Holley Help
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From: Turlock CA
Holley Help
I was playing around this weekend after this forum got my head spinning and realy wanted to see if my secondaries were opening.
I clamped down the shaft coming out of the vacuum diaphram and went for a ride. It still has great power smoked the tires and everything. I have recently rebuilt the carb and it tuned in nicely runs smooth. I have never heard the secondaries kick in is why I started checking.
First question: what would keep the seconds from opening?
Second question: How much horse power will this create once they are working?
Maybe I should leave well enough alone. Been getting great gas mileage.
jd
I clamped down the shaft coming out of the vacuum diaphram and went for a ride. It still has great power smoked the tires and everything. I have recently rebuilt the carb and it tuned in nicely runs smooth. I have never heard the secondaries kick in is why I started checking.
First question: what would keep the seconds from opening?
Second question: How much horse power will this create once they are working?
Maybe I should leave well enough alone. Been getting great gas mileage.
jd
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Joined: Oct 2005
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From: Mddl A MexCans
might be the passing gear linkage is not working right. Mine doesn't but I'm not out to spin the wheels off it. So unless the time comes that I need it to get outa the way, I hope it's a toyota corrolla coming the other way 
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Joined: Mar 2004
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From: Union, Washington
The vacuum secondaries only open when the engine needs them to open, depending on the spring in the diaphram unit. They do not open as soon as you stomp the throttle to the floor, they're not suppose to, they open later when RPMs are up higher and the engine needs more air than the primaries can supply. Unless you were pushing past 3500 to 4000 RPM with a normal setup the secondaries won't open. What do you have for and engine, what size carb, which car or truck and gear ratio in the rear end?
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From: Turlock CA
It is a 352 in a 65 F100 with 3.00 rear end gears and a 600 cfm Holley. Stock engine headers electronic igniton nothing fancy.
I don't hardly ever get it over 3500 rpm.
Bear that is interesting so if you were for example pulling a load would they open than?
I used to run a motorcraft Carb and you could hear the secondaries opening. No wonder that thing used to drink gas..
Thanks
jd
I don't hardly ever get it over 3500 rpm.
Bear that is interesting so if you were for example pulling a load would they open than?
I used to run a motorcraft Carb and you could hear the secondaries opening. No wonder that thing used to drink gas..
Thanks
jd
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Joined: Mar 2004
Posts: 6,056
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From: Union, Washington
Then the secondaries will not open with a stock vacuum secondaries set up. 3500rpm only requires about 350 cfm and chances are it will take 4000 to get the secondaries to start opening and probably never open all the way as at 5000 rpm your engine only needs 510 cfm and I doubt the engine will turn that tight high with a stock cam. If the hill was steep enough and you get onto the floor with the throttle and the rpms up above 3500 rpm, yeah, probably but there won't be a sudden power surge or anything like that. The way to get the secondaries to open sooner is to change the spring in the diaphram unit (Holley has a kit with all the springs or you can get individual spring) and while you are at it remove the check ball in the vacuum feed. Don't toss the old parts because from what you have said you will probably want to go back to stock, because gas mileage will suffer.
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From: Turlock CA
Cool
Thanks for the info.
Got another question.
If I went with a smaller carb would it help gas mileage or hurt it?
I have a hard time believing it can get any better. On a freeway trip I have gotten as good as 18MPG.
thanks again
jd
Thanks for the info.
Got another question.
If I went with a smaller carb would it help gas mileage or hurt it?
I have a hard time believing it can get any better. On a freeway trip I have gotten as good as 18MPG.
thanks again
jd
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From: tujunga, calif
if you got 18, bow down to the Gods...my 352 never got more than 11, and that was down hill with a tailwind..but I have 4.10 gears...I added an aluminum 4 barrell manifold (only becuase I bought it for $25) and a 600 cfm Holley with Vacuum secondaries and never got them to work even after changing springs...BEAR has it right, a stock 352 just doesn't need that much carb..but hopefuly is will work on the 390 we are building...but it made me mad it wouldn't work so I did the cheap trick and put screw in the secondary linkage..so I can kick them in sometimes just for funI justify this by telling myself if I don't use the fuel in the back bowl it will go bad..LOL
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Post Fiend
Joined: Mar 2004
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From: Union, Washington
Originally Posted by jd_sylvia
Cool
Thanks for the info.
Got another question.
If I went with a smaller carb would it help gas mileage or hurt it?
I have a hard time believing it can get any better. On a freeway trip I have gotten as good as 18MPG.
thanks again
jd
Thanks for the info.
Got another question.
If I went with a smaller carb would it help gas mileage or hurt it?
I have a hard time believing it can get any better. On a freeway trip I have gotten as good as 18MPG.
thanks again
jd