Hi,
What are you wanting to achieve Vince ?
More power ?, more torque ? and in what rev region ?
You have to flow the head with a purpose. What is your goal ?
You cannot undo this procedure. Be sure you find someone who knows why and what he is doing instead of someone who know what he did. It seems to be the same but it's not. Ask if he did a CB72 CB77 head before, ask if you can talk to a customer about the results, and if it was what he expected. The best example would be a before and after dynorun curves.
A flow bench isn't the most important tool when flowing a head, it's the head (mind) of the guy who has to achieve what you want from him.
Consider a mild flow, and don't use something as a fixed price, I bet that wasn't the case with your chain cover either. That doesn't mean that it has to be expensive, but that the guy doesn't stop to the point were the money is gone.
Make the intake a little smoother and equal (this will take at least two or three hours of work), and focus on the exhaust paths afterwards. Keep in mind that the head of a CB72 is a strange bird, as the left and right intake and exhaust paths are not symmetrical, technicians working on the bench are not used to that. Further more I strongly advice you to let the valve guides in tact, don't shorten the guides, or replace them by bronze guides. As you are a long distance biker, I suggest to stay away from the guides, the Honda guides are good.
Don't polish the intake's, it 's looking nice but doesn't gain anything then costs only, and isn't good for the mixture and flow either. Remember, a flow bench works with air, a petrol / air mixture behaves different then air only, and that's exactly why not to polish the intake's.
I can supply pictures of a CB72 head which is flowed as a copy as the one I have on my bike at the moment, so I know what it will do and what not and why.
Remember that flowing a head is just one step in the process, and the effect paying off when doing the other steps also, like carburetor, exhausts, etc.
Sorry for the interference of grandpa Jensen, but I saw to many heads screwed up by mis-communication between costumer and technician (and unfortunately also bad quality work).
On the other hand, there are a lo of heads for sale , so when you don't like the effect, you can go back to the original easily,
Jensen
Japan Meets BritainThat's awfully cheap for a good before and after flow numbers and valve job. Jensen is 100% on the guides. And get the valves and seats cut properly. What cam are you matching the ports to?
Jensen, wet flow and dry flow are different but for this work it's close enough I think. 350 kit with no other mods improves mid range but drops revs. A mild cam and port clean up add heaps at the top end as well. The exhausts are worse than teh intakes and don't let him make the ports too large. Pocket porting is a good way to get to what you want that emans just doing teh area before teh guide through to the seat.
Hi teazer,
Not to start a discussion into deep, but when a inlet port is polished, the mixture easily condensates on a mirror finish, making a cold start worse. And on top of that, it doesn't have any advantage over a grid 400 surface. I agree with the wet / dry flow, but I'm not aware how far Vince will go. Jensen assembly of Japanese motorcycles requires great peace of mind (Pirsig)
I'm not sure how far I'll go either -- the man who is going to do the work comes very highly recommended to me from another mechanic of mine. He has been doing this kind of work for at least 40+ years, but I can't really say how many SuperHawks he's specifically worked on (don't think I'll find someone quite that specialized in this neck of the woods!). Here again, unless someone has some other recommendation in terms of who should do this work, but this fellow seems like a good choice (and I'm sure that price could change once he actually looks at it, but I'm prepared for that). I was going to just stick with the stock cam, but if you have other recommendations in terms of one, I'm definitely open to suggestions. Do you know if Phil Joy makes new cams for CB77's, or does he just work on existing ones?
I will discuss all these matters with the port and polish man, and will definitely pass all this info onto him. My mechanic (John) thought it might be a good idea to do a port and polish, since we were going to the trouble of doing the 350 kit. And I don't need anything radical -- really just more of a cleanup than anything else. My goal has always been to maintain the reliability of this bike, and if there are ways to increase the power without going too crazy internally (or dropping a CB500 motor in the frame!), well that would be good too. If the 350 kit does in fact lower my revs, then I'll probably have to adjust my gearing. I'm already at about 5000 rpms at 60mph, and I don't think I want to go any lower than that (currently with a 29 tooth rear sprocket). I think we'll be fine though -- we have all winter to get it figured out!
Last edited by Vince Lupo on Fri Dec 10, 2010 2:16 am, edited 1 time in total.
Actually, when I asked John about porting and polishing, he said to me: "Well the only place that I can think of is Ladd's on Washington Blvd, but I don't know if they have a flowbench". Then, when I was picking up my Jetta from my other mechanic the same day, I asked him (he does a lot of drag racing and is the most knowledgeable mechanic I know and trust). He said Mr. Ladd as well, and called him on the spot for me. Mr. Ladd said that 'there wasn't a head he hasn't been able to work on' in all his years, so combine that with the two unrelated recommendations, and that seems good enough for me.
So should I also be looking at a cam too, or will the stock one be okay?
Didn't know they had a website.....
This is the place that was recommended for the porting and polishing work: http://www.laddporting.com Mr. Ladd has been in business since 1960 (I was wrong - not 40 years, but 50 years!), and he's still there at the shop.
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