Thanks to me catching my motor on fire, I'll be replacing the carb. I'll leave out the details because it still pains me so http://www.camaros.net/forum/frown.gif

I had a Holley 600 with VS and electric choke. The shop who has it now thinks I should stay away from VS. These guys really know their stuff and have a great reputation--I'm no expert. See my signature for what the motor has. The car runs the High Energy 268 cam.

I drive it a lot. It is my main transportation during dry spring/summer months. At first he said he'd recommend a 750 dp, but when I told him how I drive it, he agreed smaller would be better. But what about the secondary issue? And I still think I should stay around 600 cfm, right?

Thanks for your input.

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68 Camaro ragtop, 327, angle plug Camel humps, 202's, Performer, Holley 600, Doug's Headers, 3-speed Saginaw, 3.08 posi

I think a 600 or 650CFM carb would be great for you. I personally love mechanical secondaries, but if gas mileage is a concern of yours then I would say Vac secondaries would be the way to go. I swithed from a 750 vac secondary to a 750 DP on my car and you could feel the difference in performance (383 that's why I run a 750). Some people swear by vac secondaries, I am more of a drag race type of guy. If you have a heavy car then vac secondaries perfom fine and actually on your 327 it would probably work fine too. If you want all out performance go with mechanical, if you want easy tuning and good gas mileage go with vacuum secondaries.

Royce

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70 Camaro 383ci
69 Camaro 385ci
91 Camaro RS V8 (305 TBI)
Link to my 70

http://profiles.yahoo.com/camaroman7d

I agree that a vac secondary carb is probably better for your application. If you had a high duration cam (which you don't), I would say go with the DP. The DP carb vs. a VC carb can make as much as 4-5 mpg difference so if that is a concern, again go with the vac secondary. As far as size goes, the 600-650 CFM seems about right for a 327 UNLESS you are planning to twist that puppy past 7,000 RPM which you are not.

Don't ever run a double pumper on a daily driver. I don't know if there is a 4to5 MPG differece but there is a difference and a daily driver shouldn't have enough gear to really use a DP.

I run a 650 cfm Holley DP on my 355/auto and just got 14 MPG going to Indy last weekend.

I have heard that vac. secondaries are more "forgiving", but I like the control aspect of the mechanicals....

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Steve - Central Ohio Camaro Club (http://www.ohiocamaros.com)
'69 Camaro RS/SS-350 - Daytona Yellow
'95 Camaro Z-28 - Sebring Silver
click here to see my webpage ---> My Camaros (http://www.mindspring.com/~mccorry) (updated 8/18/01)

I'm with oger.

I tried a 650DP in a Z/28 with 3:73s. The car got way better mileage and performed the same with the OE 780. DPs are best for cars with loose converters and/or deep gears, which build rpm faster than a vac carb can respond.

Thanks for all comments. Keep them coming.

The guy at the shop said the only reason they produce VS is because they're cheaper to make than mechanicals. He absolutely isn't sold on VS.

The shop is very well known and does a lot of peformance business, so I want to hear them out. I'll explore the DP issue with him as well. I will be stressing how I drive the car.

Umm, actually, I'm pretty sure from a manufacturing stand point, a MS carb is cheaper to make. The reason OE's go with VS carbs is tuning I'm thinkin.

Anyways, to the relevance of this thread. I believe the vac. secondary carb is the way to go on your car. Better gas mileage, easier tuning. I wouldn't put a DP on a car unless I was trying to gain every last tenth I could. I'm thinkin a 650cfm vac. secondary holley will give you a good combo of gas mileage vs. performance.

Good Luck,
Joe

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79' Z28 Camaro 4-spd
Boycott Lapeer Dragway

I ran a 650 DP for many years. For a mild performance street car I will never run one again. The VS works very well and the mileage is much better.

If you put on a lot of mileage a Q-jet would be ideal. I never used to believe my dad when he said that they are the best carburetors ever built. I get more like my old man every day.

