The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: bl**dydrivers on 28.11. 2024 18:07
-
I’m ready to send my cylinder head out to get vapor blasted, get valve guides replaced, mating surfaces skimmed, unleaded conversion and rebuilt using all new parts collected.
Just don’t know of anyone here in Florida that can perform it well!
Know Wes Scott Cycles in Fort Lauderdale and is about a 20 minute ride away! However, he doesn’t have a machine shop and wouldn’t tell me who he uses.
Just don’t want to have to send it out to SRM as postage will be a killer
And my concern is a step on the right side inner edge combustion chamber.
Going to be using 8.25:1 pistons and hope they won’t hit the lip!
-
If I was going to get a top-notch job done by a top company I'd swallow the postage/shipping, as it's not much particularly when compared to the cost and value of the finished item.
A happoth of tar...and all that?
-
If I was going to get a top-notch job done by a top company I'd swallow the postage/shipping, as it's not much particularly when compared to the cost and value of the finished item.
A happoth of tar...and all that?
That’s what my gut is telling me
-
I am with Rex on this one, you need to find a specialist in Britbikes with alloy heads. Among other things one problem that can arise through inexperience is if the guides are knocked out cold which you could perhaps get away with on an iron head.
With triples some people go to the trouble of drilling out the old guide leaving a thin wall which can then be collapsed to avoid the possibility of hard carbon and corrosion tearing up the hole in the casting. Think of the amount of heat cycles that head has been through during its 60+ years lifetime, if there is alloy on the old guide after it has been removed that's your interference fit gone. Then after a season of hoping it will repair itself and wiping the oil off the head you will be taking it apart and sending it to SRM, choose wisely.....
DAMHIKT
Best Regards
Chris
-
I've had very similar work done recently here in the UK.
Guides - you need them out with the head hot then you can measure the bores and see whether you can get standard guides or need oversize. I needed oversize the the only ones available are 0.016 over so they have to be trued to fit after the bore in the head has been trued. The oversize guides come with an undersized bore for line honing (not boring) so you need that done. Then seats skimmed to line up.
With the pistons at TDC you can measure them and see it they will hit that step or not, my bet is not. If it worries you take a Dremel to it.
Go steady on skimming the joint surfaces, there's only so much metal and you want it to last!
I shopped around and found a machine shop that did general engine machining. The head work - both inlet guides, turned, fitted honed, 4 seats re-cut, £220. I run the original seats with unleaded. They did need exact instructions and did just what was agreed but i was happy with the work and the engine runs well.
-
any competent automotive machine shop can do the work I ordered colisbro guides, G and S valves and springs from SRM
I heated the head in the oven when the wife was out *smiley4*removed the original cast guides the new guides I ordered at .020 over size and measured each guide hole and had a friend with a lathe turn each guide to proper od then heated the head and fitted the guides , ordered diamond hones from Brush Research in USA and honed [ you cant ream colisbro } the guides id to spec from SRM I believe the intake clearance was .001 and exh was .0015 but SRM will give you the specs .
I took the head and valves to an automotive machine shop that also does bikes and got them to cut the seats ....I believe the cost for that was $175.00 CDN .
send an e mail to Bob Gross in Florida he used to have a shop specializing in BSA closed now but he would give you info on where to go he runs a fb site " bsa owners of North America only "
on a side note check everything is functioning as it should the springs I got from SRM 3 were fine although close to being coil bound and 1 was coil bound so I didnt use the ones they shipped and too expensive to return .
good luck
-
Everything I ordered from SRM (other than valve collets).
What I’m concerned about is the guides I ordered std and the valve springs I got from them are MCA (never had luck with MCA!).
I contacted SRM
Bead blast £59.08
Set of 4 Colsibro guides £87.96
Fit & hone 4 guides £49.64
Cut both inlet seats £25.60
Leadfree exhaust seats £120.00
Skim head face £49.50
4 valves £94.60
Spring set £32.99
Re-profile combustion chamber £52.88
Lap & assemble head £49.57
Sure adds up
-
plus shipping both ways
-
Lead free valveseats are only mony making from SRM. The original seats will last forever, there is no need to convert.
cheers Klaus
-
Lead free valve seats are only money making from SRM. The original seats will last forever, there is no need to convert.
cheers Klaus
That's my understanding too so unless the originals are worn/recessed so far they can't be recut then not strictly necessary. Although if you call SRM I'm sure they will give you a convincing reason to do it all...
You know; "while its all apart / you only want to do this once / for us to guarantee the work we always recommend this" etc.
and you are sending it half way around the world and back... :!
-
Lead free valve seats are only money making from SRM. The original seats will last forever, there is no need to convert.
cheers Klaus
That's my understanding too so unless the originals are worn/recessed so far they can't be recut then not strictly necessary. Although if you call SRM I'm sure they will give you a convincing reason to do it all...
You know; "while its all apart / you only want to do this once / for us to guarantee the work we always recommend this"
etc.
Original Valveseats are cast in and very hard to machine off complete, worst case is to discover a blowhole.
If the seats are to deep you can convert to an 1.5 inch inletvalve I had done three times.
