Jason's Carburetor & Intake Project

[Jason Edge]

I've been involved in a carburetor/intake project on my 64 Coupe DeVille and thought I would share my story and some pics with you.  This is basically a rehash of what I have read that some of you have done, although I think I found a "trick" some of you may be interested in, that will allow you to bolt the Edelbrock 750 directly up to the intake.
   

I have tried to keep my 64 Coupe DeVille original, and have started adding optional goodies for that year such as the power vent windows, limited slip/posi rear end, etc.
   

Two performance mods, I really wanted to make have been the intake/carburetor and exhaust.  Well the more I read about these the more I looked at the Eldebrock 1406 carb (600 cfm, electric choke, square bore, and similar in design to original Carter AFB) and the Eldebrock 1411 carb (750 cfm, electric choke, square bore, and similar in design to original Carter AFB).  I leaned more toward the 750, because the formulas everyone uses for CFM puts the best performance cfm around 700 cfm or so, and the fact that if I do upgrade the exhuast it will have more potential for power/gas when I need it.  (I fully understand this is a near 5000 lb car and will not be drag racing it, however when I am hitting 60 down the road and want to pass a big rig I would also like to have the power.)

  
To start with, I took an intake manifold with a broken choke tube, that was in otherwise in Excellent condition to the machine ship to have it cleaned and to remove the choke tube.  Here is an illustration of the infamous broken choke tube that many of you are very familiar with:

Before and after I got the intake back, I started posting some notes here and thinking about simply putting a choke tube back in, and had even picked up some brake lining and had it flanged on one end and ready to install.  I finally decided that these intakes are easy to remove, and I had a couple extra intakes sitting around, that I would go for it.
 

I picked up my Edelbrock 1411 and as promised it bolts directly to the intake manifold, however, the front/primary butterflies where slightly too big for the front primary ports in the intake.

These 1963/64 intakes are basically a square bore intake, and are not a spread bore like the Quadrajets with the Huge secondaries, however, the front ports are slightly smaller than the rear.  Here is a top view of an stock intake:

These also have the 4 holes that tap into the center exhaust passage.  On the top in front of the front primary intake ports you have the exhaust channel (gutter like someone else called it) and two holes that feed into the exhaust crossover passage.  You also have the holes for the internal choke tube....one on the passenger side that the  choke tube (external one attached to choke housing), and the other one is on the driver side underneath the intake.  With the choke tube removed, or broken, this is a direct outlet for exhaust gases.

OK. to seal up the 4 holes, I  tapped threads into all 4 hole, screwed bolts with JB Weld caked on the threads into the holes and let sit over night.  On the choke tube holes, I simply found the right size and length bolt and tightened.

On the exhauster channel holes I used a 7/16" bolt with an unthreaded top section about 1/2" so that it would tighten up when it hit the unthreaded part of the bolt.  The next morning I cut the tops of the bolts off with my impact cutter tool. 

That sealed my 4 exhaust holes up, but now I needed to deal with the fact that I needed to either buy one of two adaptors or do some alterations on the intake.  I found that I could use a 'Trans Adapt' #2064 or an Edelbrock 2697 (which includes a 2696 adaptor plate), to allow me to just bolt up and go. The more I looked at the pictures o fthe2696 the more I thought this might not be the most efficient adaptor, because from the pictures it looked like it went from a square bore (like on the carb) to a regular spread bore with those HUGE rear secondaries.  I also was looking at the fact that if I installed  this .850" thick adaptor, and any adaptors I might need for the air cleaner, I may never get the air cleaner under the hood.  Just fyi, but the the Edelbrock adaptor was about $60 and the 2064 was about $15.

My brainstorm yesterday morning while looking at the primaries on the Edelbrock 1411 and my intake, was that I only needed about 1/8" more opening and I really only it beveled from the top.  I found a drill bit grinding wheel just a little larger than the front primaries and was able to grind out a nice bevel on the top, and sure enough when I popped the carb down flush on the intake I had plenty of clearance!  I thing opened it up a little more with my grinding wheel, and then used a rough wire brush drill pit to really smooth it out.  After filling the 4 holes and enlarging the front primaries  (and some paint) the intake now looked like this (see the ginding tool I used below intake):

After this, the carb was able to be mounted directly to the intake (you might not how similar the

Edelbrock looks like the Carter AFB...I was told they obtained the patent for this pattern directly

from Carter):

Next, the intake, carb were mounted to the engine:

And then I installed the airfilter adaptor rings:

And finally, here is engine with air-filter on car.

