Running 8 valve racer
- Thread starter cliffa
- Start date
Fast Eddie
FULL MEMBER
- Joined
- Oct 2013
- Messages
- 23,390
Molnar is actually making progress with the 8 valve Commando head I believe.
maaseyracer
MEMBER
- Joined
- Apr 2015
- Messages
- 241
I suspect it required a bit of grinding on the pushrod bores to make everything fit.
Schwany
MEMBER
- Joined
- Apr 2020
- Messages
- 3,944
One pushrod could probably lift 2 smaller valves with 2 lighter spring rate springs using a forked rocker. Either that or one has to buy an all new engine from Molnar to get an OHV 8 valve head. Whatever the case, it won't be cheap.
What class would Andy race an 8 valve Norton engine in? Formula 1 Unlimited
What class would Andy race an 8 valve Norton engine in? Formula 1 Unlimited
hybridracer
MEMBER
- Joined
- Feb 2013
- Messages
- 424
It is a pity that Piper didn’t opt for an overhead cam design and to take time to find a way of getting drive to it.
Norton could probably have done it if they had not spent all the money at Cosworth.
Good luck to anyone still working on it at reducing the weight of the valve train.
Norton could probably have done it if they had not spent all the money at Cosworth.
Good luck to anyone still working on it at reducing the weight of the valve train.
Fast Eddie
FULL MEMBER
- Joined
- Oct 2013
- Messages
- 23,390
Correct, they’ll use a forked rocker.
Andy’s Hope is to sell them to road riding special builders as there’s no real race class for them. He knows he ain’t gonna sell many. He’s doing it coz he wants to really I think.
Last edited:
o0norton0o
FULL MEMBER
- Joined
- Apr 2015
- Messages
- 2,305
There's a lot of problems already with the solid lifter valve train wear on commandos. Adding a second spring to compress and maybe some extra weight will take some engineering to make the problem of a solid lifter pushrod engine lessen rather than increase... much like switching to an overhead cam with 4 valves also presents a problem with the shape of the commando's hemispherical head. As many find out, nothing is impossible, as much as it is complex and costly... Something I'm very familiar with... 
Of course, I do love seeing people do what seems like the impossible. It's just more fuel for me to continue my own efforts on projects that consume my retirement nest egg...
Of course, I do love seeing people do what seems like the impossible. It's just more fuel for me to continue my own efforts on projects that consume my retirement nest egg...
What a waste of energy. The Norton bottom end is as bad a starting point as it gets, IMO.
The P86/P89/Quantel Cosworth engine would be a much better choice.
- Knut
Last edited:
hybridracer
MEMBER
- Joined
- Feb 2013
- Messages
- 424
Yes, if Norton had done it it would have needed a new bottom end and transmission. (One of the reasons I preferred the 500 over the 750 in my Domi was that the 750 wore parts out which lasted forever with the 500) Norton knew that so the Cosworth was, I presume, intended as a replacement but was Overweight, over complicated and the designers handicapped by Norton’s requirements. Perhaps if Cosworth had been asked to just build a compact, lightweight motorcycle engine with >160 hp/litre we might have had something which worked out of the box and didn’t weigh nearly as much as my complete race bike! (Slight exaggeration but only by a little - I could stand beside my full race trim 500 Domi and pick it up, both wheels off the ground). Okay, I may be being a bit negative here as it did have to double up as the frame.
Quantel did a very good job with the Cosworth but for what cost and how long did it take?
Obviously not that long. The project was initiated 1984 and the bike appeared race-ready at the end of 1985. Then some further development took place with Cosworth, e.g., by adding mechanical fuel injection.
The investment and time is of no concern to us, is it? In fact, it's a great benefit as it would provide an even better starting point.
Shedding weight is easy. Shedding weight and retaining reliability is not quite as easy.
The only drawback I can see by re-inventing this engine (and it's a big one), is that it requires a completely new chassis as well. It's not a candidate for a typical custom builder. Cost of designing and fabricating all those cycle parts will deter builders.
An interesting by-note, In 1995 Triumph Motorcycles Ltd considered producing a 750 Bonneville sports bike using a trellis frame and the Cosworth twin engine as developed for the Quantel, according to Alan Cathcard in a Cycle World feature.
- Knut
Last edited:
hybridracer
MEMBER
- Joined
- Feb 2013
- Messages
- 424
You are right of course and time doesn’t matter as shown by so many who have been striving for decades to improve Nortons (I ignore other makes).
Rhind-Tutt offered me his special 1000cc twin race engine for use in the BOT, but I had to turn it down precisely because of having to build a whole new bike around it.
Time for bed I think.
Similar threads
