twin carb conversion

[bravekozak]

Listen carefully. The first sound you hear is the stock fuel pump at 12V. The second sound is the same fuel pump running at 9V.

[1990new]

Definitely a slower speed at 9V. Will running the motor over time at the lower voltage hurt it?

[bravekozak]

It should avoid getting the fuel hot in the summer due to recirculation. They say the draw will increase, but I measured an identical draw at both voltages. So it shouldn't heat up. It will definitely be a lot quieter and the bypass regulator will have a lot less pressure to contend with. I will post pictures on Saturday of the aluminum resistor I bought. I will carry around an extra fuel pump as well as my tool box until I prove it works on long trips over 400 miles. I cannot find any documentation online of anyone else who has ever done it.

[bravekozak]

I changed my search parameters and found a couple of interesting articles showing the use of a ballast resistor to slow down a pump at low engine speeds, such as idle. Our Festivas don't have the complexity of multiple relays controlling fuel pump speed.

Their ballast resistor is not as big as mine. I do not need 23 psi, only 4, so slowing the motor down by 25% should be fine for a carb. I am not going to waste any money buying a fuel pressure gauge. If the car runs fine at all speeds, then 9V is quiet enough for me.

[bravekozak]

Here is my ballast resistor that I will be installing where the evaporator assembly used to be. I will be using the two spades that are the farthest apart for maximum resistance (3.6 ohms). I presume I can use the same gauge wire as on the Revolution fuel relay.
I had to buy two of them @ $7 each because the minimum order was $10.
If anyone needs and extra, you know who to call. Depending which terminals you use there are six different resistances possible. The marked resistances are between adjacent terminals.

[bravekozak]

Always wanted to know where my fuel efficiency and power comes from.
I decided to compare the Mikuni carb bores with a Weber gasket.
The secondary bore size is identical. The primary bore size is slightly smaller.
But don't forget the fact that there are two of them! No contest. They blow the Weber away!

[bravekozak]

Engine not timed. Stock exhaust manifold. Stock cat. Stock muffler. With the exception of twin carbs. Later, I noticed that the exhaust clamp was dangling loose on the downpipe. That was probably making some rattling. After inspection, I will swap out B6 headers + Bosal and repost a new mp3.

[bravekozak]

Today I discovered why my choke cable wouldn't hold it's position. I always wondered why it would pop back every time I let go. Went to Google Australia and found out why:

KB Laser.....Adjusting manual choke friction

Can anyone tell me how to "adjust" the friction in a KB laser choke cable? Its like theres no friction stopping the choke being pulled back to the "open" position by the return spring. I'm sure I used to know how to adjust the friction to stop this happening. I know I could put a couple of kinks in the outer cable, but I'd rather do it the correct way, (if there is one)

TIA Keith
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Pull the choke out to the desired setting, then turn the knob clockwise to lock it in place. If it doesn't hold in position when doing this, then the cable is rooted and you need a new one.

--
Regards,
Noddy.

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The twin carbs make it heaps more responsive with a nice increase in power. Never had any tuning problems either. My parents have been using it for the last 1.5 years without touching it!

Cheers

Twin carbies would make more of a throatier sound when reved too...a simple proper tune of each carby and your set.


I think the differance is 54kW vs 59kW but.. theres always a but, the SS version from the factory with the twin carbie setup ran 10:1 compression vs 9:1 on the single carbie E5s.

[Bert]

Old thread but the advantages of carburetors far outweigh the reverse. I have noticed that Festys are now become a novelty/niche market and the folks buying into them tend to be younger than the cars. Carburetor engines allow anyone to escape from the drudge of owning an entirely gov't-regulated electronic-operated car. This is worth a million bucks (in my estimation) in the scheme of things. Sort of like living off the grid and heating with wood and using wind power to recharge batteries. Single carb cars are dead simple to service, and performance-oriented folks (up until the late 1970s) gravitated towards twin carbs whenever they wanted more 'oomph'. Tuning twin carbs raises the bar on competence by a considerable amount but did, and does, allow car owners to call a car their own.

[bravekozak]

Tuning multiple carbs. First set the timing. It is almost impossible to balance multiple carbs (with a great degree of precision) without an airflow meter such as a Crypton Synchro-Check. Simple to do. Just remove the air cleaner cover studs and hold it down for a reading. Adjust the throttle position screws to balance them. I was getting a deflection of just over 4 at 850 rpm.

As for vacuum, it will max itself with the most efficient burn. Gunson's Colortune to the rescue. Just remove a plug, screw in the adapter insert the spark cable between the plug and adapter, get your screwdriver ready to turn the idle screw and start the engine. The flame will change from orange to blue, indicating an efficient burn.

[sketchman]

^That's cool stuff. My Escort will be carbed "soon", so I will look into these things. I love stuff that I can work on with my hands and not my head so much.

[bravekozak]

sketch, save your money. The Synchro check is for multiple carbs. You can use a vacuum gauge instead of a Colortune for a single carb. I have one carb feeding cylinders 1 & 2 and another feeding cylinders 3 & 4.

[Hot_Wheels]

Wow thats cool. Is it ricer of me just to want 4 clear spark plugs???

[sketchman]

sketch, save your money. The Synchro check is for multiple carbs. You can use a vacuum gauge instead of a Colortune for a single carb. I have one carb feeding cylinders 1 & 2 and another feeding cylinders 3 & 4.

Ahh. Will do. I have a built CVH that I can't wait to get in my wagon, but it's a single carb.

[bravekozak]

Found this link for B6 specs.