The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Rocket Racer on 11.12. 2013 20:36
-
http://arp-bolts.com/kits/ARPkit-detail.php?RecordID=1242 (http://arp-bolts.com/kits/ARPkit-detail.php?RecordID=1242)
a balancing specialist mentioned ARP rod bolts to me yesterday, which appear to be available for BSA's subsidiary triumph 650 bonnies.
Would triumph rod bolts be likely to be common with BSA rods?
-
You can buy ARP bolts for the A10
http://www.srmclassicbikes.com/catalogue/index.php?target=products&product_id=30
I have a set in my '61. When I bought mine they came with a slip of paper saying to torque them up to 36 ft lb or some similar spec, I ended up contacting ARP's tech department and they recommended 28 which is what I did mine up to.
-
Just what I wanted to know! many thanks.
I love this forum *smile*
Order placed!
-
Rocket racer, I bought some ARP rod bolts for my '61 Super rocket,. installed them as instructed, installed the crankshaft, bolted the case half together, install the pistons and the barrel. turned the crank over by hand, and clunk the crank would only turn about 300 degrees in either direction. It turned out to be the nut of the rod bolt hitting the inside of the case. So I had to tear the motor down and put the old rod bolts in.and had no further problem. Not much room inside there.
Clive
-
Hi Clive
I bought some custom made rod bolts from a well known Mike in UK, he wanted some made for his own use so got a batch made, I might of had the same problem as you but he had found the problem before I used the bolts and sent out replacement with the bottom of the nuts shouldered (if that's the right term) just about a 1/8th or so square section taken off the outside bottom corner.
I've had no problem with them, rather different method of torquing up though, came with special lube and IIRC instructions were to torque up to required setting and then slacken off, repeated three times to same setting, came with stretch measurements too which I checked and were spot on.
Felt like a real engineer doing al that *smiley4*
-
Tim (aka rocket racer) are you using standard rods? ( I ask as torque settings will vary depending what rods are used, and whilst you will know that someone reading this in years to come might not!)
The issue with nuts hitting cases seems to be a question of luck, I fitted "lightning" brand billet rods from Thunder Engineering of the UK, with ARP bolts, to '56 cases and they did not hit, but others like the post above have found they DO hit.
I oiled the threads but felt nervous doing it, it seems more natural to use threadlock given there are no lock washers etc......
-
I had the nuts hit the cases too, but it was std BSA large journal crank, rods and bolts into a '57 A7SS case. Domed the nuts a bit to give about 60 thou clearance and problem solved.
I was told once that the std A7/10 rods only had a life span of 60,000 miles.
Cheers
-
Tim (aka rocket racer) are you using standard rods? ( I ask as torque settings will vary depending what rods are used, and whilst you will know that someone reading this in years to come might not!)
The issue with nuts hitting cases seems to be a question of luck, I fitted "lightning" brand billet rods from Thunder Engineering of the UK, with ARP bolts, to '56 cases and they did not hit, but others like the post above have found they DO hit.
I oiled the threads but felt nervous doing it, it seems more natural to use threadlock given there are no lock washers etc......
I too have has problems in the past with rod bolt nuts fouling the cases. Am in the process of doing two motors and hope to use the ARP bolts in the race motor which they may not fit using modified T140 rods with steel caps. However my '61 SR build which will have std rods can always use them...
My balancer is looking to make the crank balance variable just in case I want to experiment, given my motor is short rod, not in a standard frame and dragging a racing sidecar along, so not necessarily a std build ;)
-
Hi, I've also used the ARP bolts for A10 rods, the ones that SRM used to sell. They were a lot better than the originals and hugely better than aftermarket rubbish that I've seen . I also had trouble with them fouling the inside of the cases, but this was correctable with filing.
You may be surprised to read this, but the billet rods sold by Wassell are extremely good. They are actually made by R&R, one of the top USA performance products companies specialising in conrods (drag racing and Nascar etc.). These rods use 3/8" bolts made by ARP and are torqued to 50lbs ft and so will handle a lot more rpm than anything with a 5/16" bolt. The junction face between the rod and the cap is also serrated. I know the Thunder rods have a good name but these are also a very good product.
-
Hi All,
You may be surprised to read this, but the billet rods sold by Wassell are extremely good
There was a problem with the centre to centre distance with these some time ago
I dont know whether this is still the case?????
John
-
I hadn't heard such news and I'd be grateful to know more. Can you supply any details? My motor built up OK.
-
Hi jj
If my memory is correct the Wassel rods had 6.5in centres where as the BSA is a little shorter than this
I dont have the actual figure to hand at the mo. it led to the top of the pistons touching the head *????* *????*
Dont mention Wassel carb jets to me utter SH*TE !!!
nowhere near correct size, on both needle and main jets
John
-
Old thread, same case hitting problem.
After reading this I mocked up the motor with the new rod bolts, and they barley hit.
For you guys that modified the rod nuts, how did you do it? I can chuck them up in the lathe and either dome them or shorten them, but I have no idea how hard these nuts are and I hate to ruin one.
So the question is, did you use a lathe or a grinder to modify the nuts? *conf*
Lee
-
Hi Lee,
I would thread them onto a suitable sized bolt / stud thats held in the lathe chuck
Chamfer the outer ends of the offending nuts, and see if this will give clearance
If more is required shorten them a little at a time,
Only take metal from the outer end of the nuts, I would worry if you faced the flange you could go off square to the threads
An insert tool should have no bother with the material
John
-
An insert tool should have no bother with the material
John
*smile* Thats what we were thinking a few weeks ago with a keyed shaft (interrupted cut just like a the nut) that needed cutting. We almost ran out of inserts getting that done. Between the hardness of the shaft and the keyway pounding them too, the inserts didnt have a chance.
I will report back with the results.
I wish I had a tool post grinder, and someone elses lathe to use it on. ;)
Lee
-
OK,
Called ARP tech support before I modified the nuts. They said the nut will be fine as long as you dont remove so much material that the nut splits. This must be a common problem they hear. There was no way I needed to remove that much.
Cut these with a carbide insert. the material didnt seem that hard, I think I could have done it with high speed steel but I did not try it.
I set the compound to 30 degrees and just chanfered the outside of the nut.
The crank spins just fine now.
Lee
-
G'day Lee. You need about 6othou (1.5mm) clearance of rod and cases. You'd be surprised how much the crank flexes. I only had this problem once so I just ground off the offending side of the nut.
Cheers
-
Hi John (Chaterlea) and others,
Thanks for your earlier notification of the suspect centre to centre distance on the R&R rods. I had occasion to go looking around inside my RGS (suspected low oil pressure which turned out to be caused by a pressure build-up in the body of the glycerine-filled oil pressure gauge, meaning that with 70psi oil pressure, it showed 25 psi! Rectified by pulling out the little rubber cap holding the glycerine in and then replacing it.....
While I was at it, I measured the A10 R&R rods and they are about 28 thou inch too long. With 9:1 pistons this made the bike pink a bit around 3,500 rpm. I put in one of my (Ebor Bikes) 0.7mm compression plates and this seems to have fixed the problem.
Cheers,
Jon
-
Hi JJ
Rectified by pulling out the little rubber cap holding the glycerine in and then replacing it.
Aha *ex* rookie mistake *smile*
In industry the rubber bung is removed permanently on installation
I dont know how the gauge would fare opened on a bike though *????* *????*
John