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Installed a carb spacer last night.


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I'm not sure how many of you guys have carb spacers on your cars but I decided to add one for the heck of it.  Nothing difficult about the installation.  I do need a new way to get the tranny to kickdown but I'll solve that with the Edelbrock microswitch.  I also had to purchase studs for the carb (longer) and the air cleaner (shorter), and a low profile air filter.  Everything else stayed the same.  Took it for a drive this morning and I'm not sure if it's my imagination but the fuel delivery sounds different, in a good way.  It also helped with the hot starts and fuel bowl evaporation.

 

Thank you

Chris

 

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Edelbrock Micro-Switch? What Carburetor do you have, can't quite make it out.

The challenge is to get that transmission combo-switch to work on the linkage for aftermarket carbs. In the '64s case, no switch-pitch. Only the kickdown contacts are used,

John B.

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54 minutes ago, XframeFX said:

Edelbrock Micro-Switch? What Carburetor do you have, can't quite make it out.

The challenge is to get that transmission combo-switch to work on the linkage for aftermarket carbs. In the '64s case, no switch-pitch. Only the kickdown contacts are used,

John B.

 

John,

 

I have the Edelbrock 750CFM with e-choke.  I don't have the SP transmission so I only need the kickdown contact to engage.  Here's the microswitch: https://www.edelbrock.com/kickdown-microswitch-for-gm-th400-and-all-edelbrock-square-bore-carburetors-72280.html

 

Chris

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Getting the switch to activate the kickdown is a no brainer. Getting the switch to active the switch pitch at WOT is a no brainer.  Getting it to activate it at idle is the challenge.  (This only applies to the 65 - 67 models)

Edited by RivNut (see edit history)
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The spacer should help with hot starts, although if one changes the way one approaches hot starts, there is generally no problem without a spacer.

 

Different method of starting a hot engine

 

The spacer will probably not prevent fuel evaporation from the bowls, although it may take a few more hours for the fuel to evaporate totally.

 

Spacers are sometimes added to add power at wide open throttle, although this power addition also depends on the type of manifold and the carburetor being used. The benefit is derived because the spacer effectively adds volume to the manifold plenum (again, depending on the manifold design). Generally no more than 1~2 percent gain is acquired. But for a racecar, every tenth of a horsepower is important.

 

For other than high performance vehicles, the power gained at W.O.T. is often not worth the reduction in drivability at idle/low RPM..

 

Each individual has a different level of tolerance for drivability issues.

 

Jon.

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10 minutes ago, carbking said:

The spacer should help with hot starts, although if one changes the way one approaches hot starts, there is generally no problem without a spacer.

 

Different method of starting a hot engine

 

The spacer will probably not prevent fuel evaporation from the bowls, although it may take a few more hours for the fuel to evaporate totally.

 

Spacers are sometimes added to add power at wide open throttle, although this power addition also depends on the type of manifold and the carburetor being used. The benefit is derived because the spacer effectively adds volume to the manifold plenum (again, depending on the manifold design). Generally no more than 1~2 percent gain is acquired. But for a racecar, every tenth of a horsepower is important.

 

For other than high performance vehicles, the power gained at W.O.T. is often not worth the reduction in drivability at idle/low RPM..

 

Each individual has a different level of tolerance for drivability issues.

 

Jon.

 

Jon,

I added the spacer for sh!ts and grins.  I'm not trying to pull every last bit of power from this car.  It was more of a "hey, what else can I mess with without breaking the bank" kind of thing.

 

I never really had issues with hot starts myself but I did notice that it started immediately after being parked in my garage overnight.  I thought that was very unusual.  I just chalked it up to evap.

 

I'm still new to carbs so I really appreciate the info you provided.

 

Chris

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12 hours ago, RivNut said:

Getting the switch to activate the kickdown is a no brainer. Getting the switch to active the switch pitch at WOT is a no brainer.  Getting it to activate it at idle is the challenge.  (This only applies to the 65 - 67 models)

Curios as to why you think it’s a challenge at idle. Are you referring to a modified set up ? I think that if all the parts are original and functioning getting it to work was just a matter of some minor adjustments to the micro switch and maybe the linkage. That’s how it worked out for me and I am no master mechanic just your below average hobbiest 

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Hot start problems can be aggravated by numerous things. 

1st. & foremost is the heat riser valve is stuck in the closed or partially closed position.

