Thursday, December 18, 2014

Vintage Dual Carbs, Part 3

In part three of this treatise on dual carb Harleys, I would like to put the venerable Linkert under the proverbial microscope. First stop will be an unlikely source for an avowed Knucklehead fanatic such as myself, that being the ’48 to ’57 Panhead Service Manual. The last page of the carburetor section has a handy-dandy chart listing most (all?) of the carbs used from 1936 to 1957. Along with applications, throttle disc angles and even transfer port dimensions, we find venturi sizes listed. Hats off to those technical writers of yesteryear; if only their modern day counterpart would follow their lead.

For our purposes here though, the venturi sizes are indeed what is most useful. The first one we might note is the 3 bolt M-5/ M-55 of early 61" Knucklehead fame. They featured a venturi bore of 1-1/16". OK, so what, you might say. Well, let me put that in terms of modern carbs: 27mm (rounded off). That friends, is not a lot of area to get much air through. But as we go down the list, the venturi sizes do increase, but not much. While we do find the M-25/ M-75 with its whopping 1-5/16 venturi on 1940 Knuckles and as an option on ‘41-’48 models, most Knuckles left the factory with the 1-1/8" M-35. Finally, with the 74" Panheads a 1-5/16" venturi became the standard bearer for brass bodied Linkerts on Harleys, being the largest Linkert offered. Again let’s put those sizes into terminology which will make it easier to compare with modern carbs. The 1-1/8" venturi M-35 series carbs were only 28.6mm (again, rounded off). The big kid on the block M-74 comes in at a whopping 33.3mm (do I really need to point out that this figure too is rounded off?). As a point of reference, when Harley switched to Bendix carbs in the mid 1970s, they put a 36mm version on the XL models, which just happen to come in at very near the same cubic inch displacement as the 61" Knuckle, and a 38mm on 74" Shovelheads.

Super E on left, M35 Linkert on right

As a further point of reference, let’s mention a couple modern performance carbs. S and S (why does it bother me so much that blogger’s html will not allow the use of the ampersand?) designates their carbs by the diameter at the manifold surface rather than the venturi size. An S and S Super "E" carb which is called 1-7/8" is actually 40mm at the venturi, while the "G" model’s 2-1/8" bore is 44.7mm at the venturi. Right in between these two carbs is the flat slide Mikuni HSR42. Keep in mind though, none of these three performance carbs relies on a choke plate as a starting aid. All of the Linkert carbs employ such a plate, which further limits their air flow beyond what the already smaller venturi does. And the measured airflow through these carbs bears this out. An S and S "E" carb flows a whopping 73% more than an M74 despite the venturi bore being only 20% larger.

Knuckledragger Carbs
Right about now you may be thinking, "What about all those old pictures I’ve seen of vintage drag bikes with a pair of Linkerts fitted?" In fact, those paying close attention may even wonder why my own vintage drag bike, "The Knuckledragger" breathes through a pair of them. Speaking for my own situation, I had two reasons to use Linkerts. Nostalgia and pragmatism. The nostalgia portion is self evident. The pragmatic stems from the simple reason that the heads I had in my possession for the project were already set up with Linkert 4 bolt flanges. Had it been a more serious performance effort, I would have reworked the heads.  As it is, I still cut the choke assemblies off, added radius inlets and swapped to the somewhat larger 1-5/16" venturi's on the M35 carbs to maximize air flow.

Granddaddy Joe Smith still ran Linkerts on his Knuckle just before switching to a Shovelhead
The reason you see Linkert in old pictures of early drag bikes is also pretty straight forward, though maybe not so self evident. Many of the drag bikes you see outfitted with a pair of Linkert carbs were run on nitro methane fuel . "Nitro" as it is commonly called among racers, is quite different than gasoline in that it has oxygen in its chemical makeup. That means that rather than relying on airflow to get enough oxygen into the combustion chamber, with nitro a goodly portion of that oxygen is supplied by way of fuel flow. Remember back in part 3 when I wrote this? "The problem is very seldom getting enough gas into the engine for high performance, the challenge is in getting enough air in." Perhaps I should have more specifically used the word oxygen rather than air and fuel rather than gas, but I think you get the picture.

 That is not to say that the addition of nitro turns the Linkert into killer performance carb with no other changes. Nitro requires a much, much, much richer fuel to air ratio. For a given amount of airflow, nitro will need about 7-1/2 times as much fuel as the same engine running gasoline. This requires some substantial modifications to the fuel delivery system all the way from the petcock to the float system to the jets. The potential results however, are nothing short of awe inspiring. A switch from gasoline to nitro methane comes with a potential of just over double the horsepower. Do I need to mention that the bike and the rest of the motor needs to be strong enough to survive double the power?

