The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: sean on 13.02. 2020 17:54
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hi
having trouble finding the part number (and the parts ! ) to replace my valves and guides and springs on my 1962 super rocket .
head casting .....67-1549
in the parts breakdown they list 4 different part numbers for the intake valve and 3 different numbers for the exh valve with no mention of which head casting or year they fit or size .
I would like to buy a complete kit from one supplier ....prefrably Canada or USA .
my intake valve measures 1.455 my exh valve measures 1.380 across the valve face.
i was under the impression all big valve engines were 1.500 .
any recommendations on parts and suppliers would be a big help.
tia
sean
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Hi Sean,
i was under the impression all big valve engines were 1.500 .
I have seen 1549 heads with 1.5in valves and 1571 heads with 1.45in diameter head valves so It is not an exact science
A forum search might reveal previous discussions on these heads and valve sizes
Sorry do not know who stocks them over there
SRM in Wales have high quality hardened valves and all the other bits to suit
John
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srm dont list valve sizes or part numbers on their web site
but thanks for the reply
Sean
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sean,
Try Alpha Bearings. They have an online catalogue for valves and guides, but like everyone else don't list dimensions. A further problem is that recently the company has gone through a bad patch, and although the website and contact details look fine, I do not know if the company is still trading. Website www.alpha-bearings.com May be worth a look anyway, lots of goods stuff there.
Valves can be dimensionally the same, but have different part numbers to identify a change of material or something as simple as a variation in collet groove.
Swarfy
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SRM had this valves:
http://www.shop.srmclassicbikes.com/product/inlet-valve-a10-1-12-38mm-plasma-hardened-rgs-670961
chees Klaus
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thanks for the reply
srm valve is 1.5 mine are 1.455 on the intake
1.380 on the exh
at this point dont mind where they come from except india
I dont know if my valve seats can be cut back to accept the 1.5 valve set
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This valves are not from India. I do run this 38mm valves on my race bikes with no problems.
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I think that the valve sizes are actually 37mm & 35mm.
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Hi Sean,
SRM list both size inlet valves 67.1551 and 1.5in 67.0961 (SRM215 )
It takes very little seat cutting to accommodate the bigger valve, so if the seats are in any way pocketed the bigger valve will be fine
Last week I was working on a 52 Star twin cylinder head where the seats were pocketed and the exhausts fairly pitted
After cutting the seats just enough to get a good surface the original valves were well recessed *sad2*
Options
fit seat inserts ?
live with it?
find some larger head valves?
A trial fit of an A10 exhaust valve looked good, and the heads could be reduced if necessary?
Yesterday the new A10 valves arrived and a quick lapping showed that they were seating nicely and no machining needed
I will need to check clearances between the valves and valves to pistons but I do not anticipate problems
The Star twin head inlet ports looked quite different to each other ????
One looked to have very little "meat" behind the seat area to support a seat insert if one was going to go that route
Maybe those odd ports are a reason why some BSA's show cylinder bias *????*
John
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thanks for the reply
my valve seats are fine .... no pitting , i dont think the extra 60 or so thousandths of an inch is going to make a great difference and not really looking for performance on a 58 year old engine just reliability if possible .
this motor has had some work done but the previous owner couldnt remember what was done and the person that did the work isnt on the green side of the grass so I cant ask .
I dont know if the correct valve springs are installed as SRM seems to specify a 2 inch spring and mine are all over the place .
Sean
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Hi Sean,
I always fit new springs on rebuilds
John
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me too just trying to find the right ones
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Hi Sean,
Best to buy the lot from the likes of SRM who know their stuff
John
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Question on this. Is the 1.5 inch size across the valve head, or across the seat?
read that you multiply the diameter of the valve head by 0.98 to get the flow size. I have inlet valves on my '62 SR motor which are approx 1.53 total valve head diameter (tiny bit of give and take), but multiply that 0.98 and I get just about 1.5mm (1.4994).
So what does 1.5 inch actually mean???
Would welcome thoughts.
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Valve size should be the total OD....
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so just an update on the project ordered valve springs from SRM went to set the rocker gaps and turning motor by had it had a tight spot look at the new springs one is coil bound the other 3 had .016 clearance between the coils ....SRM says there should be 60 thou further travel when valves are fully open ......62 a10 super rocket all original valve train 357 cam
I stripped the head again make sure everything was right and it was but these springs seem a bit long only change I have made is new valves and springs from srm and seats cut to fit the 1.5 inlets the exh valve seats were just cleaned up at the machine shop .
put everything back together with the old springs and its fine ....
Sean
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Sean are the collets fitting the valve stems and collars ok? when i got srm stuff a few years back the collets did not fit the cap/collar well, having apparently been machined to the wrong angle - and thereby the cap sat low, and so the valve coil bound. i got the collets (or collars? can't recall) re-machined so they mated ok and problem solved. PITA for high price parts. maybe worth a check
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Hi Sean,
Do the springs have the same size wire or is there more turns?
A call to SRM should result in a "cure"
Recently a set of conrod bolts from them were found to have undersize threads , they replaced them without having to return the dud ones first, this saved a lot of time as B**xit has made delivery times to and from UK a lot longer than pre B times (duds are now on the way back to them)
John
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Sean are the collets fitting the valve stems and collars ok? when i got srm stuff a few years back the collets did not fit the cap/collar well, having apparently been machined to the wrong angle - and thereby the cap sat low, and so the valve coil bound. i got the collets (or collars? can't recall) re-machined so they mated ok and problem solved. PITA for high price parts. maybe worth a check
hi
yes collets are seated flush with the top cap ......high priced parts plus shipping and money conversion .....dont have time to wait for SRM I bought colisbro valve guides from them as well but they come undersize ID and need to be honed and they didnt sell the hones or know where I could get them there answer was take them to an engineering shop .....ended up with another delay waiting for a set of hones from USA .
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Hi Sean,
Do the springs have the same size wire or is there more turns?
A call to SRM should result in a "cure"
Recently a set of conrod bolts from them were found to have undersize threads , they replaced them without having to return the dud ones first, this saved a lot of time as B**xit has made delivery times to and from UK a lot longer than pre B times (duds are now on the way back to them)
John
Hi
the srm springs were taller I didnt measure the wire size ....pain in the ass having to strip the head off again ....put a set of standard springs in and it seems to be fine now just struggling to lift the motor back in the frame they seem to get heavier every year *smile* *smile*