Finding where the bottleneck is on intake

[ASMART]

I had a thought about how to tell where the bottleneck is on the intake side of any engine. Given the nature of the log head on the sbf6, there are questions as to how much value a larger carb or larger valves realy make. While what I am suggesting is not going to give you HP or torque numbers, it may help find where to spend your time and money for the best effect. The one thing I think everyone would agree on is that vacuum at WOT is a BAD thing. At least you want to keep it to a minimum. The trick is to find out where the most vacuum exist in the intake track and at what RPM. It seems to me there are several places that you would want to measure. The most obvious would be just under the carb. The next would be just outside each valve or as close as you can reasonably get. You could baseline an engine by measuring vacuum at these points with various RPM. If you improve flow down stream of the measuring point, you should see an increase in vacuum. For instance. You measure X inches of vacuum at 3000 rpm baseline. You add larger valves and do some light port and bowl work. You should be able to see X+ vacuum at the port and at the carb because you increased flow away from the measuring point. The reason for a measurment at each port is to figure out if there is 1 or more cylinders that are better or worse than the others. This would let you know which cylinder to check for additional porting, cam wear, valve adjustment, etc. If you add a larger carb(upsteam of all measure points), the vacuum level should decrease. With this you could see if the additional CFM were being used and at what RPM it was really making a difference. Of course you could also do this on the exhast side, but measuring the pressures at the high temperature would take more money than adding vacuum take offs and buying a vacuum guage.

 

[Anlushac11]

8)

I have wondered about this as well.

My dad built his own flowbench for his head porting business. He just got some probes that can measure airflow.

Is it possible to put a false plug in end of runner and stick a hollow tube into log and attached on other end is a vacuum gauge. Then start the motor and get samples of vacuum at different points of the log?

Would you have to run a power source for the gauge? or is the power just for the light?

 

[yellowstang]

i am curious,

we know the point of the carb. air/fuel takes the path of least resistance just like any other fluid. could we connect a vaccuum to the carb hole and measure the vaccuum with no intake valves at all?

i would imagine that the 3rd and 4th valves would be the highest readings, they are closest to the carb. and then 2 and 5 still lower and then 1 and 6 be the lowest reading, since furthest from the carb.

if this were true, could we do someting like this with a dremel:
1. bore open/clean up the entire length of the log.(just to clean up)
2. then using a bigger brush/stone inserted from the end and insert just past the 2nd intake runner.
3. then go a little bigger with a stone/brush and insert just past the 1st intake runner.
4. repeat from the other end of the fuel log for 4-6 intake runners

so the fuel log would have steps. widest diameter at the ends, a little wider at the 2 and 5 intake runners and then stock diameter at the center. the overall intake volume would be greater. and thus would flow more. maybe .050 to .100" steps. but would that equal out the vaccum measurements?

is the theory/hypothesis a good one??

even if the fuel log diameter is larger at the 1 and 6 intake runner, the airspeed slow down.but that should not be a problem at WOT.

would that do it??
Pete

 

[Anonymous]

so we could be saying that each of the cylinders make a different amount of power? more on the inside and less towards the outside?

if that were to be so, could we just use the scavenging effect to our advantage instead of trying to do stuff inside of the log, or would that just screw things up?

 

[yellowstang]

rogues,

yes and yes.

as far as scavenging what do you mean? when you have more overlap on your cam, the momentum of the exhaust gasses leaving the cylinder, aids(creates a vaccuum) in helping to draw the air/fuel into the cylinder --- that i thought was scavenging??

i would still like to hear from the others about my theory of a stepped log for better flow at the outer intake runners

if the vaccuum signal are different, would you put in different size valves at the outer compared to the inner. for instance 1.65I on 3 and 4,1.70I on 2 and 5 and maybe 1.75 on 1 and 6 to help. i think that larger valves all around would help it breath better. period. this would also not be my first choice for head modifications. but would the stepped log help even out the vaccuum signal at each valve?

if the area in the fuel log around at the first intake runner were larger, would the runner also need to be enlarged? flow only gets better if everything is larger right? other wise the a/f would come thru the carb, come thru the log and actually slow down(based on larger dia) and then speed back up because of the runner being the original diameter.

there is a thing in aerodynamics known as the venturi affect where as air goes thru a nozzle it actually picks up speed as it exits the nozzle. if we consider a larger flow thru a stepped log, and the intake runner were the "nozzle", then it flow would be better. and then we wouldnt have to touch the intake runner( other to clean it up a bit)

how much difference in vaccuum signal between valves are we talking anyway??? maybe 10%between valves? 30%??

i like these discussions in theory!! way to exercise the brain!!

