pyro1

I see mfgs making these from aluminum. What are the advantages of aluminum over the stock Zenoah manifold if any?? I have never had a problem with the stock one even on my full race mods.

pyro1

Ron Olson

My Feedback: (1)

Me either. Bling factor but said to eliminate warping. Don't overtighten the bolts and there shouldn't be an issue.

advanced builder

I may be wrong but I thought the composite manifold was for heat transfer. to keep the carb from over heating. I'm never going to Alm. unless I have a water cooled manifold. another post on this is going around.

pyro1

Thanks guys.

pyro1

Justaddwata

My Feedback: (3)

The aluminum manifold is shiny!! (you know how we love things we can polish or anodize!!)

They rely on a thick gasket to keep the heat transfer down. Personally I do not see the need. Isolator supplied works well (be it a little more prone to warpage) Aluminum may be an option if your going to water cool the intake - but other than that it is more a liability than an asset IMO

Ron Olson

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I saw that the water-cooled iso block is reported to add another 1-3 MPH. The next thing you know somebody will be adding a cool can. Whoops, I'd better not give anyone an idea!

mistycreekboats

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The alum intake has several advantages besides being shiny

- it does not warp like the composite ones - and it's not just a overtightning issue - can be caused by excessive heat, too tight, not flat surface etc
- can do diff carb positions thru machining like - rotate carb 90 degrees - adding diff type of carb easy tomachine one from alum where not so easy to make onefrom plastic or compsite
- can be water cooled- or heated if you run in really cool water (some of mine is 3*C)
- can be made thinner or thicker
-more secure-mine don't tend to loosenup like the plastic ones can

and can be anodized to match any color - ya bling

just my 2 cents

Ozpulse

Alloy iso blocks are also thinner than stock, which is supposed to help the top end. So Ive heard anyway, all part of tuning the intake length.

advanced builder

YOU HEARD IT HERE FIRST.

misshydro

Thats true keep them from vaporlocking. Like DODGE make a 4 barrow carb called the thermo quad ..that the center was composite. Those sucks kicks butt when dialed in wright. To get them fine tuned in you used the gas from the those propane torches to get them set wight.. some what the nitro guys do to there engine tunning. as for cool cans,I wouldnt dought that neither.. anything with real cars is possible to do with our gas boats.

MrMikeG

I've had carbs frost up, so why anybody would try to "cool" them is beyond me, if anything the water will warm them!
My most powerful engine has no carb manifold, explain that!
vapour lock, thats funny!

advanced builder

I thought vaporlock ,was when you fart the gas stay inside you pants.

Justaddwata

My Feedback: (3)

So is that an argument for or against an alloy manifold

Delinport

One advantage might be the shape of the manifold. I just bought a couple manifolds from wd200 that help get the carb away from the pull starter on a rear exhaust engine. Also the one I bought came with a fitting for running a pulse water pump. Since I am going to be using clutches, this works out well.

mistycreekboats

My Feedback: (1)

Maybe show us a picture of your 'frosted up' carb ........... that I would like to see .... I run in Northern Canada sometimes in 3 * C water and have yet to see a carb frost up ..... and I know what frosted carbs look like ..... we have these things called snowmobiles

And ur most powerful engine with intake built in .......... would that be a M&D cast ........... at the prices they charge it should be built in ............

My boat would come back with ice on it but no ;frost on carb' look at the dinghy here ....... covered in ice
http://www.youtube.com/watch?v=BLRpOOp26BM


funny

advanced builder

heat warping and freezing are we talking the shuttle or space ship. Not even a concern in the Northeastern states. Somebody smoking a vaporizer.

joseywales

funny?? Try looking at drag/prostreet cars that run cool cans down the drag strip!! The cooler the fuel that faster it burns=more power more speeds. Warm fuel dont atomize as well as cool fuel plus keeps your carb from vaporlocking on you. Those drag guys arent that stupied. They have more tricks up the sleves then you think. I've seen guys using dry ice in those cool cans instead of plain old ice.

mopartybob

Hi all, Was'nt there a thread awhile back about machined iso blocks that had swirls machined into them to increase fuel/air velocity??? whatever became of that? MPB

Ron Olson

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Bob, that might have been one of tricks from that Tornado that was pushed on infommercials. Those were supposed to help atomize the fuel for a better burn. My father-in-law got suckered into buying one of those for his car.
The only time that I've seen a frosting problem was from alky fed race engines and that was on drag cars and around the injectors or butterflies.

mopartybob

Nice to hear from you Ron, I believe it was mentioned on the "dock",and someone actually marketed them for awhile,(dyno tested and all} and showed a 3-5mph increase??? lol Maybe one of the engine gurus will pop in and clarify where this went... Scott S. where are you? MPB

lapistola28

I wouldn't call the frosting a "problem" . Usualy it's a good indicator that you have the fuel air mixture damn near dead on ! I raced powerboats and Go-Karts for a number of years and while testing this was something you looked for . And the ambient air temperature has very little to do with it as i raced in Bermuda where it gets pretty damn hot .

