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QUESTION FOR MOTOR GUYS

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1911s
Thurman Cage
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South GA ride
Ted & Chris Crownover
A

Anonymous

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Alright my boat will turn 3200 when it cool air out side. like in the morning or winter. During the heat of a summer day 2700. This is a car motor prop is a 72 34 paddle motor size 400 SB Chevy 202 fuely heads 600 cfm elderbrock carb.
I am thinking a bigger cfm carb to compensate for the change in air density and a carb spacer of 1"
What's your opinion?


if i get it to turn more or consistently turn 3200 i will put on a bigger prop.
 
I'm no motor head, but do you think your getting the carb opened all the way when it's hot outside? Seems like a big dropoff in RPM's for a carb?
 
TED I AM A BIG IN TO THE 1IN SPACER ( SWIRL PLATE) ANY WAY THE ONE THAT HAS THE FOURS HOLES IN IT ! BUT ANYWAY YOUR PROP HAS MORE WORK TO DO ! WHEN THE AIR IS THICKER AND YOUR CARB LEANS A LITTLE TOO ! :D
 
I agree Fat ...... 1" spacer, and check that both main jets are clear. That engine has to be leaning out. JMO

olf
 
I wouldn't go bigger on the carb, that 600 should be plenty big for a direct 400. There's got to be something else going on.

Carbs don't measure density either, they can only measure velocity.

I wonder if the carb isn't actually running too rich. Hot air does have less density, but the carb doesn't know that.

A bigger engine should create more velocity than a small on given the same size venturi, and will actually pull more fuel through the same jet as a smaller engine would.

How do your plugs look?

Have you called Edelbrock for advice? I would do that before making a change.

Also, I have seen lots of mixed results from spacers in mag articles, and unless you have an engine dyno to test before and after, you may make the same power or even less and not know it.

Edelbrock will help, give them a call. Just be prepared to be on hold for a while.
 
You are battling two wars first of all the hotter the air the less oxygen is present op’s (let me put it in pilots terms the less dense the air is) and also the more humid air is the less oxygen is present. So when it’s hot or humid and worse case is hot and humid there is less oxygen present in the air and to get this in exact scientific terms there is less oxygen per cubic foot. So when there is less air available it doesn’t matter what you do AS LONG AS YOUR NATURALLY ASPIRATED you will make less horsepower. Now for the second power robing villain when the air is humid it takes more power to turn a prop the same RPM’s because the induced drag is increased on a prop. I had better restate that the more moisture in the air the harder it is to turn a prop. A engine builder or any racer loves day’s at 35 to 40 degrees and being near sea level the lower you are the more oxygen is present and you pilots know what corrected altitude is. We use it in drag racing to calculate how much oxygen is present in the air so we can jet accordingly to generate the most horsepower possible. As for the spacer A.K.A. super sucker I run them on every air boat motor I build, skip the fancy billet one and just run the Jeg’s composite one pn #555-1542 for $90.
 
The CSR plate is $170 and the Brodix is over $200 to be honest I like the Jeg's composite because it's cheap and they all show about the same horsepower gain however the composite is also a heat isolator for the carb.
 
Yes that's what I am battling I already have the phenolic 1 carb spacer. But was wondering if the larger carb would help with the volume of air flowing. Yes I do know it will always have a change of pace due to the air would like to just get it a little closer to each other. If I look at what's been done so far. I do know by next hunting season I plan on going bigger on the cam and getting a dual plain intake right now it have the torquer on it. The cam is around 460 lift. was thinking about 480 lift rpm range 1500 to 4000
 
It depends on your intake and combo. It's safe to say you should gain around 10 to 13HP some motors can gain all the way up to 40HP. The reason I run them is they also direct the intake signal at the booster and I feel this improves throttle response.
 
ok so 1 inch spacer is there any gain for a 2". I have a single plane intake Elderbrock torker with a Elderbrock carb. I know it and elderbrock never again.
 
Ted, Lord knows I wouldn't pretend to answer for Thunder on this ..... him and Mike Felber are two of the finest builders in the business.

From my limited experience in engine building the purpose of the spacer is to increase the length of the intake tract. That normally increases torque. There is a point however when more is too much. 1" spacers seem to be a good place to stop for what we do.

My spacer is 1" aluminum. I wish I'd thought to buy phenolic because like Dave says it insulates the carb from heat better than mine.

olf
 
Ted no offense ment but you have about one of the worst intakes for your application the runners in a torquer are just too short and it has an open plenum on top of that. The best all around airboat intake out there is a Edelbrock RPM air gap I use this on all motors up to 550HP. You may want to consider changing intakes, spacer and carb. If money is tight just change the intake you will notice a difference in torque and throttle response and fuel economy.
 
TED SORRY! I GOT A TWO INCH ONE ON MINE ! I THOUGH IT WAS 1 IN BUT ANYWAY ! I GOT THE AIR GAP INTAKE BUT A 850 HOLLEY ! BUT I GOT A 506 CAD WHICH NEEDS MORE AT TIMES THAN I GOT! BUT WORKING ON THAT NOW ! THEY ARE HARD TO TWEEK AT TIMES OR FOR ME ANYWAY ! I KNOW ON CADS THAT INTAKE MATCH AT THE PORTS ARE NOT ALWAYS CLOSE ! I SMOOTH THE PORTS TO MATCH EXCEPT THE BOTTOM ! WHICH I LEAVE A LITTLE HUMP ! SO THE WET STUFF GET BACK IN THE FLOW ! :D !
 
Thanks I was thinking about changing intakes. I had this intake in the garage. Its Good actually to hear it one of the worst just means I have something to look forward to.
 
Ted what kind of motor is it. Intakes are one of the few things I don't mind running used. I can keep an eye out for ya as In carbs I always have ten or so on hand for testing and tuning and I always come across them also.
 
Thunder, who makes the best intake manifold gasket right now for an Edelbrock intake ..... EB or Fel Pro ? Thanks,

olf
 
i agree with the intake being to short of runner lenth and the fact that its open is killing your torque curve the rpm air gap a one inch composite spacer and a bary grant 550cfm {double pumper} carb would in crease runner lenth and most of all increase runner volicity with is were you get torque, airgap make good torque at 3000 but the torque doesnt start making torque till 4500 and not to mention its out dated the rpm will out perform the torquer across t he board on a sbc from idel to 6000 i have the combo above on my dd and it works just remeber bigger with engines means cubic inch to get torque not cam,carb,heads,or intake
 
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