Air Grabber baseplate technology

[kiwigtx]

I have been asked several times lately about this, and thought it was appropriate to post these measurements and ideas. My car came with this style Air Grabber from the factory, but previous owners have tossed or lost the vital parts, and it was only about 5 years ago I managed to source at great expense a 383 baseplate, as 440 baseplates are as rare as Rocking Horse droppings. My GTX had been fitted as a 6BBL carb setup since about 1980, and that's how I bought it, so that's how it was going to stay....until the correct parts eventually turn up.

Meanwhile I needed a more reliable carb and intake setup, as the knowledge base here on 6BBL carbs and tuning is somewhat lacking. By learning on FBBO, I picked up some good advice and ideas, and managed to source some trick upgrade metering plates for a start. Also hoping to refine the jetting of all 3 x carbs, and also eventually learn the correct plumbing of all fuel and vapour lines for the engine.

OK, I have done some measurements of the Air Grabber system on my '70 GTX.

First up I measured the stock iron intake - note that the carb face has a slope towards the front of the engine - which means that the back end is higher than the front. Front of carb face to top of block = 2-7/8" (74mm), and the back of carb face to top of block = 3-7/8" (98mm)

Next we measure the top of the block to the top of the existing Edelbrock Performer 440 Intake manifold (Part #2191) = 3-7/8" - this manifold appears to be level front to back, which gives another 1" at the front in height compared to the stock iron intake.

Next, measure top of regular drop-base aircleaner unit which only just clears the hood when shut - top of block to top of air-cleaner lid in the centre (higher than sides) = 9-3/4", and to the rim = 9-1/8"

Then by fitting the modified air-grabber baseplate and filter - from top of block = 10-3/8" which prevents the hood from closing.

Now - I started with a stock 383 air-grabber baseplate, because they were really hard to find and there were no re-pops at the time, so I had a friend cut this one down for me - measure from the base of the horn to the underside of brace for the wingnut = 1-3/8" (38mm)

I hope that helps you all out somewhat. I am posting this as a technical topic in the hopes it will help people out in the future. Hopefully I can buy a 440 air-grabber baseplate, but the two suppliers who stock them don't show any measurements, and it is a lot of money to spend and end up with the same thing. If I get an answer out of them I will post here, unless someone already has one and can share the depth dimensions.

So, please feel free to add for the benefit of me and others.

Also, if anyone can show the correct plumbing/routing of fuel and vapour hoses to and from the carbs, I would be most grateful. I also need to know exactly what the purpose of the top valve on the centre carb serves. And why some people route the hose from it to nowhere - or just above the exhaust area. :icon_thumright:

 

[Meep-Meep]

If you will go 6 BBL eventually there is nothing to worry about. All the air grabber stuff works out fine dimensionally. The only thing you will need to do is remove the front shield from the 6 BBL base.

As for carb jetting and setup that will take experimentation. Get an O2 sensor and plan on it living in your car for a while.

I'm sure someone will have a schematic of the 70 fuel vent hoses. The bowl vent with valve was an emissions thing because at one point it became bad for fuel vapor to be released to the atmosphere, thus the invention of the charcoal canister.

 

[kiwigtx]

Thanks Meeps...I saw a picture posted her recently of a centre carb with a regular fuel bowl - no vent, so I am wondering if that will OK to do with a non-emissions equipped car? And I hear you on the tinkering with jets being there and done quite a bit of that.
Looks like I'll be getting an O2 sensor & gauge.

 

[snakeyes]

wow that's a nice post on your mod, thanks good job :icon_thumleft:

 

[440+6]

Was your car a 4bbl car and you want to make it correct or are you just sick of the 6bbl?

My center carb dose not have a vent (car is late 69 build), if you need pics or info let me know.
I also have a few articles that I used to tune my carbs many years ago and they run great (I can send you copies or copy and paste them here if you like), but it depends how you plan on using them as in normal street use, street/strip or all out race.
Last time I touched an adjustment on my carbs was about 7 years ago after I they where rebuilt, they start, idle and drive as well as any four barrel car I have ever had. Personally I don't understand all the people that keep saying they are hard to tune and are unreliable.
I can't be the only one that has had great luck with these things, I'm just not that lucky.

Nice work on that base plate, good wright up.

 

[kiwigtx]

Was your car a 4bbl car and you want to make it correct or are you just sick of the 6bbl?

My center carb dose not have a vent (car is late 69 build), if you need pics or info let me know.
I also have a few articles that I used to tune my carbs many years ago and they run great (I can send you copies or copy and paste them here if you like), but it depends how you plan on using them as in normal street use, street/strip or all out race.
Last time I touched an adjustment on my carbs was about 7 years ago after I they where rebuilt, they start, idle and drive as well as any four barrel car I have ever had. Personally I don't understand all the people that keep saying they are hard to tune and are unreliable.
I can't be the only one that has had great luck with these things, I'm just not that lucky.

Nice work on that base plate, good wright up.

Yes, my car was a 4BBL originally, but it has been 6BBL for at least 34 years now. I have found the correct Holley 4BBL carb, but it is undersized for the current engine specs, and leaks like a 2-dollar hooker. I ran it for about 6 months but it felt too small, so I upgraded to the QuickFuel 780Vac-sec. Also my wife hated the smell of unburnt/leaking fuel inside the car, so she wouldn't ride in the car. The QF doesn't leak, and maintains its tune without fiddling.

I will get my Carb Builder to change the bowl on the center unit when they are rebuilt next time. And yes, I would like a hose and line layout if possible....thanks. :headbang:

 

[Meep-Meep]

You can just cap off that extra bowl vent with no ill effect. There is one in the center that is inside the air horn.

 

[440+6]

Here are a few pics of mine, hope it helps.

 

[kiwigtx]

Thanks for those pics...can I ask for another view - that of the vapour return lines to the tank ...assuming you run a vapour return filter after the pump?
Thanks :headbang:

 

[440+6]

Let me know if you need other views.







This is the fuel filter / separator that mounts to the front bolt of the fuel pump.
large bottom is fuel supply from tank, small bottom fuel vapor return to tank, top to carbs.

 

[tallhair]

Thanks RS23!

 

[kiwigtx]

Thanks RS23!

x2 on the THANKS :headbang:

Confirmed what I thought might be the case. I have that filter unit, just wanted to see how it ran to the tank. I bumped into my Carb Rebuilder guy today and he is quiet at work right now, so he might be doing the job sooner than I planned