Pete
"we all stand on the shoulders of the men who came before us!"

 

[LEROY POLL]

HELLO PETE

FOR YEARS I'VE LOOKED AT THE PROBLEM OF THE LOG. I ALSO HAVE THOUGHT ABOUT OTHER INLINE SIXES.

THE FIXED LOG WAS THE CHEAPER WAY TO GO FOR THIS MOTOR. IT WAS NOT FOR THE PERFORMANCE WE ARE LOOKING FOR. IT ALSO WAS NOT THE BEST DESIGN FOR THE MOTOR FOR ECONOMY AND FUEL MILEAGE. THE CHANGES WE SEE FROM THE ARGENTINA HEAD,GAVE BOTH MORE PERFORMANCE AND MPG.

I HAD NEVER SEEN ANY OTHER HEAD FOR THIS ENG. BEFORE FEB. OF THIS YEAR , WHEN I FOUND THIS FORUM. WHEN I SAW THE AUSSE HEAD I THOUGHT IT WAS GREAT! BUT UPON SEEING THE ARGENTINA HEAD THEIR WAS AND IMPROVEMENT IN THE DESIGN. THIS HEAD DESIGN WAS USING MORE OF AN EQUAL LENGTH AND FLOW.

COMPARE THE TWO HEADS AND YOU CAN SEE THAT THE 3 & 4 CYL'S HAVE THE AIR GOING AROUND A LONGER WAY TO GET TO THE VALVE. THIS GIVES MORE OF A BALANCE BETWEEN EACH CYL.

BEFORE COMING HERE (ON THE FORUM) I HAD DESIGNED A DIFFERENT WAY AROUND THE PROBLEM YOU ARE TALKING ABOUT. LIKE THE OFFY DESIGN THEY OPEN UP THE BOTTLE NECK BY USING TWO MORE HOLES TO HELP WITH THE POWER! IN MY DESIGN I TOOK AWAY THE CENTER OPENNING AND PUT TWO HOLES ON THE SIDE OF THE MANIFOLD, AT THE 2 & 3 AND 4 & 5 CYL'S. I WAS GOING TO USE RECTANGULAR TUBING AND WELD A LOG OUT SIDE AND NEXT TO THE OLD LOG. I WAS ALSO GOING TO MOUNT A 2100 TWO BARREL IN THE MIDDLE AND HOPED TO GET MORE POWER AND FUEL ECONOMY.

I STILL HAVE MY PAPERS AND MOCK UP ON IT HERE. THE THING THAT STOPPED ME WAS THE STOCK WAY FORD WENT ABOUT IT. MY THINKING WAS MINE WOULD WORK BUT THEIRS WOULD LOOK SOOO... MUCH BETTER. I THREW AWAY MY OLD HEADS THAT I WAS WORKING ON. NOW I'M ALITTLE SORRY, FOR I'D STILL LIKE TO TRY IT OUT.

YOU ARE TAKING EVERYTHING INTO YOUR THEORY AND I HAVE TO AGREE WITH IT. BUT THE ONLY WAY IS TO TRY IT AND SEE .....TESTING SOME TIMES PROVES THEORY WRONG. THE FUN I HAD TRYING TO MAKE THIS LOG PROBLEM GET BETTER DROVE ME TO ALMOST GET IT DONE. GET A HEAD JUST LIKE THE ONE YOU HAVE NOW, AND MAKE ALL YOUR CHANGES ONE AT A TIME AND PROVE YOUR THEORIES. EVEN THE LARGER OUTER VALVE CHANGE WOULD BE INTERESTING TO KNOW. I FEEL YOU WILL FIND THE JOY OF DOING THIS WORTH WHILE. (OH AND KEEP US INFORMED)!!!

EVERYONE HAVE A GREAT YEAR NEXT YEAR!!!

LIVE IN GRACE

LEROY POLUMBUS

 

[Anonymous]

what i was saying is, wouldnt there be more of a scavenging affect, if you took the outside exhaust ports and made them larger and then move in and make them a little bit larger and then just leave the middle ones alone, or would that not even be worth the time, or would u just get more power if u did them all

 

[LEROY POLL]

HELLO ROGUES

INPROVEMENT TO ALL WILL GIVE MORE POWER TO ALL. YOUR THEORY OF CHANGING EACH CYL'S VALVES SHOULD WORK . THE ONLY THING IS WHAT CHANGES? I'D THINK CHANGING THE OUTER CYL'S VALVES WILL WORK, BUT WHAT WOULD IT DO FOR YOUR TUNING AT DIFFERENT RPM? MAYBE AT HIGH SPEEDS IT WOULD NOT RUN AS SMOOTHLY OR MAYBE NOT.

