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Old 11-14-2004, 23:06   #1 (permalink)
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what sized carb?

Ive got a 351C 302cc heads with heaps of porting, rockers, double springs etc, fat cam http://users.bigpond.net.au/MikGan/cam_specs_web.jpg, accellerator intake port matched. I was looking at 800 or 850 but have been told that maybe 750 would be better? but by others Ive been told that 750 would be bare minimum for this setup.

so what are your opinions?
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Old 11-14-2004, 23:51   #2 (permalink)
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Re: what sized carb?

Quote:
Originally Posted by MikGan
Ive got a 351C 302cc heads with heaps of porting, rockers, double springs etc, fat cam http://users.bigpond.net.au/MikGan/cam_specs_web.jpg, accellerator intake port matched. I was looking at 800 or 850 but have been told that maybe 750 would be better? but by others Ive been told that 750 would be bare minimum for this setup.

so what are your opinions?
Yes an 800 would be too much on this combo so an 850 is out of the question.I would be tempted to try even a 650 or a 750 back to back and see which one comes out on top.I would,nt call that a fat cam so i,m not sure if the 750 is warranted.Perhaps i,m wrong. One sure way to tell is to connect up a vacuum guage and go for a drive.Under WOT if you have any vacuum evident then you have a restriction.A properly sized carb should not prove restrictive .If it is then some hp has gone begging.
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Old 11-14-2004, 23:56   #3 (permalink)
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Re: what sized carb?

Vac sec I have no idea. As for a DP carb I'd say it's more suited to a 650. I don' think it'll rev high enough being hyd to warrant a 750.

Go squarebore carbs too not spread You get better windspeed/velocity which makes you more power.

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Old 11-15-2004, 00:39   #4 (permalink)
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Re: what sized carb?

kewl I think I'll pick up a 750 and see if we cant tune it down a tad using jets, just so I leave my self somewhere to go with it in the future
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Old 11-15-2004, 00:40   #5 (permalink)
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Re: what sized carb?

oh yeah I am looking at DP's
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Old 11-15-2004, 17:58   #6 (permalink)
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Re: what sized carb?

I'm running the standard Carter Thermoquad on my 351C but have no idea of size. I have been told the have the capacity to be the equivilant of a 980 Holley and are used extensively for race applications. I have also read that the stock setup on my P6 is around 780 - 800cfm.
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Old 11-15-2004, 18:18   #7 (permalink)
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Re: what sized carb?

780 VS or 650DP

ps
you cant adjust a carby "down" or have it bigger to grow into in the future. It must be sized correctly. You cant adjust the air that goes into ca carb - only the fuel.
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Old 11-15-2004, 18:54   #8 (permalink)
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Re: what sized carb?

The cam isn't that big, an 800 or 850DP would be way overkill. These carbs are really only for high revving top HP clevo's.

It would handle a 750DP but a 650DP would give you overall better street performance, but top end HP would be down compared to the 750DP.

I view 780VS as a waste of space on earth. Been there done that. Why bother when you can have a DP and have more of everything that matters to performance?

If it was my car I would fit a 750DP because you may increase cam at a later date.
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Old 11-15-2004, 19:11   #9 (permalink)
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Re: what sized carb?

Quote:
Originally Posted by MikGan
oh yeah I am looking at DP's
Mik,

The key is velocity. The 650 DP is probably the carb of choice. The smaller base plate will enhance the vacuum signal and produce better through the venturi response. It is really tough to exceed the flow of a 650 with a 302. I ran a 347 (Windsor) that made 520 HP with a 650 DP. A stout 302 will use a 650 much better than a larger volume carburetor. The best carb for the job is the smallest sized throttle plates that will still do the job adequately. The 650 is a really good choice for a small V8 engine.

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Old 11-15-2004, 20:07   #10 (permalink)
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Re: what sized carb?

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Mik,

The key is velocity. The 650 DP is probably the carb of choice. The smaller base plate will enhance the vacuum signal and produce better through the venturi response. It is really tough to exceed the flow of a 650 with a 302. I ran a 347 (Windsor) that made 520 HP with a 650 DP. A stout 302 will use a 650 much better than a larger volume carburetor. The best carb for the job is the smallest sized throttle plates that will still do the job adequately. The 650 is a really good choice for a small V8 engine.

:davis:
I couldnt agree with Davis more. For average HP, the 650DP wins hands down.

And for the 780VS knocker above, my Cortina ran a 780VS, and i think most would agree that its power was "adequate" In fact i dyno tested the 780VS and a race prepped 650DP (not a standard one) back to back on the dyno within about 15 minutes, and there wasnt a single horsepower difference. Not one.
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