Porting and polishing,

[Terry, NJ]

Because of the bad weather and Best's Gaskets haven't arrived yet, I needed something to do. I always have a project or two that I can switch to when needed. I had started P&P a couple of manifolds. They were bored out (The easy part). Now they needed polishing, this is the tedious part. Hours of going roundy, round, inside the runners till it's shiny and smoothe all around. Later on, I was going through some old postings and I got into Pirianos dyno tests and curiously, The bored out Ford A manifold produced a higher reading with just a A zenith. The primary runner seems to be undersized. Next, I read where someone (I think it was Brent Terry, maybe not) who was observing as to how the flow wasn't really enough to feed the B carb. But then the B carb was fed through a fuel pump. The extra pressure would provide the extra fuel needed. So, maybe we could enlarge the passages to allow a greater flow to the B carburetors on our A s. Or has this been explored already? Any suggestions?
Terry

[Mickey]

I don't know but i'd be interested. My A manifold is out being bored right now to match up with a B Marvel carb.

[Dennis]

Terry, I ran an electric fuel pump on a B carburetor for a couple months and there was no difference. I never tried boring the A manifold but instead have a B manifold that I welded the carb mounting flange holes and ears, redrilled to the correct the angle of the carb and am running a B carb on the B manifold. And the choke GAV works perfect with the correct alignment.

[Dennis]

The gas line I bent from a 1/4" piece of stainless btw.

[Terry, NJ]

Mickey, Thanks for the response. A couple of things, Have you heard of the special fuel lines for Mod B carbs in Mod A s made by B and B mod A parts in Breinigsville, Pa? Bill makes them up himself and sells them (And other stuff) at local shows and meets. It's a nice clean job and I think he gets about $10 for one. Second, who's doing the polishing, you or the machine shop?
Terry

[Mickey]

Yes, I heard about B&B antique auto parts but have not been able to locate a phone number to call about the fuel line. Don't need to do that now as i'm going to stay with the A manifold and am having it bored out by Piranios down in Texas. I thought I'd work on smoothing out the runs.

http://www.modelaparts.net/index.html

[2manycars]

Pressurizing the fuel line to the carbuerator has no effect on fuel flow in the manifold.

[Mickey]

Brent how thin does the wall of the A manifold get when it's bored.

[2manycars]

Brent is absolutely correct on over polishing the manifold.

[Mitch]

Terry nothing to do? Sit back and kick you feet up, a day of relaxation won’t hurt

[Terry, NJ]

Thanks Everyone! The answer to Mickey's question is, Pretty thin! BUT, the good news is that unless the machinist does a bad job or there is a big flaw in the casting, there's nothing to worry about. I haven't heard of any breaking. This why you need a pin to locate the casting with. The pin has top reach from the top to the bottom and align the primary (?) runner perfectly with the travel of the drill.
Next, I misunderstood Brent's piece on carburetor flow, I was sure I was reading about fuel, not air. Oh well, I will probably make a lot more errors before they put me in the box! But he is correct, The carbs should be altered, modified in some way to handle more air. I have often thought of taking a venturi and opening it up, say .020 and see what happens. They're easier to polish out and blend the radius and the angle. Or really taking the bull by the horns and boring the whole thing out .020 The two halves and recasting the venturi! IT would be tricky thing to set up. but I think it could be done. Unfortunately, .020 is about all the body could be enlarged. Well, when I get my Bridgeport!
About the running debate about port finish, A while ago, I was watching a vid about P&Ping in which the mechanic gave some notice to those who believe in the rough surface theory and hoe pointed out several manufacturers who do use a mirror finish and that was what he intended to use. In watching the vids, I ran across the other side of the debate where it was recommended that one just smoothe the walls out to diminish turbulence and to finish up with a "Florentine" finish. I know what this is because we used to create a Florentine finish on the pen caps we made. It was done by putting the cap on a spinning spindle and running it past an 80 grit flap wheel. It was a nice Brushed finish. So After some thought, I've decided that a florentine finish it will be. Too much trouble to go after a mirror finish anyway!
Terry

[2manycars]

Altering the Venturi will definitely get you airflow, and this is on my bucket-list to do once I purchase a CNC mill. I feel certain there is a formula involved in designing a Venturi that can create a strong vacuum throughout the entire RPM range. It would be interesting to speak to someone who has studied this.

A fixed venturi is only optimal at a given volume of air. That is why the variable venturi was developed. That is also why a 4 barrel carb is better than a large 2 barrel. I have often thought of installing a pair of SU carbs, which produce great power and fuel economy, due to the variable venturi. Ford experimented with a variable venturi 2 barrel carb around 1980, and it made great power, and amazing MPG. It only lasted a few years, and was replace by fuel injection.