When I fired the car up I could immediately tell a difference. When I got it out on the open road I could really feel

the extra power.  I still have to do some final adjustments and retune the car, however, this is one project that went very well that I thought I would share with you.  

I have used both the original Carter AFB and Rochester 4GC with very good luck and I think these are great carbs.

this is getting a way from an original component of the car, and I can always switch back if I like.  In the upcoming months I am going to be driving this car more, and wanted to give it a little more pep and think this is a good compromise and does not give up the original 'look' of the car.  Other than the 2 wires from the electronic choke, it would be hard to tell what Lurks beneath that air breather.

Anyway, I hope I have not bored everyone silly. 

and an update posted later:

 

Rick in Florida had some excellent followup questions that I would like to post with my answers. I think this about wraps up the project. I will also post one of the pics of just the carb sitting on the engine that I meant to post but picked out the wrong pic:

The air cleaner rings, did the come with the carb?

No, I picked it up for a few bucks at PEP boys. IT was a universal type thing and I ended up using two rings to bring it to the right height.

Did you have to make any alterations to the standard air cleaner?

No, None whatsoever.

Did you have to adjust the carburetor?

Only the idle and air/fuel mixture. It was actually nearly set when I fired it up.

Lastly, where did you connect the electric choke and does it work well?

I connected the black ground wire to the carb base using an larger O ring connector than provided (a crimp type) and I tapped into the electric Transmission Kick Down switch wire that has current when ignition is on...I think it is the red wire. You could just as easily go through the firewall grommet and go straight  to a switched connection on the fuse box. I might end up doing that myself, however, I figure the choke doesn't draw much current.  This was just the easiest thing I could get to with 12 volts when ignition switched on.

Also, this brings up one issue I have yet to resolve but am sure it will not be a big deal since I even recall someone mentioning an adaptor for it.   Turbo Hydramatics used on the 1964 DeVilles, Eldos, and 60 Special Fleetwood, used an electric transmission kickdown switch mounted to the left side of the carb.  I still have to figure out how to mount my kickdown switch to the carb, but I remember someone on the 63/64 board mentioning a ready to use adaptor.

The Hydramatics use a manual kick down rod, and it appears the linkage has a place for the kick down TV rod.  Other than mounting the kickdown switch, everything was actually quite easy after the intake mods.

Thanks for asking these excellent questions and if you don't mind I am going to post part of my reply on the 63/64 message board.

If someone knows the source for the kickdown bracket/kit, please let me know. I will search the messages when I get some time.

Jason Edge

Here's another response

Well I've just about finished this round of performance upgrades and thought I would just mention a couple of things I've done since mounting the Edelbrock Carb and a couple of tips.

After I installed the carb, I kept tinkering with the timing and swapping from the timed port (no vacuum at idle) and the full advance port on the 1411 Edelbrock Carb.  Well I basically, determined that my distributor was shot, so I replaced it with a rebuilt distributor.   Along the way I decided to try a 1" straight through spacer plate between the carb and the intake.  This was the 4 hole straight-through spacer and not the 'Trans Adapt' #2064 adaptor plate which converts from a larger bore to smaller bore.  Anyway,  this seemed to  improve idling and performance.  In addition the hood still shut with the original breather and adpator ring on top of the carb.

With a new distributor, and finally figuring out that I needed to be using the full vacuum port  (left/driver side of the carb) per installation instructions.  The next add on was the Pertronix Ignitor II Electronic ignition (Part # 91181) along with the Flame Thrower II 0.6 ohm 45,000 volt coil (Part #45001).  The coils are the same as the original style and you can simply pull the label off the coil.  The only change-out I had to do to use the Pertronix setup was to replace that resistor wire that drops the voltage during normal running with a direct 12 volt wire from ignition.  I tapped into the Downshift switch wire again and just fed another wire from it to the coil.  By the way, I examined one of my wiring harnesses and the resistor wire, and downshift wire are all fed from the same wire from the fuse block anyway.  It goes a ways and then there is a split to the resistor wire, and then to the kickdown switch.

anyway, once I fed a direct 12 volt "switched" lead to the coil, it took probably 20 minutes to install the pertronix kit which includes a module that replaces your points and magnet ring that mounts underneat the rotor. I had to install one washer shim to bring the distance between the module and mangnet ring within the .010" to .060" tolorance.  When it was time to fire the car up....well it fired right up.  I think I was actually a little nervous as it seemed like magic.

