The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Sunbeam on 01.07. 2011 10:06
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Hi. I need help with my 1962 Rocket Gold Star. The rocker box was leaking and the head had to re- torqued due to the new copper gasket blowing sightly. After removing the pushrods so that I could clean the rocker box mating surface, I checked each rod for flatness on a sheet of glass. I then found that one was bent slightly (approx 3/4" from the end and another was starting to mushroom around the hardened end cap......both on the exhaust pushrods).
I have tried everywhere to get a set of steel pushrods, whether new or old stock, from usual suppliers (C&D, Autocycle, G. Prew) but they can now only get dural alloy. SRM sell Chrome / Moly rods, but looking at their website pics, end caps now drilled. Have even tried getting a decent secondhand set. Looking back at old posts, BSA fiitted hollow steel pushrods and someone mentioned that Dural pushrods can flex. Note: Have since found that Lyford Classic Services now sell HE30 solid billet pushrods with hardened EN36 ball ends.....Made in England. Any advice of which way to go would be grateful.
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I also gave up on the alum. push rods on the RGS engine. I don't understand what you think is wrong with the SRM rods, I use them and they are fine. I no longer expect them to bend.
Alan
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Thanks for the info Alan. I would not have a problem in using the SRM. When I went on their website, noticed their design mod with oil hole in the pushrod ends, similar to what AMC used on their heavyweight singles.
Howard.
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Hello Mr Sunbeam, welcome to the forum! *smile*
I think it would be wise to establish why your pushrods are bent. I would make sure your valve springs aren't coil bound. That can happen if the caps under the springs are wrong way up, depending on the type.
HTH
Cheers
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G'day Sunbeam,
ditto Andy, another cause is loose valve guides. Alloy or iron head? With alloy head they might seem tight when cold but when hot can ride up limiting the lift and bend a push rod.
I have alloy push rods in both my A's, the cafe has tapered (thick in middle, much like me) ones. I am looking at the Lyford ones for my next motor.
Cheers
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Also are the valve springs of the right poundage?
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Thanks A10boy & muskrat. Will take your advice and check valve springs / caps / guides. Suspect a duff pushrod was fitted in the past. Three of the pushrods are nice and shiney....bent one looks as if its been around a bit with a nick at the point of the bend. Suppose the damage could be historic from incorrect pushrod / rocker cup location.
p.s. still finding my way around the bike as I have been a humble AMC devotee for longer than I would like to say. *smile*
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Hi wilko. Double valve springs have been fitted, HHC RGS engine. Will check poundage if head has to come off.
Howard.
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There's nowt wrong with having an AMC in the collection, got one myself, so has Groily and MG. variety and all that. *smile*
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In fact, it speaks to your impeccable good taste Sunbeam.
Funnily enough, one meets not dissimilar problems with the tubular alloy pushrods on the AMC Twins, which can chafe themselves dangerously weak unless head gaskets are carefully pared exactly to match the drillings in the castings . . . a variation on the theme you're facing!
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Thanks A10Boy & groily. Looking at A10 pushrod arrangement where they come through head into rocker box, seems they could be easily scuffed which explains the condition of the secondhand pushrods I have come across.
Got two AMC bikes, one very long project which literaly broke the piggy bank and had to be shelved for a bit. Recent flurry of activity on the other one, would be nice to see it finished this summer. As for the 1962 RGS, well it was a moment of weakness bought from a dealer 2 years ago.
Howard.
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Hi, my first post. Just to add a little variation to the theme. I've just been reading the Australian Rolls Royce Forum. It seems Silver Shadows have cast iron inlet valve guides. These can rust to the valve if the engine is not started for a while. So when the engine is started, eight inlet pushrods like a figure S. *eek*
Regards, Nigel.
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Hi, my first post. Just to add a little variation to the theme. I've just been reading the Australian Rolls Royce Forum. It seems Silver Shadows have cast iron inlet valve guides. These can rust to the valve if the engine is not started for a while. So when the engine is started, eight inlet pushrods like a figure S. *eek*
Regards, Nigel.
Good point. Thankfully my SRM guides are some bronze alloy or other.
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hi alanp you mean the Colsibro material valve guides composed of Copper, Nickel, Silicone alloy which resists wear, corrosion, spark erosion, has a high tensile strength and can cope with rapid temperature changes, the closer tolerance enabled by using this material allows for a cleaner running engine. ive had them done on mine i also have dural pushrods in mine no probs with them i also have the tufnel valves as well
dave
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Just got a new set of SRM chrome moly pushrods. Good American site to have a look at for pushrod info.....smithbrothers@pushrods@net
Howard.
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Hi, my first post. Just to add a little variation to the theme. I've just been reading the Australian Rolls Royce Forum. It seems Silver Shadows have cast iron inlet valve guides. These can rust to the valve if the engine is not started for a while. So when the engine is started, eight inlet pushrods like a figure S
Must have missed that one.
Some of mine have not been started for over 5 years and bent push rods has never been a problem.
Leaning them without the rocker cover on is more like the cause.
The 6.7L motor has stuffed glands for valve stem oil seals which can dry out and if the engine has the rocker cover removed then you could possibly get some rust but the valves are very high nickel so should passivate .