Iron Head Valve Seat Questions.

Previously wrote:

"Hi All.

I have a Model7 to renovate................................

1) Do the iron heads have shrunk in valve seats or are the the seats formed in the casting itself?"

- The Mod 7 & 88 (up to Sept '54) had no shrunk in valve seats, just cut into the head in the time-honoured old style.

"2) Whatever the answer to Q1, what is necessary to run these iron engines reliably on unleaded fuel? Will I require new valve seats or what?"

You will only need to do (an expensive) re-machining, with new components if you are going to be driving your engine hard. Gentle use which I think is more your style, with just the occassional burst of self-indulgence, should give you none of the scary seat-recession problems.

The need for actionhas been exagerated, by companies selling 'snake-oil' additives and other firms wanting to hear their tills ringing.

Paul

Previously wrote:

Hi Paul.

Thanks very much.I hope they are ok. I suppose the only good thing is that the seats can be recut fairly easily and even opened up easily if one so desired for larger valves.

I guess the best thing is not to worry too much and just use the bike as one desires and fix any problem that may arise later. I may be tempted to use a little lead replacement fluid...just to make me feel better ...

hmmm..... looks like I AM worrying...LOL !

Many thanks once again.

Les H

PS....Does anyone know of a web site showing pictures of the iron head and it's seats etc. or a good web article on Norton Twin Heads?

Les

Hello Les,

Go ahead with the LRF; but why not save the bother & just mail a cheque to Wynns, or one of the other additive witch doctors....

Just kidding a bit.

Don't know of a good website for pictures of Norton twin (iron head) valve seats. 'DynoDave' runs: http://atlanticgreen.com/nhth.htmbut the picture there has valves fitted.

One other point about running on unleaded. It would be worth using the power-timing (vacuum gauge) method to find an ideal timing setting. Other than that, you'll need nothing doing (or adding!) to the engine or fuel.

Paul

Previously wrote:

Hi Paul.

..............................

PS....Does anyone know of a web site showing pictures of the iron head and it's seats etc. or a good web article on Norton Twin Heads?

Les

Hello Les,

I'm sure most Dommie owners will have a few iron heads kicking around.

I've just spent 1/2 an hour rummaging & am attaching a photo with this message. I hope it is clear enough to answer your question.

Paul

Previously wrote:

Hi Paul.

..............................

PS....Does anyone know of a web site showing pictures of the iron head and it's seats etc. or a good web article on Norton Twin Heads?

Les

Hello Les,

I'm sure most Dommie owners will have a few iron heads kicking around.

I've just spent 1/2 an hour rummaging & am attaching a photo with this message. I hope it is clear enough to answer your question.

Paul

leslie,peter howard previously wrote at Monday 9th August 2010. 10:04hrs

Hi Paul

Very many thanks for taking the time again to answer me so comprehensively. I am very much obliged.

Your personal iron head photo is very encouraging, showing quite fine valve seats and pretty smooth ports too. I notice theexhaust port on the top left is obviously coked up and is not showing the underlying finish.

I had imagined that somehow the iron heads would have a very rough, poorly shaped ports with no finishing, and just cast holes,but they seem pretty good, I've seen much worse on alloy heads, not necessarilly Nortons ones though. Another thing is that I recently read the iron heads had similar valve sizes for both valves, but your pictureseems to show a larger inlet valve as per Alloy versions. I hope I find the same in my one.

The webpage is excellent,I'llbookmark it. It is a very informative reference, which I will find extremely useful.

I note that it says early iron heads did have similar valve sizes, so it seems your iron head is probably a later type?

I hope my onedoes have the larger inlet valve size. Just noticed the iron head shown seems to have been sprayed silver and looks initially like an alloy one!

Thanks also again for the lead free petrol advise, most comforting.

I will probably becoming back on this sometime in the future, and may well make you an offer on that head if my one proves to be knackered!

You have been very helpful Paul.

ATVB2U

Les H

Hello Les,

First off, the head in my photo has been amongst my stash of bits for around 30 years. I remember shifting it around now & again & thinking it was just one of those old relics which I would never use. Now I am on the learning-curve, with the recreation of a standard 1954 88 DeLuxe. That means parts I own like this are in the queue for renovation.

Iâm really looking forward to seeing just how smooth it will be, with everything to original specâ, right down to the 6.7:1 compression (depending how much has to come off the joint face!). So unfortunately that head wonât be for sale.

I should explain that when I took the photo yesterday, I sploshed some diesel around one inlet seat and gave it a scrub with a plastic scourer. I wanted you to be able to see that there was no seat insert. Also, the photo was not taken with a small lens and I took it up close and in line with the inlet valve guide; so with the exhaust valve seat being closer (therefore altering the perspective & making it look larger) that created the illusion of different size seats, which is not the case. I donât believe there was ever an iron Model 7/88 head with larger inlet valves. Unless there were factory, experimental ones. I do believe Norton had developed an aluminium alloy head for the twins, by around 1950; but it was only to explore what potential there was with racing in mind.

If you must get more squirt from your Model 7, I think you would be better off finding one of the later heads for it. No problem at all with unleaded fuel while you tidy up the iron head. It would handle like a truck though, with that plunger chassis. I would leave it be and just waft around on it.

I saw a lovely, unmolested, plunger Model 7 a year or so ago. It really looked content, with its worn original paintwork, rusty (solid cast) handlebar levers, and worn down, original pedal rubbers. It had a truly dignified and purposeful aura. 60 years on and still enjoying a good gallop. Not like the restored ones, with all their repro shiny bits that are 'just another over-restored classic bike'.

Now that was areal bike!

Paul