In summary, with the 750 Eldebrock, the new distributor, the Pertronix II ignition kit, Flame Thrower II coil and the dual exhaust, the car runs the best it has ever run.

The only performance things I will try next, is to increase the spark plug gap. With the increased voltage the instructions said you can experiment with wider gaps for better performance.

In addition, I just had all new front suspension parts installed, front end aligned and all new brake components installed, and the car drives like a dream.    Oh, I still have not installed the kickdown switch, however, Todd Overton has provided some really helpful info on a setup he used to attach his kickdown switch on his 1411 carb.   I may tacklet the bracket next weekend.

Jason Edge

and another response:

Just to close this thread out, after all was installed on my car, I removed the straight-thru spacer and mounted the 750 Edelbrock back down directly on the "modified" intake and it runs perfect.  I experimented with a straight-thru adaptor while trying to get my timing right and had almost convinced myself that it helped, but it did not. In fact the carb/engine seems to run even better and be more responsive bolted directly to the modified intake manifold.  I also noticed after a few days of opening and closing the hood with the 1" straight-thru adaptor that the original air cleaner was barely stricking the hood at the front of the inlet tube...another reason to remove the unneeded adaptor.

***The main problem I had with trying to get the timing back to factory settings was having a worn out distributor.  That seems to have caused a lot of problems!

In summary what I ended up with was:

- modified intake with all 4 exh port holes tapped and plugged and the front primaries enlarged/beveled out to take the 750 Edelbrock

- The 750 Edelbrock Performer series carb (#1411) mounted directly on intake

- a 2 pc adaptor ring for the air cleaner housing

- the original air cleaner housing

- a rebuilt distributor

- the Pertronix Ignitor II Electronic ignition (Part # 91181) along with the Flame Thrower II 0.6 ohm 45,000 volt coil (Part #45001). 

The car runs stronger than it ever has at this point and if you open the hood it looks all original!  In fact I have yet to install the kickdown switch (which I have a couple of brackets for) but with the power it has now, you almost don't need it, although I am sure I will get it hooked up in the by and by.

Jason Edge

And another:

 

I will try to answer a couple of the questions....PEP Boys, Advance and Auto Zone all seem to carry the carb to air breather universal adaptor rings when I did my project a couple of years ago.
 

I think if you click on "first" on this message thread you will see some subsequent discussion on the kickdown adaptor setup.  I have the parts but never got around to installing it.  Another member has done this setup and I will try to find the info.

Once I installed everything on mine, it really boosted the power to the point where I don't seem to miss the kickdown function. I know that is just a lazy excuse, and do plan to go back and install it.

If you have a defective choke tube in your intake (which it seems 90% do) you will never be able to use the intake and choke as it was originally designed unless you plan to remove the intake and have a machine shop install a new choke tube that runs diagonally thru the cross-intake exhaust channel.....or if you are one of the lucky ones that have a perfectly fine intake and choke tube. In other words, if yours does have a bad choke tube, never plan to fix it, and will not be going back to the original type choke setup....then you might as well plug it up.

As far as the steel shim not sure if you are talking about the one that was used on the Carter AFB, if so it blocks an air passage so the Carter AFB will idle correctly....not to block exhaust.  If you are talking about using the block off plates to close the block off the exhaust openings in the intake manifold, well there should be any reason to close the 4 openings with bolts and JB weld...as long as you are sure the exhaust openings are permanently blocked. I just have a gut feeling that in time, it will eat thru, but could be completely wrong.

Jason Edge
 

And the last main reply:

 

I have some update info on my carb/intake project that I think some of you might be interested in......(for those that want to see all the questions/answers you will need to click on "first" to go back to the first replies in this message thread)....

I recently added a Trans-Dapt TRD-2446 0.375 " (3/8") insulator spacer.  On a recent road trip over 100 miles the car ran great for the most part but on the way back in the afternoon heat, seemed as if it was trying to start vapor locking and running intermittently rough slowing down and going through small towns.  The short insulator spacers should provide better air fuel mixing and of course takes the heat of the engine off of the carb.  I gave installed the adaptor this weekend and the car has never had as much power since I bought it back in 1995.  I am thinking the 3/8" spacer might be enough for the butterflies on the Edelbrock 750 1411 to clear the intake when it swings open but I am not sure. 
 
