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Delay Secondaries

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tbrodes

Regular Contributor
"Hey guys, new to having Crusa

"Hey guys, new to having Crusader engines. With gas prices sky rocketing, I am trying to make my engines efficient as possible, and I use the term efficient loosely. I have read about “delaying” the secondaries… I have also read that the secondaries open around 3200ish RPM.

So…what is delaying the secondaries…how does it affect the engine…and how long should it take a mechanic to do and is it worth pursuing?"
 
Bondo...hate to say it I do no

Bondo...hate to say it I do not know. The boat is a 1991 with 1991 Crusader 454's. It is located about 2 hours away at my summer house tucked away in the driveway. Could you possibly explain what delaying them would do...?
 
"Ayuh,....

2ndaries on a bo

"Ayuh,....

2ndaries on a boat carb a Vacuum actuated,...
Delaying them Might yeild a tiny amount of economy,...
At the cost of a Potentially Lean condition......

A Lean condition in a boat can lead to drivability issues,...
Or,.. Possibly a Total Melt-down of the motor.....

I'm not saying it Can't be done,....
Just that it must be done with Great Care......"
 
"Narw! Where'd you get th

"Narw! Where'd you get that baloney?

Assuming you have Quadrajets, a linkage arm can be removed to prevent the secondaries from opening; and if you're just cracking them all the time, this will help economy. Secondaries are like a light switch: they should be all the way open or cosed for best economy.

If you have Holleys---get back to me.

Jeff"
 
"So, will I loose the ability

"So, will I loose the ability to bring up the throttle to a certain point if I do delay my secondaries. I have never actually had the boat to WOT...this spring will be the first time...I feel the boat has plenty of power and I'm on a plane at 1900-2100 RPM. But, I do want to have the option of bringing the throttles to 3600 RPM to get out of a storm if I need too. I just dont want to loose that option....will I??"
 
If you have mechanical actuate

If you have mechanical actuated they are probably progressive in their opening. Vacuum activated are all or nothing.

You might be able to move the secondaries linkage to another hole and delay the opening. You could also just completely disconnect the secondary linkage if you have sufficient power without them. Your mixture won't be affected as long as the secondary butterfly valves don't open. It would be just like running a two barrel carb.
 
"Ok cool, the boat has power t

"Ok cool, the boat has power to spare. How would I see if they are mechanical or vacuum? What should I look for...any major differences that would jump out? Thanks so much guys for answering all of my questions...I'm trying to learn as much about my boat as possible"
 
"The quadra jets are vacuum op

"The quadra jets are vacuum opperated. once rpms reach a certain number the pressure in the carb drops and the vacuum pot releases the upper butterfly valve. The upper butterfly can be adjusted. There is a spring and a tensioner screw. I have not messed with this but I understand it can effect the rate the butterfly opens up.

Quadrajet was developed as a fuel saving carburator. small primaries and very large secondaries. Small primaries cause higher velocity of air which mixes the fuel better and gives a more efficient burn.

Why not try to disconnect the secondaries and see how she runs, would be curious. will not hurt anything. If you have flow scan you should be able to doccument any difference in fuel use. Yes you will no longer have the top end but it doesnt sound as if you need it. If it doesnt work out then simply hook it back up.

On Qjet you can simply zip tie the arm shut no need to take anything off."
 
not allquad's are vac. min

not allquad's are vac. mine are mech.just stay in the primary range and you'll be fine .
 
"If they are like my crusaders

"If they are like my crusaders, they are spread bore holleys and not Quadrajets, I run mine normally @2800 and they don't open usually til at least 3,000. Have someone run the boat while you are looking at the linkage and you'll know when they open. If you mess with it you might not get WOT like you're suppose to, which is up at 4400."
 
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