Good day all:
I recently bought a new Edelbrock 1405 carb for my 81 Z-28.
http://performanceparts.com/part.php?partID=467

Some of the engine specs are:
Engine: GM 350 (not original Z28 engine)
Cam: .447 lift, 290 duration
Intake: WEIAND 8004 dual plane (See link) http://www.performance-curve.com/index.asp?PageAction=VIEWPROD&ProdID=1070

Ignition: Stock HEI with MSD 6AL
Transmission: Automatic TH350
K&N Air filter
Old Carb = Holley 4011 650 cfm, single pump, dual fuel feed.

My car sat for over 3 years after a minor car accident while I waited for insurance money (sigh). After this time, I rebuilt most of the car and and rebuilt the carb. However, fuel is still bypassing the idle circuit of the carb...powervalves are ok, etc etc. I decided to buy the 1405!!! One thing that is confusing me is the "adapter plate" requirement. I keep reading that this adapter "may be required" but I don't know what the plate does exactly, and if I REALLY need it. I placed a link to my intake (above) which says "Spread bore and square bore carburetor mounting flange" so why would I need an adapter. Can you please explain exactly what the adapter does and if I require one with this combination of parts and why.

Question #2: I assume this is a "ported" vacuum car as opposed to manifold vacuum?

Thanks in advance.

Well - since you have already bought the Eddy carb, just put it on and go. That intake in drilled for Holley/Eddy & Q-Jet patterns so you shouldn't have a problem. Personally, I would of stuck with the Holley, but it's not my ride. IMHO

Here's your link. http://holley.com/8004.asp

I think the reason they say an adapter might be required is the large opening on the manifold for secondary throttle plates on a spread bore carb. One way to tell if a plate is needed would be to lay a new carb mounting gasket on the intake and see if there are any gaps. Do you have a fuel pressure regulator? Limit the pressure to 5.5 pounds max. I have two of the 1405's on my car and love them.

You need this:

http://store.summitracing.com/partdetail.asp?part=SUM%2DG1420&view=1&N=700+150+301568+

If you pust a square bore carb (Holley or Eddy) on a spreadbore manifold like your 8004 you will have a gap around the edges of the carb on the secondary side (big vacuum leak), where the intake is "wider" for a spreadbore carb.

You'd better be up to at least 10 to 1 CR. or you won't like that cam!! 11 to 1 is best!

And fwiw, that cam is probably the great old L-79, 350hp/327, -151 cam!

I ran it in my 350SS engine way back in the spring of '67, 1,200 miles from new for several years as my daily driver!

Sucker pulled like a freight-train from low 2nd to the top of 3rd!! It was about a 10 to 1 engine..

pdq67

Hey guys. Thanks for the replies. Check out figure 4 & 5 of the install instructions here: http://www.edelbrock.com/automotive_new/misc/tech_center/install/1000/1405.pdf

Also notice that there are adapters and adapter plates (which are different) located here: http://www.edelbrock.com/automotive_new/mc/install_items/adapters_spacers.shtml

I think an adapter PLATE is only used if your intake has the wrong bolt pattern which I don't have to worry about. Tomorrow when I remove the carb, I will see if the new gasket sits OK on the manifold like Show7d3 said. I will get a fuel pressure gauge and regulator as well. That very well could have been my prob with the Holley. When I closed the idle mixture screws, the car stayed running so there was a fuel bypass somewhere.

pdq67: The only thing I remember about that cam was that I think it was the one used in the 90's corvettes.

Can anyone confirm the vacuum question? I believe I will hook up the ported vacuum line to the distributor and plug the other since the tranny vacuum line hooks up to the manifold vacuum. Cheers.

Trust me, you just need the plate I posted the link to. I've put a few squarebore (Holley) carbs on top of old Edlebrock Performer (spreadbore) manifolds before. That plate is what's required (plus gaskets on either side of the plate). Has nothing to do with the bolt pattern- your intake is drilled for both. Has everything to do with preventing a massive vacuum leak.

