Crank build for racing engine

[greg brillus]

I guess it varies from country to country what you can/cant get away with.......Its all cheating to a point......latest Terry Prince head, but very heavily re worked........welded up the valve guide bores and started again........The valves, well we thought we were the first to do what we've done, but turns out Steve Hamel beat us to it........Simply another round collet groove machined half way up the stem, then a pair of modified standard collets with the outside machined parallel with a small hat section left at the base for the stock collar to press down on to.......Had some ney sayers about how it will work, seems to be ok using 140 Lb seat pressure springs and 600 lift at the valves.......taken it to 7000 no problem.......Just kept pulling like a train.......We aren't doing anything special that hasn't been done before........just not sure its been done with an original type Vincent engine.....Maybe maybe not.......It's our own personal challenge.......My single is the guinea pig to my mates twin......If mine is anything to go by, his twin will be a monster......Main trouble we've had is modifying Titanium valves.......once the special coating is gone, they wear badly........on the stem, it chews the stem and guides out rather quickly, and on the valve face it starts to abrade the face quickly causing the tappet to close up........not a big deal, just needed to get the valves re coated by a tool company that supply machine cutting and lathe tools.......Vic should know what i;m talking about......Once these items are sorted, it should be all guns blazing........Cheers......G.

 

[oexing]

To be open, I would not have the balls to run titanium valves, maybe in racing for periodic exchanges. Same with alu conrods, great when you replace them each year or more often, the drag racing guys have them.
Problem with titanium is the poor properties when in plain bearing applications, like in valve guides - I would not want to picture them in almost redhot conditions for ex valves. The Balzers company offers exotic coatings like shown in my link below. Vincent Speet may have tried some in his engines, cannot tell about experiences myself as I´d have to send parts somewhere and no job for home.
While I can imagine finding a great coating for the valve stem I would not think there was a way to prevent wear on the seat of titanium valves. Typically you´d find sort of stellited faces for unleaded and Diesel valves for extreme mileages - kilometers too. But then, I don´t quite see the point of modifying old classics to these extremes so in the end there is not much left of the familiar character of the bike when it should be just the fun of having a great time on safe race tracks and producing sounds we remember from long gone times. After all, there is nothing to earn from that racing, just maybe a tin pot to collect dust at home.
What I criticise most in these communities is the cheating about details in their engines: I bet most of them got big bores and way more capacities than what is listed in papers. So all spectators and fellow racers get cheated about extreme modifications. So anybody who sticks to near original specs will be frustrated by not dealing at roughly same levels and nobody admits what he´s done .
Some time ago I got asked about producing an extra hot camshaft for the 1928 BMW R 63 ohv 750 twins for classic racing. The guy would not tell me much about what origin his 750 had and what was done already on the engine, so a biiig secret about that bike. After some discussion about attitudes I was unwilling to take part in spectators and fellow racers cheating and ended that phone call. Remember Troy Corser beating a Manx with the R 57 from 1928 so you can imagine there is next to nothing in his engine made by BMW, it would expode at half that speed definitely.
My mods on the Vincents are no secret as most here will have seen for a while but then no racing is the motivation just a dead solid engine is the plan, no compromises for poor details.

Vic

Balzers coatings

Troy Corser BMW racer 1928

 

[greg brillus]

People have been modifying and blowing up engines since the beginning of the internal combustion engine........The Vincent name is well known for speed work so nothing new there.......Most super fast classic race bikes run no original parts (Molnar Manx) for one.......An original Manx would have near no hope of winning against these modern replicas........I agree with what you say, but some of us still like to get more from what we have......a lot more fun and semi productive that just dreaming about it........Costly yes, but not too bad........I suppose an exclusive club membership to an elite Golf club or out catching a Marlin from a super expensive fishing boat would be better........for some......Not me.......When you come out of a corner and wrap open the throttle and feel the pulling power like taking off in a jet........On a single cylinder classic race bike.......it actually feels like you've done something just a little bit special.......well better than scratching your head fixing years of butchered cases and heads from years of abuse.......Its nice to do something that actually goes instead of some asthmatic steam engine.......If we cant enjoy something, then what else is there.

