crossover

[guzzigray]

I'm building a vintage racer with a 1997 Sport engine in a Tonti frame and i'm figuring out exhaust options..... i'm hearing good things about having a crossover up near the heads (my street bike has a BUB system with an upper crossover that works really well and i'd like to replicate that). I have the Sport headers but there's no crossover provision and custom exhausts are spendy. a. would a V11 header/crossover system fit the Sport and b. if it does would sombody like to comment on whether it would be a good idea and c. if it is does anyone have one for sale. Look forward to hear from anyone. Regards.

[Greg Field]

It should fit. Another idea is the headers with cossover from an '03 or '04 EV/Stone/Al/Ti. If you do not care what they look like, I may be able to find some scuffed takeoffs.

 

As for efficacy of the crossover, I'm a believer, based on what people whom I trust have told me. That said, I trust Todd Eagan, and he says there is no benefit. Who knows? But I remain a believer, FWIW.

 

I'm building a very similar bike. I'm going to use Lafranconi Competitione mufflers with their headers with crossover in 40mm, assuming they ever build more in 40mm size.

 

What will you use for forks and wheels? What frame?

[Guest ratchethack]

Guzzigray, I learned a few things about the front crossover when a buddy with a '04 LM had horrific problems with his and wound up welding the headers shut as a way out. Per heaps o' dyno runs that Todd E has personally run, as Greg mentioned, Todd doesn't see any benefit a-tall. My Pal could detect no power effect wotsoever of getting rid of it, but his aggravation level did drop considerably.

 

I'd learned that the front crossover was designed to work with increased valve overlap on the cams in the bikes where it was installed, to increase mid-range torque. IMHO it was one of those "improvements" where the results never manifested themselves in production.

 

If it were me building the bike you've described, and particularly if you're using the cam that came with it, or one of the "classic" hotter cams, these aren't designed with enough valve overlap for a front crossover to have the effect they were designed for in the first place. I'd forget the front crossover and be pleased to've avoided a dark, rough road that doesn't go much of anywhere anyway. . .

 

BAA, TJM, & YMMV

[Skeeve]

I'm building a vintage racer with a 1997 Sport engine in a Tonti frame and i'm figuring out exhaust options..... i'm hearing good things about having a crossover up near the heads (my street bike has a BUB system with an upper crossover that works really well and i'd like to replicate that). I have the Sport headers but there's no crossover provision and custom exhausts are spendy. a. would a V11 header/crossover system fit the Sport and b. if it does would sombody like to comment on whether it would be a good idea and c. if it is does anyone have one for sale. Look forward to hear from anyone. Regards.

 

Um, what happens if someone protests your circa '97 "vintage" racer? I'm not certain I follow this...

 

Anyway, the LeMans I/II had the welded front balance tube [no nasty leaks like Ratch' is talking about] which was likely intended for maximum f/x w/ the B10 race cam, but since the P3 cam that comes in the '97 Sport motor is even hotter than the B10, you should derive some benefit.

 

If I had my druthers tho', I'd be having a true 2>1 like on the Dr. John racers made up, but as you say, that gets spendy in a hurry...

[motoguzznix]

Gray

 

Mistral offers a header pipe set with front crossover with 42 mm ID. For Tonti frame Guzzis.

The 1100 Sport headers have the right diameter and I would not expect very much powerwise from a front crossover.

Worse will be the use of the much smaller Cali header tubes, with or without crossover.

The V11 headers may will not fit the Tonti frame very good - check that first.

My opinion: restrictive mufflers benefit more from the front crossover than open mufflers.

[guzzigray]

Thanks guys for the replies. Interesting comments. I should clarify my question: i'm not necessarily looking for outright power at 8000rpm, i've heard that the upper crossover increases mid-range which is an area i'd like to maximize (i'm hoping to rely on the torque and great handling rather than outright power). I'll be dicing (or should i call that following) 110 HP Z1's and CB's and in Vintage Superbike so i have to pick my battles......

 

I've noticed that the '03 V11's have the upper crossover after not having them in prior years so i figured Guzzi were up to something??

 

Greg, i'm using 38mm SP forks with Maxton internals and T-3 wire wheels. I'm also using the La Franconis but i'll cut off the first few inches of taper to fit the larger diameter headers. Also using a Mk 3 frame so i can use the frame as a breather.

 

As regards eligibility of the 97 motor..... like technology!!!! i'm entering it as a MK3 (bored and stroked) and i'll be well within class limits and truthfully if someone protests my measly 85 hp and 480lbs then they would need to get a life.

 

Other specs are: stock bore, Mike Rich heads milled for 11:1 compression, Carillos, x10 Megacycle cam, Ti pushrods, Mikuni carbs (39.5mm) and Dyna ignition driven off the cam.

 

I've spent the last year gathering parts and i'm close to starting the mock up. I'll be posting pix soon. Any further comments or advice will be hugely appreciated.

[Greg Field]

38mm forks? Must be aftermarket Marzocchis. Those're good to have. Sounds like a fun projet. Are you running the broad sump and oil cooler?

[guzzigray]

38mm forks? Must be aftermarket Marzocchis. Those're good to have. Sounds like a fun projet. Are you running the broad sump and oil cooler?

 

 

I think the forks are off a SP111, definitely not Marzocchi's. We spoke last week regarding the sump plumbing. I'd like to run the cooler, as i guess it wouldn't hurt but it's one of the things i've heard differing opinions about. Regards, Andrew.

[motoguzznix]

I've noticed that the '03 V11's have the upper crossover after not having them in prior years so i figured Guzzi were up to something??

 

 

Other specs are: stock bore, Mike Rich heads milled for 11:1 compression, Carillos, x10 Megacycle cam, Ti pushrods, Mikuni carbs (39.5mm) and Dyna ignition driven off the cam.

Gray

 

The V11 sports extremely restrictive mufflers an thus benefits a lot from the front crossover - the torque hole around 4000 is not so deep in fact. But with open Lafranconis the benefits will be much smaller if there are benefits.

 

Your specs sound powerful.

Has the dyna ignition you use an ignition advance curve? I only know about a Dyna to replace the contact breakers and this system works with the mechanic advance curve given by the distributor.

[guzzigray]

Gray

 

The V11 sports extremely restrictive mufflers an thus benefits a lot from the front crossover - the torque hole around 4000 is not so deep in fact. But with open Lafranconis the benefits will be much smaller if there are benefits.

 

Your specs sound powerful.

Has the dyna ignition you use an ignition advance curve? I only know about a Dyna to replace the contact breakers and this system works with the mechanic advance curve given by the distributor.

 

 

Thanks for the reply. I'm having the Sport engine case machined to accept the distributor and will run the Dyna with that. I almost went with a crank fired system (Silent-Hektik) but decided to go with the Dyna so i can access parts overnight in an emergency (and they are much cheaper).