CHANGING THE BORE SIZE WOULD MAKE A BIG CHANGE. BAL. AND OTHER THING TO THINK ABOUT. THEN MAYBE THE VALVE CHANGE WOULD BE LIKE CHANGING THE BORE SIZE....... : ????!!!

BUT THE EXPENSE WOULDN'T BE AS GREAT TO MAKE IT ALL THE SAME AGAIN.

THINKING TOO MUCH!!!

LIVE IN GRACE

LEROY POLL

P.S. ..OH THE WHAT IF'S OF THIS WORLD....!

 

[yellowstang]

i think more so now that there wouldnt be any possible way to make the vaccuum signals the same from 1-6. for this i agree the Oz head does that.

but what for the log heads?i agree that all intake valves should be opened up to at least 1.75. this definitely allows the 200 to breath better.

i would like to know what affect the engine would have if the first and 6th cylinder had 1.88 Intake valves. given the same cam profile for each valve this would allow more flow into 1 and 6. would you have more horsepower in 1 and 6, since there would be more air/fuel? how can you measure cylinder to cylinder horsepower? could it be a function of temperature? since there is more fuel this would mean it would be hotter?

i still believe that the high compresion setups, illustrated here are great. the engines themselves breath better than stock. i also think that the turbo 200 would help to equalize the difference in cylinder to cylinder differences. since i am here in denver, where air is less which means performance would be less. i am going for the turbo route.

let me know what you think about hp as a function of temperature? has anybody ever taken any cylinder to cylinder tempertures?

Pete

 

[LEROY POLL]

HELLO YELLOWSTANG

I HAVE NEVER TAKEN A TEMP. READING. BUT I HAVE TAKEN READING OF MY PLUGS.

I HAVE FOUND THAT MOST TIME MY PLUGS READ THIS WAY: (THESE ARE ALL TAKEN AT SEA LEVEL AND IN SAN JOSE.)

STOCK JETS #62
(1 & 6) LIGHT YELLOWISH/GREEN TO NO COLOR
(2 & 5) LIGHT TAN TO MED. BROWN
(3 & 4) DARK BROWN TO BLACKISH IN COLOR

JETS #68
(1 & 6) MED. BROWN TO VERY DARK BROWN
(2 & 5) BLACK SOOTY TO BLACK MOIST.
(3 & 4) BLACK/MOIST TO BLACK WET.

JETS #64/65
(1 & 6) LIGHT TAN
(2 & 5) MED. BROWN
(3 & 4) BLACK/SOOTY

FROM THESE READINGS I RUN #65 IN THE WINTER AND #64WHEN I TRAVEL AND IN THE SUMMER.

NOW THESE READINGS ARE TELLING ME THAT I'M NOT MAKING THE SAME HP IN ALL THE CYLINDER. THE FORD 300 WITH F/I WILL ALL LOOK THE SAME AND THEY ARE PROBABLY ALL MAKING THE SAME HP.

PLAYING WITH THE VALVE SIZE AND CHECKING THE PLUG READING WOULD ANSWER SOME OF THESE QUESTIONS WE ARE ASKING.

EXHAUST TUNING WILL HAVE LESS LOW END EFFECT BUT WILL MAKE SOME DIFFERANCE AT HIGHER RPM'S. WHILE (I BELIEVE) THE IN TAKE WILL HAVE AN EFFECT OVER MOST OF THE RPM RANGE. ( ALL THIS IS ON A MOTOR IN GOOD SHAPE.) OURS IS TO TRY TO MAKE ALL CLY'S TO RUN EVENLLY/EQUALLY/SMOOTHY SAME HP.....! THIS IS THE PROBLEM ALL INLINES HAVE.

FROM MY JET READINGS I CAN MAKE MY OUTTER CYL'S RUN AS I WOULD LIKE BUT AT THE EXPENSE OF THE OTHER FOUR CYL'S!! TWO CARB. SET-UP WOULD HELP OUR MOTOR AND LOG PROBLEM.

LOOK TO THE AUSSIES F/I CROSSFLOW IS WHAT FORD FOUND TO FIX THESE PROBLEMS.

LIVE IN GRACE

LEROY POLL

 

[ASMART]

I didn't think I would spark this much conversation. I didn't mean to say that the ultimate goal is to make the same power in every cylinder regardless of everything else. The real goal is to make as much power as possible. The idea I had was a way of identifying what cylinders were having trouble and then trying to find the culprit. It would be interesting to see the differences made by the following.
1. boring the log
2. big log versus small log
3. porting
3. larger carbs
4. small log vs big log vs aussie vs argie
5. stock exhaust vs header