Now it looks like this series will drag out into yet another post. God willing, I plan to wrap it up in a post encompassing my thoughts on what makes a viable street application for vintage style dual carbs.

Tuesday, November 25, 2014

Thanksgiving: What, When and How

this is the second half of the post started here...
We should give thanks for other Christians and churches.  1Thessalonians 1:2   We give thanks to God always for you all, making mention of you in our prayers;

We should thank the LORD for deliverance from the world.  1Chronicles 16:35  And say ye, Save us, O God of our salvation, and gather us together, and deliver us from the heathen, that we may give thanks to thy holy name, and glory in thy praise.

We should give thanks for salvation and sanctification.  2Thessalonians 2:13  But we are bound to give thanks alway to God for you, brethren beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and belief of the truth:

We should give thanks to the LORD that he has made us fit to share in the inheritance of the saints.  Colossians 1:12    Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light:  

We should give thanks to the LORD when it is not convenient.  Psalm 119:62   At midnight I will rise to give thanks unto thee because of thy righteous judgments.

We should give thanks to God when we pray.  Philippians 4:6   Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God.

We should give thanks to God continually.  Hebrews 13:15  By him therefore let us offer the sacrifice of praise to God continually, that is, the fruit of our lips giving thanks to his name.

We should give thanks the God at all times.  Ephesians 5:20   Giving thanks always for all things unto God and the Father in the name of our Lord Jesus Christ;

We should give thanks to the LORD into eternity.  Psalm 30:12   To the end that my glory may sing praise to thee, and not be silent. O LORD my God, I will give thanks unto thee for ever.

We should give thanks to God when we come together with other Christians to worship.  Psalm 35:18   I will give thee thanks in the great congregation: I will praise thee among much people.

We should give thanks to the LORD when we are among non-Christians.  2Samuel 22:50 & echoed in Psalm 18:49   Therefore I will give thanks unto thee, O LORD, among the heathen, and I will sing praises unto thy name.

We should give thanks to God when we are with the younger generation.  Psalm 79:13   So we thy people and sheep of thy pasture will give thee thanks for ever: we will shew forth thy praise to all generations. 
We should give thanks to the LORD by singing songs dedicated to him. Psalm 95:2   Let us come before his presence with thanksgiving, and make a joyful noise unto him with psalms.

We should give thanks to God by praising him and blessing his name.  Psalm 100:4   Enter into his gates with thanksgiving, and into his courts with praise: be thankful unto him, and bless his name.

We should give thanks to God by joyfully declaring what he has done.  Psalm 107:22   And let them sacrifice the sacrifices of thanksgiving, and declare his works with rejoicing.

We should give thanks to the God by calling on his name.   Psalm 116:17   I will offer to thee the sacrifice of thanksgiving, and will call upon the name of the LORD.

We should give thanks to the LORD by doing everything in his name.  Colossians 3:17  And whatsoever ye do in word or deed, do all in the name of the Lord Jesus, giving thanks to God and the Father by him. 

These are just some of the thing that scripture tells us about the thanks giving.  If I were to summarize, I would say that the biggest reasons why we should give thanks to God are who he is and what he has done.  The when and where are that we should give thanks to God wherever we are and constantly.  How we should give thanks to our Lord is by praising his name and living for him.  And what we should give thanks for are all things, but especially for salvation.  God provided a means by which sinners like you and me could be saved from both the bondage of sin and the penalty of our sin.
That salvation is found in the sinless life of the Son of God, Jesus Christ, who paid the price for all of our sins, past present and future, on the cross at Calvary.  He suffered and died in our place, then rose again from the dead on the third day, that we might be declared righteous before God and live a life of thanksgiving to him.

Thursday, November 20, 2014

Thanksgiving: Why?

One week from today is the day which our nation sets aside every year as a day of Thanksgiving.  For the Christian, this is a day set aside to give thanks to our great God and Savior, the creator and sustainer of heaven and earth.

The Bible has a lot to say about giving thanks.  I have selected a number of verses and grouped them into five categories.  Those categories are: Why we should give thanks, What we should give thanks for, When we should give thanks, Where we should give thanks, and How we should give thanks.  Today I would like to look at the WHY.

