Gapp & Roush drag Holley

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BCjohnny
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Gapp & Roush drag Holley

Post by BCjohnny »

I was sorting through my junk earlier and came across an old Gapp & Roush centre squirter dated 1977 .... number on it is GR031

I'd always it assumed it was a 660 4224, but a closer look shows the venturis and throttle plates look on the larger side

I know they put the 850 (?) baseplate on the 660 but other than that ...... drilled butterflies and venturies

I'll post up some pics & dims tomorrow

TIA
BCjohnny
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Re: Gapp & Roush drag Holley

Post by BCjohnny »

Throttle bores 1.750", venturis approx 1.500"

50cc pump (I think)


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Any first hand comments welcome
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ustahava67
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Re: Gapp & Roush drag Holley

Post by ustahava67 »

That carb has some interesting mods.... I would post these pics here
https://www.tapatalk.com/groups/racingfuelsystems/
There are some folks there who might be able to give a little insight
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Re: Gapp & Roush drag Holley

Post by frnkeore »

Could we get a look at the bottom, with the throttle plate off?
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Re: Gapp & Roush drag Holley

Post by Geoff2 »

There was a #4223 Centre pump model, 850 cfm 1 9/16" pri & sec venturiis, 1 3/4" t/bores, 50 cc pump.
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Re: Gapp & Roush drag Holley

Post by BCjohnny »

frnkeore I'll flip the blades open and take another pic

The baseplate looks 'matched' to the body, not 'chamfered' or blended such as when a larger baseplate is attached to a smaller body ...... on cursory inspection anyway

Geoff2 wrote:There was a #4223 Centre pump model, 850 cfm 1 9/16" pri & sec venturiis, 1 3/4" t/bores, 50 cc pump.
Ok, I didn't know that, thanks ....... I think you could be onto something there .......

The baseplate looks 'stock' to the carb, I'll measure the venturi dia again but I'm pretty sure it's 1 1/2"

Carb was only ever used on a 351c drag engine singly, to the best of my knowledge
BCjohnny
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Re: Gapp & Roush drag Holley

Post by BCjohnny »

Geoff2

Thanks you were spot on ...... gauged a rule over the venturi initially but vernier now shows it's 1.562" ish

Metering blocks are 5800 / 5802, 50cc pump, downlegs, ...... so it's a 4223 850cfm

Just goes to show what happens when you assume things, only had it nearly a quarter of a century, lol

I'm guessing the drilled TPs & venturis are extra idle air bleeds to keep the butterflies out of the T - Slot when setting the idle
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Re: Gapp & Roush drag Holley

Post by Ks Fats »

The drilled throttle plates will help with the idle richness but the holes at the bottom of the venturi taper are above the throttle plates and will be active when the throttle is open. In theory they should lean the transition and the main circuit. They might have been utilized for a very specific engine combination as there are other ways to do that. Yours is the first time I've seen that practice. Interesting piece for sure.
BCjohnny
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Re: Gapp & Roush drag Holley

Post by BCjohnny »

As it's piqued a bit interest some more pics :

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1 : 1 linkage

Did a bit of digging and there are references to Chevy 427 & Edelbrock Hi perf ..... I guess it's just an over the counter one, modded by G&R, but no choke horn so no number

Only made for a couple of years, apparently
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C.A.R.E.
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Re: Gapp & Roush drag Holley

Post by C.A.R.E. »

Here is some pictures of a Stock R-4223 850 center squirter carb I have It has the Venturi holes but not the throttle plate holes. Also the cam type secondary opening has not been ground to delay the secondary opening like the G&R has. Don't know why the pictures turned ?
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BCjohnny
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Re: Gapp & Roush drag Holley

Post by BCjohnny »

Thanks, nice to see the venturi holes are factory .......
Don't know why the pictures turned ?
It's to do with the default settings within the phone

If you post them on a site where you can't re-orientate the pics, you must remember to to hold the phone horizontal (on it's side) as if taking a landscape pic, with the shutter 'button' to the right side of the screen ...... apparently

You most likely took them vertical, as in a portrait pic ....... and the default flips them 90 degs when posted

Even a couple of mine came out wrong, because I held the phone too 'flat' in the planar horizontal looking down ...... #-o
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Re: Gapp & Roush drag Holley

Post by piston guy »

4223 - 850 CFM center squirter . Production , over the counter. Throttle blades drilled for idle. Their "special" carburetors were done by the late Harold Droste and had hand stamped serial numbers.
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Re: Gapp & Roush drag Holley

Post by Walter R. Malik »

The holes in the side of the venturi were put there to introduce a blast of air going over the throttle shaft to keep gasoline from leaking out through the shaft.
Almost any brand carburetor had something like that before 1972 when the EPA started measuring engine compartment hydrocarbons. Any air leakage points in carburetors were discontinued and carbon canisters became the newest thing.
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Re: Gapp & Roush drag Holley

Post by 408swinger »

From an old Holley Spec book
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BCjohnny
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Re: Gapp & Roush drag Holley

Post by BCjohnny »

Thanks for the replies, all info helpful

It's likely been allocated a use, at long last
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