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CARB CFM

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Holeshot View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Holeshot Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2018 at 2:55pm
660 Center-Squirters were designed for 2x4 operation & were outstanding on my 390 with an UltraRam. It had 9.2~1 TRWs & only a 292 cam, but dynoed 518 HP to the wheels with a CarbShop 950 4bbl...Ran WAY better with the 660s. Will run better next time around @ 12.2~1 with a bigger 2.1" intake valve & LARGE solid roller cam....
|'69 AMX BBO 390 9.88 qtr. | '71 AMX 401 w/Richmond 5-spd | 2012 Hemi Challenger R/T 6-spd w/Sidewinders | Michigan 49120|
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jpnjim Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2018 at 4:44pm
Originally posted by Holeshot Holeshot wrote:

660 Center-Squirters were designed for 2x4 operation & were outstanding on my 390 with an UltraRam. It had 9.2~1 TRWs & only a 292 cam, but dynoed 518 HP to the wheels with a CarbShop 950 4bbl...Ran WAY better with the 660s. Will run better next time around @ 12.2~1 with a bigger 2.1" intake valve & LARGE solid roller cam....

I don't disagree,
but I see 3 issues with this:

1)The Offy 2x4 is a smaller port, lower RPM intake

2)Somehow people got the idea that those 660's were made out of Gold and want top dollar for them (I settled for a pair of slightly bigger, but much cheaper 4778 700DP's for my UR, if it ever ends up on an engine)

3)This post is from 6 years ago LOL

Its worth reading an old post to hear about a UR'd 390 though Clap

518 at the wheels is pretty amazing!
71 P-code 4spd Javelin/AMX
some Jeeps and some Fords
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2018 at 5:42pm
I ran two 625 Carter Comp series AFBs on several AMC V8s with an automatic
and a 4 speed.

On the street as a daily driver.

The primary jets needed a step up in the jet and metering rod to make it perfect. The larger jet and metering rod made for small change.

290 thru 390 I have only one issue, the secondary air valves opened too slowly.
I was forced to lighten the weights .

No BS, these worked great right out of the box
and better with minor changes.

BLOCK the heat stove!!!!! The Offy stove is big and over heats the carbs.

I blocked the heads and opened the stove cross over for a poor man's air gap on my 1970 390.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Holeshot Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2018 at 6:43pm
The deal with the 660s is that the butterflies open symmetrically, from the center, right where the squirter is. So if you mount them sideways, they open directly in the center of the intake, feeding all 8 equally. I dont know about folks thinking 660s are 'made out of Gold', but I paid almost a grand for a new 950HP a couple years back. Not even sure if they make Center Squirters any more but mine are like new.....
|'69 AMX BBO 390 9.88 qtr. | '71 AMX 401 w/Richmond 5-spd | 2012 Hemi Challenger R/T 6-spd w/Sidewinders | Michigan 49120|
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Holeshot Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2018 at 7:06pm
This is my original STR-11, with the OE linkage & List 4224 Center Squirters with the big center-hung bowls....Some day I hope to use it! This particular intake is stamped "X-1" & the lid bolt bosses have all been countersunk & use countersunk Allen bolts...
|'69 AMX BBO 390 9.88 qtr. | '71 AMX 401 w/Richmond 5-spd | 2012 Hemi Challenger R/T 6-spd w/Sidewinders | Michigan 49120|
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2018 at 7:52pm
4224's are AWESOME drag race carbs but mine lacked power valves
and a part throttle circuit. I cant imagine them as a street carb.
But they were drivable. Barely... But they made excellent power.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote one bad rambler Quote  Post ReplyReply Direct Link To This Post Posted: Sep/17/2018 at 7:54pm
Originally posted by PHAT69AMX PHAT69AMX wrote:

Whatever is decided for carbs, think I'd avoid the Holley list 9776 450 cfm carbs.  They're mechanical secondary carbs but do NOT have a secondary accelerator pump..... have yet to figure out what Holley was thinking when they made those carbs like that.  Maybe that has something to do with there being no info available on the Holley website about the list 9776 450 cfm carbs, at least none that I can find.....  Yet they are still available brand new from Jegs and Summit for like $260 each.  And I'm pretty sure the original Holley list #4584 carbs called out originaly for the AMC Crossram intakes were the same screwy mechanical seconday with no secondary accelerator pump style of carbs....  Where during the same time period what Holley developed for the Chevy TransAm Camaro 302 CrossRam was a dual feed mechanical secondary List #4295 carb with dual accelerator pumps like all mechanical secondary carbs should be, aka a "double pumper".

I had those Holleys on a SB Vega when i was in high school they were the one`s that came with the tunnel ram package from summit back in the early 80`s...Switched to 600`s due to poor drivability and performance....
68 AMX 390 4 Speed,68 American,64 American 2 Door Wagon Altered Wheelbase,78 Concord Build 360,727,8.8
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PHAT69AMX Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2018 at 9:58am
I tend to agree with Sanchez 1st post, the Edelbrock carbs made for 2x4 intakes.
The Air Bleeds, Idle Feed Restrictions, Rods, Power Piston Springs, etc all already set-up for 2x4.

