Nostalgia Drag Bike part 4

I now have in my possession another original piece of the Gorilla, a Knucklehead dragbike from the early 1950's, that being the transmission. And a fine piece it is. Simple, effective, and a down right cool piece of drag racing technology/history.

note the huge trans sprocket

When I began drag racing in the mid '80s, Harley specific drag racing was something new, and it lured all lot of racers out of retirement. These were the men who had kept Harleys on the track through the 70's when it was getting increasingly tough to compete with the Japanese imports which came from the factory with such amazing performance. The Harleys of that era were still pretty impressive when you consider the farm tractor technology they were based upon, but they just were not keeping up on the strip. Some of these Harley racers who pulled their dragbikes out of the dark corners of their garages for one last stab at glory were still using this same basic transmission from 1950.

"finger" on the shift fork. springs would hold the fork in 3rd gear

shift lever pivots here

That is a pretty long lifespan for any type of racing innovation, and whoever came up with it deserves a round of applause (if anyone out there knows who this person was, please let me know)

So, the transmission is a stock Harley 4 speed case, modified to work as a two speed. Internally, there is mainshaft 3rd and 4th gears, along with countershaft 3rd and 4th gears. One shift fork does the gear change from 3rd to 4th via a handmade top cover that takes the place of the old "jockey" lid.

Back in the 1980's, I was lucky enough to have another racer explain how the transmission worked, so I have not had to spend time scratching my head and speculating. Obviously you would start the run in 3rd gear. A "clutch lever" was hooked to the arm on the shift fork on the custom lid. Once underway in 3rd gear the rider would begin to squeeze the lever as the bike got near the shift point. Once the engine passed its peak and the horsepower started to drop off, it would unload the shift dogs enough to allow the shift fork to slide over into high gear. Clutchless shifting under wide open throttle in 1950! Amazing!

In modern day motorcycle drag racing, you will only see Top Fuel bikes with 2 speed transmissions. Nearly any gas dragbike will have multiple gears to get as much mechanical advantage as possible. Three, four and five speeds are not at all uncommon. So why did this early 2 speed work with even the gas bikes of the time? The answer has a lot to do with the tire technology (or lack of it). There just was not enough traction available to take advantage of any lower gearing. Couple that with the near impossibility of shifting the old jockey lid 4 speed quickly, and you can see why this transmission was a winner. The approach that seemed to work the best was to gear high, and spin the tire through much of the pass.

inside the 2 speed

Clampitt breaks into the 9's

Recently I wrote about Flow Area and Cam Selection In that post I mentioned Jason's dragbike heads as an example. Well, last week I finished up his heads. I was quite happy with the results, since I picked up 10 cfm from .200" lift and above on the intakes, and 20cfm on the exhausts. I was also able to get the valve to valve clearance so he could leave the 1.7:1 rockers in the engine. One drawback was that we lost a little compression ratio due to sinking the valves. Jason somehow managed to get the bike together for the weekend, and called me Monday with the results.

The bike had been running 10.13's consistantly, but even with a gear change that Jason thinks (and I aggree) hurt him, the bike is now running 9.96's. Congratulations Jason!

Of course we all know that you never want to make more than one change at a time, but in this case Jason didn't have much of a choice. He had found that the bike had been built with a misalignment between the transmission and wheel sprockets. The only sprocket that he could get on short notice to align things lowered his gear ratio. His 60 foot time increased (got slower) and the bike was practically nosing over before the finish line, yet he still lowered his e.t.'s by nearly two tenths. That's kind of exciting!

Now before you "turn up your nose" at e.t.'s in the 9.90's, keep in mind that this is only a 98" engine and Jason is a big guy (over 300 suited up to race).

Jason's dragbike last fall at the Kokesh Drags

We are all looking forward to what a gear change and a little more tuning might reveal!

From each, according to his ability; to each, according to his need

I have often heard this quote used by conservative talk show hosts to "ambush" unsuspecting liberals. Usually it is offered something like this: Would you agree with this statement; From each, according to his ability; to each, according to his need?

Of course the punch line is that if they agree with the statement, they have been unmasked as a sheep in wolf's clothing communist.

"From each, according to his ability; to each, according to his need." This is a quote from Karl Marx, and yes communism did arise largely as a result of his philosophy. Yet many of us in this day and age are quite historically challenged (myself included). While most would correctly link Karl Marx with communism, how many of us realize that he lived and died before the actual rise of it. Marx lived from 1818-1883, putting him in the grave long before the communist revolution of the 20th century.


