Aftermarket alloy singles barrel and piston.

Singles, twins and fours.
malcolm.johnson
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Aftermarket alloy singles barrel and piston.

Postby malcolm.johnson » Tue Jun 04, 2019 8:50 pm

The pictures show an unused alloy barrel and piston that came with a quantity of singles parts from a deceased enthusiasts collection. He was I believe building a trials/green lane 350 using an aftermarket frame and NH engine. I raised a post about this frame several months ago and I have progressed with the dry build of the machine and currently building the engine, but I have some questions about the barrel and piston. I suspect they are from the mid 1990`s and the engine is 1958.
6. Barrel and piston assembly (3).jpg
6. Barrel and piston assembly (4).jpg

Q1. The 5th hole for the base studs between the push rod was piloted ready to be drilled for a 5-stud crankcase, which I have done and made extra length studs to suit the thicker flange, but what is the purpose of the corresponding drillings going part way down from the upper face?
Q2. The threads for the cylinder head are 3/8 x 16tpi. This is a coarser thread than the iron barrel as expected, but should studs and nuts be used into the alloy, or 4 bolts, to hold the head down? What torque would be used tightening into the alloy if using bolts?
Q3. The piston rings are missing and the grooves look to be sized like three compression rings, ie no oil control ring. Any thoughts where I might obtain these. Bore is standard 72mm.

pete.collings
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Re: Aftermarket alloy singles barrel and piston.

Postby pete.collings » Tue Jun 04, 2019 11:41 pm

I can't answer Q1 or Q2, but would advise the piston is of the type used in the wartime WNG model, and if using it with three compression rings, it is advised (elsewhere on the forum) to use the earlier oil pump with a smaller feed plunger, to avoid oil making its way into the combustion chamber.
I have seen this type of piston modified to take an oil ring by enlarging the bottom land and drilling some holes to allow oil to pass back into the sump, and thus enabling use of the later larger feed plunger type of pump. If used solely for short distance competition use, the overoiling problem may not be so much of a problem.
It may be possible to get compression rings via the club single spares scheme, I believe the original rings had angled ends rather than butted ends.

Simon.Gardiner
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Re: Aftermarket alloy singles barrel and piston.

Postby Simon.Gardiner » Wed Jun 05, 2019 12:04 am

Q1 - no idea, I'd ignore it for practical purposes
Q2 - I'd go for the studs and sleeve nuts as per the alloy head VH engines - 3/8x16 is too coarse for the 'standard' head bolts used by the 350s, it might be the same as the studs for the VH. However, the holes in the head might only be 3/8" which would be too small for the standard VH sleeve nuts, or there again they might have already been enlarged in which case the decision's probably been made already!
Q4 - looks like a standard (probably NOS) older 350 piston, so probably uses standard rings (Drags seem to have them) - are there any numbers on it anywhere?

Re. Pete's remarks about oil pumps, personally I'd go with whichever pump you've got and see how it goes.

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

nevhunter
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Re: Aftermarket alloy singles barrel and piston.

Postby nevhunter » Wed Jun 05, 2019 12:49 am

Use the reduced section studs and a coarse thread is suitable in alloy . Definitely don't use bolts. The studs normally stay in place so tighten them in without undue force, or Loctite. Use a quality stud. Good high tensile material and the "usual" with alloy sleeve nuts. Some of those pistons don't have quite enough metal to widen the groove and not affect strength. 3 comp rings with the oil relief below the bottom ring is fine. It's easy to change a pump but I don't go for a high flow in singles. The early one (in good nick) with the oil return supplying the rockers like all the later alloy head ones are should work fine. Nev

malcolm.johnson
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Re: Aftermarket alloy singles barrel and piston.

Postby malcolm.johnson » Wed Jun 05, 2019 11:47 am

Thankyou for the replies. I am building this bike as a "green laner" or long distance trials, so I anticipate longer runs. The oil pump I have is 1/4 inch dia for delivery side and 3/8 inch for scavenge, so hope this will do for starters. The alloy head has 3/8 inch holes right through. For my purposes would waisted 3/8 studs with machined washers and conventional steel nuts suffice, at least in the short term? I could get the head machined at a later date to take sleeve nuts. Why alloy ones Nev?

Simon.Gardiner
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Re: Aftermarket alloy singles barrel and piston.

Postby Simon.Gardiner » Wed Jun 05, 2019 1:08 pm

For info, pic of VH/VHA/HS/HT head stud
The coarse thread is the barrel end and is 3/8x16
On the 500, when they're screwed in and the head is in place the top is about level with the top of its hole in the head.
If the 350 head is shallower and sits lower there might be enough thread to use with a nut.
I wouldn't have a problem using steel nuts (probably prefer to 'cos there's less chance of stripping them).

Headstud.JPG


HTH

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

malcolm.johnson
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Re: Aftermarket alloy singles barrel and piston.

Postby malcolm.johnson » Wed Jun 05, 2019 5:47 pm

Thanks for the picture Simon. I could make some similar studs long enough to take a standard steel nut and also machine some sturdy washers to go under to spread the load? I meant to add that the only ID on the piston, is stamped small on the crown, is 434C7V. There are no cast in marks on the inside at all.

Simon.Gardiner
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Re: Aftermarket alloy singles barrel and piston.

Postby Simon.Gardiner » Wed Jun 05, 2019 11:19 pm

Alloy head 350 would have originally had steel washers under steel head bolts, I think.
Possibly ally washers might avoid the chance of the steel 'biting' into the contact area on the head (your head might show some signs of that) but the ally-head VH just has the steel sleeve nut with nothing underneath it. (That doesn't stop some people trying to fit lockwashers under them - as my head bears witness to - and in my book that's NOT a good idea!)
Pity the piston has no ID on it but I think it's fairly easy to conclude what it is.

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

malcolm.johnson
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Re: Aftermarket alloy singles barrel and piston.

Postby malcolm.johnson » Fri Jun 07, 2019 12:29 am

Simon, I have found that using a conventional length stud would not allow the removal of the cylinder head with the engine in the frame. I am sure if my measurements are correct, l will need a shorter stud and sleeve nuts, to enable the head to be lifted clear without fouling the inlet valve cap on the underside of the frame top tube. Any chance of a picture of a sleeve nut next to a measure? The 350 alloy head is approximately 2 1/4inches thick. Thanks, Malcolm.

john.whiting
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Re: Aftermarket alloy singles barrel and piston.

Postby john.whiting » Fri Jun 07, 2019 1:49 am

Its common to use waisted studs in alloy heads to allow for differential expansion......straight studs often break in the threads,or just tear out of the alloy.


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