The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: mikeb on 03.10. 2015 09:08
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I’m having trouble getting sufficient installed spring height on new valves, springs, caps, keepers on a ’61 super rocket (alloy head, 67-1547). All the new stuff is from SRM. They cite a minimum installed height on 1.375” for a 356 cam (which I’ll use) or 1.400” for a 357. SRM say that BSA never published a figure for this but that’s their recommendation. On the Eddie Dow ‘twin tips’ sheet with a 357 cam he suggests 1.312”: http://bsa-a10.hailwood.com/tt11.html
When I measure the new srm setup I get an installed height (from the underside of the top cap to the top of the bottom cap) of 1.26”. When I measure with the old valves, caps, keepers I get about 1.30”-1.32” – so that would match the Eddie Dow figure but way short of srm figure. The valve seats are actually a bit recessed (see pic) so I don’t think they are shortening the spring height. If anything I may need new valve seats which would further shorten it.
The srm stuff is pretty much exactly the same dimensions as the old stuff. I’ve noticed some of the new srm keepers don’t sit well on the valves/caps and hence the top cap sits a bit low, which could account for some difference from my old valve gear. srm suggested I send them back for checking (that’s a 24,000 mile round trip and more delays) or maybe I could take to the back of them with some emery paper. But even if I fix this I’ll still be far from 1.375”. I could get maybe another .025” by grinding down the underside of the bottom cap.
I’ve searched a lot and not found any good info on this. A couple of britbike threads suggested others have had this problem and ended up just installing them and testing for coil bind. But that doesn’t explain what the problem is (if there is one).
I’ve also attempted to calculate the valve lift but I clearly don’t know how to do this. The cam lobe is about 0.3” lift (from the atlanticgreen pic and my measurements), the rockers approx 1.31” from shaft centre to tappet, and 0.85 from shaft centre to pushrod cup, so 0.3 * 1.31/.85 = 0.45”valve lift… But that makes no sense as the outer springs compress to 0.95” + 0.45” lift = 1.4” min spring height on the 356. So I’m wrong.
All this means I’m confused. So questions:
Anyone else had this problem?
What height to aim for / figures to trust?
Would shaving a bit of the keepers be achievable/wise?
Thanks
Mike
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I'm no expert here, but aren't keepers usually flush with the top of the cap? It looks like there is about 0.050" there. Then, in the top picture, I think I'm seeing a shadow under the bottom cap. Is it all the down over the valve guide? I'm almost sure I must be wrong, but can't understand the shadow.
Richard L.
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but aren't keepers usually flush with the top of the cap?
You could have a point there Richard, I cant recall if mine protruded over the top cap or not, springs would put pressure there of course so might be a bit of space to come.
I think I'm seeing a shadow under the bottom cap.
You would, that's correct, they are similar shape top and bottom, if I recall correctly the flange is of different widths, I do recall wondering which way they went
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Hi mike and All,
Attached photos of an SR thats on my workbench for far too long *sad2*
As Richard says the collets should be about flush with the cap
When I went to build this engine found that one collet (new) was not profiled properly where it fits into the groove on the valve, the bump was more "square" than semicircular if you can follow my meaning??
have you fitted the bottom washers the correct way up? another possibility??
When you fit the cap and collets can the cap be "rocked" from side to side?
If it can then thats a problem *problem* that needs sorting or you will wind up in tears *warn* *warn*
HTH
John
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Bill,
Yes, I forgot the collars were shouldered on both sides.
Richard L.
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helpful pics John. yes i think my keepers are not sitting in well and thereby holding the cap lower, hence my idea of taking some emery paper to their tapered side.... is this wise? did you get your misfitting keepers from the same place as me?
the bottom cap is the correct way up - quite a bit of shadow partly coz the camera/light and also it has a foot on the underside that i could make a bit lower - maybe save .025". a pic below showing the srm stuff and while only one side of the bottom cap shown i think it is the underside (both sides are similar in having the stepped areas, tho the radius is less of that on the underside).
but even then I might get back to 1.315" installed height which remains a long way from the 1.375" srm are recommending.
???