We should give thanks to God because of who he is.  First of all we should give thanks to him because he is holy.  Psalm 30:4 Sing unto the LORD, O ye saints of his, and give thanks at the remembrance of his holiness

We should give thanks to the LORD because he is sovereign over all things.  Revelation  11:17  Saying, We give thee thanks, O Lord God Almighty, which art, and wast, and art to come; because thou hast taken to thee thy great power, and hast reigned.

We should give thanks to the LORD because it is a good thing to do and because he is the most High God.  Psalm 92:1   It is a good thing to give thanks unto the LORD, and to sing praises unto thy name, O most High:

We should give thanks to God because he is good and because of his great mercy.   Psalms 106, 107, 118, and 136 all begin with these same words which we also find in 1 Chronicles 16:34.  1Chronicles 16:34   O give thanks unto the LORD; for he is good; for his mercy endureth for ever

We should give thanks because the great things he has done have revealed him to us. Psalm 75:1   Unto thee, O God, do we give thanks, unto thee do we give thanks: for that thy name is near thy wondrous works declare.

We should also give thanks to the LORD because his judgment is always right and just.  Psalm 119:62   At midnight I will rise to give thanks unto thee because of thy righteous judgments.

And not only should we give thanks because of Gods righteousness, we should give thanks because through his marvelous gift of salvation we may also be called righteous and be counted among them spoken of here in Psalm 140:13  Surely the righteous shall give thanks unto thy name: the upright shall dwell in thy presence.

We should give thanks to God because he is the one who provides salvation.  Jonah 2:9   But I will sacrifice unto thee with the voice of thanksgiving; I will pay that that I have vowed. Salvation is of the LORD.

We should give thanks to God because it leads to our being able to live in peace.  1Timothy 2: 1-2   I exhort therefore, that, first of all, supplications, prayers, intercessions, and giving of thanks, be made for all men;   For kings, and for all that are in authority; that we may lead a quiet and peaceable life in all godliness and honesty.

We should give thanks to God because it is his will that we do so.  1Thessalonians 5:18   In every thing give thanks: for this is the will of God in Christ Jesus concerning you.

We should give thanks to God because it magnifies him.  Psalm 69:30   I will praise the name of God with a song, and will magnify him with thanksgiving.

We should give thanks to LORD because it brings glory to him.  2Corinthians 4:15   For all things are for your sakes, that the abundant grace might through the thanksgiving of many redound to the glory of God.

Wednesday, November 12, 2014

...a brief intermission...

This will be short.  No sooner did I mention that I did not recall ever seeing a pair of SU carbs used on a dual carb Knuckle than I received the pictures below from Glenn in Australia.  It seems that his friend Billy campaigns a Knuck with just such a setup.

The 79" Knuckle motor is reported to put 96 HP to the rear wheel on methanol.  Everything else about it is a secret.

What is there to say but WOW!

Friday, October 31, 2014

Vintage Dual Carbs, Part 2

Airflow.  That's what its all about, at least for the performance enthusiast.  More air (carrying the proper mix of fuel of course) = more power.  Even what is often the first modification, open exhaust, falls into this category as evidenced by the fact that a less restrictive exhaust will require richer jetting to go along with the increase in air intake.  Obviously the same goes for the air cleaner.  So what's next after that? 

Bigger carbs, bigger valves, and porting are all the radar screen for those in search of horsepower, and that's not a new development. If I am not mistaken both Chet Herbert in the late '40s and George Smith Sr. in the '50s ran Riley carbs on their famous dual carb Knuckle drag bikes.  The Riley carbs were originally a racing part for Model A Ford engines.  I can only speculate at this late date that the reason for their existence was for increased air flow. 

 So perhaps this is the appropriate point to mention a few fallacies.  One is that when running one carb one each head (aka individual runner), you need to use smaller carbs than when using one carb to supply both heads.  Think about this for a moment.  On a V twin engine, both intake valves are NOT open at the same time.  Ignoring for a moment any tuned length/ram effect, that means a carb that is too small to be a performance carb with a conventional intake manifold will also be too small to be a performance carb when used on a one carb per cylinder set up.  As a matter of fact it seems that the experts, i.e. anyone I regard as smarter than me (a long list to be sure), suggest that on a individual runner set up, the carb actually needs to be larger than for conventional set up due to the lack of a "plenum effect".  If I follow the reasoning correctly, it is because a plenum will actually help to dampen the large fluctuations in pressure in the intake tract from the valve opening and closing.  This effect would be smaller on a two cylinder than 4, 6 and 8 cylinder engines, but present none the less.

