Victoria! Zeke's CB175 Build
- Thread starter Texasstar
- Start date
No Ti valves for me. Too rich for my blood. Even Ti retainers are really spendy and aluminum is almost as good. I wouldn't drop the $$$ on Ti unless your goal was 15K RPM +. Way more bang for your buck in other areas first.
For paint, try baking the parts at 300°F for 20 minutes prior to spraying your first coat. Another 20 minutes after the last coat dries will help it to cure.
For paint, try baking the parts at 300°F for 20 minutes prior to spraying your first coat. Another 20 minutes after the last coat dries will help it to cure.
Texasstar
Can't is a four letter dirty word
Update: talked to Zach at R/D valve springs and the lash caps will work if we have .065 is clearance from the tips to the keepers. The pocket of the lash cap is .060" deep. So we will check that later.
http://www.rdvalvespring.com/lash.html
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http://www.rdvalvespring.com/lash.html
Sent from my iPhone using Tapatalk
Sonreir said:
Ti valves are worth the expenditure and allow much higher revs before valves float BUT, they don't work well in a rocker environment and tend to gall and get hung up in bronze guides. Ti valves gall and need regular replacement, Stock valves can drop heads and stainless valves are spendy too. It's a case of choose which compromise best meets your design intent and budget.
I love Ti valves and in a shim under design I'd use them in a heartbeat. On a single cam rocker design, I'd think long and hard about it.
Texasstar
Can't is a four letter dirty word
So the most important flow numbers to check are at shared overlap creating volumetric efficiencies of + 100%. So is more cfm ideal at this point or a higher velocity? Is that why the megacycle cam that has the longer duration and less lift can have a higher volumetric efficiency than the other megacycle cam with higher lift and less duration? Is that why cam cards are at .040" lift?
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Overlap is important but I don't believe it is the critical factor. We want to improve flow at all lifts if possible.
The pressure drop is just a number but flow at higher pressure drops is faster and may become turbulent at higher lifts because of port shape or irregularities.
Higher compression creates proportionately higher combustion pressures and more power at any engine speed but at very high revs, the pressure rise is too fast and that restricts power because of the revers thrust. Imagine lighting the fire way too early, pressure rises as the fuel burns and pressure will rise too much before TDC pushing back at the rising piston and tending to resist its upwards motion. Too much compression does the same thing at high enough revs.
Peak flow velocity will tend to occur at peak piston velocity which is 84-90 degrees ATDC on the intake
At TDC on overlap, piston velocity around TDC is very slow to zero with a lot of latency. What improves flow during overlap is intake inertia and exhaust gas pulses. In an ideal world we would arrange the exhaust waves so that the negative wave arrives at TDCto pull the intake gas through and then the positive (stuffing) wave would arrive just before teh exhaust valve closes to stuff some of that fresh mixture back into the head. Creating a strong suction wave at the right time is easy. Getting a stuffing wave back at the right time is less easy to organize.
Lash caps are there to stop the end of teh relatively soft valve stem from being battered to death by the hardened rocker adjuster.
Rocker geometry is important to minimize side thrusts which are friction and wear out valves or cause them to gall. In theory changing rocker geometry also changes the lift curve slightly.
Cams are timed at 1mm or 40 thou because they have long silencing ramps where the lift changes only very slightly over a huge range or rotation and that makes it really hard to determine opening anc closing points. By the time the cam has generated 40 thou of lift, it's off the ramps and it's easier to see what is happening. That's also why cam grinders often specif lift at TDC as a way to make sure teh cam is timed correctly.
The pressure drop is just a number but flow at higher pressure drops is faster and may become turbulent at higher lifts because of port shape or irregularities.
Higher compression creates proportionately higher combustion pressures and more power at any engine speed but at very high revs, the pressure rise is too fast and that restricts power because of the revers thrust. Imagine lighting the fire way too early, pressure rises as the fuel burns and pressure will rise too much before TDC pushing back at the rising piston and tending to resist its upwards motion. Too much compression does the same thing at high enough revs.
Peak flow velocity will tend to occur at peak piston velocity which is 84-90 degrees ATDC on the intake
At TDC on overlap, piston velocity around TDC is very slow to zero with a lot of latency. What improves flow during overlap is intake inertia and exhaust gas pulses. In an ideal world we would arrange the exhaust waves so that the negative wave arrives at TDCto pull the intake gas through and then the positive (stuffing) wave would arrive just before teh exhaust valve closes to stuff some of that fresh mixture back into the head. Creating a strong suction wave at the right time is easy. Getting a stuffing wave back at the right time is less easy to organize.
Lash caps are there to stop the end of teh relatively soft valve stem from being battered to death by the hardened rocker adjuster.
Rocker geometry is important to minimize side thrusts which are friction and wear out valves or cause them to gall. In theory changing rocker geometry also changes the lift curve slightly.
Cams are timed at 1mm or 40 thou because they have long silencing ramps where the lift changes only very slightly over a huge range or rotation and that makes it really hard to determine opening anc closing points. By the time the cam has generated 40 thou of lift, it's off the ramps and it's easier to see what is happening. That's also why cam grinders often specif lift at TDC as a way to make sure teh cam is timed correctly.
Texasstar said:
It can, but it's not the only factor. Primarily, the cam is used to move peak torque around the RPM band. More lift and more duration (some engines respond better to one or the other and not necessarily both) mean peak torque comes in at a later RPM. Since horsepower is a calculated value based on RPMs and Torque, having the same torque at a higher RPM means more peak horsepower. This comes at the expense of less torque and horsepower lower in the RPM band.