2nd. is the heat passage under the carb. in the manifold. We don't drive these cars everyday as everyday transportation that needs to operate in ALL the adverse conditions one might face when new.  ONE of the best solutions is to block those so there is NO heat under the carb.

DO NOT block the passages in the heads as this will normally cause a hesitation even when warmed up.

This should be done for racing applications ONLY.

Just my thoughts of the subject at hand.

 

Tom T.

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32 minutes ago, arnulfo de l.a. said:

Curios as to why you think it’s a challenge at idle. Are you referring to a modified set up ? I think that if all the parts are original and functioning getting it to work was just a matter of some minor adjustments to the micro switch and maybe the linkage. That’s how it worked out for me and I am no master mechanic just your below average hobbiest 

 

33 minutes ago, arnulfo de l.a. said:

Curios as to why you think it’s a challenge at idle. Are you referring to a modified set up ? I think that if all the parts are original and functioning getting it to work was just a matter of some minor adjustments to the micro switch and maybe the linkage. That’s how it worked out for me and I am no master mechanic just your below average hobbiest 

I was referring to the Edlebrock unit that was referrenced.

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9 hours ago, telriv said:

Hot start problems can be aggravated by numerous things. 

1st. & foremost is the heat riser valve is stuck in the closed or partially closed position.

2nd. is the heat passage under the carb. in the manifold. We don't drive these cars everyday as everyday transportation that needs to operate in ALL the adverse conditions one might face when new.  ONE of the best solutions is to block those so there is NO heat under the carb.

DO NOT block the passages in the heads as this will normally cause a hesitation even when warmed up.

This should be done for racing applications ONLY.

Just my thoughts of the subject at hand.

 

Tom T.

 

Tom - I rarely disagree with your posts, but respectfully believe one should look carefully at the issues before blocking the cross-overs on a street car.

 

When I built my ultra-high performance (really, too high performance for the street) Pontiac years ago, I listened to the internet and blocked the cross-overs. Even with a MANUAL transmission, and a carburetor with an automatic choke, this car was a challenge in town for about 30 minutes after start-up. I really got to practice my heel-and-toe, which I hadn't needed in 40 years since I sold the TR-3. I finally got tired of the stalling at every stop sign/stop light if the heel-and-toe wasn't perfect, threw in the towel, and installed a carb with a MANUAL choke. By working the choke until the engine was completely at operating temperature, problem solved (there is generally a work-around, if one tries). After complete warm-up, the engine idles nicely about 850~900 RPM, and can be driven without the use of the choke.

 

Have had lots of customers with idle issues who had blocked the cross-overs. As far as I am concerned, this is a race-only modification.

 

Of course, all of us have our own level of tolerance on driveability.

 

Respectfully.

 

Jon. 

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This has been brought-up before. I think what is meant by blocking the Cross-Over is to run with a cold intake. Not good as the intake manifold is already divorced from the engine on the nailhead. I think Tom meant blocking at the carburetor flange. ("no heat under the carb" or no heat under the plenum?)

 

Chris, I am curious on the Edelbrock AFB Clone carb assessment on our nailheads. How is the drive-ability? Any adjustments? Fuel consumption? 750 CFM good for a 401 too?

 

As for micro-switch, the aftermarket is for kick-down. The original is for idle on switch-pitch transmissions (1965 & up). Nailhead parts are so difficult to find nowadays, I have accumulated SBB HW . The micro-switch for 1964 300 cu. in. is on the dashpot and is a direct bolt on to our nailheads. Probably easier to adjust too.

 

John B.

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Jon,

 

    This doesn't particularly  pertain to the "NailHead" as the intake is still heated by the exhaust, head passages, in the  intake.  All we're doing here is blocking the heat directly under the carb. & NOT the manifold itself.

    Everyone thinks an "air-gap" manifold is the latest & newest thing since sliced bread.. The "Nail" has had an air-gap manifold since it's inception in 1953, same as Pontiac.

    In this instance you need heat in the manifold to be able to help to "Flash" the cat pee fuel we have available to us today.

   Jon we are talking about something different here with the "NailHead.   I was into Pontiac's too at one point in time & on my car blocking the heat from the intake could prove to be a challenge, BUT using a Ramair IV intake that was aluminum it warmed & cooled much quicker than a cast iron manifold. I know that the Pontiac design is also somewhat of an air-gap manifold, BUT more so on a "Nail" as it has a LARGER  air-gap under the manifold than a Pontiac & more out in the open than a Pontiac.

