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509 cadi

S

stan

Well-known member
picked up parts from the machine shop last friday. woke up early saturday morning and my buddy hunter arrived at the house about 9:00.It being darn hot and weren't no signs of get any cooler we set in assemblin his engine in the kitchin .Now cheryl shes is pretty understandin when it comes the needs of my airtboatin habits , just can't use her sink as a parts washer ( been there, done that ,not real good for the mariage) any how all went well and we finaly got the old motor on the boat ,cam broke in and the prop on. so heres the specks
hull 16'8"x8' hartline (big a** boat)
500 cadillac direct drive bored .040 over makin it a 509
600 holley carb, eldebrock intake ( wished we would have had a stock one)76 cc heads ,stock rockers,kb pistons and hasting rings From Potter top ring gaped .035,stock rods ,crank turned .010,all machine work and balancing was preformed by S.O.B. racing engines out of Samsula, FL. Hunter bolted a 72" sensenich narrow 3 blade propeller set at the number 2 mark and reved it up to 3000 rpm and set the timin at 34 degres , air fuel ratio runin about 12.49 wot and 13.50 at 2000 motor seems like its gonna make it ,however i believe it wants a better carb after 2000 rpms the engine starts pullin the vaccum secondaries open makin the throttle real sensitive between 2000 and 3000 rpm. we'll put her in the water sadurday at crystal river and we'll see how she does.
What carb would be a good choice for this application?
 
Stan: I have run these for 30 years, 18 of them direct drive. The stock 800 cfm quadrajet when done right works very well and lets you get good mileage. I also ran a 850 Holley DP for many years. I can do the math and calculate the cfm req't and I have heard all the folks tell me that that carb is too big. Its not with proper jets. These big cubic inch engines, at least under heavy load, need more at WOT--period. And BTW, that Edlebrock will kill that stock intake hands down. Even from 1000 to 3000. Not to mention it weighs 25 pounds less.
 
Hey Stan! Sounds like you used KB Hyperutectic pistons, fast burn quench engine. Sounds like pretty much the same setup I'm building. I bought a 600 Holley Double pumper, won't know how it works for a while but If YOUR secondarys are starting to open at 2000 RPM that would be two thirds the air/fuel requirement being provided by the primarys. I would think a 600 CFM would be enough and mechanical secondarys would give you more control. Or you might want to try a stiffer secondary spring. :wink:
Pretty understanding wife! :lol: I don't need to use our kitchen but I have used the dishwasher for like signal lights, door trim and the like. I have heard dishwashers work pretty good for engine parts but havn't had the guts to try it. :lol:
Have a blast on Saturday! 8)
 
Yeah, Was wondering about putting in an O2 sensor and mixture gauge. Price is quite affordable but does anyone have any experience with them. Also egt could be an option but a little more money!
 
Cold, I think you can tell a lot just from reading the plugs. I always try to keep something as basic as possible, and the money saved should buy several gallons of that high priced gas of yours .... :) .

I feel for ya' man. The oil companies owe us all big time.

olf
 
I also have an Infrared at work that measures HC/CO, 02 and C02. Do a trailer set up should work. :wink: The prop noise at the airport won't bother anyone but the sight of it is sure to attract some. :lol: I hate attracting attention ! :lol:
 
ran a small 4bl on my caddy when dd i thought it did well put a q-jet on it and gained 400 rpm's ran that until i broke a spring and it backfired through the carb till i got back to the boat ramp didn't feel up to the challenge of rebuilding it so i bought a 750 holley vac seconds rpms stayed the same with the q-jet but it took some trail and error to finnally get it tuned to my thought of pretty good but i still believe it would take more carb now with the gearbox.my vote is q-jet for dd.i know that the motor is together now but if you take the edelbrock off in the future smooth and polish about 1 and 1/2 inch of the runners it will give you some more midrange.doesn't take long either.
 
Ruagatr":1a2d7qob said:
Stan: I have run these for 30 years, 18 of them direct drive. The stock 800 cfm quadrajet when done right works very well and lets you get good mileage. I also ran a 850 Holley DP for many years. I can do the math and calculate the cfm req't and I have heard all the folks tell me that that carb is too big. Its not with proper jets.
Click to expand...

