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I will have to account for this and be more generous with my squish clearance.[/quote]

You guys lose me on squish. I don't do it that way or use a postive deck height. I do it the VHR way for mph with a slight negative deck height.

I did start with a negative deck hieght of -.005"
but i got fooled by the gaskets compressing more than i had allowed for.When i took it apart my piston was now flush with the deck. But i still didnt hit the head so i learned something.I can run at .036" clearance. but i never run this big block in the heat of summer. so it may have been a problem waiting to happen?? i wont know how low i can go untill i hit the head at max temp. I really dont want to go there.lol:woohoo:
What is the VHR way?

mark1122 wrote:

I did start with a negative deck hieght of -.005"
but i got fooled by the gaskets compressing more than i had allowed for.When i took it apart my piston was now flush with the deck. But i still didnt hit the head so i learned something.I can run at .036" clearance. but i never run this big block in the heat of summer. so it may have been a problem waiting to happen?? i wont know how low i can go untill i hit the head at max temp. I really dont want to go there.lol:woohoo:
What is the VHR way?

I will PM you with that answer. Last time I stated it on this site, everyone treated me like I was crazy. I felt bewildered so I contacted Byron again to see if he had changed his line of thinking over the years. He got back to me with his answer. It only changed a little bite.

Idle thought about cam timing change, since chain distance/length is greater from crank gear to cam gear at intake, it seems reasonable that intake timing would retard more than exhaust with chain wear. G

Mark Please check my line of thinking (yes it did hurt)
I need to know if I'm on the right track or not.
If you advance the intake cam to solve the reversion problem the valve overlap goes up and takes away your bottom end/mid range torque. I don't want to split hairs over the power differance. We are not talking about tearing the pockets off the back of your pants here. I will assume you want the intake and exhaust to have the same lobe center. I'm not the smartest guy here but this is how I see it.

112* L/C has a timing of 18*-62* / 62*-18* (36* overlap)
(this is int. retarted 4*/exh. advanced 4*)

110* L/C has a timing of 20*-60* / 60*-20* (40* overlap)
(this is int. retarted 2*/exh. advanced 2*)

108* L/C has a timing of 22*-58* / 58*-22* (44* overlap)
(this is stock RC timing)

106* L/C has a timing of 24*-56* / 56*-24* (48* overlap)
(this is int. advanced 2*/exh.retarded 2*)

104* L/C has a timing of 26*-54* / 54*-26* (52* overlap)
(this is int. advanced 4*/exh. retared 4*)

It looks to me that the lower the lobe center #, the more overlap you get. As you close the intake valve sooner, the power curve is moved upward. You might be able to find a different timing choice OR live with what you have OR Use cams that have a sooner closing point(stock without advancing or retarding)
Well my friend thats the best I know. I wish I could help you more.........KZZ1p

A few more thoughts since this is still alive.

your 110/110 lobe centers should be fine. Moving the lobe centers tighter will increase overlap and might make your revesion problem even worse - as pointed out by kzz1p.

In my experience, reversion is not related to carburetor slide postion. It is a fuction of intake port shape, exhaust design, cam spec and engine RPM. If an engine is reverting at a given RPM it will do so regarless of the carb slide position.

Big intake ports cause reversion probems in the low and mid range. They make carbs difficult to tune, decrease midrange torque and throttle response. Mark, unfortunately, your intake ports are big - though there is a solution.

The "choke point" I was refering to is the area in the intake port just before the port turns down toward the valve. The port should gradually get smaller from the carb throat this point. In your case it should start at 34mm and gradually neck down to around 26mm. This will substantially increase the velocity of the air/fuel charge in this area just before it enters the cylinder. This high velocity is very important in eliminating revesion and aiding in combustion turbulence. For an indepth explanation of this, refer to The Sport Bike Performance Handbook page 69. I recommend this book to anyone interested in anything motorcycle performance related. It was recommended to me by another member.

It is possible to epoxy the floor of your intake ports to produce this high velocity area. I did it. So did Exitpupil. You can see the results here: kzrider.com/index.php?option=com_kunena&...ew&catid=2&id=235189 I wouldn't recommend all the trouble of making them removable. But would strongly suggest epoxy or a different head with smaller ports before you bolt it all back together.

Keep us posted on how it turns out.

After thinking about this some more, more and some more. I will give it one last shot.

Davel has some good points. I know that you spent good money on this head and want to use it. If it were Me, myself and I, this is what I would do:

Advance both cams - This will increase your torque in the bottom end and mid range, while closing the intake valve 6* sooner and not increasing the overlap or raising the power curve.