    I had, at one time, a '68 Firebird fully complete stock car using a Ram-Air V block, D-Port stock '68 heads, ported at home, a Ram-Air IV intake & cam, Ram-Air V giant rods & pistons with the domes almost completely milled off the best I ran in the late 70's early 80's was a 10.81@121MPH.  Not bad for the time.

   In the 50+ years I've owned my '64 Riv. the heat under the carb. has been eliminated, plugged up, NO HEAT RISER VALVE at all, for more than 50 years with NO adverse affects.  The ONLY thing I noticed when I was driving the car on a daily basis is when it's very cold outside, like 32* or below, it's kinda finicky for the 1st. 10 minutes or so from starting cold which can be attributed to "Frosting" on the initial start.  After that ALL IS OK.

 

Tom T.

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If your wife was driving this car to work daily and you lived north of the 40th parallel, you might want to keep things stock.  For the way that we drive these cars, doing as Tom T. did is probably something makes some sense. There's a Conoco station around the corner from me that sells no-ethanol premium for the same price that other stations are selling 93 octane 10% ethanol fuel. (I bought it @$1.91 per gallon last week.) No "cat pee" as Tom refers to it.  Probably won't evaporate as fast. 

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3 hours ago, XframeFX said:

Chris, I am curious on the Edelbrock AFB Clone carb assessment on our nailheads. How is the drive-ability? Any adjustments? Fuel consumption? 750 CFM good for a 401 too?

 

As for micro-switch, the aftermarket is for kick-down. The original is for idle on switch-pitch transmissions (1965 & up). Nailhead parts are so difficult to find nowadays, I have accumulated SBB HW . The micro-switch for 1964 300 cu. in. is on the dashpot and is a direct bolt on to our nailheads. Probably easier to adjust too.

 

John B.

 

John,

 

I will preface by saying, I am by no means an expert on carbs and this is the second car that I've owned with a carb on it.  The first was a poorly tuned 66 Impala with a 283/2bbl.  That car ran fine, never stalled, but always seemed a little on the edge of dying.  With that said....

 

After realizing the prev owner used a later model carb and had bailing wire holding the choke to an always open state, I ended up buying the 750CFM Edelbrock.  I bolted the carb on and it fired up with zero issues.  Out of the box driveability is great.  No stumbling, hesitation, or misfires.  I feel consistent power throughout the RPM range up to about 3500 or so.  I rarely heavy pedal the engine.  It's not in me anymore.

 

I did do a tune on it using a vacuum gauge and it didn't seem to detract from the performance.  Meaning, it felt right out of the box.  I attribute this to my locale with respect to Edelbrock's factory.  I am in Temecula, CA and Edelbrock is a little ways west of here.  I believe Edelbrock tunes and tests the carbs at the plant under Southern CA conditions, so as long as the engine is happy, the carb should perform well for So Cal customers.  Again, that's my assumption...it makes sense in my mind at least.

 

So to answer your questions;

Drive-ability:  Great!  No issues and I have no fear getting in the Riviera and taking it a long distance.

Any adjustments:  No internal adjustments.

Fuel Consumption:  Couldn't tell ya!  It's probably terrible by today's standards.

Good for 401:  I'd say go for it, there is also a 650CFM AVS2 series which may work well with the 401 if 750 seems too much.

 

Regarding the microswitch, I've already placed the order with Ecklers.  If it works I will report back!

 

Chris

 

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I think that, because small block Chevies are like flies on honey - there are so many of them, Edelbrock built their AFB clone to work on most SBCs rightbout of the box, anyone else using one needs to learn how to deal with their frustrations.  My 64 Riv had a manual choke Edlebrock on it when I bought it.  I tried tuning it to no avail.  I bought the correct OE Carter off Ebay, bolted it on, and the car ran like a dream. I never touched a screw on it.  Carbs are not meant to be universal.  My 64 Chassis manual shows that even the AFB's for the 401 and 425 are different.  Sure, they'll bolt on, but there are noticeable differences between the two. 

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I had a Ford 302 that boiled gas in the carb. Combination of desert heat and CA gas. A 1/2" wood spacer almost completely resolved it. Worked even better than the plastic ones. I later put aluminum heads with no heat crossover. Even in the summer, it was a grumpy car. Lesson learned. 