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Hi Mile,
Check each collet in turn, degrease them and a light coat of engineers blue or a felt pen
then fit each in turn to a valve, rotate the valve/collet relative to each other
See where the collet rubs along the valve stem, it should contact the stem evenly along the collet length
and not be held away by a too thick part that fits the groove
I would not use emery on the tapers *eek*
I checked some SR valve springs and they have 6 1/4 turns 0.145in diamater wire
Yes, the bottom collars go bigger step upwards, (other way up when using the goldie spring conversion)
It was only one dud collet out of the set that gave me problems,
Do you have any of the original BSA components to compare with ?
HTH
John
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I’ve measured up the keepers and found variance of upto .006” at the top wall thickness – these measures not the most accurate but are repeatable. They are all a little longer that the old (worn) keepers. When matching biggest with biggest new keepers etc and selecting the most fitting valve stem they now can fit almost flush into the caps with no movement – see pic. John I haven’t check the fit to the valve stems yet with blue – will do. I still get an installed height of 1.275” – way less that the old 1.315” or the srm figure of 1.375
The new springs are mca brand - 6 ¼ turn x 0.144” wire thickness. The old springs – no idea what they really are – were 6 turn x .158” wire. With that extra ¼ turn the new springs compress to 0.95” approx. whereas the old to 0.91”. so I lose another 040”. everything else new vs old measures up about the same.
One thing I just can’t find is data on the actual SR valve lift or the rocker ratio. I crudely measured the rocker ratio as about 1.5 (making 356 cam valve lift as 0.45 – that’s not right) and on the bench tried measuring the rocker movement directly by depressing the pushrod cup 0.30 -> 0.38” tappet movement – but these measures are too rough to calculate what spring height I need.
Does anyone have this data?
*idea* John – if that SR engine on your bench is complete with a known cam, would you be willing to turn it over and measure the spring/tappet movement????
Cheers
Mike
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See where the collet rubs along the valve stem, it should contact the stem evenly along the collet length
and not be held away by a too thick part that fits the groove
This made me remember I had a similar issue, and made the groove in the stem a tad bigger to suit, while trying to maintain same length from valve head....was a bit of a minor shiffight if I recall; had to compromise some *work*, and ulimately just threw it together to find out
If it's any consolation, I dug out my notes on spring compressed lengths; collars from SRM and collets same (I think); Inlet valves SR I think from a BSA packet circa 1980, Ex-Valves modified stainless Gemini items, seats are cut but not deep, but a few thou here and there adds up *eek*.
Valve Spring compressed lengths;
Left Ex; 1.363 Right Ex; 1.348
Left In; 1.351 Right In; 1.364..... *conf*, so in my case could explain a slight difference in plug colour L/R..?
I can't find any subsequent notes, so may be as is... runs ok though
Mike posted while I was doing that *conf*
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hey Mike, You only mention one spring? I guess it's not relevant here,but how about the inner..?
Just though I'd add as comparison;
My SR Valve spring specs (as far as I can decipher my notes *eek*), maybe not sourced from SRM
outer inner
OD 1.386" 1.064"
Wire size 0.144" 0.114"
Coils 5,1/4 turns 6,1/2 turns
Length 2.157"-2.174" 1.990"
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thanks Dutch. i overlooked the inner as it compresses shorter, so the outer is the limit.
you've still got 090" more installed height than me... *conf2* .. where has mine gone!
are you running a 357 or 356 with those figures?
you didn't happen to write down in that notebook the actual SR valve lift did you?
mike
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you've still got 090" more installed height than me... *conf2* .. where has mine gone!
*dunno*...only thing I can think of at the mo is either my stems are a bit longer (I have measurements/drawings for that somewhere), or the seats are cut deeper....or.. *dunno2*
I'm running a 357 that's been ground,
you didn't happen to write down in that notebook the actual SR valve lift did you?
Like you, I think I was trying to work it out and gave up for a while *problem*
I'll have a dig later and see what else I can churn out
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Hello Mike,
another way to get a solution is to know the presure of the springs.
I do racing with A10 an converted to one spring. IHMO i belive in knowing the valvespring pessrue when the valve is closed and in hight lift opened. I use megacycle cams with 1 mm more lift as the 357 at my racer. The road bikes are also converted by using the 357.
The original valvlespring pressure is low and causes in shifting wrong gear to valvle masher.