On the other extreme I have had someone with a dual carb set of heads, upon hearing my opinion that the carbs were too small, state that, "Yeah, but hopefully I can jet them up enough to work."  Well, sure you can jet them "up" to work.  All that takes is the right jet to maintain the correct fuel/air ratio.  The problem is very seldom getting enough gas into the engine for  high performance, the challenge is in getting enough air in.  That's what makes a carb too small for a performance application; lack of air flow, not lack of fuel flow.  But more on that later.

So, what was the hot set up for dual carbs "back in the day?"  Well, I suppose that would depend a lot on your exact definition of "back in the day."  Forty years ago (back in the mid '70s) a large round slide Mikuni was a common performance upgrade to replace the aging Linkert, as were SU carbs adapted from British automobile applications.  The Mikuni was a natural for dual carbs, though the popularity of said dual carb builds was on the wane primarily due to the more flow friendly intake tract of Shovelheads and Sportsters. I can't say I remember ever seeing a dual carb Harley with SU carbs, though the constant velocity design would seem to be nearly ideal for the job.

Going back a little further in time, it seems that Italian made Dellorto carbs may have been one of the most popular for use on dual carb heads.  Their SSI series slide type carbs were available in sizes up to 42mm making them a good choice.

highly modified Knuckle from the mid '60s sporting Dellorto carbs

Ron's vintage Knuck also features early Dellortos - more on this bike here

"Famous" Doug Gall used a pair of later Dellorto carbs

Now, cool as the Riley and Dellorto carbs may be, due to their scarcity one will probably not find many of them being used on modern "period correct" builds.  What you will generally find is Linkerts.  Yes, they seem to be constantly rising in cost, but compared to a Riley carb they are still dirt cheap. 

pair of modified Linkerts on The Knuckledragger

So, how does the Linkert stack up as a performance carb, you ask?  We'll look into that in part 3.

Thursday, October 2, 2014

The Kingdom

There has been a question that had been on my mind for a number of years now.  I cannot say that the question has been bothering me, since that would infer more prominence for the question than it actually held, but it has often led to my pondering it.  The question is simply this: "Is there a difference between the Biblical terms kingdom of God and kingdom of heaven?"  I have often wondered if I was missing some nuance of scriptural truth in treating them as one. 

If one would venture to do an Internet search on this question, you would get both yes and no answers (Spoiler Alert: Someone on the Internet is wrong!)  In fact some would be so bold as to proclaim that without a proper understanding of the difference between the kingdom of heaven and the kingdom of God, it is impossible to form a correct understanding of Ecclesiology (study of the church), Eschatology (study of end times), Anthropology (study of humankind), or Arachnology (study of spiders – Okay I just threw that one in to see if you were still paying attention).

But, in preparing to preach an upcoming sermon (Oct 12 at ValleyView Church if interested- you're all invited) I stumbled upon this passage which I do believe answers the question.

In Matthew 19: 23 Jesus exclaims how hard it is for a rich man to enter the kingdom of heaven, and then in verse 24 he goes on to say “And again I say unto you, It is easier for a camel to go through the eye of a needle, than for a rich man to enter into the kingdom of God.” (Emphasis mine).  If Jesus differentiates between the kingdom of heaven and the kingdom of God, would he not have used the term “also I say unto you” rather than “again I say unto you”?   The word “again” would infer that Jesus was speaking of the same rich man entering the same kingdom.

Sunday, September 21, 2014

Vintage Dual Carbs, Part 1

Undoubtedly one of the most popular topics on this blog is that of dual carbs.  As I have mentioned before, I tend to be a sucker for exotic carburation myself.  Judging by feedback, both via email and in the comments section, I am not alone. 

Most of us are at least somewhat familiar with the fact that the Factory (as in Harley Davidson Factory) dipped their foot in the waters of land speed racing, placing legendary racer Joe Petrali on board a specially modified dual carb Knucklehead, during the spring of 1937 at Daytona Beach.  The result was a new one mile speed record of 136.183 mph; a record which would stand for 11 years.  The heads on that bike were modified in the conventional manor of one carb on each head.

This is a pic I snapped at the 2008 Cincinnati Dealer Expo.  I assume that it is a replica of Petrali's mount since the original color is normally portrayed as blue.

Less common are Panheads modified in like manor.  Though it seems that George Smith modified a number of them in days long gone by.

This is a shot of the George Smith dual carb Pan heads on a bike Teach did a few years back.

Though modifying the heads for dual carbs was a popular performance trick of the day, it was not the only way to achieve dual carbs.  One of the alternatives that I suspect to be a very early example of a dual carb manifold is shown below.  It was a mass produced aluminum casting made to fit the early "small port" Knuckle heads and featured a 3-bolt Linkert pattern.  IMHO it suffers from a couple of design flaws, but certainly was nicely done and the (unknown to me) originator was on the right track.

