Carburettor

From the Jensen FF Mk1 sales literature regarding the carburettor: “Carter 4 barrel carburetor with automatic thermostatically controlled chock. Large capacity paper element air cleaner”

Photo of engine from the offside. The carburettor is a Carter AVS 4682S C.A.S. identified by the triangular aluminum tag. Note the Mopar Workshop Manual at page 14-42 (fuel system-AVS ) states that the 383 engine was fitted withAVS-4736S or AVS-4732S. This evidently refers to other Chrysler engines and not the Jensens’ 383.Other Jensen 383 engines of this age also have the AVS 4682S. Note the adjusting screw in the center of the carburetor. I don’t know what it does?

I asked the Jensen list about my carburettor:

“I have just removed the carburettor. It is a Carter AVS C.A.S. It has a triangular aluminum tag identifying it with the reference 4682S beneath that No. is the code 2618 and to the right side is “95”. The Mopar Workshop Manual at page 14-42 (fuel system- AVS ) states that the 383 engine was fitted with AVS-4736S or AVS-4732S. I appear to have an AVS-4682S. What carb. do I have? Was it a replacement and does the “95” refers to the date? Is this good or bad”.

The List response was:
1. “Assuming you have an E-series engine, the AVS 4682S is correct in the application used by Jensen. The numbers quoted in the Mopar manual will refer to applications other than Jensen, possibly lower compression ratios or manual gearboxes etc. Actually, E-series Jensen engines are listed by the Jensen factory with the AVS 4682SA, the A suffix denoting (I think) automatic transmission. Not to worry. My E-series had the same AVS 4682S so if you have an E-series car you’re OK without the A.”

Replacement Edelbrock Carburettor

My choke was giving me problems and appeared to stay on after just a short journey of 5 minutes. This resulted in difficult starting. I asked the list about a manual choke.

The Lists response was:

1. My FF retains its auto choke. I use it in conditions varying from -25C to +30C. I often start with one of those short trips to the kindergarten/school. No problems. Check the setup for proper operation before you discard it
2. Same here. Bought new Carter AFB autochoke two years ago. Works perfectly under all conditions.
3. Yes, I agree that the autochoke on Carters (at least, the bimetallic one) is crude and overactive (like Ocker?). My conversion used a “universal ” manual choke conversion kit from Canadian Tire (our Halford’s equivalent) and a choke cable from a Triumph 2000 (I think). I used the kit for the cable clamps and pinch bolts, and the Triumph cable because it has positive détentes. After a bit of fiddling, I was able to adjust the cable so that the first two détentes move the fast idle cam only, while the last four operate successive levels of choke flap. On mild mornings, choke is required for less than ten seconds on start.

4. Check your accelerator pump. The diaphragm is subject to splitting or it could be set wrong (three positions are available rich medium and lean. The pump is the one connected to the throttle by a lever. Good luck.

Then I decided that the spindles were worn, that I wanted more power and that after all an electric choke was tempting. So I bought an Edelbrock 1406 Having bought it with the impression that it just bolted on I discovered a few problems.

I asked the Jensen list about my carburettor:

I’ve bought and now part fitted an Edelbrock 1406 (600cfm) carburettor to the 386 “E” series engine in my 1969 FF. I presume, from the fact that the air cleaner doesn’t fit without fouling the throttle levers that a spacer is required in my case. The Edelbrock manual mentions adapter my reference numbers. So I can ring Customvile or Rodley motors here in England and order the correct spacer does anyone know how thick this circular spacer is?. again I consulted the list…..Only problem at the moment seems to be fouling of the air cleaner by the throttle lever/kickdown linkage. The one inch spacer shoved the air cleaner to high and fouled the bonnet, but sorted the throttle lever fouling. . I cut it in half (now an half inch spacer) and the throttle linkage fouled on the air cleaner again.( and the eclectic choke). Still puzzled by the fact that the instructions say the existing steel fuel inlet pipe wont fit and mine does? and again I consulted the list……So what’s the difference between my 1406, 600cfm someone’s 1905 and the 1411 750cfm? Can anyone tell me if I chose correctly for my 383 or have I just dropped an expensive clanger? I looked at some Jensen notes where there was a reference to either using an half-inch or a three quarter inch spacer between the carb. and air filter. However, I’ve sent for one inch and hope it won’t hit the bonnet when I close it? Someone mentioned the need for a kick down linkage. There was also reference to some cars having square bore manifolds and others having spread bore manifolds.