[Mitch]

A fixed venturi is only optimal at a given volume of air. That is why the variable venturi was developed. That is also why a 4 barrel carb is better than a large 2 barrel. I have often thought of installing a pair of SU carbs, which produce great power and fuel economy, due to the variable venturi. Ford experimented with a variable venturi 2 barrel carb around 1980, and it made great power, and amazing MPG. It only lasted a few years, and was replace by fuel injection.

Bill
Funny you should mention the VV carb. I was working at the Ford dealer when those hit. They ran decent when working properly, but overall the mechanical design was a major flop. There was a large vacuum diaphram in the back which constantly failed from being fuel soaked. The other settings on that carb needed to be perfectly set up too run properly. Most dealers started putting holley replacements on instead of repairing and wasting time with those.

22B989ED-2AA0-49CA-B98A-E76A9D0A943B.jpeg

[BNCHIEF]

Brent is correct in what he says you want to port for smooth flow however you do not want to get so smooth you have no turbulence for the fuel air mixture, we used to do racing engines quite a bit my experience was with motorcycles mostly,i did do some porting on my model A and a little clean up and polishing on my weber manifold.

[BILL WILLIAMSON]

Fords' Variable Venturi was VERY LEAN----Tore down & cleaned them, bought a kit & assembled & adjust things EXACTLY as the Instruction sheet specified & they ran SUPER!
Did that on my '68 Datsun Pickup, with a '79 Mustang-2800 V-6 & C-4 Automatic & it ran like a SCALDED DOG! I also had years of experience with S.U.s' CVVV carbs. They're an amazing SIMPLE Carb!
Dad Gofast

[2manycars]

Bill
Funny you should mention the VV carb. I was working at the Ford dealer when those hit. They ran decent when working properly, but overall the mechanical design was a major flop. There was a large vacuum diaphram in the back which constantly failed from being fuel soaked. The other settings on that carb needed to be perfectly set up too run properly. Most dealers started putting holley replacements on instead of repairing and wasting time with those.

22B989ED-2AA0-49CA-B98A-E76A9D0A943B.jpeg

I was also working in the dealership when they were in use. The first ones were simple, before the feedback computer system was added, but you are correct about the crappy diaphram that should have been fuel proof. I was going to install one on my F100 with a 302, but I wanted more power, so I swapped out the 302 for a 460 with a C6. That truck would pull hell off it's hinges if I could get the traction.

[Mitch]

Yea the only VV's I worked on was those feedback jobs. Pure

[Tom Wesenberg]

There are more veterans of dealerships on here than I realized. I worked at both GM and MoPar dealerships, but not Ford, so I only had to work on a couple of the Ford VV carbs. The first time I saw a variable venturi carb was in 1964 when I traded my 12" antique TV to a neighbor for his 1942 Evinrude Speeditwin. The throttle was the variable venturi. It was simple and very effective. Foolishly after snapping all 3 prop blades within an hour on the Mississippi river, I changed the Speeditwin into a go kart engine. I removed the carb and installed a Stromberg 2 barrel. That kart moved like a dragster until the clutch blew apart.

[2manycars]

The first variable venturi carb I worked on was on my 1964 Honda CL72 scrambler. I inatvertanly installed the slides in backwards, and it ran very rich. I noticed the problem at once and swapped them. That was in 1966.

[H. L. Chauvin]

FWIW:

Many always often realize that with the 1.00" A diameter intake compared to the 1.25" B diameter intake, this work involves the removal of only a thin, 1/8" layer of cast iron material from the inner circumference of the intake manifold.

However, many seldom realize the large "increase" in the B's intake cross sectional area over that of the A cross sectional area.

For example, (with cross sectional area = pi X r squared), and with the inner A radius of 0.5" squared X pi ........ vs ..... the B radius, of 0.625" squared x pi ........... the inner area of the A intake manifold is, (A = .785 square inches) .............. vs. the inner area of the B intake manifold which is (B = 1.226 square inches); hence, the intake's area increase of the B over the intake's area increase of the A results in a "whopping" increase of 156 %.

This is an enormous increase of atomized fuel flow indicated while using hydraulic flow calculations according to Manning's Engineering equations.

If carburetor gaskets are protruding into the intake manifold area; and/or if sharp, inner cast iron intake corners exist inside the block; and/or if hanging round lips are occurring on bottoms of valves; etc.; these obstructions are contributing to less atomized fuel flow; hence, resulting in less Model A performance.