My next experiment, is to take the intake off, and enlarge the front port all the way down to where they empty out in the belly of the intake so the width is uniform all the way down.  As it is, with only the top section bevelled, the port narrows slightly to accomodate the 1411 front butterflies (for direct bolt on) ubt I am thinking widening the port all the way down should even further improve performance.  I am in no hurry, however, and will savor the current power and performance increase.  If interested in the adaptor I bought it from summit racing (www.summitracing.com) and you can click on this link to go directly tot he adaptor: http://www.summitracing.com/parts/TRD-2446/

Jason Edge

Added July 19, 2013

Aaron when running the Edelbrock 1406 750 cfm with the larger butterflies (valve body blades), , the idea of a spacer perhaps preventing the need to bevel and port out the front primary intake ports something I had thought about. 
Just a quick side note first: Tony the front "barrels" are the primaries that have the smaller ports, and the rear "barrels" are the secondaries that opens when the front primaries are almost fully open.  The front smaller ports on the intakes are what I call the primary ports and the rear larger ones are the secondary ports. I use this to match the name of the Carb nomenclature.

Aaron, this is the problem if you don't at least bevel when using the 750 with larger butterflies  (even if the raised spacer prevents from hitting): if you don't at least bevel it out you will be drawing the air/fuel down and it will hit a hard ridge due to the narrow front intake primaries. You need to at least bevel it out. You can see the results of just beveling it  in my Carb Intake project thread (Click Here to go to it) in the Help Pages, but when I rebuilt the engine last year I had the machine shop to port the front intake primaries out more and to polish both ports to  hopefully increase the air/fuel delivery from the square bore Edelbrock  to the Cadiillac Intake which is sort of a cross between a square bore and spread bore since the rear secondaries are larger than the front primaries but not Huge like on the Quadrajets.

Advantages of the Edelbrock 1411 750cfm vs Original Carbs:

#1 with a bullet: POWER!  I had run a couple of rebuilt Carter AFB's on my 64 CDV early on, and they were ok with mediocre performance (I come from a hot rodding background), but was never satisfied not to mention the choke was tough to set, and of course the choke tube issues.  I posted several videos driving the car after Edelbrock Carb install, but before the engine rebuild,  and you could punch it at 50 and be at 80 in like not time. The 750 just made a world of difference in terms of sheer fuel delivery and power when I needed it. 

Other advantages were the elimination of the manual choke and problematic choke tube,  better fuel efficiency over the original carbs (as long as I laid off the gas pedal), and other than the beveling of the intake, a bolt and go setup where the throttle linkage was the same, as was the fuel line (Carter AFB style), and with the Edelbrock design very similar to the Carter AFB with air breather adaptor rings and 3/8" spacer/insulator it looks stock until I take the air breather off.

Disadvantages of Edelbrock vs Original:   not many. You will need to get creative to connect the Turbo Hydramatic kickdown switch (not sure about TV Rod) and the idle speed up control for AC equipped cars.  You also need to use adaptor rings to use the stock air filter housing, and address the heat through the intake by blocking passages.  I've yet to install the kick down switch, or idle up speed control, but with the "kick in the pants" power I have never ever felt under power when I needed a "passing gear", and as you all know the A/C is a not-yet-started project for me so these two items have not matter.  The sheer power boost, and the fact I am running a new (well it was new then) carb instead of haggling with trying to rebuild a carb with 50 year old corroded and fatigued parts just makes it a better option for me.

- Advantages of Edelbrock 1411 750 cfm over the 1406 600 cfm --> Power  

- Advantages of Edelbrock 1406 600 cfm over the 1411 750 cfm -> Fuel Efficiency and no need to bore out/port front intake primaries (but it still might give you some performance gains since Edelbrock is a square bore carb.

Below you will see the final result of the intake during recent rebuild:

 

 

SUMMARY INFO ADDED AUGUST 18, 2013:

When I first did my intake and carb project, I only blocked the 2 internal choke tube end openings and the 2 top gutter openings.  I did not initially block the center cylinder head to intake exhaust channel.

