Another 8-valve attempt.

fiatfan · Dec 21, 2020

Came to think of this when I read about the Merlin 8-valve. I saved this pic a couple of years ago, it´s a Swedish build.... It consists of a widened Norton crankcase which also has been reinforced on the drive side. And on top of that supposedly a bit of a Fiat DOHC engine ..... Sorry but I have no details other than the Fiat is an 8-valve engine and the cams are driven by a chain in the middle of the crank. I don´t know if it has been published here before and I can´t vouch that it´s a Fiat.

johntickle · Dec 21, 2020

The cylinder head is from a Yamaha V-Max. The cylinders look home made.

Fast Eddie · Dec 21, 2020

Wonder if it ever ran?

lcrken · Dec 21, 2020

Fascinating! Not my cup of tea, though. I'm ok with the 4-valve pushrod conversions, but once you get into OHC conversions, it seems to me that you've gone too far from the basic Norton nature, whatever that is. But that's just a personal preference. But it is still interesting in terms of thinking outside the box. A friend of mine drew up some possibilities for a three-valve conversion that would keep the external appearance of the stock Commando head. But it never got beyond the concept stage. An interesting thought, though.

Ken

concours · Dec 21, 2020

Fast Eddie said:
Wonder if it ever ran?

no.

fiatfan · Dec 22, 2020

johntickle said:
The cylinder head is from a Yamaha V-Max. The cylinders look home made.

Yes, found out late last night, had not seen that myself but someone in a forum here in Sweden saw it.

fiatfan · Dec 22, 2020

Fast Eddie said:
Wonder if it ever ran?

I´m interested to know as well, trying some Swedish forums too.

jan nelder · Dec 22, 2020

fiatfan said:
Yes, found out late last night, had not seen that myself but someone in a forum here in Sweden saw it.

and there was a racing engine in the USA with Saab parts, all heavily modified.

fiatfan · Dec 22, 2020

jan nelder said:
and there was a racing engine in the USA with Saab parts, all heavily modified.

Wow! Norton based? Pictures?

grandpaul · Dec 22, 2020

Hey, I have the correct "turn out" manifolds for that head!!!

acotrel · Dec 22, 2020

A complete re-design based upon the 500cc Paton twin, might bring results. The main limiting factor is probably the rev limit. A four-valve motor usually revs higher to get it's horsepower. The ports in the head are bigger. Apparently the motor being discussed here, has a restructured bottom end. It might work. I doubt it would have a 360 degree crank. Then there is a vibration problem.

EstuaryBoy · Dec 22, 2020

Sleeve valves!! Shouldn't be too hard to knit a pair

Fast Eddie · Dec 22, 2020

We all draw the line in different places regarding what mods overstep the line with old Norton’s.

But to me, something like this clearly does so.

To the builder it looked liked a great way of improving the top end of an old motor. But to me it looks like grafting a wholly inadequate bottom end onto a perfectly good modern head!

Not so much upgrading the old, more like downgrading the modern !

concours · Dec 23, 2020

grandpaul said:
Hey, I have the correct "turn out" manifolds for that head!!!

I have V-Max cams & lifters....
Do I smell stone soup cooking?

Dogsbody · Dec 23, 2020

BMC Minis are converted to 4valve by fitting BMW K1100 heads, so if the will is there .............

bill · Dec 23, 2020

Yea build a 10,000rpm top end on a 7.000 rpm lower end. Sure sounds like a GREAT plan to me

acotrel · Dec 23, 2020

bill said:
Yea build a 10,000rpm top end on a 7.000 rpm lower end. Sure sounds like a GREAT plan to me

That seems to be the problem. You make a choice - mid-range or top end. Then you have to be able to ride the bike if it is nasty. A big Norton is often well able to break the rear tyre free and still go nowhere. As you increase the overall gearing to keep the revs lower, you change the way torque is used, but there are limits. Perhaps we need 7 speed gearboxes like the 50s Gileras had ?

bill · Dec 23, 2020

acotrel said:
That seems to be the problem. You make a choice - mid-range or top end. Then you have to be able to ride the bike if it is nasty. A big Norton is often well able to break the rear tyre free and still go nowhere. As you increase the overall gearing to keep the revs lower, you change the way torque is used, but there are limits. Perhaps we need 7 speed gearboxes like the 50s Gileras had ?

You did not catch my point as usual. The lower end is NOT fit for a top end that would make the power at the rpm range the 4 valve allowe’s

concours · Dec 23, 2020

bill said:
You did not catch my point as usual. The lower end is NOT fit for a top end that would make the power at the rpm range the 4 valve allowe’s

I blame the "Monster Garage" TV show for much of the madness we see.

RoadScholar · Dec 23, 2020

I think the Drouin proved the point that the head and cam(s) can produce more power than the bottom end can tolerate. So, you say you like look of an engine that has spit-in-your-eyes power adders? I applaud the engineering and craftsmanship that goes into such projects and the challenges that the builder overcomes; a good mix of art and science, and, if ridden with great restraint will provide the builder with years of satisfaction and a high sense of achievement.

I have no idea how much reliability the Westlake 8 valve head cost the pre oil-in-the-frame Triumphs, and there was a similar short lived 8 valve head offered from the factory for oil in frame Triumphs. Anyone have any comments about these.

My son built an '03 twin cam, supercharged Mustang Cobra form 390 HP to 720 HP, it didn't last long.

Your Norton won't last long either if you ask too much from a stock bottom end.

Best.

Another 8-valve attempt.

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