Just in case anyone would like to "seriously" consider dynanometer tested Model A engine performance results involving .......... "before-porting & after-porting":

Please call Mr. Ron Kelley, "RK Designs", Royse City,TX, (advertised in the MAFCA's The Restorer) at (972) 771-1911.

[Dennis]

I've often wondered what the total cubic inch comparison would be...

[CarlG]

...swapped out the 302 for a 460 with a C6. That truck would pull hell off it's hinges if I could get the traction.

I swapped out the 360 in my '71 F100 for a 429 (same block as a 460) with a C6 with the same results. It could pretty much climb trees.

[Mitch]

I used to have a 70 F-100 with a 360.

[CarlG]

My son still has my '71

[Terry, NJ]

Henry, If anyone had asked me an hour ago, I would have said 1" too. However, I couldn't remember 1/8 coming off the walls of those manifolds when I drilled them. It was much less than that. So s, said I, I will be sure, I will measure it! My un drilled manifolds are all drilled so I measured the next best thing, a carburetor! The results were 1.156 (1' 5/32) One inch and an eighth for all intents an purposes. As I said, I was ready to believe it myself, 1" bore, yeah, yeah thats right, but it isn't! Plus, the inside is more like the interior of a cave, the bored out finish is much more efficient. Also, The model B engine was the same displacement (200 cu in)as the A. It just couldn't breathe as well. (The A engine)
Terry

FWIW:

Many always often realize that with the 1.00" A diameter intake compared to the 1.25" B diameter intake, this work involves the removal of only a thin, 1/8" layer of cast iron material from the inner circumference of the intake manifold.

However, many seldom realize the large "increase" in the B's intake cross sectional area over that of the A cross sectional area.

For example, (with cross sectional area = pi X r squared), and with the inner A radius of 0.5" squared X pi ........ vs ..... the B radius, of 0.625" squared x pi ........... the inner area of the A intake manifold is, (A = .785 square inches) .............. vs. the inner area of the B intake manifold which is (B = 1.226 square inches); hence, the intake's area increase of the B over the intake's area increase of the A results in a "whopping" increase of 156 %.

This is an enormous increase of atomized fuel flow indicated while using hydraulic flow calculations according to Manning's Engineering equations.

If carburetor gaskets are protruding into the intake manifold area; and/or if sharp, inner cast iron intake corners exist inside the block; and/or if hanging round lips are occurring on bottoms of valves; etc.; these obstructions are contributing to less atomized fuel flow; hence, resulting in less Model A performance.

Just in case anyone would like to "seriously" consider dynanometer tested Model A engine performance results involving .......... "before-porting & after-porting":

Please call Mr. Ron Kelley, "RK Designs", Royse City,TX, (advertised in the MAFCA's The Restorer) at (972) 771-1911.

[Mitch]

the inside is more like the interior of a cave,

Does it look like this

[Terry, NJ]

Question! as I understand it, The problem with too high a finish is that the fuel somehow drops out of the Gas/air mix as it's moving through the runner? From what I'm able to reconstruct, the mental picture that I have in my mind is of the air/gas mix dripping gas as it flies through the manifold. I have an easier time envisaging dirt leaving the air flow of a vacuum cleaner. Where does this dropped gas go? It can't just sit there, resisting the force of the flow going past it. Sooner or later, It winds up in the cylinder to be burned. In some research I did, the discussion was framed as Laminar vs Turbulent. The discussion soon spiraled off into intellectual space with references to Darcy/Weiss..... Tables. Important stuff, I'm sure, but it made my head hurt. However, I did learn that there is a most efficient surface profile, but I think it was for velocity. But I have no plans to try to create anything remotely like it.
Terry

[BNCHIEF]

Terry the term is atomization that is what you are after it is kind of like making kool aid if you just dump it in the water it is not a s good as mixing it up, same with air fuel mix needs to atomize to get the most out of the mixture, that is a simple crude way of saying it I am sure others can explain it much better.

[H. L. Chauvin]

Makes lots of sense.

It is like a dog hiking his leg and peeing on a Model A wheel.

The Yellow Pee comes out heated, gets atomized when it hits the cooler Air, and it remains Yellow after it puddles on the ground;

hence, according to Mr. Zenith, Esq., P = Y x A square.

[BNCHIEF]

Except after awhile it will freeze with the proper conditions.

[Terry, NJ]

I'm laughing too hard!

[Terry, NJ]

Ai Yi Yi Ai! My pills quick! OOOffah!