vaccum or mechanical secondaries? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

shelby987 · 12-17-2005, 03:51 PM

I was just wondering what the opinion was on vaccum vs. mechanical secondaries, in terms of mpg, performance, responsiveness, problems?? Pros and cons of each and any experiences anyone can specifically note would be appreciated.
Thanks

crazy longhorn · 12-17-2005, 04:35 PM

For heavy/street, I like the vac secondary carbs. I run a 3310 Holley on my 383, with nothing but some minor jetting,& my favorite spring(purple on the secondaries). it seems to give a good balance perf/economy, & is very responsive. set up properly, I think the vac carbs can have better throttle responce than a DP (on a heavy vehicle). For all out effort/race, & no worries about milage......that DP is no doubt the ticket.

L

**Stocker** · 12-17-2005, 05:14 PM

I was told many years ago that mechanical secondaries are generally for racing only. Vacuum gives better drivability and fuel mileage under the widely varying conditions a street-driven vehicle will encounter. FWIW, years ago I owned a few fairly hot (factory) street machines, and all had vacuum secondaries.

67chevemall · 12-20-2005, 12:09 PM

If you like to play with the carb all the time go mech. with a jet kit .

12-17-2005, 03:51 PM	#1
shelby987 Registered User Join Date: Mar 2005 Location: Just outside Durham, NC Posts: 894	vaccum or mechanical secondaries? I was just wondering what the opinion was on vaccum vs. mechanical secondaries, in terms of mpg, performance, responsiveness, problems?? Pros and cons of each and any experiences anyone can specifically note would be appreciated. Thanks __________________ 1969 SS 350 Camaro Sold 2008 1970 3/4T K20, stock height with 33's, 250 I6, 3 on the tree, and locked front and rear 4.10's 1980 Chevy Malibu 2 dr Sold 2007 1993 Olds. Cutlass Ciera Wagon Traded 2006 2003 Saturn L200 w/5pd. D/D My list spans 5 decades with One common thread.....GM!

12-17-2005, 04:35 PM	#2
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,402	Re: vaccum or mechanical secondaries? For heavy/street, I like the vac secondary carbs. I run a 3310 Holley on my 383, with nothing but some minor jetting,& my favorite spring(purple on the secondaries). it seems to give a good balance perf/economy, & is very responsive. set up properly, I think the vac carbs can have better throttle responce than a DP (on a heavy vehicle). For all out effort/race, & no worries about milage......that DP is no doubt the ticket. L __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

12-17-2005, 05:14 PM	#3
Stocker 20' Daredevil (Ret) Join Date: May 2003 Location: Jefferson State Posts: 13,809	Re: vaccum or mechanical secondaries? I was told many years ago that mechanical secondaries are generally for racing only. Vacuum gives better drivability and fuel mileage under the widely varying conditions a street-driven vehicle will encounter. FWIW, years ago I owned a few fairly hot (factory) street machines, and all had vacuum secondaries. __________________ - Mike - 1972 K20 LWB 350/350/205 RIP El Jay

12-20-2005, 12:09 PM	#4
67chevemall Registered User Join Date: Apr 2003 Location: NB Posts: 3,367	Re: vaccum or mechanical secondaries? If you like to play with the carb all the time go mech. with a jet kit . __________________ 1968 Chevy C10 307 3ott fleetside 1967 Chevy C/10 V8, 3spd, fleetside lwb.Sold 1967 Chev C/10 step, 383, M21. SOLD



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