The List response was:

1. The difference in the cfm rating is down to engine size. The 383 is 6.3 litres, whereas as the 440 is 7.2. The cfm figures really only come in at maximum RPM, where a 650 cfm would be a little small on a 440, but perfect on a 383 (it will also work very well on a 440, giving excellent throttle response due to the smaller chokes, and better fuel consumption, at a loss of max. RPM power). This should be an excellent carb for your engine, requiring little or no tuning to give spot on results. Mine has transformed the car. The 1406 is the model number of the carb. My 1411 is an electric choke model. The manual choke version is a 1407. The spacer goes between the carb and the manifold (I used the Edelbrock air filter, so I don’t know if you need a spacer to fit the Jensen filter.. In the Edelbrock all 4 choke are the same size (square bore). You will also require the Edelbrock to Chrysler kick down linkage
2. The 600 cfm carb you have is perfect for the 383. A 650 is arguably better but only at full rpm the 600cfm will give you better throttle response. A much better choice in this age of controlled speeds (at least you’ll get there faster)
3. The Carter AVS is a square-bore carb, as is the Edelbrock Performer series you purchased. The spread-bore carb used on the Mopar products is the Thermoquad. The 383 should have a square-bore manifold so only a spacer is needed, not the adaptor. BTW, even if you have a spread-bore manifold, you do not need a spread-bore/square-bore adaptor since the Edelbrock has holes for both. What you would need is a thin metal plate to seal the passages on the bottom of the carb, and it should come with the carb. A spacer with gaskets would suffice. But since both carbs you are working with and the manifold are square-bores, you only need the spacer and gaskets. The Edelbrock/Mopar linkage adaptor is a simple piece to install so you shouldn’t have any problems there. A 1″ spacer is going to cause problems on a 440-powered Interceptor, but I don’t know about the 383. It might be close, so watch your air cleaner/stud and don’t dimple your hood! Until recently I ran an Edelbrock 1412, an 800cfm carb on my 440 with good results. I’m sure you’ll be happy with your carb choice.
4. Not sure for the 1406 but I fitted the 1905 and the spacer (which goes between the carb and manifold) is about an inch thick. For the 1905 it is apparently a must have in order to keep the carb body a little cooler – I think.
5. Some people are confusing the spacer that goes between the carb and manifold (to help insulate the carb. and help keep it cool) with the spacer that must go on top of the carburetor to give you the clearance you need for the linkages to move and to accommodate the round electric choke that you have on the Edelbrock and didn’t on the original AVS.

6. You will need to remember to check to see if the distributor is timed and use the correct vacuum port on the carb to connect the vacuum pipe between carb and distributor. I can tell you now that for UK cars it is the drivers side port on the carb. that you use (your Mk 1 FF will be timed.)
7. With regard to clearance, you may need the air base from your air cleaner plus a shallower air cleaner top or go for an Edelbrock air cleaner. Earlier carbs (smaller c.f.m.) had smaller throats so you can’t use a CV8 one for instance
8 The 1406 (600cfm for 383) is an Edelbrock performance carbs so you’ll be OK
9. Here is some useful stuff on carbs I’ve collected:
· For the 383, a single 600 CFM rated carb is sufficient unless the engine is to be operated at sustained wide-open throttle for significant periods of time. Unless you have higher than stock compression, non-stock cam, intake, or other features, this size rating should be sufficient. The carb will need to be tuned to your car to take into account the rear axle ratio, weight, altitude and etc. All carbs, are supplied with jets and enrichment systems set up for the standard calibration — i.e.: sea level, 70 degrees Fahrenheit. If you are not operating in that environment, the carb should be adjusted in order to realize the best performance. Edelbrock/Carter carbs for the Interceptor are simpler to adjust than the Holley and do not seem to be as leak prone due to their gasket design being above the fuel level. They also require less re-tuning than the Holly. On the Carter/Edelbrock carburettor the main jets and needles plus enrichment springs may need to be changed to get the best from the carburetor. The manual supplied with the new carb will take you through the adjustments for needle and jets, as well as spring settings for enrichment. The Carter/Edelbrock design makes it easy to carry out needle changes (which changes the rate of fuel flow). There is external access on the top of the carb. Changing timing by 2 degrees has the same effect as changing jets one size. With respect to fuel mixture delivery, retarding the timing acts like richening the carb. And, advancing is like leaning the carb. It is important not to make drastic changes when rejetting a carb. Make jet changes of no more than one Jet/needle size at a time for the Carter/Edelbrock
. The Carter AVS is named for its Air Valve Secondary venturis. The rate of opening of these is governed by the resistance of an adjustable spring (unlike the Carter AFB). By 1957 engine sizes had increased to the point where a larger four barrel carburetor was necessary To meet this need, Carter introduced a completely new, lightweight design, called the AFB (for Aluminum Four Barrel).” -whose secondaries are governed by non-adjustable counterweights).
· Flat spots can be a problem when increasing the performance of your car. The Edelbrocks are notorious for bits in them. You should take it to pieces first and clean it. If you get any flat spots I was told to always check the accelerator pump first as the diaphragm may have failed, or may simply be set wrongly (there are three lever positions: lean, medium and rich). The pump is located high on the carb body, and is connected by its lever to the throttle sector.
· They (the engines) need a good burn out once in awhile or they get hotspots from deposits in the chambers, especially if they are tuned to be a bit rich on the lower settings. Harder to do with an automatic car. Take it out on a deserted road and do some full bore acceleration runs – get it up to 5000 rpm or so even if you have to leave it in second to do it. Should improve matters unless it has gone too far. Then you’d need to pull the heads
· Although the Edelbrock carbs appear to be based on the old Carter AVS design (since they include the ‘weighted flap’ to control secondary transition within the secondary metering circuit) They are actually the old Carter AFB design and are good, reliable and inexpensive.
· Providing a cool air source will improve the engines performance and need not be plumbed directly into the air filter as long as it directs an airflow into the intake area, on race cars air is often ducted past the radiator area and dumped near the open carbs. V8 air cleaners, however, do lend themselves to being hooking up directly to air ducting. The more oxygen you can jam into a cylinder, the bigger bang you should get (assuming fuel mixture is adjusted appropriately for the more oxygen). Cooler air has oxygen molecules that are closer together, and therefore, you have more oxygen.
The final result was:
  

