what type of carby?

[mr j-man]

Hey guys! just wondering if you could shed some light on what type of carby should i run? its currently running a 650dp holley! it seems like an overkill! any suggestions?
this is how i had the VH 308 motor rebuilt!

Block:Chemically Cleaned Bored 60thou Decked
Heads: Ported, Big as can be fitted stainless steel valves, Flow tested 500-600HP
Chemically cleaned
Crank reground, Standard 308 rods
ACL Flat top pistions, ACL molly rings
Performance big end bearings, Performance main bearings
Standard 308 push rods, Crane Solid Cam Grind no# cc-280-2
Crane solid lifters, Dual row timing set
High volume oil pump
Engine balanced
Elelbroc performer intake manifold
High performance air filter
Electronic ignition 'Holden'
New mechanical Fuel pump

thanks

[vkberlina]

Properly tunded quaddy


Scott

[ari666]

+1

quaddys can be tuned for 50 horsepower 253's
quaddys can be tuned for 500 horsepower 545's
quaddys can save your grandmothers burning house.

[RazzaCaine]

quaddys can save your grandmothers burning house.

really? IM COMING NAN!!! haha

[soop]

That's if you know how to do it.
On the other hand a 650DP holley will do the same trick and anyone with half a brain can tune them.

[ari666]

meh, only tricky part of a quaddy is adjusting the secondary metering flap, all the rest is exactly the same as a holley. in fact, there is probably less to think about with a quaddy, unless you want to push it to its absolute maximum. holley needs to have the right primary and secondary jets, powervalve, primary and secondary pump cam, pump shot, THEN the idle mixtures need to be adjusted, both fuel bowl needs to be adjusted perfectly etc

quaddy is just bolt on, attach hoses, adjust idle mixtures, adjust secondary flap. drive. save fuel.

[soop]

Can't say I've ever really had any Drama's with Holley's, that said. Quady's have always been scary and evil sitting on the top shelf in the shed. So I never bothered with them.

[mr j-man]

what size quady would suit

[soop]

Quady that came from the factory.

Apparently when done right they can flow something silly like 750-800cfm.

[ari666]

they only come in one size, they all can flow up to 730 and the biggest i have seen is 1000cfm

edit* the biggest modified one is 1000

[DerekP]

Sorry to highjack but - I'm a fan of quaddy's too, but not really sure why! What IYO makes a quaddy a better carby over a holly?

[soop]

They tend to be allot more efficient when done properly.

[ari666]

What IYO makes a quaddy a better carby over a holly?

one word: rods

[IMO] rods make for a much more efficient means of metering fuel, as vacuum decreases, the primary rods rise. they higher they rise the more fuel, then the secondarys flap opens as the air rushes past it, the more air, the further it opens and lifts the secondary rods with it. so fuel is metered perfectly, and air is metered as and when you need it, rather than holleys which are basically, here is WOT. whether you need it or not. (hey that rymes) and more often than not on our little 253's and 308's, we dont need it, in fact our engines often do better without that much air/fuel.

[ari666]

just so it makes a bit more sense, primary metering rods:



secondary metering rods:



as they lift out of their holes the gap around them gets bigger and allows more fuel through. pics copied from here: how to rebuild/ modify quadrajets (also vac hose diagram)

[soop]

You can tune holleys to work better then that though,
You jet them down, essentially strangle them and use different throttle cams and so on. Holleys are like bloody lego.

[ari666]

anything you can do to i holley i can do to a quaddy and i will always get better fuel economy

[soop]

Yeah, but Holleys are like painting with numbers, hard to stuff up .

[mr j-man]

do the quaddys bolt straight onto a squarebore spacer??????

[soop]

Don't think so, could be wrong but I think the Holley stud pattern is different.

[DerekP]

one word: rods

[IMO] rods make for a much more efficient means of metering fuel, as vacuum decreases, the primary rods rise. they higher they rise the more fuel, then the secondarys flap opens as the air rushes past it, the more air, the further it opens and lifts the secondary rods with it. so fuel is metered perfectly, and air is metered as and when you need it, rather than holleys which are basically, here is WOT. whether you need it or not. (hey that rymes) and more often than not on our little 253's and 308's, we dont need it, in fact our engines often do better without that much air/fuel.

Hence the term 'vacuum secondary' I assume? Thanks for that (I'm a little late on that I know!) - you're an absoluert wealth of information ARI, top bloke.
Cheers