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Correct cylinder and head?

Posted: Sun Jun 28, 2020 10:13 am
by Will L
Hi all,

First post, so please, go easy on me. I acquired a 1959 NH as a restoration project, (hat tip to Bennet for dating). Now seems more of a basket case.

I have started the strip down and noted that I have 5 cylinder head bolts, but only 4 holes on the cylinder. From what I have seen on the internet etc, it appears I have an earlier cylinder and possible head. The cylinder has external push rod tubes and the head is iron.

I have no idea if this ever ran, the bike was said to have been laid up at the back of an engineering workshop for 35-40 years.

Is this a viable combination (clearly not for the purists) of crankcase and cylinder? Or do I need to add a 5 stud barrel and matching head to the every increasing parts required list.

Thanks is advance,

Re: Correct cylinder and head?

Posted: Sun Jun 28, 2020 1:37 pm
by will_curry
Firstly, some photos always make things easier.

A 1959 NH would have had an alloy head on an iron barrel.

In my experience all alloy heads had barrels with integral pushrod tubes.
The NH alloy head had 4 bolts and the VH head had 5 - actually studs and sleeve nuts.
Both VH and NH iron heads had barrels with separate pushrod tubes and 4 head bolts.
Another difference to be aware of is that barrels with separate pushrod tubes have 4 studs
securing them to the crankcase while barrels with integral pushrod tubes have 5.

Knowing the engine number will help - it's on the drive side of the crankcase where 'ARIEL'
is cast in.

On a note of hope - Yes, these things can usually be made to work.

Re: Correct cylinder and head?

Posted: Sun Jun 28, 2020 1:50 pm
by Simon.Gardiner
Hi Will - welcome!
That head and barrel will be fine (even if not authentic for the year). The only issue you might have could be the push rods, if they're alloy (ie as for the alloy head) the cold clearances will be pretty big and things could be quite clattery (this point has been recently discussed).
If you've got the crankcases for the 5-stud barrel flange you might need to put a cut down stud into the unused hole between the push rods to blank it off but that's a fairly minor point to deal with.
As per the previous post, I think the alloy NH head only used 4 bolts, the equivalent VH head used 5 studs. Still, better off having one bolt spare rather than being one short!

Edit: one caveat, the size of the flange at the top of the barrel (and the profile of the finning - but that's a cosmetic issue), changed in the early 1950s. With a 'basket case' bike it's probably prudent to check that the head matches the barrel in this respect.



Re: Correct cylinder and head?

Posted: Mon Jun 29, 2020 4:18 pm
by Will L
Gents thanks for the rapid responses.

The crankcase is stamped CAMA 5596, which matched the frame number CAPR 13939.

I've attached some photos. So looks like I need to source some non-alloy push rods and see if I can get the engine to run before I expend any more effort of the frame etc.


Re: Correct cylinder and head?

Posted: Mon Jun 29, 2020 5:51 pm
by Simon.Gardiner
To judge from the prominent finning above the push rod tubes that's a '54-'55 head and with a matching 10-fin barrel, so at least it's authentic for a swing-arm frame!
Steel push rods for a 350 shouldn't be too hard to come by, but there are different lengths (owing to changes in cam base circle diameters) - it does sound like you've at least got a set of alloy push rods to compare with.
(As you've been in touch with Bennet about dating you might already be in the AOMCC - might be worth asking the club's 'Singles Spares' man...)


Re: Correct cylinder and head?

Posted: Mon Jun 29, 2020 6:06 pm
by will_curry
Thanks for the photos and the number. The crankcase is right for the year and the head and barrel are
the later sort of iron ones. You'll need quite a number of fixing bolts - 4 for the head and 8 for the rocker
boxes that aren't the same as the later ones. The rocker boxes too aren't the same but they should
fit. As Simon says that fifth stud in the crankcase mouth may need modifying. Gudgeon pins
were the same so as long as you have a piston to fit the barrel you should be able to use it. Don't
bore the barrel unless you absolutely have to. It should be beautifully hard by now and so last for ever.
If you bore it that lovely hardness will be lost. Another thing you might have to find is an exhaust pipe.
the later ones pushed into the head, not over a stub. I think the angle differed as well. A pipe for a
1954 NH should do the job.

Finally, if you haven't already, do join the club. Amongst other benefits they have a wonderful archive
including parts lists which you will find extremely helpful.

Re: Correct cylinder and head?

Posted: Mon Jun 29, 2020 8:00 pm
by Will L

Thanks for the rapid follow-up. I have set of alloy push rods, so can measure to give me some idea (I assume it had been running given the oil and dirt that was covering everything in sight.) The 5th (now extra stud) clears the barrel and initially confused me somewhat as to why it was there.

Thanks for the tips on the rocker studs, the ones I removed were packed with washers and in once case an extra nut to get them to tighten. So a new set is required.

I have a piston with rings and there appears to be no barrel wear, only issue was the small end tolerances. A new one on the list.

The exhaust systems was one of the many, items missing. So will be on the look out for an early push one now.

Joining the club was the first I did and so far the archive documentation has been extremely useful. Once I have a better list of bits, I'll certainly be troubling the clubs 'Singles spares' man :-)

Re: Correct cylinder and head?

Posted: Tue Jun 30, 2020 10:02 am
by andyhughesflattankarielpre25
Single spares is always worth a call,if Pete doesn't have it he can often point you in the right direction.