Carby Question

[Anonymous]

Hi Everybody.


Just a quick question,

The guy that is building my motor said i should use a 600 vac or a 600 dp

I am looking for a holley 600 or 650 vac secondary's for and was wondering whether a squarebore or a spreadbore would be better.

Cheers

Simon

 

[xctasy]

I might get in trouble, but PM alloydave. His Falcon runs one.

My opinion. Follow your engine builders advice if you've got others to vouch for him. But get a 600 vac sec, don't get a double pumper. Here's why...

The good old R1850 600 cfm 4-barrel is hard to beat. It's a 4150 series carb, with metering block, and vacum secondarys. It has four 1.5625" throttles. It is very versitile. Set-up and calibration is dead easy. It is less of an issue which way you sling them, because its symetrical. The Spreadbore has a couple of really small primaries (1.375"), and huge secondaries (2.000"). Theres 45 years of engineering thats gone into this baby since it first saw duty on 7 litre Mercuries, Edesles, and Lincolns.

The 4165 (metering block jets) and 4175 (metering plate, no jets) Holley Spreadbores are a stock Thermoquad and Q'Jet replacement, and are very different. There aren't so many parts for them, but they are easier to calibrate than the Thermo and Q'Jet. The 50 extra cfm is nothing. They don't like big cams, but are less effected by them than the 600 cfm carby. Newer carb, but is only used for ADR emissions replacements on Falcon and Holden V8's. It's a lot longer, and is harder to package. The OHC Pontiac packaged one of these QJet sized carbs, but the 600 is a better bet.

 

[Anonymous]

Thanks for the reply.

As you said i will go with the vac 600 sqaurebore.

Also do you know where you can purchase a Ultraflow manifold.

Cheers

 

[addo]

Contact Matilda Foundry to get in touch with the Sprint marketers.

 

[Anonymous]

This is a quote from MarkZE that i came across when i was looking up about manifolds

There has been many people ask about Ultraflow manifolds for fitting two barrell carburettors to the Ford crossflow six cylinder engines.

These manifolds are by far the best available if you want to run a carburettor. Better than any four barrel setup and comparable to multi carby setups in performance.

The person to contact about these manifolds is Bruce price From Ultraflow

You can email him:

Bruce_price@bigpond.com

or phone

(07) 3800 9188

or 0417 612 807

He is based in Brisbane.

Joip

 

[Anonymous]

Thanx for the replies, much appreciated .

I will email him now.

Cheers

Simon

 

[xctasy]

Do whatever, tags281. You can't go wrong with a good intake like that, and a bigger carb, even if it is a two-barrel.

A 2-barel 350 cfm 7448 or 4782 #2300 Holley can do 175 flywheel hp on a six fairly easily, but it has a very small venturi that hates big lift cams. The profile is like a slinky ladies hips, [ dimensions 36.5,30, 36.5] and any pulses from a big cam can upset this carb. The two barrel 500 cfm 4412 or 4783 #2300 Holley has a less restrictive venturi, [43, 35, 43] and likes to flow up to 220 flywheel hp on most engines.

Just remember that a 600cfm flys around on two barrels most of the time, sort of midway between the 350 and 500 Holley, and can only deliver 185 odd hp off the secondaries. When the secondaires open, they only open to flow the amount the engine needs. So it may never see the 375 hp a 600 cfm carb can supply. If your engine is going to go over 220 hp, get a 600 cfm 4-bbl.

Enough of the theory. I'm off to the Hardcore Tech room to get my self in trouble...

 

[Anonymous]

Thanks for the reply,

I Have now got a 4 barrell Holley 600 vac sec, Do the ultraflow manifolds come designed for 4 barells as well, By the the way people talk they are only made for 2 barrel carbs.

I originally had a holley 500 2barrel on a redline intake but it was not big enouph so i sold them and bought a 600 and im looking for the manifold.

simon

 

[addo]

AFAIK, the Ultraflow manifolds are only there for the twin barrel carbs. I reason that if they went to that much trouble, there would have been some research in it. With a four barrel, it's Cain or Redline to my knowledge.

Cheers, Adam.

 

[Anonymous]

Thanks for clearing that up for me, just as i checked this i got an email back from the people who sell them.
(see below)


Simon
I'm sorry we do not manufacture a manifold to suit a 4 barrel carby for an Alloy 250 X-Flow. We only make one for the 2 barrel Holley. The reason we don't make a 4 barrel manifold is due to the fact that it is very difficult, if not impossible to get good fuel distribution with a 4 barrel carby on an inline six cylinder engine. Also a 500cfm 2 barrel Holley will supply all the air that a 250 X-Flow needs. We have customers that are claiming to get 325+ HP using one of our 2 barrel manifolds and a 500cfm Holley.
The cost of the 250 X-Flow "Limited Sprint" manifold is $440.00 plus freight. The best method for sending the manifold to you is COD Australia Post which should cost approx. $15.
If you would like to phone me, you can contact me on 07 3800 9188.

