I asked al taylor what does he think of cvo 110 heads and here's what I got...opinions?
What I need to do is measure the port volume on these heads I have seen pictures, have not had a set in my hands yet I pioneered that chamber design back in 1984 on evo heads. The H.D. motor is not as sensitive to port volume as some would like you to believe.It is important But the short intake tract lets the motor see a small port even if it ground way out. What it does affect is the cam. Depending on what bike the motor is in (weight is a big factor in the engine combo) will determine the extent of the modifications and torque gains. For the most part the H.D. engineers are not stupid and have matched the port volume to the displacement O.K.
PAY CLOSE ATTENTION NOW Most people get confused with this. I had a hard time explaining this to many of the best engine builders in nascar! And proved it on the dyno to all of them. Most engine builders think you need a larger port to make more peak power. You have to balance the port volume. In the old days most heads did not have enough meat in them to be able to to ported to large enough volume to get that balance.So of course as they ground them out they make more and more power untill they ground into the water jacket or fins.
A normally aspirated engine loses efficencey as rpm's increase above peak torque.(That is why I will have fuel and air flow meter on my dyno) As rpm's increase there is less time to fill the cylinder with air. Thus less bang per powerpulse. So how come horsepower goes up as tq. falls off? The best way to explain is by example.
WE have a single cylinder engine that makes 1 hp per powerpulse at 1000 rpm, thus producing 500 hp in 1 minute (4 stroke fires every other stroke). Now we change porting + cam. Now the motor will spin to 2000 rpm, but to get it to do that we shrunk the port or put in a smaller cam. As a result we lose tq. but pick up Hp. So now our motor makes .75 HP per powerpulse. Less efficient, BUT we made 750 hp in the same period of time. Who wins that race?
A too large port kills velocity and too small is a restriction. NOTE: we can get away with a larger port on an injected motor ( with injectors pointed at the valve) because the air now does not have to carry it's big fat buddy (fuel) with it. This depending on port size would lower the rpm point of peak tq.
The hard part of building engines is balancing the port size with cam to obtain the tq. and hp. in the range you want. A typical bandaid fix is to use a smaller cam when the ports are too big or a bigger cam with too small a port...both have major drawbacks.
HD has figured this out and is using bigger ports to make tq. and limiting the peak power as a result. I would not weld in the chambers or the port but mill the head to increace C.R. then balance with the approrate cam. Welding the chamber will hurt flow. I would only weld the port if it was huge. The other big factor in making tq. is maximzing ignition timing...just a few degrees of timing will pick up as much as 5 or 6 ft lbs This is where chamber shape, size, dual plugs, C.R. and a dyno come into play. You scan see that increasing and decreasing the port size will effect the point (rpm) and amount at which you will see peak Tq. and HP.
I would try flow testing $75.00 (includes checking port volume). C.C ing the chambers, milling the heads and setting C.R, $80.00. Disassembly ,cleaning and assembly $75.00 / $95.00 if we install hi lift springs. Blueprinting would not be a bad idea, then clean up the areas @ the seats for better throttle response. 275.00 Upon dissassembly if we see any problems(pitted seats, worn guides etc.) we will call the customer. With the flow,volume and compression ratio data in hand then we can make a proper cam choice. The price of course depends on the type of cam. We will need the heads + Pistons and the deck height (how far the piston sits down in the bore.) He will need to dyno it afterward to see the full potenial of the work. Turn around 7 days after I receive them.
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Topic: our approach to making power (Read 3617 times)