I would really question just how good these guys really are. The VS is cheaper to build? That's a poor way to choose a carburetor. Ask him why GM used VS on almost every factory built high-performance street car. GM knows just a little about how to choose a carb.

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The Red Beast http://www.geocities.com/casanoc



[This message has been edited by CarlC (edited 09-04-2001).]

Mech secondaries work well with steep gears. I have a 700 DP on my car and it's great. I get 14.X mpg too and I don't drive it like a wuss. With your 3.08's, etc. I think you'll be happier with VS's.

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Rick Dorion
69 RS Conv,355,M20,4.10's

ckaram, this is what www.holley.com (http://www.holley.com) has to say about your concern; QUESTION How do I know if a vacuum or mechanical carburetor is best for me?

ANSWER For streetcars the vacuum secondary carburetor works best on midweight or heavyweight cars with an automatic transmission. They are more forgiving than a double pumper is because they work by sensing engine load. The mechanical secondary carburetor is best on a lighter car with radical camshaft and a lower gear and manual transmission or on a car that is going to be used for racing purposes.
Hope this help...




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Our affair with Camaros is a live sentence without the possibility of parole www.geocities.com/c68ss (http://www.geocities.com/c68ss) http://home.coqui.net/borench

ORENCH, I read the same thing at the website yesterday.

I've printed out the tech stuff from Holley and I'm going to show it to them.

Also--looks like I have to pay for the carb out of my own pocket. The insurance company will only insure the damage, but they WON'T COVER THE CAUSE OF THE DAMAGE, THE CARB. What a crock.

I wanted to try the new Holley Street Avenger 670 (VS). But it's a ton of money. Looks like I'll be ordering whatever carb I need on my own. Anyone have one of these carbs?

I should mention, this shop is renowned for squeezing every bit of HP out of car to get the most bang. So I guess I'm not surprised at his recommendation afterall.

The guy at the shop doesn't know what he's talking about (VS being less expensive to make than MS) - it doesn't take a genius to look at the two and figure out that a piece of bent rod is cheaper than a vacuum diaphragm and linkage.

You'll be much better off with a 600 or 650 VS - better driveability, throttle response, and fuel economy. If all-out performance is what you're after and you enjoy tuning for streetability, go the MS route.

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JohnZ
'69 Z28 Fathom Green

I agree that VS is the way to go on the street.
A MS is more expensive to manufacture..
More machining of carb body.
Secondary squirters.
Metering block compared to plate.(in most cases)
Accel pump. (50cc)
Secondary bowl has more machining.
4 corner idle circuits. (in some cases)


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Don~ ZZ430DropTop (http://hometown.aol.com/zz430droptop67rs) Pro-Touring.com DropTop (http://pro-touring.com/featured_cars/Camaro/Don%20Seefeldt%2067%20Camaro/don_seefeldt.htm)
67 RS/SS Convertible, 70 RS/Z28

[This message has been edited by ZZ430DropTop67RS (edited 09-05-2001).]

I had the same delema..except for the fire....I had a quadrojet that was on its last leg, I went to the pro's in my area they set me up with a zink finish Holley 600cfm VC...with a spreadbore it ran me about $260 performance wise it does pretty good, gas wise its great, I have my foot in its azz all the time and gas milage is better then I expected!
P.S. how did the fire start?!!!!

sixt9d--

I kept having to adjust the rear float level; car would bog and die when I hit the brakes. I've had to do it a couple of times (with success).

Well...this time I couldn't get the level to go down. Meanwhile it soaked the towel I had wrapped behind the car to catch the fuel pouring out of the plug....dripped on the header...whoosh. I always had to f**k with this carb. Something wasn't right.

Had the fire out within 2 minutes. Hindsight is 20-20. I should have adjusted it down w/ the engine off after the first couple tries didn't take. There's about a dozen other things I probably should have done. Gone over it enough in my mind.

But insurance is coming through. And I really was lucky.

Lucky you didnt burn!
Holley does make a clear view plugs for the float bowl, i've seen em in the jegs cat.(1800-345-4545) for about $4 bucks, i was thinking about getting a set for myself