Hi, new to this, i'm restoring an 1971 xy ford and its carb selection time,
motor is freshly rebuilt 351 ,bored 30",new ACL race series pistons, DOAE rods, reground 4MA crank, Crow cams hydraulic21689 grind with advertised duration... in 280 ex289.....in222@50"..ex230@50"
in valve lift .5129 ex valve lift .5190....lobe separation106 deg.
Heads are old school 4V's left wide open reco'd for unleaded/gas fitted with performance springs.
standard 4V cast iron intake, 4-1 headers/extractors into low restriction dual exhaust.
properly put together by a place that builds V8 race boat engines.
Car is 4-speed manual with 3.0 rear end gears.
Thinking Holley 600 //650//750//780 and probably with vac sec's given weight of car and 3.0 gears.
I already have a couple of vac sec 600's (1850 list 3515 //and 1850 list 4452) both unknown so would need rebuild,what I've gathered from various online forums are that 600 holleys are popular with this size motor but can suffer from off idle stumble with a reasonable cam,unless reworked and modified.
theres various rebuilt holleys on the market in the above sizes,theres 750cfm / 4010 series carbs at a good price but on the american sites there seems to be bias against these series carbs.
I would like to throw the floor open to this forum,hoping to get"the good oil"
Thank You,
Chris

hey mate, I had a 750 double pumper on my 4V 351 which has similar specs to yours but a weiand xcellerator manifold, 3.89 gears and a toploader. It went ok. It was set up by Kostecki in Perth.

I thought those old gils had Holley 780cfm carbs on them.....
A slightly better set of gears would be 3.25's....still good on the highway, and good in town.

Yes the GTHO phase 2 clevo and phase 3 ran 780's, which can go for silly money on ebay for a carby of unknown condition.In the last week I've scoured many sites on the net looking at the pro's and cons of various carbies,given the weight of the car and the fact that I'm running a 3.0 locker rear end I would be foolish to whack a large double pumper on it as I'd be blowing fuel out the exhaust.
I found a place on the net that did me a good deal on a rebuilt 3310 series 750 vac sec squarebore list number 4160,a carby that Holleys sold over 2 1/2 million of. They fitted a metering block to the secondaries as well and the whole deal with postage was just a smidgin' over $400,even threw in a 2nd hand fuel line as well. The twin plate clutch is all set up and tested on the floor, had to shorten the slave cyl. pushrod a fair bit and had to lathe down the new throwout bearing to get clearance as well. So all goes well I will get it in this w/end, engine bays all painted,trial fitted the extractors and theyre a nice set plenty of room around both the slave cyl. and the starter motor, will have to sit them in first of course then lower the motor in and bolt up the extractors as it goes in,then I'll fit the toploader to the bellhousing from underneath. Bolt on the carby when it arrives during the week,sort out the wiring, get oil pressure, spark, and fuel, and "kick 'er in the guts charlie".
Then back to fitting up the panels and spraying the topcoats.

G'day motorbikerx. I've had good results in the past on modified street motors with Holley double-pumpers fitted with a vac sec primary metering block. I had a heavily modded XAGT 351 4V (revved to 7500, manual, 4.11 gears) with an 800 DP fitted with a 780 vac sec primary metering block and an XF with a 289 Windsor (revved to 6200, manual, 3.5 gears) with a 600 DP and 600 vac sec primary metering block. The DP metering blocks run bigger idle circuits and smaller power valve restrictions (needing bigger main jets) so they run richer as they where designed as a race carb. By running the vac sec primary block you can jet smaller and idle leaner but still have the secondary response of a double pumper. Maybe something to experiment with later.

Yes Frog if I end up dropping the rear end ratio I may try a pumper,but for now I'll concentrate on getting the rest of the car finished. Then when its run in and on the road I will really know how the total package is going to perform.

Sent my specs to Nigel at Xtreme Fuel Systems in Campbelltown NSW. and he suggested 2 possible choices out of the reco carbs he had in stock.Armed with the list numbers theres a wealth of info on Holleys on the net,with charts showing all the list numbers and particular applications they were designed for as Holley 'tailor made ' carbs to individual vehicles for several auto manufacturers.
Out of the two he had available there was one that got a good rap the list no 3310 // 750 vac sec,a carby that Holley produced over 2 1/2 million of evidently.Its basically a 780 rerated at 750cfm,on discussion with Nigel we decided to get him to fit a secondary metering block as vac sec carbs just have a preset plate,the secondary metering block gives me more tunability on the secondaries.Also he tapped out the blank inlet side of the primary bowl to accept fuel delivery from the passenger side of RHD as per the original 780 with the fuel delivery going out the opposite side to the secondaries at the rear.The carb came well packaged and looked so good when I opened it that I almost slept with it that night.Yet to fire her up,still a fair way to go before she hits the road but when I do I will report back on how it performs.

My preference lately has been for the holley street avengers, for some things like your i'd use a 670 avenger. with the quick change sec spring and a proper metering block on the sec side, it will make tuning very easy

i had a 600 vac sec on my 351-C / top loader powered ZD Fairlane and put a 750 vac sec on and it was sweet as used more fuel but hey the Clevo likes a drink anyway

Well here she is boys(and girls) started her up last monday week, got a mechanic mate over to help,got oil pressure, put juice in the tank, dialled in the timing and WHAMMO! kicked 'er in the guts.
Ran for 20 mins at 2 grand to run in the camshaft properly.
Got fumed out severely and it was quite warm under the bonnet.Things were falling off shelves.
The 750 vac sec with added secondary metering block ran great straight out of the box and once the exhausts hooked up and she's run in a bit more it's up on the dyno to extract peak performance.
All old school no filled in ports for torque and drivability here,no tri-y extractors,no auto trans, no power steer, no air.no kilowatsies, no turbos wastegates or chips......... Just good ol'fashioned horsepower.
http://www.youtube.com/watch?v=9mfd2Ov_qu8

Sweeeet noise there! well done glad it's sorted!