 

I'm going to put a wood spacer on the Riv, because I suspect it'll boil gas too.

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Wood?  Isn't wood mixed with gasoline pretty flammable?  Why wouldnt you use a phenolic spacer?  The one pictured here wouldn't allow any heat to the carb bowl.

 

carb_spacer__21372.1425321870_500_290.gif.f8dff1a54958f46a9365f415f7fa9c95.gif

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To add to Ed's post:

 

When Carter was still making AFB carbs, and got into the aftermarket, they basically made aftermarket carbs for small block Chevvies ONLY!

 

WHY?

 

There were production performance single 4 AFB's for the 409

There were production performance dual 4's for the 409

 

There were production performance single 4's from 625~939 CFM for Pontiac

There were production performance dual 4's for Pontiac

 

And Buick (factory duals), and Ford (Shelby duals), and Chrysler products (wedges and hemis).

 

There were no AFB's for Oldsmobile, but the calibration is similar to that of Pontiac.

 

By this time, there was little demand for performance carburetors for Cadillac.

 

If one looks at the calibrations for the various performance carbs CALIBRATED BY CARTER, one finds 2 major (and quite a few minor) differences in calibrations for "torquers" and "screamers" when it comes to engines.

 

The above is simply to whet the appetite of the reader to do their own research. Look particularly at the attack angle and mass of the weights of the auxiliary air valves; as well as the rod diameter differentials (high vac to low vac) and the air bleeds and idle circuits.

 

When Federal Mogul bought Carter from ACF, FM continued the application for the aftermarket carbs; although they did redesign them to sell much cheaper (wonder how)? :mad:

 

Federal Mogul had a lot of difficulty selling the redesigned AFB's to Carter distributors (we were one at the time - about 1986). They needed to sell them to someone.

 

I won't get into transmission linkage, because not my field; but a totally wore-out 1963 Pontiac carb (if one cannot find a totally wore-out Buick carb) can be refurbished for less than trying to recalibrate the aftermarket carbs built for "screamer" engines; even when starting with genuine (before FM) Carter aftermarket carbs, let alone the clones, and will function quite well on Buicks.

 

Jon.

Edited by carbking (see edit history)
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4 minutes ago, carbking said:

To add to Ed's post:

 

When Carter was still making AFB carbs, and got into the aftermarket, they basically made aftermarket carbs for small block Chevvies ONLY!

 

WHY?

 

There were production performance single 4 AFB's for the 409

There were production performance dual 4's for the 409

 

There were production performance single 4's from 625~939 CFM for Pontiac

There were production performance dual 4's for Pontiac

 

And Buick (factory duals), and Ford (Shelby duals), and Chrysler products (wedges and hemis).

 

There were no AFB's for Oldsmobile, but the calibration is similar to that of Pontiac.

 

By this time, there was little demand for performance carburetors for Cadillac.

 

If one looks at the calibrations for the various performance carbs CALIBRATED BY CARTER, one finds 2 major (and quite a few minor) differences in calibrations for "torquers" and "screamers" when it comes to engines.

 

The above is simply to whet the appetite of the reader to do their own research. Look particularly at the attack angle and mass of the weights of the auxiliary air valves; as well as the rod diameter differentials (high vac to low vac) and the air bleeds and idle circuits.

 

When Federal Mogul bought Carter from ACF, FM continued the application for the aftermarket carbs; although they did redesign them to sell much cheaper (wonder how)? :mad:

 

Federal Mogul had a lot of difficulty selling the redesigned AFB's to Carter distributors (we were one at the time - about 1986). They needed to sell them to someone.

 

I won't get into transmission linkage, because not my field; but a totally wore-out 1963 Pontiac carb (if one cannot find a totally wore-out Buick carb) can be refurbished for less than trying to recalibrate the aftermarket carbs built for "screamer" engines; even when starting with genuine (before FM) Carter aftermarket carbs, let alone the clones.

 

Jon.

 

Jon,

 

That info is very thought provoking.  It's definitely from a perspective from a guy that's been there done that.  I appreciate the input to this thread.  I'll have to pick up a book on carburetors and see how they actually work.  For now I'm happy knowing my car has no issues even though it has so much more potential.

 

Chris

 

 

 

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