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Valve Question

Newt - April 26th, 2011 at 11:45 PM

Hi Guys,

Finally got round to getting my heads done up (faced and guides). They are quite old and a little different.

As part of the process, I want to replace the valves as they have a variety of score marks in them.

Now looking at the valves, they are made by Dufor with a single ridge clip.

In measuring accross the top of the valves, they came in at 36mm and 43mm respectively.

Now, looking at the after market valves, they seem to come in steps. ie 35.5mm, 37mm etc and 42mm, 44mm etc.

Given that my valves seem to be an inbetween size, do I buy the slightly larger size and find a head man to turn them down a bit?

Cheers

Newt

vw54 - April 27th, 2011 at 06:22 AM

What size engine and heads do u have ??

with a single clip they sound like 36 hp ??

matberry - April 27th, 2011 at 08:47 AM

Quote:

Originally posted by vw54
with a single clip they sound like 36 hp ??

All the CB heads are using single groove keepers these days. It is important to have the keeper match the retainer, but also if the guides have been replaced or relined you have to get the seats and valves done too, this is normally done at the same time. To answer your question....a knowledgeable head dude should be able to make a sloghtly larger valve fit by either turning down the valve to suit or cutting the seat to suit, but your standing on thin ice, how do you know the original valves were right in the first place?
Can you post some pics of the heads, valve seats and the old valves?

Edit: by memory the old 043's had 43 x 37 valves.

Newt - April 28th, 2011 at 12:27 AM

Head A

Newt - April 28th, 2011 at 12:28 AM

Head B

Newt - April 28th, 2011 at 12:28 AM

Head C

Newt - April 28th, 2011 at 12:29 AM

Head D

Newt - April 28th, 2011 at 12:30 AM

Inlet E

Newt - April 28th, 2011 at 12:31 AM

Exhaust F

Newt - April 28th, 2011 at 12:32 AM

Valve H

Newt - April 28th, 2011 at 12:32 AM

Valves I

Newt - April 28th, 2011 at 12:33 AM

Inlet J

Newt - April 28th, 2011 at 12:34 AM

Exhaust K

Newt - April 28th, 2011 at 12:34 AM

Inlet L

Newt - April 28th, 2011 at 12:36 AM

Exhaust M

Newt - April 28th, 2011 at 12:55 AM

I dont know why, but Im figuring that the heads date back to the 1980s (or earlier).

It was an 1875 with an AP3 cam (264 duration) but am leaning towards a 1955 with a Web Cam 218 (280 duration).

Cheers

Newt

Newt - April 28th, 2011 at 01:00 AM

One More

dangerous - April 28th, 2011 at 05:20 AM

Those valves look much like datsun valves.
Any head shop should be able to identify them(to confirm) and get you replacements.
Or just buy some CB valves collets and retainers, nad have them turned to size.

matberry - April 28th, 2011 at 09:33 AM

Mmmm as Dave said, get a good head guy to fit some quality valves and do the seats. They fitted K-liners by the looks which is an insert that freshens the guide, but definately now the seats need to be redone.

If you want to get some performance, start with those heads, chambers, unshrouding the valves, a good 3-5 angle seat job, some portwork etc, then even the cam you have might work :lol:

Newt - April 28th, 2011 at 11:37 PM

Thanks guys.

K-Liners it was as the chap didnt want to risk damaging the top where it had been machined for dual valve springs.

Matt, dont like the choice of cam?

Cheers

Newt

matberry - April 29th, 2011 at 08:31 AM

Not so much the cam as those heads are crying for some decent chambers/ports.

modulus - April 29th, 2011 at 03:40 PM

Hi Newt,
It's probably only a small, pedantic difference, but you should be measuring between the blade tips of your digital calipers, not the main part of the arm, i.e. measure with the ground-down tapered blades

hth