That's what diagram 5 of your instructions is showing.

What I don't get is that Fig. 4 says "Don't use an open adapter".

Eddy's usually don't need the adaptor they have enough width to cover the spread bore outter edges.Holleys do need the adaptors since they are not as wide on the outer edges.

From item #4:

You must use Edelbrock Adapter #2696 or Adapter & Fuel
Line Kit #2697 when installing a Performer Series carburetor on
a General Motors Quadrajet or Chrysler Thermoquad intake
manifold.

That is NOT what you are doing. Your manifold is NOT an original Qjet manifold. It is a universal manifold that is open under the carb. All you need to do is make sure there is no vacuum leak and you're good to go.

I'll defer to 79Z-28's exerpeince on this. An Eddy may well have enough "meat" on the baseplate to cover up the entire carb flange opening on your intake without the use of any adapter whatsoever. But it will DEFINITELY work with the adapter plate I posted. I don't use Edlebrock carbs very much.

The eddy carbs will in fact work on the eddy perform Q jet spreadbore intake w/o the plate.

I ran that combo on my car for a couple of years. (1405 600cfm eddy carb, on the performer spreadbore intake w/o an adapter plate.)

Holley carbs needs the square bore to spread bore plate to work on a spreadbore intake though.

Like Damon said the bolt pattern don't really mean much at all.. It's the shape of the carb mounting flage on the intake, and shape of the bottom of carb.

You have spread bore (like your intake), Then you have square bore (like the shape of your carb or a performer RPM intake)

Now I never ran the weiand intake like you have so I can't say if the squarebore eddy carb will work on it with out the adapter plate though, but like Damon said it for sure 100% will work with the plate.

You have the same intake as I do. I also have the same carb if your getting a performer. So we have the same setup. If you just use normal spacers and not the one you need, you will have a big gap atleast oh mmm enough to fit your pinky in if you squeeze. However RTV and formagasket will fix it for awhile, if your running on a budget...thats what I did. But im pretty happy with what it does, its pretty decent if you ask me.

Alright fellas. I yanked the ole Holley off the intake this morning. Here are some pictures of the intake, and then some with the gasket in place. There is no "spacer" for this carb in the box...gasket only. I had a spread bore spacer in place with my old carb but obviously no good for this application.
Note that there are no spaces on the outside of the gasket in any area. On the left hand side, you can see the flange protruding a bit on the outside of the gasket, but I think there is sufficient coverage there by the gasket(no gap by any means). What do you think?

It's not about what the gasket covers, it's about what the carb baseplate covers. If the gasket isn't "sandwiched" all the way around completely sealing off the intake flange opening you WILL have a big vacuum leak. Drop the carb on without a gasket and check by eye to see if you can find any gaps or places where it's just barely covering the opening.

I will do hat you said, but isn't the gasket cut to match the carb base plate in the first place? If the gasket fits over the flange, then so will the carb...? Will get back to you after I throw the carb on when I get a chance.

I used a spread bore gasket since the eddy has both set of holes.If you want that adapator plate I have one I will send you it still barely covers the edge.If you are going to get an adaptor here what you need http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D2696&N=700+0&autoview=sku to do it right.

that eddy adapter deal is kind of expensive...

isn't the gasket cut to match the carb base plate in the first place? If the gasket fits over the flange, then so will the carb...?

In a word.... no, not necessarily.

Yeah that is a little expensive...$36 + shipping plus conversion to CAN dollars, and I need to get the carb steel fuel line to drop the fuel inlet down and in front of the carb....another $60+ and a new inline fuel filter. My local GM muscle head (who has a 70 pontiac w/a 400, and a 80 with a 350 and he built both engines) said I don't need that adapter. I will check to see how the carb fits on that intake w/o the gasket after work. If it looks like it will seal OK, I will try it with gasket and bolt her on.

Thanks for everything guys.