But a history lesson is not the point of this post. What I really wanted to point out is the similarity of this quote of Marx and something from the Bible. But, as Solomon said in Ecclesiastes 1:9 "The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun."


So whether Marx knew he was restating a passage of scripture or not, the thought was not original with him. Of course if Marx took the idea from the Bible, then he used it totally out of context.

Acts 2:41-47 Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls. And they continued stedfastly in the apostles' doctrine and fellowship, and in breaking of bread, and in prayers. And fear came upon every soul: and many wonders and signs were done by the apostles. And all that believed were together, and had all things common; And sold their possessions and goods, and parted them to all men, as every man had need. And they, continuing daily with one accord in the temple, and breaking bread from house to house, did eat their meat with gladness and singleness of heart, Praising God, and having favour with all the people. And the Lord added to the church daily such as should be saved.

Acts 4:32-35 And the multitude of them that believed were of one heart and of one soul: neither said any of them that ought of the things which he possessed was his own; but they had all things common. And with great power gave the apostles witness of the resurrection of the Lord Jesus: and great grace was upon them all. Neither was there any among them that lacked: for as many as were possessors of lands or houses sold them, and brought the prices of the things that were sold, And laid them down at the apostles' feet: and distribution was made unto every man according as he had need.


Hard to deny the similarity isn't it? So.... does that mean all of the right wing conservative Christians are wrong? Does the Bible really promote communism? Hmm....


I have wondered for some time how these passages from the Bible may have affected early 20th century Christians when they were confronted with the rise of communism. When I became a Christian about 9 years ago I became immensely more interested in whether or not any of my forefathers had been Christians (and I am using the term Christian here in the strictest sense, as in born again). One of the ancestor's I considered was my great grandfather LJ Schlattman. Though he died in 1938 he was pretty much legendary in my family. Not only did he homestead land in the 1800's where I grew up , he was the first organist as well as one of the organizers of Pepperton Methodist Church. Later he was a weekly contributor to the newspaper in the nearby county seat. Some of those writings along with a book of his poetry that he had published gave me a much better glimpse into his life than of my other ancestors.


One conclusion that I came to from reading LJ's works was that he tended towards socialism. Adding 2+2 I came to the further conclusion that he may have based this at least in part on these verses from the Bible. At least I hope so. I would also like to think that he may have reconsidered later in life, when history unfolded to show how badly communism worked in practice.


So, is this to say that the Bible is wrong, or the example of the very early New Testament Church given in the book of Acts is a bad one? No, not at all. I will say this though; the only way communism can work is with a church. And I think that statement may need to be narrowed even further; to a church with mostly wheat and only a few tares. Yes, that 1st century Church successfully practiced communism, but even they needed the stipulation added from 2 Thessalonians 3:10 "For even when we were with you, this we commanded you, that if any would not work, neither should he eat. "


If you could find yourself a Church full of genuine Christians led by dedicated pastors and teachers that walk closely with the Lord, then a modern day commune could work. But if comes down to a secular government, led by ungodly men (not matter how well meaning), well.... not so much.

Flow Area and Cam Selection

This is something you need to be aware of if you are building a hi performance engine. A person might think that the best way to select a cam is to look at your cylinder head airflow and pick a cam that has about the same lift as the point where the head's flow peaks. Yeah, you might think!

Or inversely a person might have a cam lift in mind and pick a set of heads with the most flow at that lift. And the more lift the better, right? Yeah, you might think that too!

In reality it is a little more complicated than that. In fact it is a lot more complicated than that, but I don't plan to address all of the complications in this post. Just one; Integrated Flow Area.

This is sometimes called "area under the curve" and is a result of plotting cam lift in crankshaft degrees and adding the cylinder head flow for those lifts. This allows you to compare total effective airflow for two different heads with one cam (or two different cams with one head). This takes into account the cam duration and head flow at all lifts rather than just peak lift.

It can be quite an eye opener! It allows you to see why a head with a great high lift flow may not perform as well as a head with less high lift flow, but better low/ mid lifts.

This came to the forefront this week when Jason from Kokesh Motorcycle brought down the heads from a dragbike he purchased last fall. They happened to be the same S&S castings as I had ported for another local racer a couple years back. They also had the same valve sizes. Interestingly they were stamped with the I.D. numbers of one of the legends of Harley drag race porting.

Now, before I go any farther, here is a disclaimer: I have no way of knowing what changes have been made to these heads since they left the aforementioned legendary porter. Any shortcomings I mention hereafter may have nothing to do with the original porting job!