Scott Schneider

I am sitting back watching & reading what peoples feelings are .... water cooled manifolds and all
So much misinformation once repeated enough times gets heard as facts by those who really should know the why's and what fores before taking whats said as truths.

** The term "Vapor Lock" applied to a 2 cycle engine using a case pulse pumper carb as we do is different than what a 4 stroke carburetor fed engine suffers from.
In our pumper carbs the fuel system of pump and metering is 100% wet meaning NO air is touching the fuel at any time. Crank case pulse on the back side of pump diaphragm makes the fuel pump move fuel and create fuel pressure, Fuel under the Metering diaphragm only flows out threw jets when a low pressure is created by air movement down throat of carb. When enough fuel is drawn out diaphragm drops opening inlet needle and fuel pump replaces it. At 18,000 rpm this cycle happens 300 times per second !!
* Vapor lock is when the temperature of the liquid gas changes from being a stable liquid wanting to boil and vaporize itself into an atomized gas, This creates air/gas bubbles within the liquid gasoline and this air/gas aborbs fuel pump and metering energy causing carb to stop delivering fuel consistently or if engine is off not discharge fuel at all. The OEM Manifolds being a composite are so heat when engine is shut down does not conduct into carbs body heating up the fuel and causing an internal vapor lock. An engine using a solid metal non insulating manifold started out as cool and as first started engine will conduct very little heat into carb because the atomization of fuel into the airstream has a cooling effect and that effect negates conductive heat so long as engine remains running at above modest rpm settings.

Next is how fuel relates to heat once delivered into the airstream, cooler the fuel LESS it atomizes, Warmer the fuel GREATER the atomization .... so having cool/cold fuel within carb a good thing preventing vapor lock, but a bad thing once delivered leaving fuel to pick up conductive heat from engine so the fuel atomizes best.

When people say an intake manifold that is cold creates greater HP, it could be true only IF it cools the air itself creating greater air density as an inter cooler does for a exhaust driven turbo charged engine does. Sadly the surface area and length of intake tract actually as so little contact with air molecules passing threw it, conductive cooling of the air passing threw it is negligible at best.


** The depth of dynamics of all that is going on said above only scratches the surface .... but knowing the what & why only leads to correct decision making when the hype being sold had little to no truth in actual application.


JMO ....
Scott

mistycreekboats

My Feedback: (1)

Scott

Nice desc of vapor lock

Not sure I understand the HOTair theory ...........kinda throws my 42+ years of building rod/street engines out the window . we always tried to cram cold air in

Idon;t understand then why guys like CC sell alum intakes with teflon gaskets to insulate the carb? ... maybe they should be used with paper gaskets then for more power??

do u use alum intakes then ?

Scott Schneider

What I am saying is YES we want coldest air we can get so air density is highest, want fuel cool WHILE INSIDE OF CARB .... but do want fuel to pick up heat once inside engine before combustion so it atomizes better and burns more efficiently creating higher BTU's

And YES, all I use is aluminum manifolds of which most are 1/2 the thickness of an OEM one

Slow Motion

to make the best power in a typical v8 4 stroke engine you need to keep the gas as cold as possible. thats because the gas is being stored in the carb fuel bowls dirrectly above the rising heat of the motor. the hood of the car is holding all that heat in.
i don't think cooling the int. isolator on our boat engines can hurt but the air and fuel is moving through the carb and int. so fast at 18K+ that there is no time for the fuel to warm or cool before its burned and gone. we arent holding our fuel in heated float bowls. even at a 5K idle speed the fuel and air will stay well atomized by the thrashing crank counterweights. keep your boat fuel as cool as you can in the jerry can and the boat and it will be fine. the big advantage to aluminum isolators is they dont warp and cause air leaks. and with the isolating teflon gaskets the carbs dont get heat soaked while the engine is shut down and possibly cause hard restarts. cool the intake if you want but it wont make more power in our little boat engines and can be another source of water leaks.