I have not the best experience with SRM, they had done my first engine for a high price and it last only one year or 10 thousend kilometres. One piston split parallel to the piston bolt, one loop from the cam has gone and a valveguide come loose. So no more missions to SRM.
cheers Klaus
and you are sending it half way around the world and back... :!
-
All these jobs are surely well within the expertise of a local machine shop, when us Limeys see the work carried out on your custom car and bike shows, nothing is impossible.
Original seats are best left, as stated, unless really too far gone to recut. Even then, local fitment gives a greater chance of getting exactly what you want.
Swarfy.
-
Had another look at your photos. The combustion chamber is a bit strange looking on the one side isn't it. Have you accurately measured the volumes with a pipette and some kerosene? I think I would, just to be sure you're getting even compression, never mind piston clearances etc.
-
those seats look shot to me .as for compression mine has been running erm thrashed for ages with one piston 10thou lower than the other after having the big end re done when some fool had shaved off the cap to stop an engine knocking , i only found this out when putting the engine together years ago with different rods. i was saving the original polished rods for the berger build but put thunder rods in, polished rods have now been sold.
-
I agree with BagoNails... Measure the swept volume and compression space volume correctly before you do anything. You just don't know what has been done to it in the past, the compression ratio might be WAY out. When I got my engine, it had been used as a grasstrack racer and had been skimmed to about 12:1 to run on Methanol. Easy to get back to correct 8.75:1 using a compression plate under the cylinder base. But it could have been messy if I hadn't checked it. Your head 'looks' unskimmed, but check the cylinders too they could have been skimmed. (Or maybe I'm just being a paranoid alarmist!) *eek*
-
Now I’m really concerned!
What am to do if the seats are not salvageable?
Can you run the original exhaust seats on unleaded? Every shop here doesn’t mention about unleaded like SRM does
How can I measure the swept volume and combustion space volume without any valves?
I know I have another cylinder head and is complete presuming it will need work too but is in UK and would have to get my Father to ship it over
-
Mate, re: the seats, I don't think I'm mistaken in saying that Klaus has raced his A10 with standard seats. So unless your seats are heavily recessed you should be fine.
I haven't noticed any posts on this forum complaining about lead-free valve seat problems. Anyway you can get a lead additive for your fuel if you're worried about it.
You CAN check your ratios without valves, simple to make thin plywood or plastic discs to glue onto the valve seats to seal them for measuring. Sure it needs a reassembly of your motor, but that's just good practise anyway. Hahahah!
Surely there must be good engineering expertise in your part of the world to help check/fix your motor as Swarfcut says. Nothing here is super difficult to refurbish, its just head stuff.
What they do if valve-seats are beyond 'salvation' is they set the head up on a lathe or Milling machine and cut out the old seats, not nice because the valveseat steel is VERY hard, so hard to cut.
Once the seat is cut out a new seat needs to be made to very close tolerances, and shrunk into the head. Bit of skilled work there but nothing 'super difficult'
So why don't you get the other head sent over to you? then you have 2 to work with?
-
Yes you can run modern fuels to the old vavle seats.
And yes I racing with 10,5:1 pistons and original seats with no problem. I use Aral 102 octane for this.
So, if the seat will be fine with a 1.5 big valve leave it. For inletvavles are only 1.2 to 1.5 mm contact surface nescessary.
cheers Klaus
-
I think its also worth mentioning that while we fondly remember 5 star petrol (101 octane) most ran on 4 star (98) or 3 star (92). I ran my C11 (iron head) on 2 star and I seem to recall there was still some 87 octane about. With manual ignition it was easy to pull the timing back a bit a live with the power drop for the savings. These engines coped fine.
-
The other head is at my Fathers, as I was more concerned bringing the big heavy items back with me to get the project going and left that there as I already have one here.
Brought back, crankshaft, crank case, cylinders, inner/outer timing covers, inner/outer primary covers and shipped the gearbox. Now I have everything here other than fuel tank.
Left the fuel tank there too and can get another original needing allot less work here in the near future.
I reached out to an engineering shop over here that has a YouTube channel and waiting for a response.
There’s also another one about 45 minutes ride away. However they are only open on weekdays and I’ve got to work those days.
-
Lots of useful stuff here. My two penneth - Has anyone tried lined valve guides? I took my A10 iron-head along to the local engineering workshop (owner has run tritons for years, so bike savvy) and his solution to the worn guides was to leave them in situ, bore and ream them and fit phosphor bronze liners to the guides themselves. Apparently there's a commercial kit available for doing this. The final job is really neat, but, not having run them yet, I can't tell if it's a good way to go. Saved cash, though. As for unleaded fuel & valve seats, pop along to your nearest general aviation airfield with a container and fill it with low-lead Avgas. Just add some to your tank every couple of hundred miles - more than enough lead there to protect the standard seats.
-
Colisbro guides? Bit overkill as standard guides are so cheap to buy and fit.
After 60+ years of being bashed many times a minute, those valve seats are glass-hard, and unless they're really pocketed just run as they are and see if there's any problems. There shouldn't be.