there.
What I was alluding to was the fact that TurboD had stated in an early post that the flow bench he was using at home only had a vacuum facility .

I went back and added a thought to the post but good to know some of this stuff is sinking in Sorry about adding to my posts after the fact. The power was out and I was trying to use my wife's android My phone is text and calling only, and the text part is VERY limited

TurboD you are getting me pretty pumped about getting my head porting equipment. Between this post and following MReick's work I have enough to go by for the F3 head I want to use. I'll be sure to post a thread when I get into the porting side of things. I'm pretty sure the K6 head is a practice piece

TurboD this thread is very well put together and the knowledgeable are helping it along nicely. Thank you for your time, I'm feeling mighty edgamakated

[Greg H]

For some reason that last post didn't work out  . What I was alluding to when I questioned how TurboD was going to establish whether his work on the exhaust port had increased flow , was based on the fact that he had mentioned in an early post that he was only able to test intake flow on his flow bench .

[TurboD]

Greg To answer your question. Without currently having a exhaust flow bench here at home, I simply do not have a 100% way of being sure that the work has helped. That said, At this point I can only go off of the "trust" that the last 25 years of porting  heads , intakes , carbs etc. has taught me something.    In all seriousness the ports in these heads are somewhat basic and the tricks and techniques that have been around for years easily apply to them.

Adam My hope was that this thread would be helpful and show everyone that with a little work, that a decent bit of performance could be gained by someone at home with a few basic tools.

[Greg H]

TurboD,  I'd  say that you've definitely proven your hypothesis . Also , as my old man used to say "there's no substitute for experience" 

[EnginebyAdam]

I was re-reading "cylinder head airflow figures" http://forums.sohc4.net/index.php?topic=105411.50 and was wondering how much variation exists between flow benches even when both are tested @ 10"?

The reason I ask is because the '72 std K2 cyl head with light emery clean up in the "cylinder head airflow figures" shows .400 lift - 65 cfm  on the inlet. A picture of the K2 port is in the link I posted. TurboD's F2 head shows .400 lift on the inlet, before-54.3 cfm, basic cleanup-57.7 cfm, light reshaping- 60.0 cfm. I would of thought that the F2 head would be showing better flow numbers right out of the gate.

Was hoping to get a little clarification as to whether or not this is a difference in flow bench's or the K2 head has more work done to it than TurboD's F2 head at time of testing?

Cheers.

[TurboD]

Adam Like I posted in the first post, numbers from bench to bench as well operators will vary. My bench that I used for testing the F2 head is slightly on the conservative side (a little Stingey Lol). When I used to do work, I never had a problem if someone took something I worked on and retested it and got better numbers. I could add 2-3 CFM to my numbers posted and not be out of line.

I can't comment on the K2 head, I will say the standard for a stock KZ 900/1000 head with 36mm valves tested at 10 inches and .500 lift is typically in the 67-68 CFM range,

[EnginebyAdam]

Adam Like I posted in the first post, numbers from bench to bench as well operators will vary. My bench that I used for testing the F2 head is slightly on the conservative side (a little Stingey Lol). When I used to do work, I never had a problem if someone took something I worked on and retested it and got better numbers. I could add 2-3 CFM to my numbers posted and not be out of line.

I can't comment on the K2 head, I will say the standard for a stock KZ 900/1000 head with 36mm valves tested at 10 inches and .500 lift is typically in the 67-68 CFM range,

I kind of figured that was the case from bench to bench, so that much makes sense. The thing that is throwing me for a loop is that the k2 head is flowing better than the F2 head at the same lift and also tested at 10". The work done looks along the same lines. Everything I am reading suggests the F2 head has better initial flow numbers than any other stock head for the cb750 sohc. So even with the difference in benches the K2 should not flow better or even the same, even providing the two benches have a 5 cfm difference in numbers, with the same work done.

It looks to me the two heads have similar work , maybe a little less on the K2. That being said I'm going off pictures and limited experience. Johno was the work on the K2 head similar to what TurboD has performed? I'm just trying to get my head wrapped around how all this works and why the numbers are what they are.

Cheers,
Adam

Edit: I apologize if this was a little of the original topic.

[johno]

I was re-reading "cylinder head airflow figures" http://forums.sohc4.net/index.php?topic=105411.50 and was wondering how much variation exists between flow benches even when both are tested @ 10"?

The reason I ask is because the '72 std K2 cyl head with light emery clean up in the "cylinder head airflow figures" shows .400 lift - 65 cfm  on the inlet. A picture of the K2 port is in the link I posted. TurboD's F2 head shows .400 lift on the inlet, before-54.3 cfm, basic cleanup-57.7 cfm, light reshaping- 60.0 cfm. I would of thought that the F2 head would be showing better flow numbers right out of the gate.

Was hoping to get a little clarification as to whether or not this is a difference in flow bench's or the K2 head has more work done to it than TurboD's F2 head at time of testing?

