What carb for 400 block stroked to 451

[Challenger_7]

Hi All.
This is always a tough question as every one has his different opinion, but based on experience, it becomes worth hearing about.
I have a 400Source stroker kit being fitted to my 400 block changing it to 451, including a 484 performance cam that will give me a good response, push me to 6000 rpm but remain smooth enough at low rpm, which is what I asked for before purchasing the kit.
Brandon of 440 source recommends a 750 cfm carb. What I need is a carb that will be reasonable on fuel on lower rpm but must give me the kick needed if challenged. I will not be racing the car and will drive it often on week ends, but also need the power occasionally.
What carb do I choose, there are so many of them. It must also have a powerful accelerator pump in order to get immediate response when I step on it.
My car is manual by the way.
Any recommendations please.
Cheers.

[Chryco Psycho]

I would not use anything less than 800 cfm , probably a 850

[nivvy]

750 carb is way too small........... 

[Chryco Psycho]

the Proform 850 double is extremely responsive & tunable , 870 Avenger Holley is a good choice if you need a choke but Holley doesn`t have a 850 HP series carb

[hemiken]

Hey Guys,

I think that Farouk may be in the market for a Vacuum Secondries carb for cruising and occasional burst of power...........

[Challenger_7]

Thank you all for commenting.
Yes, as Hemiken mentioned, that is really what I want. Something not to put a hole in my pocket on every drive as I do drive much especially on week ends, but must be responsive and give full power when challenged.
I had spotted a WORLD Hardcore carb at yearone with 375 primaries and 525 secondaries which sounded perfect, but they say it has been discontinued. So, something along those lines should be nice.
Any recommendations?
Ken good to hear from you. I will be making progress again on my restoration job and will give feed back soon.
Cheers

[moper]

A 451 is the same package (3.75 stroke, 4.385 bore) as a 440 bored .060 over. Treat it as such. For what you intend, the 770 street avenger VS would be my call. That equates to about an 820 in the 4150 series. The old school 3310 VS is a tad small, but it would also work. Just not pull as hard.

[hemiken]

What if Farouk bought a 750 Vac Sec with the rear metering plate to help tune the car a little bit better, would this be enough for the mild engine he has in mind ?  Is trhere a part number for this carby or does everyone just have to add the plate themselves 


Hey Farouk,

Look forward to your updates buddy

[73EStroker]

Farouk - isn't the gas price in Lebanon (that's where you live isn't it?) cheaper than us? My friend lives in Bahrain and commutes the bridge to Saudi Arabia every day and their prices per litre are 19c / 12c CDN respectively. His wife sometimes uses a tank a day in the SUV and it costs $9 to fill.

Anyway I use a 950 Proform on my 451. Excellent throttle response and no stumble or hesitation. Of course I don't care about vacuum as I have installed a hydra-boost brake system off a Chev Astro van. My cam is a solid Lunati 0.586 lift and about 255 deg @0.050" lift. And it revs way faster than a 440 from idle as there was 8LBs approximately removed from the rotating mass as compared to a 440. That should equate to a bigger carb.

[Challenger_7]

What if Farouk bought a 750 Vac Sec with the rear metering plate to help tune the car a little bit better, would this be enough for the mild engine he has in mind ?  Is trhere a part number for this carby or does everyone just have to add the plate themselves 

Hey Ken, ok pleased explain as this is chinese to me From what you are saying, does this mean there is a plate to resize the primaries to make them smaller, thus more economical? Also every one seems to say 750 is too small, are you suggesting it driven by my "econoy" statement?
Cheers

[hemiken]

Hello Farouk,

You can buy a 750 Vac Sec Holley carb.  You then buy a special second metering block that converts your carb by removing the rear fuel bowl and replacing the metering plate that is on standard Vac Sec carbs with a rear metering block, this will allow you to tune the engine by feeding the carb with 4 jets instead of the standard 2 jets found on the front metering block only.  So each metering block will have 2 jets on each, thus giving you a total of 4 jets between two metering blocks.  This will help the tuning of the engine that you want to build as a mild 451 big block.


Do a search through Holley and look up the conversion metering blocks.

[hemiken]

Hey Farouk,

Here is a link to Summit for a rear metering block conversion.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY-34-13&N=700+400178+115&autoview=sku

[Challenger_7]

Oh, I understand what you mean now, but having all four running, what exactly will be the advantage I will gain from this? Obviously better tuning but probably more fuel consumtion, right?
I will  check the link you sent, thanks.

[hemiken]

Hi Farouk,

Here is another link for the type of carb to use with the metering block conversion kit.

http://store.summitracing.com/partdetail.asp?autofilter=1&part=HLY%2D0%2D80508S&N=700+4294919007+400178+4294908128+115&autoview=sku

If you can tune a carb more evenly and efficiantly, you will have it tuned better and therefore will have the economical fuel consumption you were after.  A well tuned carb will be far more fuel efficiant than a carb that is struggling to deliver fuel evenly throughout the carb.

[Challenger_7]

Ken, I visisted the links and see what you are recommending, but please bear with my basic questions
If I go your way, certainly I will have better fuel efficiency, but not necessarily economy, unless one puts fairly small sized jets on all four barrels, right?
If I am correct in this statement, then when you need the full power, you may not get it becuase of the small jets.
If, however my statement is wrong, and you put bigger jets on all four barrels, then you are sacrificing economy for power.
Pls shed some more light here to help me decide which way to go.
Thanks