I blocked the 4 openings to the center exhaust channel since:

1)  the Edelbrock 1406/1411 has the electric choke and did not need the choke tube to feed the hot air to a mechanical choke

2) the center choke tube often rots & cracks allowing fire hot gases out the choke tube ends which can be dangerous (so both ends of the choke tube were blocked)

3) The new Edelbrock Design did not need the blast of exhaust gas directly underneath the carb via the gutter (so those two gutter holes were blocked)

NOTE: When originally set up, I was also running dual exhaust and did not have the heat riser, which on cold start-up shuts off the exhaust flow out on the left driver side exhaust manifold forcing hot gases across the intake channel for faster engine fuel/air heat-up.  Even so, you still get unforced bypass exhaust gases flowing across that channel as I noticed my paint continuing to burn off in this area.  I measured the temps with a heat gun and was still getting a 300+ degree reading across the center port .  I have posted video showing the difference in temps on the intake with heat riser removed but with the center cylinder head to intake channel still open.  Just from the bypass gases the center is about 305 degrees vs the 195 degrees on the ends of the intake.  Here is a link to the video: https://6364cadillac.ning.com/video/1964-cadillac-intake-heat-temps

May 2012 Upgrades:- Intake was ported out as seen in last picture above to make the front m primaries better match the venturi of the Edelbrock 750 cfm
- Original Exhaust was installed, however, the butterfly was removed from heat riser and center exhaust port between the cylinder head and intake manifold was blocked using heavy guage galvanized roofing steel because I wanted to further reduce the heat on the center exhaust channel across intake as seen in previous video link. To be able to do that and run stock exhaust I had the butterfly removed from my heat riser on the stock single pipe exhaust I am now running.

UPDATE Sept 2023: if you want something more professional than my fabricated plates, Olson Gaskets sells an intake gasket with the block-off plate built in. Click Here to go to their website.  GGasket sets are about $50 the last time I checked.

NOTE!: If you are running the stock set-up with the heat riser intact and functioning you cannot block the cylinder head to intake center exhaust port as seen above. If you do, your left exhaust will be blocked and engine will run like crap on startup until heat riser opens. 

SUMMARY: If you are running a 1406 or 1411 you need to block the ends of the heat choke tube since you are not using it and leaving it open even if you have a solid internal tube, could eventually lead to problems if it ever cracks or corrodes open exposing the both ends to fire hot gases. You also want to close the top gutter holes to prevent those same hot gases from hitting the carb insulator.  IF, and a big IF, you do not plan to use the heat riser you can block the center cylinder head to intake channel further reducing the temps on center of intake beneath carb.

Update 11/26/16 regarding carb to original Air Cleaner Adaptor:
Since the top of the Edelbrock is 5 1/8” wide and the original air cleaner housing is about 4 3/16” to fit the Rochester 4GC or Carter AFB you will need some sort of adaptor to use the original air cleaner.
My First Solution - The Universal kit I first used was OK, but the rings were flimsy and the cleaner just sat loosely in the funnel formed by the adaptor rings. Thus, you did not have a good seal and I am sure some outside air was probably sucked in.  It gave me a total effective raised height of 7/8” above the carb. (Details are on this link: https://6364cadillac.ning.com/profiles/blogs/edelbrock-carb-to-air-... )

Second/Better Solution: The adaptor Russ Austin is selling is a much better adaptor. Very solid. It raises the air cleaner 1 3/16”... which just clears the hood if using a 3/8” intake to carb spacer. If you go any higher the air cleaner will probably hit to hood. 

Rejetting:
Once you get your carb set up you then my want to adjust jetting to fine tune your particular setting.
On my 1964 429 with the 1411, I ended up going with the .073 x .042 for 4% richer mixture on both cruise and power mode.

Calibration Kits
You can get calibration kits from Edelbrock that has an assortment of metering rods, jets, and step-up springs.
The kit tailored for the Edelbrock 1406 600cfm carb is the 1487 kit.
The kit tailored for the Edelbrock 1411 750cfm carb is the 1489 kit.
Below is a picture of the 1489 kit which I used:

[Jason Edge]

Thomas,  You want to use  a thick metal plate that is not going to get sucked into the exhaust port. This is an outlet so at works you debris, etc in the exhaust systems. Not good. Main thing is to address the heat riser valve ---> remove butterfly, install spacer, run straight duals out without the Y pipe, etc. but you don't want that port blocked when the heat riser is shut on cold start up. That would be the time a great amount of force would be exerted against the LH side blocked port. With the heat riser butterfly not closed (however you resolve to do that) you should only have minor pressure against the metal plate as the exhaust gases will exit the free flowing exhaust on LH side with butterfly gone.