 

[greg brillus]

Getting back to cranks/rods and the like.......A seemingly common issue I've seen and talked to others about, is an issue where the little end and in particular the pins show signs of extreme heat and turning blue....... Interested to hear others opinions of what is causing this problem.......we think we've come up with the answer but interested in others thoughts........Cheers.

 

[Peter Holmes]

Does it point to the lack of adequate lubrication?

 

[greg brillus]

It could be a degenerative condition......It has to do with the side play and rocking of the rod little end, coupled with having a piston whereby the little end rod to piston clearance is too much......That is the gap that you can move the piston sideways on the rod with the pin in place.......If the rod supported by its big end does not rock too much from side to side, then the issue is not so bad.......If this condition worsens due to wear, or more clearance given due to racing specs (verses a road engine).......In service, the rod can and will favor rocking to one side.......This in effect jams the pin in the little end......This then causes the friction to go skyward.......Thus the pin and little end of the rod get hot and turn blue.......With our new pistons we had made (at a huge cost) by CP in the USA......we had them make the inside of the pin boss on each side much narrower.......so we now have a side to side clearance of about 30 thou total......we also got them to move the pin to the rear towards the thrust face.......we also got them to move the pin much higher up towards the crown to offset the normal huge "Top heavy" pistons you end up with when running high compression......All these features should hopefully stop the "Also very common" issue of these pistons suffering from bad scuff marks on the front and rear skirt faces......I have ran the engine for about 1 1/2 hours total with this new piston and so far it all looks very promising.......My earlier hand finished piston suffered major cracks around the pin boss on both sides.......16.5:1 Comp will do that.......Too high, so back down to a better 14.8:1 now.......It is my belief that this excess side clearance between the rod and the pin boss on the underside of the piston causes this excessive heat build up.......And you should not run too tight a fit of the pin in the little end bush as well.........Especially on a race engine.

 

[oexing]

Basically when annealing steel parts you watch these colours for knowing the temperature you want to have for correct hardness. But to this purpose you´d degrease the parts first so you will get "true" colours. With conrods I´d think they will be a bit oily all the time so maybe it is not purely the annealing colour effect but some oil film discoloration too. I see same discoloration on my BMW wrist pins plus polished conrods but never care, just thrash the thing. I do extra close fits of piston pin in conrod bush as I believe when you got pistons with easy push fit pins the pins will float anyway in the piston once the engine has run half a minute. Lots of car engines got pins pressed into conrods for floating in the piston only.
I do not support the idea of excessive side clearance small end to piston faces inside for heating up the place. When there is a lot of sideways motions of conrod upper end you got some more serious flaws: The big end roller/needle bearing faces were not made dead parallel within microns - or the conrod is bent and twisted - most of them are . These flaws typically like to push pin securing clips out of the piston as you can feel ridges at both sides of the piston pin bores. I strongly suggest to restore side clearance of your conrod small end to piston insides. When having extra close fits you only mask over other defects in the crank assembly you´d better not want to have or even produce more lethal defects . In my photos one piston is from the old Jag and the smaller one from a Laverda 750. Both show brownish rings from discoloration and nice polished rest of piston pin , no contact onto piston inner faces obviously, else there would not be the brown rings remaining. And the Jag conrod even got a looong drilling from big end up to the small end for pin lube !
Coming back to those faked and modded classic racers - what is the attitude in this community down under and elsewhere: Is there openness and honesty about all mods done, especially about real capacity ? Seems to me many competitors are very tight about telling what they have done, possibly because they got their mechanic and don´t quite know what has been done.
In the racing business engines get checked for correct capacities else they get banned from participating. Not so in classic racing so my grumble about that fraternity is the cheating widely done it seems and that I find quite unfair for fellow competitors and spectators as well. When one keeps to original capacity it is obviously no match to overbored engines with 20-30 percent more capacity. So then this is no real contest about tuners´ skills about finding extra power from the original correct capacity. I do believe there is not much honesty about mods done to these engines - for ridiculous reasons like giving no advantage to competitors who may like to copy your ideas. Well, you only provide your ideas but it is a very different thing to really do the special mod and turn into a reliably working engine - that is the bigger challenge.
No, not my world, too much cheating and aggressiveness in an amateur sport .

