OB_cbxchris
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Need to use aftermarket pistons...the valve pockets will probably be to shallow for the additional lift.....
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Web Cams
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I want to make sure I understand correctly, aftermarket cams require aftermarket pistons? If correct thats a huge factor, I say this because I just purchased cams from erion racing for the XX. They are a drop in mod that requires nothing more than slight valve adjustment and your done. They yield a 15hp peak improvement over pipe alone. Looking at frank and brocks threads I noticed several references to the mild grind of the stock cams. I would think plenty of usable horsepower could be gained from moderate bumps instead of going the route of replacement pistons. Isnt there a milder grind that adds power as a drop in such as the erion's?
OB_cbxchris
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yes the yosh cam does...I would be very careful using the webs with stock pistons...it may be alright to use the stockers but you may have to deepen valve pockets a little. ..the intake cam adds around 33 thousandths lift...usually that is not a problem but its better to be safe than sorry...
OB_Ghost Ryder01
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Question: What is the expected horsepower gain by changing to Web Cams? The one I'm looking at is the medium cam. I'd like to use stock pistons. Anyone using this combination or anyone have any idea what would be the advantages of using this combination? Thanks for your help.
Maui,
Normal recommended clearence is 1mm on intake, and 1.5mm on exhaust. These are general rule of thumb and vary slighty dependant on application, i.e. Ti rods stretch more. Needs to be checked at various points to ensure accuracy. I have run tighter clearences on some applications but don't recommend it for the small gain in power.
Dave
Normal recommended clearence is 1mm on intake, and 1.5mm on exhaust. These are general rule of thumb and vary slighty dependant on application, i.e. Ti rods stretch more. Needs to be checked at various points to ensure accuracy. I have run tighter clearences on some applications but don't recommend it for the small gain in power.
Dave
OB_A Daddy Busa
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hello
Maui,
The clay method will work fine. It will tell you the minimum PTV clearence. It will not tell you where this is ocurring, but that is not crucial. A note of caution: be careful when installing the cams using this method....On a FZR engine I got a 'false' reading because during the bolting down of the cam the lobe opened a valve earlier effecting the measurement. This was because the cam was out of time until the chain and tensioner were installed. I normally check clearences now with the engine assembled. Hope this helps....
Dave
The clay method will work fine. It will tell you the minimum PTV clearence. It will not tell you where this is ocurring, but that is not crucial. A note of caution: be careful when installing the cams using this method....On a FZR engine I got a 'false' reading because during the bolting down of the cam the lobe opened a valve earlier effecting the measurement. This was because the cam was out of time until the chain and tensioner were installed. I normally check clearences now with the engine assembled. Hope this helps....
Dave
OB_cbxchris
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You can use extremely soft electrical sorder to check clearance 60 thousandths is a good #
thanks Jay, DaveO, cbxchris
I don't work on too many bikes. I'm mostly just curious on the specs. On our Dragster it only takes about ten minutes to yank the motor, Heads come off pretty fast, If I change cams I usually strip the heads for a VG & check seats pressures (320 installed). With those kinds of spring pressures I can't push down the valve to easily. Gotta use clay. Last year (Oct) we lost a roller lifter which took out a cam with 6 passes on it ($$$).
I don't work on too many bikes. I'm mostly just curious on the specs. On our Dragster it only takes about ten minutes to yank the motor, Heads come off pretty fast, If I change cams I usually strip the heads for a VG & check seats pressures (320 installed). With those kinds of spring pressures I can't push down the valve to easily. Gotta use clay. Last year (Oct) we lost a roller lifter which took out a cam with 6 passes on it ($$$).
OB_GSXRTURBO1
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Thanks Maui, but I was just curious. Can you imagine where Top Fuel would be now if they allowed the whipple (screw type) blower?