The "point" of all my "bs" below is the development of the use of 2 4-barrel carbs on a V8...
and how it may be useful information for ones carb selection when doing so today...

Doing more Holley History research lately, have a theory, but no proof... yet, but indications are:

The 1968 "final version" Chevy 302 CrossRam Holley List 4295 585cfm Carbs, GM #3957859,
were the 1st Holley Double Pumper Carburetor and had Center Hung Dual Inlet Fuel Bowls.

The 1st Holley Center Hung Dual Inlet Fuel Bowls apparently were introduced in 1965
on a number of OEM Holley Vacuum Secondary Carburetors on Chevrolet Engines,
including GM #3878261EH Holley List 3310 780cfm on the 1965-1/2 Z-16 Chevelle 396,
and GM #3886101 Holley List 3247 ???cfm on the 1965-/12 Corvette 396 425HP.
Story is these 780-ish cfm 3310-ish carbs were the end product of 2 2-Barrel Carbs "cobbled together"
(edit) by Holley employee Ralph Johnson at Smokey Unick' Shop in 1962-3 for a Pontiac.
The Vacuum Secondary 3310 now rated at 750cfm is still going strong.
Conversation just today, Holley List 3247 also a Dual Line, 1965-1/2 Corvette 396
also a 1st Dual Line right at same time as the 3310 on the 396 Z-16 Chevelle
and maybe other 1965 OEM Chevy Holley Carburetors.

The 1st Holley "Modular" carburetor we all know was the Holley List 1848 465cfm on a 1957 Ford.
Conversation today, Holley List 1272 on 1957 Ford 312 was also a 1st modular Holley Model 4150/60.
Those are the "grand daddy" of all the modular Holley Carbs since...
The Holley List 1850 600cfm Vacuum Secondary arrived in 1958 on a Ford and is still going strong.

Development started in 1967 on the Chevy 302 CrossRam.
Chevy started with the GM #3906631 Holley List 3810 585cfm from the '67 Corvette 327 300/350 HP
which was a Model 4160 Side Hung Single Inlet Vacuum Secondary Carburetor Single Pumper.
I'm still a little "fuzzy" about if at this point in late 1967 Chevrolet 302 CrossRam development
had converted it to Mechanical Secondary actuation yet, but was still a Single Pumper.
There was pressure to have it "in the system" for the 1968 12 Hours of Sebring.

Then within months changed it to Center Hung Dual Inlet Bowls, GM #3941140 , Holley List 4210.
GM added the Dual Feed Center Hung Bowls from the 1965 3310, but still a Single Pumper,
and I'm still "fuzzy" if this is when they also made it Mechanical Secondary actuation.
Secondary Main Air Bleeds where made very small making the Secondary Boosters rich and Start-Up
very quickly to compensate for no Secondary Accelerator Pump at the cost of cruise drive-ability.

Within months GM changed CrossRam Carbs again about mid 1968 and made them a Double Pumper!,
GM #3957859 List 4295, the 1st Holley Double Pumper ! as best as I can tell at this point...

So... from all this "bs"....  uh.... History, it is my * opinion * that the "suppliers",
Holley, Edelbrock, Hurst, etc... "Double Dipped" and used the "Throwback Middle Version"
1968 Chevy 302 CrossRam Holley List 4210 Single Pumper Mechanical Secondary 585cfm Carb on the
1969 Hurst S/S AMX CrossRam Intake and re-numbered it Holley List 4584, AMC #4487187.
There are pictures of what are claimed as the original carbs on the Sheriff of Nottingham AMX
and the carbs are vibra-etched with the AMC Numbers, close inspection of the vibra-etching
seems to show to my tired old eyes GM #3941140 and List 4210...
The Hurst S/S AMX CrossRam 570cfm Holley List 4584 AMC #4487187 Carburetors are used nowhere else.
Conversation today Holley List 4584 spec'd as 570cfm in 1975 Holley Catalog....
May have had different Boosters than the 585cfm List 4210 Chev Carb, ergo 15 fewer CFM...

The 1958 Ford List 1850 Venturi and Butterfly dimensions are the same as
all of the above carburetors except for the 1st original smaller '57-58 Ford Modular
4150 carbs List 1272 and List 1848, the 1965-1/2 GM 780cfm Vacuum Secondary
List 3247 on the Corvette, List 3310 on the Z-16 Chevelle 396, and subsequent List 3310's.


Edited by PHAT69AMX - Sep/19/2018 at 10:50am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Holeshot Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2018 at 1:09pm
I ran 660 Center Sqirters on the street, on an UltraRam, & they ran great. That was with a DNE 5-speed, too...
|'69 AMX BBO 390 9.88 qtr. | '71 AMX 401 w/Richmond 5-spd | 2012 Hemi Challenger R/T 6-spd w/Sidewinders | Michigan 49120|
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Post Options Post Options   Thanks (0) Thanks(0)   Quote WesternRed Quote  Post ReplyReply Direct Link To This Post Posted: Sep/18/2018 at 5:26pm
Could just run dual Fitech EFI throttle bodies and probably have the best of everything.
I've finally given up drinking for good...........now I only drink for evil.
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