Just to add, if you want something more professional than my fabricated plates, Olson Gaskets sells an intake gasket with the block-off plate built in. Click Here to go to their website.

[Thomas Richey]

This may come off as a dumb question, if you seal off the exhaust ports on the head that goes to the intake to block the heat off, is there any possible damage that could happen to the head or anything in the head(valve, rockers, springs) if any of that materials being used creeps it way down further than it needs to be? Where does that port lead to? Again, sorry for a strange question, just trying to learn as much as possible and get this car back on the road after sitting 30 years!

[Jason Edge]

"so the 2 blocking plates weren't fixed in the cylinder head? ", No. they were just metal plates meant to block the fire hot bypass gas from flowing thru from one side to the other. I am not sure how one would put them "in" the cylinder head. This is a cheap man's version of the Olsen's gaskets that already have the metal plate in the gasket. I simply cut two small plates from galvanized steel roofing just wider than the opening, tacked them up there, laid the gasket over them and sealed it up.   

[Jason Edge]

"what epoxy did you use for the blocking of the exhaust ports in the cylinder head?" --> I think just think a bit of that copper head gasket spray. Just something to hold it in place until I could get the gasket and intake on, which wasn't much. 

[Jason Edge]

I was searching for something else today and ran across this short article about heat soak and the Edelbrock Carbs: http://www.edelblog.com/tech-tips/resolving-heat-soak.  This is just referencing the heat soak in general, not to mention the huge heat up you would have with the original design with our 63/64 Cadillac heat riser/center intake exhaust channel system of pushing hot exhaust gas across the center intake port at cold start up, or the bypass gas that still heats the center channel up to over 300 degrees if the center port is not blocked.  I block the ports AND use the 3/8" Trans-Dapt TRD-2446 0.375 insulator spacer. There is also the physics of better air/fuel mixing and distribution by getting the carb up a bit.   A 1" to 2" spacer would, in theory, boost performance.... but you have the height issue if running the stock air breather. I usually don't post to this thread as it is already so long winded, but do hope to someday rewrite and consolidate everything!

[Jason Edge]

Tony, what temps are you getting across center of intake beneath your carb and do you have a functioning heat riser? Without a heat riser I was getting 300+ degree temps just from bypass exhaust gas leaking over. With a heat riser forcing almost all LH exhaust gas across the intake it would probably be considerable higher at startup..As indicated before, the metal shim really provides no real heat insulation. You also have no use for the PCV nipple on a stock insulator as it was incorporated into the Edelbrock carb base. Finally, Edelbrock recommends an insulator spacer with their carbs. The bottom line is I would take another look at the temps hitting your Edelbrock. If you have an IR temp gun, get temps at center channel then up at the front of base if carb near front primaries and report back.

[Jason Edge]

Tony, What type of insulator are you using? If using the stock intake to carb insulator then YES you need to use the shim or something to protect the carb! As noted these channels circled in green below allow exhaust gases up to the bottom of the carb if intake exhaust channels are open.  
 If you are using the Trans-Dapt TRD-2446 insulator I am using (pictured below) or any of the Edelbrock recommended insulators you do not have that issue since there is no direct open channel beneath the carb.

[Jason Edge]

The main thing here to consider is that the original Carter AFB and Rochester 4GC were designed to utilize additional heat at the front base of the carburetor near the front primaries at cold startup. With the heat riser closed, hot exhaust gasses were forced across the center intake exhaust channel, and up into an exhaust gutter at the front top of the intake carb mounting platform.  And, a critical part of this is the fact that the intake to carb insulator had a channel above the intake exhaust gutter to allow the exhaust heat up to the front carb base.

The BIG difference in the two carbs was the fact the Rochester had a separate steel bottom throttle body, where as the Carter had an aluminum throttle body that was an integral part of the main carb assembly.  To protect the aluminum bottom of the Carter AFB a Stainless shim was used.

If you are using an aftermarket carburetor such as the Edelbrock you DO NOT want to use the stock insulator, especially, if you have not blocked the exhaust gases, as it will allow the extreme heat right up next to the carb through that channel.  There are many aftermarket spacers for the popular carbs such as the Edelbrock.  The  3/8" Trans-Dapt TRD-2446 works well for me but there are many others!

