Mechanical vs Vacuum secondary

CalgaryChris

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With all the carb talk going on I was wondering about mechanical vs secondary. Most everything out there including the Holley site itself says mechanical is only for big power light vehicles. Looking for some advice as I really like the thought of my foot controlling the gas instead of vacuum. I currently have a 2 barrel Holley on a torker 351 intake ( that's how it came) but am headed to grab a 650 with mech secondaries. It's only a $100 so I figure if it doesn't work out should b able to get my money back.

 
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droptop73

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For a street driver with an automatic trans go with the vacuum. For more of a "race" set-up with a manual trans go with thw mechanical. Whatever carb you get it will take some tweaking to get it right. A mechanical secondry carb will take more set-up time to get everything optimized.

 

Wolverine

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Born an I-6, spent the teenage, 20 and 30 years as a 302, but at 40 will reach full potential as a 351C.
There is a lot of C R A P talk about mechanical vs. vacuum secondary's. There is also a lot of G O O D advise. How to tell the difference?

Buy a VACUUM secondary carb, put 500 miles on it. Tell us about the performance and gas mileage and how you drive.

Then replace it with a MECHANICAL and put 500 miiles on it.

Someone here would probably lend out a carb for the cause. We look forward to your write up!!!

 

hyena429

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For a street driver with an automatic trans go with the vacuum. For more of a "race" set-up with a manual trans go with thw mechanical. Whatever carb you get it will take some tweaking to get it right. A mechanical secondry carb will take more set-up time to get everything optimized.
I agree...Plus a vacuum secondary 650cfm flows just as much gas and air as mechanical..Its just mechanical carbs hit faster for racing...At about 40% throttle i beleive...Both carbs can handle mass power...vacuum will be alot easier to handle in town.

 
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Tnfastbk

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No issues with my MECHANICAL secondaries:huh:

 

c9zx

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As usual the answer is,"it depends". Gear ratio, convertor stall speed, tire diameter all determine whether or not a DP works properly. Either way count on calibrating the carb to your vehicle. If the gear and convertor are stock it is likely a vacuum secondary carb would work the best. If it is a working 650 DP for $100 buy it anyway and make a quick $50.00-$75.00 if you sell it. Or you could find someone who has a vacuum secondary carb and wants a DP. Chuck

 

CalgaryChris

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Probably going to go with the try both and see what i like. Just trying to get ready for a safety inspection this week and once its actually on the road I'll begin seeing what i'm dealing with.

Managed to run new e-brake setup today. Not ideal rubbing across exhaust but it works.

 

marks73

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I had a screw on my mechanical secondaries that I adjusted for race days and moved back for dailey driving. Worked out pretty well once I found the sweet spots.

 
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