Vintage dual carb manifold for early, small port Knuckle heads.
My critique of this manifold stems from a couple points.  One is that the aluminum material of the manifold would be unlikely to hold up well to the sealing system of the day, that is "plumber nuts" with brass seals.  If you have perused a well worn OEM steel manifold, you have no doubt noticed how badly deformed the surface that the brass seal rides on becomes from use.  I suspect the relatively softer cast aluminum would fare much worse. 
My other issue has to do with airflow (not surprising since I deal with airflow for a good bit of my livelihood).  The mere fact that this manifold is an aluminum casting limits the airflow in this particular case.  Since the "spigots" of the manifold need to be the same O.D. as an OEM steel manifold in order for the  plumber nuts and seals to fit, it follows that the I.D. must be smaller that stock in order to provide some strength.  My educated guess is that an aluminum manifold nipple that shares the steel manifold's .075" wall thickness would probably not hold up to even the first tightening of the plumber nut.  On a similar note, and of even more concern on this particular manifold, is the runner diameter.  Ideally, the cross sectional area of the manifold runners would remain constant.  In the case of this particular manifold, the entrance of the port is nearly round at the carb mounting surface, as it is at the exit where it feeds into the head.  In between these two points, the runner takes an elliptical shape, maintaining a constant height, but  suffering from a severe narrowing in width.  The third picture above shows this, and yes...  it is as bad as it looks. The major reason for this was to keep individual runners, in other words keeping each cylinder's intake tract isolated from the other.  More on this later.
Now, given the tortuous path that a Knuckle or Pan present to the air/fuel mixture as it finds its way from the carburetor to the combustion chamber, it would not surprise me to learn that this manifold provided a performance increase despite it's inherent flaws.  Recently it appears that someone has undertaken the task of reproducing these vintage performance manifolds, since I often see un-finished versions for sale on eBay.  One notable change on these new ones is a flange the shape of the 4 bolt Linkert.  Few details are given and one cannot tell from the pictures whether any other improvements have been made.  If anyone has real world experience with this style manifold, either the original or new, I would be happy to hear about it.

Another early example of the quest for dual carbs is the "Seeley" manifold, something which I have written about previously here.

 The Seeley manifold was basically a re-imagining of the stock Linkert manifold, putting one carb on each side of the engine.  An obvious minor drawback to this type of dual carb manifold is leg clearance on the spark plug side, particularly if the relatively "long" Linkert is used.  In fairness though, the customary modification to Knuck heads for dual carbs suffers from the same issue.  As a side note, I am certainly no historian of the Seeley manifolds, but I have seen pictures of an aluminum version very similar to the steel one pictured above.  And that brings up a question; was the steel one an early prototype or was it possibly a home made copy?  The aluminum version is stamped with the Seeley name, the steel is seemingly unmarked.  One thing I would note is that the aluminum version suffers from the same drawback as the dual 3 bolt manifold mentioned earlier with its thicker walls on the spigots.

Over the years there have surely been many variations on these three basic dual carb designs, and probably a few that I missed as well.  The fact is, I have built a number of variations myself.  During the 1980's and '90s I modified a number of Knuckle heads for dual carbs as part of my quest for drag strip performance.   The fact that even then I was three generations removed from the latest technology in Harley head design would seem to reveal something about "where my head was at" (as they used to say). I wanted performance, but was not willing to entirely give up the "cool factor" (as they also used to say) to get it.  I would venture a guess that the same could be said for many today who  are drawn to the concept of dual carbs on vintage motors.

Of course motivations will vary from one man to the next, and where you fall in the spectrum of desire for "the look" verses "performance" will have a lot to do with how you approach a dual carb conversion.  If the look is more important to you than the performance, then any of the designs listed above will fit the bill nicely and I say go for it.  If, on the other hand, you lean more toward the performance end, then there are a few other things to consider.  One of the biggest of these is air flow.  Face it, even in the vintage world, today's motors tend to be larger than yesterday's, and a larger motor wants more air.  In the early days an 80" Knuckle was a big motor, and possibly the most common size used for drag racing.  In the years since, 84 and 86 inch engines have become common for street builds.  What I am suggesting is that what may have been a performance upgrade on a 61 inch motor could very well be a restriction on a 96 incher.

Airflow and how it relates to these vintage style dual carb modifications will be the subject of a soon (hopefully) upcoming post.