So I prefer a closingpressure of 35 kg and at hight lift 85 kg.
The easy way to find out, is to press the springs with all components on a scale.
Messure the hight in fit condition and with the real valvle lift by full opening.
If you get a result nearly the the named kg, every think is ok.
cheers Klaus
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Hiya Mike- I dug ou the other notes I made, and am now understanding why I'm not an academic *conf*....I measured just about everything I could think of, and the best I can decipher is;
357 Cam- calculated lift (measured with digital sliding caliper)=
Cam Lift; average 0.337 " give or take 2 or 3 thou
O/A Length of Valves 3.933 +/- a few
Head of Valve to
Tip side of ~3.787 to 3.798 <----- I figured this is fairly relevant
Collet groove ?
I can't quite figure out the measurements of the rocker arms, it seems both arms of the inlet rocker (p/r>shaft< 'tappet' *rant*), are different to both arms of the exhaust rockers (p/r>shaft< 'tappet' extra*rant*)... *????*...I think about that point I just threw it all together *pull hair out*....but that was 3+ years ago*smile*
The figures I have are maybe these, read at own risk *smile*;
Inlet (p/r>shaft) = ~0.750" & shaft> 'tappet' extra*rant* = ~ 1.245-1.273" * 1.517" (unsure what this is)
Exhaust (p/r>shaft) = ~ 0.993-1.008 ? & shaft> 'tappet' extra*rant* = ~ 1..487 * 1.790" ditto
I've added a pic of one of my valves closed as a indicator of where the collets/keepers are sitting after I had the grooves made bigger to fit,
and I also found some other "installed spring height" figures, but am not sure what was the reference point (0.0, maybe from head, not the spring seat); range of 1.456" - 1.506"
And don't forget that more winds in a spring makes it softer...
*beer*- you'll need it *smile*
Klaus, I had a notion the reason double springs are used is something to do with reducing valve bounce, because the two springs have different load rates, so they counteract each other...or something along those lines *dunno*???
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Klaus, I had a notion the reason double springs are used is something to do with reducing valve bounce, because the two springs have different load rates, so they counteract each other...or something along those lines *dunno*???
Hi duTch,
a lot of work to messure *countdown*
most old engines use double valvle spring, I gues this is caused by fear of spring breaking.
Modern steels are much better, so my intension is to low wight by moving parts.
The original spring set with all parts is 101 gramms. The one spring conversion is 61 gramms.
This will reduce the oszillating masses huge and give the engine a longer life, an dbeing sure the tappets will not bouce on the cam.
cheers
Klaus
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Dutch - thanks heaps for all your figures!!! very helpful. I'll sit down with the calipers tomorrow and compare.
how did you get those keepers so low in the caps??? how did you re-size the stem groove? any concerns about fatigue?
I've been re-measuring the inlet rocker ratio again this time more accurately with dial gauge etc - but it still works out wrong so I'll try again in the weekend and post back. a guy on a britbike forum post said he measured .340 travel on the collar with a 357 cam but the lobe pushes that much without a ratio *eek* I wished I'd measured this before i took the bike apart
Klaus - I don't quite understand why spring pressure will help resolve this. don't i have to know the travel distance first?
cheers
Mike
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Mike- just be aware that all those measurements are kind of arbitrary and inconclusive and not necessarily right or correct, I was just measuring stuff for the heck of it out of curiousity, figuring it may be stuff I'd need in days of the future- passed *smile*...the rocker measurements were a fair bit of calculated guesswork...
how did you get those keepers so low in the caps??? how did you re-size the stem groove? any concerns about fatigue?
Just lucky I guess, it was a headfar-que for a while but took them to my mate and explained and he sorted it on his lathe or something- I had cups of tea and bikkies with his Mum... *smile*, didn't really think about fatigue,
but my eyes did almost fall out once or twice *eek*...and hadn't considered stress on the valve tips until you mentioned it *smile*
I've also been looking at the way the valve-lash adjusters(some call 'em 'tappets') engage on the valve tips; as per pic ->and compared to previous pic (last page), having trouble with photos since I threw the last phone up the driveway *bash* resolution is all different
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So Dutch all those measures pretty much match what I have, and I’ve compared my old and the new srm.
