750 or 800 CFM Carb?

[goingballistic]

OK, I'm coming down the home stretch of the rebuild and am finally buying the last parts for Dyno prep at the end of July. I am wrestling with buying a 750 or 800 CFM carb and not sure what performance difference I'll get between the two or potentially sucking it (750) dry .

the block is bored 60 over ( 388 ), high volume fuel pump, AFR 195 heads ( 74cc) and the Edelbrock RPM Airgap intake. Being that there is a $100 price difference in the carbs from Edelbrock, I'm wondering what performance gain might be had by using an 800..........I was settled on a 750 until last night and am now questioning the wisdom.

Does anyone have any facts or experience with both of these carbs that may be able to clue me in to the performance differences that justifies $100??

Thanks.

 

[Drjohn]

Don't get one that's too big.


Here's a link that gives some basic sizing calcs:
http://www.holley.com/HiOctn/ProdLine/Products/FMS/FMSC/FMSC.html

Or... call one of the tech guys and ask them : ...............(270) 781-9741

 

[warren s]

Yeah, always the smallest carb you can not the largest. What type of carb also matters, like vacumme or mechanical secondaries? spread boar or square boar. etc etc

 

[JohnZ]

750 will work just fine - you won't notice any difference with an 800.

 

[goingballistic]

Thanks guys, I talked to Edelbrock tech support yesterday. The 750 is about right actually may be oversized but anything smaller may be too small so 750 it is............


Thanks for the input and the advice, kind of why I like this forum so much, it's not bull, good tech advice from people who have "been there, done that"

Paul.

 

[Drjohn]

Too big is a problem. 750 should be fine.

Hey, I lived in Rochester for 10 years, and grew up in WNY.

You need to move south. You'll have more driving time.

 

[WayneLBurnham]

Depends GREATLY on type of carb....

If you are looking at the really solid, dependable AFB Edelbrocks (they make all sorts except a Holley type), over carburetion is nowhere near as critical as with a Holley due to the flow weighted action of the secondaries. If your are looking at the standard 750 Performers versus their new adjustable secondary/twin fuel connection 800 the real difference in price is those nice upgrades and not the flow.

I very reluctantly changed to a Holley on this disastrous, problem infected and massively overpriced custom small block because the response on the dyno was so much quicker than with my AFB I had always preferred. The numbers weren't significantly different, but the throttle response was night and day different. I still debate having done that and may plop the AFB or one of the new AVS 800cfm versions on there yet.

Performer AFB's are on every other vehicle I own (except the late model ('85 )) gutless but dependable bad times van.

 

[goingballistic]

Kind of like the cold in the winter and the change of seasons. I lived in Vegas for seven years and moved back here.........you need snow to go fast

800 twin Polaris, three feet of snow and 30 below is my idea of a good time when I can't drive the vette. With 196 track studs that thing gets up and moves like my vette.

Too big is a problem. 750 should be fine.

Hey, I lived in Rochester for 10 years, and grew up in WNY.

You need to move south. You'll have more driving time.

 

[Drjohn]

I don't miss the snow at all.