Vic

BMW R 69 S with 734 cc :

 

[davidd]

Hats off to Greg for pushing the limits with no secrets. I went to the effort of publishing a book about my racing experience, so there are no secrets here. I built the engine in David Tompkin's Racer in 2018, and its only maintenance has been installing a new piston a few times. The bikes usually do about a hundred racing miles at the smaller tracks per weekend, including one day of practice. At the longer tracks, that will double or triple based on the need for practice.

I began ordering Carrillo rods with some extra clearance in the small end about 20 years ago. I did the opposite of Greg's by lowering the rings to get them away from the piston's exhaust pocket, which showed signs of melting. This was a mod that Carleton Palmer did on the original JE pistons. The compression ratio on petrol is 11.23:1, but the Mk2 cam knocks that down to 10:1 dynamic CR when running. There is scuffing on the piston, but to date, there seems to be no reduction in reliability. Dave did not change the piston this year.

The wrist pin does show bluing, but it has not been a problem. The heavy valves show no problems and rev happily to 7000 year after year. The Mk2 will only make about 39 plus HP at the wheel, but it seems to do it reliably for long periods. I think the reliability has been a boon to a rider new to racing, as most of us are. A professional racer would probably be bored. But the bike is a joy to ride. Dave won three of his first four races this year, and his average speed at Roebling Road was 82 mph. Not bad for a Comet!

David

 

[Alyson]

To be open, I would not have the balls to run titanium valves, maybe in racing for periodic exchanges. Same with alu conrods, great when you replace them each year or more often, the drag racing guys have them.
Problem with titanium is the poor properties when in plain bearing applications, like in valve guides - I would not want to picture them in almost redhot conditions for ex valves. The Balzers company offers exotic coatings like shown in my link below. Vincent Speet may have tried some in his engines, cannot tell about experiences myself as I´d have to send parts somewhere and no job for home.
While I can imagine finding a great coating for the valve stem I would not think there was a way to prevent wear on the seat of titanium valves. Typically you´d find sort of stellited faces for unleaded and Diesel valves for extreme mileages - kilometers too. But then, I don´t quite see the point of modifying old classics to these extremes so in the end there is not much left of the familiar character of the bike when it should be just the fun of having a great time on safe race tracks and producing sounds we remember from long gone times. After all, there is nothing to earn from that racing, just maybe a tin pot to collect dust at home.
What I criticise most in these communities is the cheating about details in their engines: I bet most of them got big bores and way more capacities than what is listed in papers. So all spectators and fellow racers get cheated about extreme modifications. So anybody who sticks to near original specs will be frustrated by not dealing at roughly same levels and nobody admits what he´s done .
Some time ago I got asked about producing an extra hot camshaft for the 1928 BMW R 63 ohv 750 twins for classic racing. The guy would not tell me much about what origin his 750 had and what was done already on the engine, so a biiig secret about that bike. After some discussion about attitudes I was unwilling to take part in spectators and fellow racers cheating and ended that phone call. Remember Troy Corser beating a Manx with the R 57 from 1928 so you can imagine there is next to nothing in his engine made by BMW, it would expode at half that speed definitely.
My mods on the Vincents are no secret as most here will have seen for a while but then no racing is the motivation just a dead solid engine is the plan, no compromises for poor details.

Vic

Balzers coatings

Troy Corser BMW racer 1928

Hi Vic, please correct me if I'm wrong, but, does not the BMW S1000RR use titanium valves in their engines ? I can personally attest to the performance of that machine

 

[oexing]

Alyson, these generations of BMWs are way beyond my scope, in fact even air heads from 1970 on not my thing. You may be right about titanium valves in some of these but I would not believe that was a factor for high performances. I think a few days ago my friend reported about a titanium valve failure, with 7mm stem possibly, don´t remember exactly . So you see nothing that bothers me much. It is a different matter when selecting material for high mileage road use or short time racing - in extreme case just for one single race before swapping for new.

Vic