Cheers.

There is more difference between head castings than flow benchs eg that K2 head I flowed was picked from 4 heads, there was up to 5mm difference between the castings in the port position and shape.........thats a lot
So if you just tidy up the port your following the castings and getting what you got
johno

[EnginebyAdam]

Okay that makes some sense. I'm just trying to take in all the information I can. I'm still learning about port shape and all that. The most I've done so far is pocket ported my dohc 750 so I've got lots to learn.

[cbr954]

I have seen large differences between ports on the same head also.  I have a home made flow bench that is basically just a manometer.  I use it just to keep track of impovements when I change something in the port, so I dont have any cfm numbers.  But it is very interesting to see how much difference in flow there is just between ports on one head let along beg differences between different heads.

[scottly]

the ol play do makes life fast and easy for guide shapes

Hey johno, I prefer modeling clay to play-doh. 

Hey Scotty, mine is blue  and yours is pink     whats that saying 
johno

Every pussy I ever poked was pink; never poked a blue one??

[HondaMan]

Wow, port-shaping deja vu!

http://cb750k2.honda4.nl/Technical/porting/Porting_the_Honda_Head.htm

My book:
Chapter VI, pages A-9 thru A-15 .
 
I remember that Branch Flowmetrics article well: it was what got me started with the 750 porting in 1972 or so.

The one thing I would add that was intimated in the Branch article, but not detailed: with the stock carbs and intake hoses, a cam lift of .335" was already more than the head could suck in, given the stock valves' shape (unpolished). I still believe this was the thinking "Pops" Yoshimura applied to these heads with his 85- and 90-HP cams, at .335" lifts. To go beyond the limits imposed by the valve shape, a thinner stem was required, along with a flatter top side: surprise, this is the F2/3 valve and the later aftermarket types.

[Jerry Rxman Griffin aka MuthaF'er]

the ol play do makes life fast and easy for guide shapes

Hey johno, I prefer modeling clay to play-doh. 

Hey Scotty, mine is blue  and yours is pink     whats that saying 
johno

Every pussy I ever poked was pink; never poked a blue one??

Yeah but I bet they were blue when you finished! 

[dragracer]

What kind of tree is that in the background of the picture?

[bear]

A good old Ozzi banksia by the look of it.
Johno?
Are you a bit of a gardener Frank?

Cheers,
Brian

[dragracer]

A good old Ozzi banksia by the look of it.
Johno?
Are you a bit of a gardener Frank?

Cheers,
Brian

Just curious about native flora. Especially ones i've never seen before. That one just caught my eye.

[johno]

yes a Banksia, ozzy native.    They have unusual flowers and flower prolifically if you look after them........alas I dont.
But they are different to most flowering trees, the low stuff along side is the famous ozzy saltbush, zero maintanance
my style of garden
johno

[Sam Green Racing]

Are they common in Aus Brian?

Sam.

[bear]

Are they common in Aus Brian?

Sam.

They are Sammy, and they come in many colours and varieties.
Our native birds luv 'em.

Cheers,
Brian

[bear]

The kayos of our garden doesn't hold a candle to your ordered "English Garden" Sammy but it's a haven for the lovely Evelyn and I.

We are fighting a loosing battle against the 40deg.C heat at the moment.

Cheers,
Brian

[Sam Green Racing]

That's nice Brian, wish it was summer here. My garden looks a real mess in winter due to grubs messing up the lawn and the fact that there are no leaves on the trees.
The reason I asked about the tree was because I have a sapling and I believe it is some sort of tree native to Aus. I've asked my son to photograph it so I can send it to the RHS to find out what it is.
I've got a sneaky feeling it might be a Wollemi Pine but I can't be sure.
When I found it, I thought it was a fern but as it started to grow, it started to shoot out branches like a tree.
I guess only time will tell as long as it don't snuff it.

Sam.

PS, sorry for the hijack.

[PeWe]

Nice climate for a biker! :-)
I'm waiting for warmer weather and dry roads, +10-15C so I can perform road tests on by me restored CB750 I brought back in my garage from a friends barn autumn 2009. Maybe April.... :-(

[johno]

Sam !
At least Brians lawn is nicely mowed, NOT like  Retro's  effort

Mind you, my moneys on Ev pushin the lawnmower, Brian's always banging his leg or foot racing to get out of it.
johno

[dragracer]

The kayos of our garden doesn't hold a candle to your ordered "English Garden" Sammy but it's a haven for the lovely Evelyn and I.

We are fighting a loosing battle against the 40deg.C heat at the moment.

Cheers,
Brian

Very nice garden Brian. After you told me the name of the tree, i spent 30 minutes reseasrching it on the web. I'd like to try growing one here in our climate- it seems the tree is hardy enough to take the fluctuations and would be suited for the soil conditions here as well.