You're exactly right. It's not the size of the carb venturies that matter, it is the booster signal that the jets get that pulls and atomizes the fuel.
This becomes apparent when you examine a direct-port fuel injection system that can have a 1000 or more CFM throttle body and still produce excellent low end and driveabiliy.

This is easier to do on a carb with a smaller venturi though since the carb doesn't have the advantage of fuel pump pressure to spray the fuel through the injectors.

Quadrajet works well because it has small-diameter primaries and vacuum secondaries that only open as needed.

I think you better know what you're doing if you want to put an 850 double pumper on a direct drive airboat.
 
IMO, you need to do away with the vaccume advance. Re-do your timing to 34 again. In my experience, when you are slow cruising, the timing can creep as high as 50 deg, that'll kill KBs. Make sure you are able to enrichen the carb. Most edelbrocks don't have the fuel circutry to handle a cadillac. I have only been able to get the 1413 comp edelbrock fat enough. Even redrill/jetting, the regular ones don't go high enough. The stock Qjett can be made fat enough with proper prep. The 1413s are around 300 bones give or take.
 
Well saturday hunter droped the old boat in the water at crystal river and other then a hose clamp malfunction.The old 509 hung in there al day long we put 3 hours of deep water runin on the boat, I say deep water cause every were we ran was either manatees or dolphines under the boat .
From what we could tell uin's were correct the 600 holley has got to go ,(were do ya get the the 1413 for 300 bones?).plugs looked good,air fuel ratio checked out with a lm-1 innovate motor sports wide band O2 was right on , timing good and the prop is to loud at 3000 rpm.
 
Good evening Cadi Clan,

Try to keep it in mind that these Cadi's are a differnt critter. Carbs and timming and such need to be right for the best performance and the life of the engine. Just like the rocker system, when you start getting past that 4000 rpm mark, things need to done right. As stock engines, they would stand 4000 all day long.

For those interested, Cadi engine builder Buddy Branch is recovering from a kidney transplant. His spirits and energy level are "HIGH", but he will in the recovery mode for a while. I spoke with him today and attended a fund raiser the for family of the young girl who past away and donated a kidney to him. What a wonderfull experience for all concered.

Okay, back to those Cadi,s. Do your research, talk to folks like Buddy Branch, Potter Automotive and keep the legend alive. For big block power and performance at reasonable price , they can't be beat.
 
Good morning all,

As requested by"Courage Honor and Loyalty" here is the address for donations for the cause, Mrs. Marsha Evans, 3518 Loury Dr., Wesley Chapel,Fl. 33543.

Tiffany Evans was 19 years old and died due to injuries she received in car crash. Due to her wishes to donate her organs, not only did Buddy Branch receive a life-saving kidney, but all total 73 people will recieve organs, tissues etc. Thats a lot of lives saved or helped.

Don't know how much money was raised last night, but there was a great turnout. I donated a full days charter, and there were three tables of goodies that went for raffle.

Any donations will help because there was no health insurance and there was a long stay in intensive care before the familly had to make the decision to turn off the machines. If anyone makes a donation, please make it in honor of Tiffany's gift to Buddy. That way they will know it where came from. Make donations payable to Marsha Evans.

Thanks for everything.

Sincerly,

Capt. Catfish
 
THANKS CAPT ! WE ARE ALL IN THIS TOGATHER! ITS A GOOD FAMILY HERE ! WE FIGHT .WE TALK. WE BS ! BUT IN THE ALL OF THINGS WE CARE ! IT COULD BE ONE OF US SOMEDAY ! WE ARE A DOING SITE ALREADY PROVE THAT ! AND HOPE HER CHILDS GIFT GIVE S HER PEACE! THANK YOU SIR ! I AM NOT WORRIED ABOUT BUDDY HE WILL BE ALRIGHT ! :D
 
I'm getting confused... in one of my Airboat World mag's it said for better performance in DD application to us a holly 500 cfm 2-barrel. On here I'm reading 850 cfm and 750 cfm. I also read that using a 425 iron intake would help a bit as well. I run a 500 with a 600 edlebrok vacuum secondaries and it runs good. (as always would love a few more rpm but hey) My uncle runs a 472 with the edlebrock alum intake and an 850 double pumper on it and its a terd. no throttle response and it wants to hesitate when he stomps it. He tried one of his 650s on it and it was better. Would like a good real life explaination of what works. Anyone tried a preditor carb? or do they suck because they aren't made to idle?

Dan
 
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