104* L/C intake cam
112* L/c exhaust cam
108* lobe speration angle
26*-54*/62*-18* valve timing
44* overlap (same as RC recommended at 108* L/C)

This is 4* advance for both the intake and exhaust cams........Now I will shut up!

kzz1p wrote:

After thinking about this some more, more and some more. I will give it one last shot.

Davel has some good points. I know that you spent good money on this head and want to use it. If it were Me, myself and I, this is what I would do:

Advance both cams - This will increase your torque in the bottom end and mid range, while closing the intake valve 6* sooner and not increasing the overlap or raising the power curve.


104* L/C intake cam
112* L/c exhaust cam
108* lobe speration angle
26*-54*/62*-18* valve timing
44* overlap (same as RC recommended at 108* L/C)

This is 4* advance for both the intake and exhaust cams........Now I will shut up!

I agree with your theory. advancing both is the way to go.
After i get my head back i will check valve to valve clearance at all posible sinarios. then i will likely go with something like 106int,110 exht.we'll see.

davel wrote:

A few more thoughts since this is still alive.

your 110/110 lobe centers should be fine. Moving the lobe centers tighter will increase overlap and might make your revesion problem even worse - as pointed out by kzz1p.

In my experience, reversion is not related to carburetor slide postion. It is a fuction of intake port shape, exhaust design, cam spec and engine RPM. If an engine is reverting at a given RPM it will do so regarless of the carb slide position.

Big intake ports cause reversion probems in the low and mid range. They make carbs difficult to tune, decrease midrange torque and throttle response. Mark, unfortunately, your intake ports are big - though there is a solution.

The "choke point" I was refering to is the area in the intake port just before the port turns down toward the valve. The port should gradually get smaller from the carb throat this point. In your case it should start at 34mm and gradually neck down to around 26mm. This will substantially increase the velocity of the air/fuel charge in this area just before it enters the cylinder. This high velocity is very important in eliminating revesion and aiding in combustion turbulence. For an indepth explanation of this, refer to The Sport Bike Performance Handbook page 69. I recommend this book to anyone interested in anything motorcycle performance related. It was recommended to me by another member.

It is possible to epoxy the floor of your intake ports to produce this high velocity area. I did it. So did Exitpupil. You can see the results here: kzrider.com/index.php?option=com_kunena&...ew&catid=2&id=235189 I wouldn't recommend all the trouble of making them removable. But would strongly suggest epoxy or a different head with smaller ports before you bolt it all back together.

Keep us posted on how it turns out.

i like your way of thinking Dave But i have to put my trust in Larry, here. I paid for his expertise. I will trust his porting and try adjusting the cam timing . Closing the exht sooner makes sence. If i exhaust all options and cant make it work Larry's way i will try it your way.
I got an email from a local race shop/ dyno shop. He said there should be no discoloration in the intake runners. This is contrary to some saying its normal. This kind of stuff makes it very difficult to learn on the net. It seems there are always dif opinions. Its hard ,without a lot of experience, to figure out who is right.
The big thing that stops me from experimenting on my own is i don’t have the resources (I’m actually getting a pay reduction due to the economy )to run it on the dyno to prove my work. for now it does run very strong with no carb issues, just dirty runners.
Thanks for the link I re- read that post (its been a while). It is a keeper.
I have that book, The Sport Bike Performance Handbook , i will re-read pg . 69. I kind of like that number anyways. lol

gane wrote:

Idle thought about cam timing change, since chain distance/length is greater from crank gear to cam gear at intake, it seems reasonable that intake timing would retard more than exhaust with chain wear. G

Lets hope thats right.

mark1122 wrote:

The big thing that stops me from experimenting on my own is i don’t have the resources to run it on the dyno to prove my work.

A very good and no cost way of evaluating engine performace is to perform a top gear roll-on acceleration test:

Take a digital wrist watch with stop watch funtion and secure it to the left handle bar in a position that you can start/stop the timer with your left thumb. Find a straight, flat and empty strecth of highway and put your bike in 5th gear. Then time how long it takes to accelerate from 40-60, 60-80 and 80-100. This will essentially tell you how well the engine is perfoming from about 3000-7000RPM - where most of your street riding will take place. Perform each test a few times until you get consistent times. Record the results, then you can repeat the tests after making engine mods to verify the change in performance.

This is an easy test to perform because, unlike 1/4 mile times, it elimiates a lot of variables like clutch engagement, launch RPM, wheel spin, shift point, etc.

Also, intersting to note: If you have a broad, flat torque curve, times for the three test (40-60, 60-68, 80-100)should be very similar. Any flat spot in carburation or dip in the torque curve will show up in this test.

That’s a good idea Dave. i have thought along those lines before but never followed through. I will make an effort to find a suitable watch to use.
Thanks for the advice.