On the bench I’ve set up the head/rockerbox/light springs/barrels/pushrods and with dial gauge measured valve travel against lift under the cam followers (on the correct angle) using a range of drill bits to match the height of a 356 and 357 lobes. With lots of measures there’s a fairly linear relationship between the two (I had though the change in rocker angle would shape the curve). The summary is between 0.291-0.352” cam lift the rocker ratio is about 1:1.135 on the inlet and 1:1.119 exhaust. This means for my 356 cam at 0.305” --> 0.346” inlet valve travel + 0.95” (spring compressed) +060 gap = 1.356” install height. That’s more than Eddie Dow says for a 357 (1.3125”) and less than srm say (1.375” for 356) so either these springs are longer than Eddies when compressed or I’m still missing something *conf*.
Does anyone have a measure on the outer spring when fully compressed? If so do you know the brand?
Apart from springs, the keepers don’t sit deep enough in the caps. The keeper ‘bump’ is a bit squarer than the shape in the valve stem, tho otherwise appears to make good contact with the stem – no movement. Maybe the keepers are too fat or the taper in the caps too tight. Can anyone recommend how I could get all these to fit better?
Or maybe I could try your trick Dutch and have tea and bikkies with a friends Mum and see if that works ;)?
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Or maybe I could try your trick Dutch and have tea and bikkies with a friends Mum and see if that works ;)?
*smile*...well it's worked for a variety of things i the past, but won't be with Kels' Mum anymore, she's since departed....
Mike, I'm absolutely no engineer or other 'expert', but unless I'm missing something, I can't figure how the compressed spring length at rest (valve closed) is going to affect anything other than a possibility of binding if too many winds for the amount of travel...?
If the valve is closed, it's closed- and will perform its duties as shafted by the cam to the lift available (hopefully consistent L<>R, which is more important the way I see it *dunno2*), whatever the spring length...
Did you put the keepers in the collars and measure between the 'bumps', and at the same time the virtual stem measurement which will vary depending where they sit in the keeper?? *dunno*
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Dutch i'm certainly no engineer either... don't quite know what i'm doing most of the time, especially on BSAs. this is all about avoiding coil binding when the valve is fully open. between the top of the seat and the underside of the top collar i need at least enough for the full amount of valve travel (hence my measures) + the fully compressed spring (coz thats when its not getting any smaller) + a bit of a gap (for good luck). at least i think i do. i might not be understanding your point, nor this bit:
the virtual stem measurement which will vary depending where they sit in the keeper??
??? time for a sleep here in NZ *sleepy*
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this is all about avoiding coil binding when the valve is fully open. between the top of the seat and the underside of the top collar i need at least enough for the full amount of valve travel (hence my measures) + the fully compressed spring (coz thats when its not getting any smaller) + a bit of a gap (for good luck).
Oh yeah that's right, so I was kind'ov on the page ..got lost in translation *smile*
i might not be understanding your point, nor this bit:
Quote
the virtual stem measurement which will vary depending where they sit in the keeper??
I mean measure the internal diameters with the keepers in the collars with no valve in place (virtual)- keepers at max insertion (when the two halves meet), and/or keepers/collars flush at top of collars
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Just had a thought re;
I mean measure the internal diameters with the keepers in the collars with no valve in place (virtual)- keepers at max insertion (when the two halves meet), and/or keepers/collars flush at top of collars
(If you haven't already done it), while the collets/keepers are in the collars, you could slip the valve tip into the keepers so the 'bumps' are sitting on the tip, and see how far in the taper they are, and even invert the valve and do the same, but with the keepers in the grooves and something to simulate stem thickness at the pointy (bottom)side- might be able to see how the tapers match. but if there's not improvement, I say there's not much can be done...so long as the collets are fully in the groove *smile*, and I suggest minimally deeper and wider grooves will be better than 'snug'...hope that makes sense?