Regards

Bruce

 

[xctasy]

Boy, Im cheesed off. What an epic!

The only way you can get 325hp + is with a carb better than a stock 500 cfm Holley. Ultra~flow have publicly quoted 290 hp with their intake manifold. With a full house 650 cfm 2-bbl, they'd be right. But these carbs a 'race' pieces.

Under exceptional circumstances, with a cam, compression and carb gas-flowed, I would concead 325 hp might be possible, but only on a race engine. It would be pulling a good deal of vacuum at wide open throttle, and would have no low speed tractablity, sort of like a NASCAR or AVESCO racer. All the anecdotal evidence is clear on this.

Eg. 1 The Barry Grant fuel systems have a gas flowed 2-bbl 500 cfm carb, either petrol or alcohol, with a set of 50 thou over bored throttles. Part number 4412S3B for gasoline, and 9647S3B for alcohol. The BG manual states for race only engines. Source: BG Fuel Systems Tech Mnaual and Catalog Vol 6, 1997.

Eg. 2 This follows on from the old days before 1980's, where there was a race only #2300 650 cfm 2-bbl (part number R-6425AAA) with the same throttle blades that Barry Grant uses, plus venturis bored out 62.5 thou and a Dominator style velocity stack. But it was for 400 cubic inch V8 engines, and in the build instructions it stated "not for use in engines running under 4000 rpm". Source:Super Tuning and Modifiying Holley Carburetors, by Dave Emanuel, upadted edition of 1988.

In both cases, these carbs were only 354 to 460 cfm stock. Gasflowed, they may be more, cetrainly the BG 500 flows more than 500 cfm at 3
"Hg. That's 220+ to 290 hp, tops.

Now this is what I propose you do. Buy the Ultra flow intake, and do what my next door neighbour did with his 265 Charger. There used to be a Carter 2-bbl to 650 #4175 (Rochester 4M Quadrajet rip-off) adaptor, made by Griffiths Speed in Auckland. It was about 20 mm tall, made of tooling plate alloy, and situated the secondaries right over the centre of the two barrel intake. The primaries discharged off centre, on to a lip over the front of the two-barrel carb flange.

It's okay, it worked really well. The 1974- 1978 V6 Mustangs and Capris used this set-up using the Weber 2-bbl carb, and it actually improved intake fuel distrubtion.

There is an issue, though. The 20 mm is enough to push the carb out the bonnet.

AlloyDave runs a 4-bbl on a Cain intake manifold. We've seen people modify the stock 2V to hack 500 cfm of Holley 4-bbl. Way back in a 1995 Street Machine article, Kev Bartlett ranked a 4-bbl 600 cfm Holley equiped cross flow as the second best engine to a 302 Windsor and a 351 Cleveland.

 

[alloydave]

hey guys, ill try to put some dyno results in here in the next few months.
ive got REDLINE 4 barrell manifold with a 465 vac sec holley,well i had a 465 holley im now running a adapter to a 2 barrell 500 holley .I havent got the falcon on the road at the moment as im saving hard out for my trip to Bathurst.But in the next few months im going to get it run up on the dyno.Both my holleys are second hand and have been cleaned and kitted and bushed ,but i thinking of selling off both and getting a 525cfm DEMON 4 barrell carb ,i have to try and find a smaller carb in body size as
mounting either holley 2 or 4 results in the vac pot on the 4 barrel sitting about 4 mm front the shock tower (its hit it a few times ) or turn it around
and the throttle linkage is about 3mm away and i dont wont this to catch on anything.As for the 2 barrel the extra 10mm for the adapter makes it contact the bonnet so im just got the bonnet raised at the back just a fraction and took a bit out ouf the rib on the bonnet.Ive tried at Weber Carter 4 barrell and there bigger than a holley .Ive got the old efi manifold and bits under the house and its getting close to being pulled out if i cant get this problem sorted .On the other hand if i get it going any better the stock 200 3speed and diff which are due for replacement might have to be done a little bit sonner than i expected.

