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Discussion Starter · #41 ·
1/4" thick Heat Insulator. Ive reused mine a few times now. Seals great and helps if you have hot fuel from the heat crossover.
 

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Discussion Starter · #42 ·

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Discussion Starter · #45 ·
BTW... The Eddy fuel filters are cleanable and rebuild able, although that is never mentioned in any literature.
 

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Started this an hour ago and getting back to it. Noticed that Army has posted a lot of info since I started composing my response so some of mine will be a little redundant.

The plate supplied with an Edelbrock aluminum manifold like the Performer or Performer RPM is a flat steel plate sandwiched between two gaskets, and the plate is designed to work with the spreadbore carburetors on these manifolds that include the spreadbore opening. The problem spot is the sealing area to the outside of the large secondary cutouts and gasket match gets a little thin there if the carb is bolted on with no plate. Most new AFB and Holley carbs seal up, but some of the early Holley carbs were a little narrower and might not seal. Even on newer stuff the gasket imprint with some carbs will only show about an eighth inch of overlap.

Then we have a true adapter spacer that is necessary to bolt on a squarebore carb to an original cast iron spreadbore manifold. The squarebore butterflies will hit the cast iron manifold if just placed directly on it. The best adapter is 1" thick and has tapered holes that perfectly align with both the squarebore holes in the carb and the spreadbore carburetor, and holes are a partial cone shape. Doesn't seem to be any performance loss with the adapter. I've run the adapter on top of the '67 iron manifold with an Edelbrock 800 AFB carb and a 3" open element air cleaner. The combo fits under the hood of a '67 GTO with about a half inch clearance to the hood.

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Since I see weekly carb postings on this site, and no one seems to love Edelbrock carbs or include them in the GTO options, I figured that I'd make a post to at least enlighten folks about why this carb can be great.

First of all, Edelbrock has improved their carbs and they now have an AVS2 line. Don't assume that all Eddy carbs are AVS2. It offers a dramatically improved fuel delivery circuit, which atomizes the fuel better.
Nice write-up. I picked up a pair of 500cfm AVS2's for the 461 stroker build in my '66 (see attached mock-up) & I'm anxiously awaiting the machine shop wrapping things up in the next couple of weeks so I can hear it run!
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Super cool looking ! Love the air cleaner and carbs and you matched the element to the red fittings, nice detailed touch 👍
 

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Since I see weekly carb postings on this site, and no one seems to love Edelbrock carbs or include them in the GTO options, I figured that I'd make a post to at least enlighten folks about why this carb can be great.

First of all, Edelbrock has improved their carbs and they now have an AVS2 line. Don't assume that all Eddy carbs are AVS2. It offers a dramatically improved fuel delivery circuit, which atomizes the fuel better.

  • Edelbrock carbs won't work well with more than 6psi of fuel pressure, so include the cost of a pressure regulator or fuel pump with your purchase. The Edelbrock fuel pump has an advantage over a regulator, because it's clockable, rebuildable, high perf, and it handles ethanol.
  • Eddy carbs have no filter, so include that in your purchase, too. And while we're on the topic, they do have a brass barbed inlet, so you can just hook up a rubber hose and GO! But they also have a banjo, chrome inlet setup, which reroutes the line to a better location, and is available with an inline filter. So consider that too.
  • Edelbrock also makes a braided stainless "pump to carb" line, for Pontiac, which uses 6an fittings and will adapt directly to their fuel filter and banjo line, if you chose to go that route.
  • If your heat crossover is active and youve had issues in the past with heat, Edelbrock makes a heat insulator gasket, which is reusable.
  • Even though the secondaries are noticeably bigger than the primaries, the Edelbrock AVS2 is a SQUARE BORE carb. HOWEVER, contrary to Edelebrocks claim that "you need an adapter to mount one on a spread bore manny", YOU DO NOT. Not Only have I done it twice, but I also confirmed with Edelbrock that it's an inaccurate instruction, in their manual.
Why do I like these carbs? All areas of fuel delivery are easily tunable, without draining fuel, in less than 5 minutes. So you can separate and tweak:
  • Idle mixture.
  • Choke.
  • Off idle transition speed.
  • Off idle transition taper/ delivery.
  • Cruise.
  • Primary.
  • Secondary.
  • Air Flap.
I've been collecting and working on Pontiacs, nearly exclusively for about 35 years. During that time, the best tuners and accomplished racers who Ive met, have all agreed that Pontiac and Chevy engines arent at all alike. Carburation is a primary area where that is evident. Pontiacs nearly all accept "more fuel", than their Chevy counterparts, so don't under carb!

A 650 isn't adequate for a Pontiac 400. I run the 800 on mine and I love it. I can easily jet it down to be as economical as I wish, or open it up to fan the flames.

I'm no expert on carburation, but I do hang out with a bunch of experts and I do all of my own work, so this is from the horses ass mouth.

One thing that I'll say about pricing is: Compare apples to apples. Edelbrock carbs may appear cheaper, and maybe they truly are, but just make sure to include the cost of gaskets, pressure regulation, and lines.

A final note for anyone who's considering a Quadrajet. People have mistakenly given Quadrajets a bad name over the last 55 years. The internet set the world straight on this. Quadrajets are awesome! HOWEVER, "quality cores" are nearly non existent and parts chain rebuilds are extremely hit or miss, usually miss. Reputable rebuilders like Lars and CLiff will not even touch a parts chain rebuild. So keep in mind when you hear "Use a Quadrajet", that advice is often 15 years old when good Quadrajets were readily available.

If you insist on a Quadrajet, a reputable one will start at $800, in 2022, which it is as you read this. Not that you wont get lucky with a Summit or Amazon rebuild, but beware, very few people take a carb back once it has fuel in it.

This is the best resource that I've found for Edelbrock information.
Awesome artivle since reading this I read up on the AVS2 and love the fact they have the annular boosters in ther venturis. Makes alot of sense.
 

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I bought the recommended Edelbrock adapter plate as well, and when I was installing the carb, I wondered what it was actually accomplishing. Then I became friendly with a top dog at Ede, and during a conv with him I questioned it. He said it wasnt' needed.

So when I did my GTO, I left it off. Been that way for a year now.

I guess I should post a few links...
Keep in mind that the AFB/AVS carbs have differing primary & secondary bore sizes. The early Carter AFB's can also have a different air horn diameter, 4 1/2" and 5 1/2" which can affect the air cleaner assembly where it sits down on the carb if the diameters are different.

I don't think it an issue with aftermarket aluminum intakes, but using a factory cast iron square-bore intake, 1967 (early intake/AFB carb) and earlier w/Carter AFB, may be an issue as the bores seem smaller and installing a large bore carb like the 800 AVS may cause interference to the throttle blades where they won't open fully and I am not sure how well it will seal on the intake as designed- so here an adapter might need to be used, so always check the carb function/fit.

Carter AFB Throttle Body Sizes ......... 1 7/16" x 1 11/16"
Carter 750 -Throttle Body Sizes ........ 1 11/16" x 1 11/16"
Eddy AFB 600CFM......1.44" x 1.69"
Eddy AFB 750CFM......1.69" x 1.69"
Eddy AFB 800CFM......1.75" x 1.75"
AVS2 650CFM.............1.44" x 1.75"
AVS2 800CFM - Throttle Body Sizes..........1 3/4" x 1 3/4"

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Discussion Starter · #52 ·
On that manifold you posted, I could see where tolerances could be tight. The adapter plate that the Ede manual states is required, is merely a 1/8 steel plate with two gaskets. Not an aluminum spacer type.
 
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