The first thing I noticed was that the valves had been "backcut" on the combustion chamber side to increase the valve to valve clearance. Upon further inspection it became clear that this was done in part to the use of 1.7: 1 ratio rocker arms. (stock is 1.625:1) This increased the TDC lifts of the valves, and indeed without the extra machining the valves would have hit each other during overlap. Trouble is, that extra cut invariably hurts the airflow.



the silver ring on the edge of each valve is the backcut for valve to valve clearance

















pointing to the backcut below the margin








Comparing the flow figures for these heads with that of the heads I had previously ported, I found that they were from 13 to 21 cfm in the .500" to .650" lift range. The exhaust was even worse, being down 20 to 25 cfm from .200" lift and up. Much as I would like to chalk this up to my work being better, obviously a big part of the difference is due to the backcut on the valve.

However, by comparing the integrated flow area on my Port Flow Analyzer software (the flowbench program I use), I was able to determine that Jason' bike would have better overall airflow just by going back to a stock rocker arm ratio and leaving the chamber sides of the valves uncut!

Of course that is not what we are going to do. That would be too easy. And besides, we are talking drag racing heads here. You always want to make more power if at all possible. I have some valves on order which have slightly different profiles, and hope to gain some flow not only through the valves, but also with more porting work.

How does this apply to your engine? Well, if your heads are already ported or you already have the cam you are going to run, then perhaps not a lot. But if you are in the process of designing/building your engine then it is something to keep in mind. When you are choosing your cam and valve size, there very well may be times when a larger valve with a milder cam may be a good option.

Recently this was on my mind due to a conversation I had concerning an early drag bike. I was told that this particular Knuckle used a 2 1/4" intake valve with the old Lightening cam. This got me to wondering. With a wilder cam, there likely would not be enough room (valve to valve) for that big an intake valve. (the largest I ran in my own drag bike was a 2.100") Would the better flow from the 2.250" valve make up for the milder cam?

Just for a quick point of reference, I ran a comparison using the flow figures I have for two different sets of FlatheadPower Knuckle heads I had ported. Though both sets used a 2" intake, one set was dual carb heads and the other stock style so I thought they may give similar results as two different valve sizes. For cams, I ran Leineweber's #5 Knuck cam with the stock style heads (simulating the smaller valve) and the Lightening with the dual carb heads (simulating a larger valve). Sure enough the milder cam with the better flowing heads showed a larger "integrated flow area" number than the hotter cam with less flow. Very interesting....

Of course this is not the whole story in selecting a cam and valve sizes, but it sure is something to consider.

The Blessing of God

Over the past several weeks our pastor has preached a number of sermons about our risen Saviour. This Sunday morning we looked at Jesus Ascension as recorded in Luke 24.

Luke 24:51-52 "And it came to pass, while he blessed them, he was parted from them, and carried up into heaven. And they worshipped him, and returned to Jerusalem with great joy:"

He blessed them. The blessing of God naturally leads to worship and great joy! The words which Jesus used to bless the disciples are not recorded here, but we can be sure that there was power in the words he used. We do not know the words Jesus used then, but we can look at other scripture to get an idea.

Numbers 6:22-27 "And the LORD spake unto Moses, saying, Speak unto Aaron and unto his sons, saying, On this wise ye shall bless the children of Israel, saying unto them, The LORD bless thee, and keep thee: The LORD make his face shine upon thee, and be gracious unto thee: The LORD lift up his countenance upon thee, and give thee peace. And they shall put my name upon the children of Israel, and I will bless them."

What a great blessing of God that he will keeps us. What a great blessing of God it is that he is gracious to us, for by the very definition, we do not deserve it. And what a great blessing of God it is that he gives us peace. Not only peace with God, but also the peace of God!

Comforting as these blessings of God are to us, there is also another verse to consider when we study this subject.

Matthew 5:44 "But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you;"

We all need to work a little harder at this one!

Donnie Smith Bike Show 2008

We are nearing a month since the Donnie Smith Bike Show was held in St. Paul this year. As usual, it was a huge success, and enjoyed greatly by exhibitors and spectators alike. This year's event drew over 16,000 through the doors.

One of the neat things associated with the show, was that my friend and customer Joe had his Flathead Big Twin displayed there. This is the bike who's engine was the subject of my series on a stroker Flathead engine build. Technically this was not its debut, since he rode it around Sturgis last summer, but certainly it was the first time it has been entered in a bike show. Congrats to Joe for taking home a couple trophies! His Flathead not only took best in class in the "Vintage Modified", but his display took an overall 2nd place for best display.