 

[xt falcon]

ok the 600vac on a redline manifold i have found to work fine on my cross flow i had it dynoed and the stock jetting in the carb i was told was fine with around 12:1 fuel air all through the rev range and it pulled 173hp to the wheels which isn't to bad for a mild motor.

excute what sort of ET's could i expect when running a supra five speed.

thanks Aaron

 

[Anonymous]

Sounds very good to me Aaron. can you tell us anything else about it. do you have any idea of the cam. I remmember in a previous post you said it had a mild idle.
Just curious because I suspect (against popular opinion) that a 600 4 bbl will still give a good improvement even a mild engine, as yours seems to confirm.

 

[xctasy]

For the xt falcon, Kicking the Virtual Reality Drag Strip into action, your cars details are:-

power is 173 rear wheel hp
the rear gears are 3.23
and i run 225/65 r14
a w55 supra box 3.55 first gear.

Weight is was 2850 plus 400lb's or driver, passenger, and fuel. Want to make it conservative. The XT wasn't really slippery, but hey, it was 1968.Drag co-effcient is estimated 0.48, frontal area is about 24.2 square feet. Thats what a cop sees before he books you on instant on mode with his K-band radar!

Top gear speed per 1000 rpm is 37.1 km/h.

Since 173 rwhp*1.264 for a manual is 218.7 hp at the flywheel, all we have to do is pick where peak power comes in. I'd say 4600 rpm (estimated value. Specific power is rated at 5250 hp*rpm, which is fairly typical for a hot street six. BA Falcon, 244*4750 rpm has a specific power of about 4750 with a twin cam six. The lower the better. )

Top speed, assuming 0.48 cd, 24.2 foot front area, and about 11.2 hp of tire drag at 127 mph.

Lets try 127mph (204 km/h)

imperial formula is

target speed 3*drag factor*frontal area(found in books) all over 147773 to get rear wheel horsepower reguired. To that you must add required tire rolling resistance. Target amount is 8 hp for a 195 section tire on a 2000 pound car


(127*127*127*0.48*24.2)=23794017. Then this gets divided by 147773.

Rear wheel power needed is 161.0 hp, plus 11.2 hp, which is 172.2 hp.

*Answer is top speed of just over 127 mph. If it has a 0.80 or 0.86:1 top gear, then it will do that at between 4400 and 4750 rpm. Perfectly geared!

*Standing Quarter Mile 14.32 sec ( @ 95.18 mph[153.2 km/h] from another formula I found)

*Rpm at end of I/4 mile(1320 ft) = 5400 rpm in third gear at 153.2 km/h

*Standing 1/8 mile (660 ft) = 10.06 sec

*Standing 330 ft = 6.80 sec

*Standing 60 ft = 2.55 sec.

Just my opinionerfectly geared. Don't change a thing!

 

[xt falcon]

ok Tim i am not 100% sure on the cam but i think it is a crow 770 or 892 as max power came in just before 5000rpm and the cam has 0.510" of lift the engien is 30thou over has roller rockers and extractors and was blueprinted by previous owner.

Excute thanks so i am looking at mid 14s which is not to bad i guess. i just need to practice how to take off without just losing traction and sitting there.

 

[xctasy]

A quick note. In theroy, a 350 cfm 2-bbl carb can do 155 hp net easily, and a 500 cfm 2-bbl 220 hp. In practice, on street cars, I've not seen over 130 hp for the 350, and 170 hp for the 500.

I'm trying to find reputable sources of good dyno runs showing more than these figures for street cars, but they are all on race engines for mandatory 2-bbl econo-class racers in Aussie and the US. All the info I have says for low end work, a 500 cfm 2-bbl carb that is tunned for 350 hp won't deliver an even fuel/air ratio at low speed. The very high air speed can be compensated for in performance installations, where a special cam or high revs can be used to gain more power even if the carb is tecnically too small. Holleys discussion on rare 650 cfm 2-bbl carbs, very similar to 500 2-bbls, says it won't work well below 4000 rpm on a 327 to 400 cubic inch V8 engine.

We all know NASCAR engines can get 650 hp from a 650 double pumper, but thats at 7500 rpm. I doubt the fuel metering at 1500 to 6000 rpm is very good. Information on drawthrough turbos used by Jack Flynn on his 400 hp 600cfm Holley 4-bbl 2000 cc Pinto said that the carb developes poor metering (it gors haywire) when the air speed goes up on these engines. So a small carb on a big power engine starts to cause problems at high air-speeds.

So keep an open mind. For a wilde six, the carb needs to be sized for adequate power, and until I can find a good streetable 300 hp 500 Holley 2-bbl, I'd say use a 465 to 600 cfm Holley 4-bbl, or a 650 if you don't car about fuel efficiency.