Dyno Run - New Heads and cam!

[Tonerjockey]

1st run with Mike R. heads (glue and screw) and new megacycle cam.

Kept the RPM down due to noise and I didn't wanna blow this thing up just yet.

75HP @ 5,000 RPM. A good improvement from the previous incarnation.

 

[Hudriwudri]

hi porco rosso,

75 hp sounds really good considering that the cam surely supports higher revs than the mentioned 5000rpm´s with the later intake closing point.

Are you obliged to use the old squareslide dellortos or could you use as well some period correct roundslides like amals??

Reason im asking is:

1. They have a reputation over here for being somewhat mediocre in fuel polverization and droplet distribution (sorry in case i sound esoteric) :roll:

2. I assume without having had measured them that their flow numbers might be not too thrilling (meaning quite some turbulent throttleing vortices around the slide guides) besides being just 30mm i think.

3. I remember that i read once that (i think) that jerry branch measured some carbs and the old amal concentrics gave really nice numbers. :whistle:

keep up the good work and kind regards from italy

christian

 

[Tonerjockey]

Hi Christian,

I am hoping for a few more HP up around 7,600 RPM or so. That will put me at 127-130 MPH....

The class I run in P-PP requires specific, date and model of manufacture carbs. They didn't like the round slides I tried once.
:roll:

My head/manifold/carb setup at .400" valve opening was measured at 103.1 CFM.

Alex

 

[GTM®]

Alex, thanks for posting.

So it looks like you are using a bench dyno... something you made? Where are you measuring the power?

 

[Tonerjockey]

Hey Todd,

I am using a Stuska water dyno. The brake etc is mounted on a frame made by a neighbor Jim True.

The dyno is now at my buddy Joe Cassanova's shop.

Here's a fuzzy shot of the control panel:

The big gauge shows the torque at the water brake. A little math (indicated value * (RPM/1000) ) and ya get BPH. Figuring the foot pound of torque is possible also but I simply use the HP for my purposes. My main concern is whether or not my changes and "improvements" are actually increasing the engine output.

Here's the drive. I used a 17 tooth gear on the dyno input shaft as well as the Guzzi lay shaft. This allowed a 1:1 ratio at the brake. Simpler math and the brake tach shows true engine RPM.

Hadda make all the cables, clutch release mech, etc etc on and on.

Great fun and I am extremely lucky to have friends that will not only let me use thier tools, but will show me how to do it while not killing myself in the process.

Alex

 

[Hudriwudri]

Hi alex,

thanks for the nice pictures as i have to set up this winter also my dyno which is a semi old laboratorium dyno kinda like the ones that branch or axtell´s big red (although mine is acceleration)used where one has to remove the rear tire and bolt the swingarm in, meaning a lil difficult for shaft drive motorcycles or mono swingarms.
I might do a similar solution as yours!

Anyways to get to more substantial and important agendas/topics.
I take it that the 103cfm were measured at 10" of wc (seems mike rich uses a SF110?)?
So my math tells me that you have about 162cfm at 25" which seems imho kinda lowish for the valve lift and either reflects small intake valves or throttleing carburetors.
As i assume that the heads have after Mr´s work allready (if so possible) bigger intake valves and are nicely ported, im inclined to think that the carbs are severely limiting.
Therefore: Do you still have the original carb diameter and if, would you be allowed to get the carbs modified??
Im asking as i know that some race associations let you modify the carbs as long as they appear original (and boy have i seen at times some sick sh.. :lol: )
Anyways long story cut short:
I think that on the VHB´s 30 substantial flow increases could be still found if the venturis are bored out (there should be quite some meat left)and the venturi is if possible enlarged ovaly versus the top giving at the end the flow rates about of a 32-34mm carb.
Surely this might sound now perhaps a little esoteric or exaggerated but i have seen it being done on a regular bases on race bikes or sleepers.
Also after having looked closely at your pictures i noticed you still seem to use the original bent intake manifolds which leads me to ask you if you would be allowed to straighten them out as this might also increase a lil the flow or at least the distribution of the fuel in the ports.
In case you might be allowed to modify the carbs im happy to assist if i can !

cheers and happy research

Christian

 

[jr1967]

From personal dyno experience, I found that longer velocity stacks not only bumped up torque significantly but made the horsepower continue until over 8000rpm instead of dropping off after 7300rpm. In my case it resulted in a 2-5 hp increase over the whole rpm range without changing the jetting. Never checked later on what the hp increase was with larger main jets since dyno time was limited. Anyway, just thought to share the info. I don't know if you have the formula's for calculating intake tract lengths and exhaust header lengths? For the latter you need exhaust gas temperatures, but once you know that, it's pretty straight forward to figure out if you could for example add a few inches of header length to move your peak hp a few hundred rpm up or down.
Great project!

 

[Tonerjockey]

The rules in my class demand original carbs, intake manifold, and air cleaners. The air filters don't need to be installed.

After modifying (destroying) several VHB30 carbs the max bore I can do is 32mm wide by 33mm tall. At this ID the walls of the carb are either paper thin in spots or open. A little JB weld helps stregnthen the walls and some gas tank sealer helps keep gas off the JB weld in the breakthroughs.

The heads are Mike's handiwork and so are the manifolds. Very pretty work BTW.

I used this tool to determine intaker legnth, exhaust diameter and legnth:
http://www.mez.co.uk/mezporting/exhaust_length.html

Mike did his math and came up with slightly different values. I used Mike's this time.

The stock intake plumbing before the carbs is as long as I can make it and still fit.

The exhaust is 18g mandrel bent steel to the required legnth. I need to redo the pipes as they are not the same in shape. This was my 1st effort at header making and the next pass should show an improvement. In this case the important factor was ID and legnth to see the desired performance. I am happy with these combinations.

The engine is now mounted on the frame. Once I get the bike fully assembled I am off to El Mirage to run it on the 1.3 mile track under SCTA. November 9-10
http://www.scta-bni.org/events.html

We'll see if this configuration can beat Big D from Texas' Norton 750 Commando.

Alex

 

[Hudriwudri]

Hi Alex,

uhhh pitty, i thought you might have still the opportunity to rework the carbs!
Hmm from what you write it seems that the carbs are squezzed out like dry oranges.
I would not know what one coud still do on the carbs.
I heard once rumors that "supposedly" in england they sold some models of the V7 with Amals which might perhaps open a backdoor into the rule bending book?
Anyways just out of curiousity and since i work a lot on heads: Which size valves are you sporting on the V7 and on which size bore (82ish i guess)?

Thanks for your thorough answers and

best wishes for a good race

Christian

 

[Tonerjockey]

Ciao Cristian,

44mm intake 37mm exh.

Stock displacement pistons 82.5mm diameter.

Pistons made from billet because I couldn't find any forged stock big enough:

Alex

 

[Tonerjockey]

New exhaust pipes. The fit is good. Now to have my buddy TIG weld them up and I can move on to finishing the electical.

1 5/8" OD 18 Gauge mild steel.

Alex