OB_cbxchris
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Maui, the way I have always checked and made sure the valve pocket is big enough is...take a valve and put on laithe...turn tip of valve to exact point...put valve in guide upside down...this is with pistons in block on rods on engine...head would need to be semi bolted down.. bring each cylinder to top dead center...lightly tap valve ...which will leave small prick marks at center of each valve on piston in each valve pocket. Put piston on piston vise on milling machine..using digital readout on mill it is easy to see if you need any more pocket material removed for valve clearance ...depth is another matter and methods above are all good...the method I described is the only way to go with oversize valves...just my 2 cents..hope it helps.
OB_GSXRTURBO1
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4 valve heads...less spring pressure. Hey Maui, whatever happened to the 4 valve hemi motor..McGee or something like that.....? Had lots of potential but wouldn't stay together, also had some other very unusual problems. Anyone have any favorable results with one? Any still around? Seems like it would make a bulletproof alcohol motor.
Both Phil and Chris McGee have their own shops now and are building Briggs and Stratton engines for junior dragsters.
Their 4 valve motor suffered, amoung other things, from the same thing that the 4 valve Suzukis do in top fuel, warped exhaust valves. The small stems can't survive a full quarter mile and stay straight.
But mainly it was political. No one wanted to devote the time and money to make it work only to then have it outlawed, as it is now.
Some are still used on alky in pulling tractors.
Jay
Their 4 valve motor suffered, amoung other things, from the same thing that the 4 valve Suzukis do in top fuel, warped exhaust valves. The small stems can't survive a full quarter mile and stay straight.
But mainly it was political. No one wanted to devote the time and money to make it work only to then have it outlawed, as it is now.
Some are still used on alky in pulling tractors.
Jay
Yes, smaller valves can run lighter springs. We're also opening .780", and want the valve back on the cam right away.
I think NHRA made them (McGee) add weight to compete. They finally couldn't keep up with the cost of doing business in top fuel. They're still around, I'm not sure what they're doing but I can find out if you want. I don't know if their stuff would be allowed in alcohol by today's rules. Do you remember the rotary valve motors? The biggest gain in alcohol today is the Whipple blower (IMO).
I think NHRA made them (McGee) add weight to compete. They finally couldn't keep up with the cost of doing business in top fuel. They're still around, I'm not sure what they're doing but I can find out if you want. I don't know if their stuff would be allowed in alcohol by today's rules. Do you remember the rotary valve motors? The biggest gain in alcohol today is the Whipple blower (IMO).
Maui
As Dave said, you have to know where to check for PTV clearance. When the cams are in the overlap position, That is at the top of the exhaust stroke, when both the intsake and exhaust valves are open at the same time. Ehhaust almost closed and the intake just starting to open. that is when the valves are the closes they will be to the pistons.
The clay method is fine if you have the engine apart, but if you put a mild cam in an assembled motor and want to check it for PTV, you can put in into the overlap phase, put an indicator on the bucket, zero it out, and push the bucket on down until you feel the valve touch the piston. Take a direct reading from the indicator.
I have not had the chance to do this on a 'busa yet, so I don't know how much room there is to get on the bucket with the cam lobe in the way. On the older GSXRs and GS motors with rocker arms, this is by far the easiest way to check the clearance.
Jay
As Dave said, you have to know where to check for PTV clearance. When the cams are in the overlap position, That is at the top of the exhaust stroke, when both the intsake and exhaust valves are open at the same time. Ehhaust almost closed and the intake just starting to open. that is when the valves are the closes they will be to the pistons.
The clay method is fine if you have the engine apart, but if you put a mild cam in an assembled motor and want to check it for PTV, you can put in into the overlap phase, put an indicator on the bucket, zero it out, and push the bucket on down until you feel the valve touch the piston. Take a direct reading from the indicator.
I have not had the chance to do this on a 'busa yet, so I don't know how much room there is to get on the bucket with the cam lobe in the way. On the older GSXRs and GS motors with rocker arms, this is by far the easiest way to check the clearance.
Jay
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