Photos showing the the kickdown linkage hole on the old Carter carb and the larger hole on the new Edelbrock carburettor .An adaptor is available but as I wanted to use the car that coming weekend I made up a suitable bush to fit the larger diam. hole and take the smaller diam. spindle that operated the original kickdown linkage.

I had to remove the old automatic choke (because the new Edelbrock carburettor has an electric choke)

The instructions with the Edelbrock carburettor says that the original metal fuel line will not fit and must be replaced? Mine fitted perfectly after removing the small gauze fuel filter.

In order to get the throttle cable to fit properly/ function I had to make an adapter. There was inadequate adjustment in the throttle cable in its original location (basically the cable was to long).

I now understand that if I had been sold the kickdown linkage adapter at the same time it would have saved me this hassle as well as having to make up the bush (mentioned above).

Drilling new mounting ponit for the throtle cable bracket. ( wouldn’t have had to do this if I had known about the adaptor)

I tried a proprietary plastic spacer (photographed above) that went between the carb and aircleaner to give me the necessary clearance o stop the throttle linkage and electric choke fouling on the base of the aircleaner. It was rubbish and kept deforming and dropping inside the air filter box. It rarely needs a metal ring. I cut the original one inch spacer down to about half an inch.Finally ended up replaced it (temporally? with a buggy wheel rim)

View of the Edelbrock carburettor with home made adaptor ring (correctly sized pram wheel bought from B&Q with the hard plastic spokes and rim bashed out to leave the moulded ruber tyre.

At this point I came to an impasse. The air filter still fouls the bonnet but any lower and the linkages foul.

Photo of the Edelbrock carburettor showing the correct I hope vaccum tube attachment.

I also ended up hammering a dent in the underside of the filter box to accommodate the electric choke. I haven’t found a solution to this one yet. I’m just driving round with the bonnet slightly open

I asked the Jensen list about increasing the performance of the Edelbrock carburettor:

..………….The 1406 Edelbrock performance carb I have must be factory set with needles, (called rods in the USA?) to give a basic? economic? type of performance? What might be a simple rod change to effect an increase in acceleration. (A close friend has challenged me to drag race on a local airfield and his 3 liter Peugeot 406 coupe does 0-60 in 7.5 seconds)
The List response was:

David Crowne has a 383 engine. He recommended the 1406 Edelbrock carburettor and a 1487 Edelbrock Calibration Kit. He said “the 1406 Edelbrock carburettor (with electric choke mechanism) is set up for economy at low altitudes, which is not exactly what we want in an Interceptor. Here in sea level San Diego I changed the stock setting (after a good deal of experimentation) so as to use a number 1456 metering rod (.073″ X .047″) and a number 1426 main jet (.095”), which is about 6% richer than stock overall. Consulting my records, I find that in the high altitudes of that magnificent “Million Dollar Highway” from Durango to Ouray I changed to a number 1449 metering rod (.070″ X .037″) and did not change the main jet. (which would provide a leaner mixture) (These are Edelbrock numbers, by the way.) The change for altitude made for a mixture about 6% leaner in the cruise mode and 10% leaner in the power mode, which produced no loading up and no stumbling or pinging. Then, once in Utah, as I said, I went back to the previous combination.”
The calibration Kits have a variety of rods, jets, and springs. He indicated that to change the rods is a 2-minute job and a 5-minute job if you change the jets as well.
With reference to an earlier posting of yours and your website David, had the following advice about the 1406 and the 383 engine “The 1406 carburetor is a 600 c.f.m. device. A lot of people think that any big-block Chrysler needs a 750 c.f.m. or larger carb, but if you do the arithmetic you’ll see that there is no way that a 383 cubic inch engine can suck in anything like that much air at the revs we normally operate at. MAYBE a 440 could use a 750 c.f.m. carb, but a 383 would definitely be over-carburetted with one of those unless you’re going to turn 7000 and more rpm, and I’m definitely not going to be doing that. I’m very happily running Edelbrock aluminum heads on my Interceptor, with an Edelbrock Performer aluminum intake manifold. My compression ratio is close to 10:1, which is about a point and a half higher than stock, but still allows me to use mid-grade gas (89 octane here in California). ”