Joe's '44 Big Twin Flathead

Joe's display featured blown up pictures from the movie The Wild One. My guess is that hardly anyone there caught on to all the details of his display. He even had a trophy made up with the character portrayed by Marlon Brando's name on it!

More of Joe's display

Besides helping my friend Neil Ryan (the show's promoter) with set up, I also had a booth there to promote my business. Since the latest project bike I had in the works was nearly done, I spent the extra time to finish it up for the show. While I decided to display it in my booth rather than enter it in the show, I must say it received rave reviews.

In case anyone is interested, P2 (as I refer to it) is an 80" Knuckle using S&S flywheels and a Paughco frame; for sale at $23,900. Here are a couple pictures.

Check out the Holley downdraft carb!

My latest completed project.

A few other bikes which I had at least a small hand in over the last year are pictured below.

I fit the main bearings on Jason's Pan. He took it from there.

Kevin's Knuck motor was completely rebuilt in my shop, finished just in time for the show.

Hard to believe that just 2 weeks prior to the show I was replacing the exhaust spigots on Dave's Pan. Kokesh did the balance of the work.

Measuring Compression Ratios

Have you ever considered what the actual compression ratio of your motor is? Are you sure that you took everything in to account or are you going by the rated compression ratio of your pistons?

The simplest way to measure the actual compression ratio of your engine is to have it assembled, at TDC, and then "oil out" (old school term for measuring the volume) the combustion chamber. But to do this you must also be able to position the engine so that the spark plug hole is at the very top of the chamber so that you don't get an air bubble trapped which would throw off the measurement. Pretty awkward to say the least!

Every other method involves measuring separate components and calculating the ratio mathematically. Here are a couple of things to consider when doing so.

• cc of a cylinder = diameter x diameter x 12.87 x height

This formula is especially handy for an old time Harley guy like me since you enter the specs in inches, and the constant (12.87) converts the answer to cubic centimeters.

• Head Volume

The normal way to cc a Shovel, Pan or Knuck head is to place a piece of Plexiglas with a small fill hole across the gasket surface. When you do this you will be measuring not only the chamber, but also the space into which the fire ring on the cylinder fits. That means that the volume that the fire ring displaces must be calculated and subtracted from the head volume. Treat the fire ring as a cylinder and use the formula above. To get the cc's of the fire ring it is only necessary to calculate once using the o.d. of the fire ring and then subtract the volume found using the i.d.

• Gasket thickness & gasket bore diameter

Think of it like another really short cylinder and use the above formula to compute the volume.

• Piston deck height

If your piston only comes within .010 of the top of the cylinder, it is just like running a .010 thicker gasket.

• Piston dome volume

This can often be found in manufacturers specs, but not always. You can grease the piston rings, install the piston into the cylinder so that the top of the dome is just below the cylinder top, and then measure the distance down to the deck of the piston. This will serve as the height inserted into our magic formula above, which allows you to use the bore diameter to compute the volume of the cylinder formed from the piston deck to the top (if it did not have a dome in it). Once you have that volume you can oil it out and subtract to get the dome volume.

• Valve stem protrusion

How far the valves were sunk into the heads from previous valve jobs. Now, if you just finished oiling out your heads, this is of no consequence in computing your actual compression ratio. But it will help explain why your compression ratio is not as high as your piston manufacturer claims. Low and behold our handy dandy little formula comes to the rescue again. If you use the valve diameter in the formula along with the amount that the valve is sunk deeper than the minimum spec as the height, you might be surprised how much compression ratio you loose.

[as an example, stock size valves in a Shovelhead when sunk .050" will increase the combustion chamber size by 4.39cc, lowering the compression ratio by about 1/3 of a point]

This is especially relevant on the older motors which usually have a lot of valve stem protrusion and the valve un-shrouding which often accompanies it. In performance applications, the valves often have to be sunk to maintain valve to valve clearance with the hotter cams that are available, so that is also something to take into account when selecting your cam and pistons.

Now perhaps you think all of this doesn't much matter on your average cruiser. Well, maybe. On the other hand, keep in mind that higher compression ratios make a more efficient engine, and thus better fuel economy and power. On the other hand too high a ratio can lead to hard starting and worse yet, pinging. Another consideration is that all cams have a compression ratio range that they will work the best in.