Finally, since we have recently discussed the Carter AFB Spoil Port (holes drilled to force the reinstallation of the stainless steel shim), the insulator, and the shim I thought I would post some pictures that may make it easier to understand what is going on:

The first pictures shows the separate steel Rochester 4GC throttle body. It was a stout steel base and did not need the stainless steel shim as it was already steel:
The next picture shows the bottom of the Carter AFB with the spoil ports drilled just in front of the from primaries. Note, that the throttle body with throttle valves is aluminum.

The next pictures shows the Intake to Carb insulator without the required shim.
NOTE the exposed idle spoil ports, but more importantly consider that in the stock setup, hot corrosive exhaust gases will enter the exhaust channel in center of intake, go up through the intake gutter holes, go through the gutter and up to and against the aluminum base of the carb. THIS WAS THE REASON FOR THE STAINLESS SHIM!

Now, lets back up and put the stainless steel shim on the carb. Note the idle spoil ports are blocked, but more importantly you have provided a shield against the aluminum throttle body base:

And, finally see the insulator now installed next to the shim. This still allows the cold startup exhaust heat to enter the channel and go up next to the front base of the carb, but the carb is not subject to the intense corrosive properties of the exhaust gases.

[Jason Edge]

Metal is a poor insulator against heat. The purpose of the shim was to help prevent long term corrosion of the base of the Carter AFB from exhaust gases and really nothing to do with it's insulation value. Also, it was not used on the Rochester 4GC. The stock bakelite intake to carb spacer with PCV nipple would have provided considerable insulation and I am not sure why Cadillac felt the need to use the shim but they did. They not only used it, they drilled spoil ports into the bottom of the Carter AFB so they would not idle with out it, requiring the Cadillac Service Centers to reinstall it.

As far as Edelbrock applications, running a decent insulator/spacer like Trans-Dapt TRD-2446 0.375 " (3/8") I am using should be fine. Raising the carb a bit off the intake will provide better air/fuel mixing and dispersion. As noted in my write-up, even if you remove the heat riser, which forces exhaust gases from LH to RH side of engine across intake and under carb, your intake manifold will still heat up to 300 degrees or more across the center from the bypass exhaust. 

While the insulator will absorb a lot of that heat, you also have the choke tube that runs through it. If it breaks, then you have a direct exit out the bottom of the intake which is a fire hazard not to mention it will give you a nice exhaust leak sound.  When I started my Edelbrock project I thought I could simply remove the heat riser, block the top 2 gutter ports, and the choke tube ends and be done with it.  Per the video I previously posted, (Click Here to check it out), it was heating up to 300+ degrees on the intake directly below the carb.... not good. So, I blocked the exhaust port between the heads and the intake. That stopped any exhaust gas or extreme heat from going under the carb. I could have just as easily just blocked at the head/intake port to start with, but as they say you live you learn.

My recommendations are as follows if running an Edelbrock:

- use a spacer/insulator - get it off the intake and provide some insulation. The Trans-Dapt TRD-2446 0.375 " (3/8") insulator spacer is a good one to use and lifts the car up off the intake about the same amount as the stock intake to carb insulator.

- remove the butterfly from the heat riser, or replace heat riser with a spacer AND block the exhaust port between intake and cylinder head.   Plugging the top gutter holes and choke end is optional if blocking at the intake/head junction. I

- If it makes you feel better use a Carter AFB shim. (I just pulled a very nice one and will sell it for $15.) BUT NOTE: the front primary openings will be too small for the 750 CFM Edelbrock 1411. I looked at the one I pulled closely today and they have smaller front primaries to match the intake. The front butterflies on the 1411 will be too big.

As Tony says, Enjoy.

[Jason Edge]

Tony, no!  He already has the insulator spacer I used beneath the carb and his exhaust channel is blocked.  If you have absolutely nothing between carb and intake and you do not have the exhaust channel blocked, then sure, it might help, but again the shim was designed specifically for the Carter AFB with the Spoil ports. Also, for the 1411 with the larger primaries it might not even fit!  Tony, you periodically have mentioned using the Carter AFB shim on the Edelbrock. And ... I have to go back and explain that it is not needed with the Edelbrock. I have been running an Edelbrock for what 15 years and have never used a shim as it is not for my carburetor.  Hopefully it will sink in this time around.