Triumphrat

ohiorider · 04-16-2006, 06:00 AM

With most of the mods discussed on this site centering around rejetting and freer flowing exhausts, I was curious if anyone had experimented with various length intake headers? It would be difficult using the standard airbox setup, but it would seem a natural for those who have eliminated the airbox and installed external air filters.

Also, has anyone not gone with the big bore kit, but installed higher compression pistons, perhaps along with having the head flowed? Maybe different cams?

Although the old adage says 'there ain't no replacement for displacement', it would seem that the design basics of the Bonneville engine in either 790 or 865cc size, namely:
- 4 valves per cylinder
- oversquare design (bore greater than stroke)
- relatively short stroke (68mm)
would be capable of a bunch more horsepower without increasing the engine size.

Or perhaps the original design was intended not as a high horsepower engine, but one that felt, ran, and sounded like Bonnies of old, and it's an uphill and expensive battle to get more than 70-75hp to the rear wheel.

Regards to all on this Easter Sunday morning,

Bob

vitabrew · 04-16-2006, 07:52 AM

I installed South Bay Triumph intake manifolds which are shorter than stock, roughly by a cm. I did it mainly because I got tired of wrapping my cracked intake rubber tubes with duct tape. I can't say I noticed any performance difference for better or worse.

I don't know of anyone making high compression pistons for our bikes, outside of those in big bore kits. Thunder Bikes are working on cams for the 360 degree motors, they released cams for the 270 degree motor and posted some nice dyno results.

RaceDweeb · 04-16-2006, 09:56 AM

I too have played with runner length by using a combination of T100/TBA/SBT manifolds and Thruxton spacers. If there is a difference, it's rather slight.

Mike