Going by the photo ahlf way down page one, they aren't too bad, but can see further in would be better I guess
*spider*
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I thought I'd post up the happy ending to this story for the next person sweating over a lack of installed height on a alloy head a10. I rang SRM and they said if I sent the caps and keepers back they'd turn out the inside of the caps so the caps sit higher on the keeper (why not size them before mailing I wonder?). the inside angle of their caps they say is 10 degrees. being 12,000 miles away I got someone local to do the job - my maths said at 10 degrees +.020" diameter would raise the cap by .100". hence the pics below - you can see the cap sits much higher and I have +.100" more installed height and enough for my measurements of valve travel (for a 356).
in case you are wondering the springs are soft ones for a test installation
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Just a follow up post;
How'd you get on Mike? I had to hunt for this to follow up *????*
Sorry guys, I realized I took over up theer ^^ didn't mean that *shh*
I hadn't forgotten, but when I checked my valve gaps the other day, I finally forced myself to check the actual valve travel with dial gauge as promised:
Actual Valve travel (with a 357 cam as below) measured with dial gauge on valve caps, as best I could;
L Ex 0.3575” R Ex 0.3605” (0.003" variation L/R)
L In 0.371" R In 0.3675” (0.0035" variation L/R)
This is with reground 357 Cam lobe; two different readings(?)
(1) 0.348” 0.350" 0.3565” 0.347”
(2) 0.3455” 0.3515” 0.350” 0.3455"
* not sure what the two different readings are…maybe dependent on tongue angle :P
Strangely, the cam lift of the 357 I'm using are greater than the new (aftermarket/pattern?) cam I bought somewhere in UK '81 *dunno*
Lift on New 357 *may well be pattern copy;
Cam Lobes- new 67-357 from base circle to top of lobe;
LIn LEx R Ex R In
(In") (0.3285 ) (0.3415) (0.3375”) (0.3505)
Hoping that makes sense to someone, It was confusing that each cam had a variety of readings in the course of their revolutions *????*
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how did you get those keepers so low in the caps???
has someone also said this - Rocket and Flash keepers are of different design (I have both) think the Rocket one do sit lower
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has someone also said this - Rocket and Flash keepers are of different design (I have both) think the Rocket one do sit lower
*dunno2* Dunno if it's been said Bill
I'm not sure if there's an easy answer, as (obviously) the caps/collars are different profiles, and I think the RR/SR valves are longer(?), so may appear to sit different *dunno*
Just another thought that I wonder if Mike was supplied mismatched collars/collets from RR/SR?SS ? (Shooting Star different p#'s)
Note; I've amended my above post, realized I had stuff where it shouldnea been- I think fixed now *conf*.
This is the relevant stuff in answer to Mikes question;
Actual Valve travel (with a 357 cam as below) measured with dial gauge on valve caps, as best I could;
L Ex 0.3575” R Ex 0.3605” (0.003" variation L/R)
L In 0.371" R In 0.3675” (0.0035" variation L/R)
** Note that this is lifted with a reground 357 may have slightly different specs from standard. *ex*
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hi Dutch
good to have your data posted - its gonna help some other poor sufferer of a10 valve height weirdness. I've had people say "its just a low-spec a10, it should just work", but mine would not have without the extra effort. getting the collets re-machined (as per the post above) did solve the problem and leaves me thinking that no matter how much money you spend at whatever flash shop you've still got to check them all in detail. i did Plasticine tests and all. the supplier (see above) only sells alloy head ones, so i assume no supply mix ups re Bill's comment about flash vs rocket
the bike is now back together *eek* *eek* and as of yesterday road legal *smile* *smile* - sounds awesome. shakeout run this weekend. can't wait. i might even finally get a picture of it on the pictures forum....!
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Congratulations, have fun on the 'shakedown' I hope not too much shakes off *eek*
the supplier (see above) only sells alloy head ones, so i assume no supply mix ups re Bill's comment about flash vs rocket
The Shooting Star is the A7 version with alloy head, and I've got mahself carried away and found all the numbers(except springs *countdown*). It's not to say somediffreent numbers aren't the same part, but why would they be(BSA *pull hair out*)
A7,A7S/S,A10 29-0410 Collet*
A10 S/R 65-1624 Collet Also RR 56/7
A7,A7S/S, A10 67-0034 Collar*
A10 S/R 67-0960 Collar Also RR 56/7
'A' Group to '57 67-0033 Valve cup (bottom)also later Models;
A7,A7S/S, A10 67-0033 Valve cup (bottom) except S/R
A10 S/R 67-0886 Valve cup (bottom) Also RR 56/7
*beer*