Tuning Big Block Sports Guzzi Engines

[Kristian]

Here's little tidbit for those trying to extract more power from Guzzi big twins. These Guzzi motors are very old-fashioned air-cooled, 2V, pushrod twins, with seriously outmoded Hemi heads. This is early 1960s technology. My 1995 Sport 1100 is rated at 90 HP ex-factory, mine had 77 HP at the wheel recently, which is just over 90 crank horses. By Dr. Wittner's accounts, this version of the big twin was fully hot-rodded from the factory, with very little else to give without sacrificing reliability. This gives the Sport engine a specific output of 84 HP/liter, which is *very* good for such ancient technology, especially given how reliable they are.

Compare with other, similar, engines. The old air-cooled flat-six from Porsche--who employs the best automotive engineers in the world--in its best, last, 3.6-liter iteration as used in the 1994-1998 993-series 911 was 3.6 liters with 282 HP, for a specific output of 78 HP/liter. That's from a superior engine design--air-cooled, 2V, Hemi-head, apart from being an OHC design. That engine is probably the best air-cooled performance street engine ever designed.

Ferrari--whose engine design engineers are no slouches--had their 4.4 and 5 liter 2V, Hemi-head, OHC, flat-12 in the '70-80s BB512 and Testarossa. It was 5 liters with 390 HP but water-cooled, for a specific output of 78 HP/liter.

The baddest 2nd gen. '60s Mopar 426 engines-7 liters-were rated at 425 HP, for a mere 60 HP/liter.

But, Ducati's '90s 900SS engine-similar configuration except OHC-had 80HP from 900CCs, for 88 HP/liter, though with half the Guzzi's longevity and much more fragile overall.

So, Guzzi did an amazing job with these engines; no wonder it costs a mint to extract a little more, with a large loss in reliability. They're already maxed out.

[John A]

There is always room for improvement on a mass produced engine if careful thought is used. I agree with Kristian that the more the original engineers have done, the more careful thought is needed before any improvement can be realized . If for instance you had a highly tuned sport bike , you would be in for a world of learning if you started to modify it without some specialized knowledge . I've seen a lot of bikes that someone has turned into an un rideable pig but went like stink when you got them into the range where everything worked. Successful tuning can be made to Guzzi engines without a loss in reliability  but not blindly. Good post!

[lazlokovacs]

yes good post

[molly]

Good post putting everything into perspective. My 1100 Griso 2v motor is a sweet thing to ride and I really wouldn't want to compromise that experience with further tuning.

[lazlokovacs]

food for thought as I've currently got a 1100 cali motor on my bench, gonna balance it and set proper squish,

this post reminds me to not go looking to get any major extra performance out of it

[Tusayan]

I think a good automotive comparison to the 1100 Sport is the pushrod 2V per cylinder GM engine used in Corvettes.  That one makes 460 HP from 6.2 liters from a very well engineered, inexpensive, reliable engine.   Either one does as well as the Porsches etc, which are over compicated toys, ridiculously expensive for what they do and not the best engineering as far as I'm concerned..

The Guzzi engine made use of pushrod V8 developed technology in the form of the Crane cam and (in the Sport Corsas) Carillo connecting rods.  A little more can be extracted from them with good porting, another 5-8 HP or so without any reduction in driveability.

Motorcycies do have an advantage over cars in that their power to weight ratio allows them to function with highly tuned engines relatively lacking in low end torque.

[John A]

http://mikerichmotorsports.com/index.html
Mike is one of the best but he got tired of starving, catering to us cheap Guzzi types and has branched off into automotive stuff but I believe he still does Guzzi stuff. I had him dual plug and stage1 porting on my hotrodded Bassa. Very good work and it woke that engine up! He will tell you what works and what doesn't . My highest recommendation

[guzzisteve]

+1 or Ace

[Aaron D.]

The early Ducati twins weren't so hot, really wide valve angles that racers altered to get decent output-the Guzzi was better at that point.

BTW the latest Classic Bike has reprinted John Surtees' test of the V8, well worth reading.

[John A]

+1 or Ace

+1 on Ace!