I have a 74 2.0 with the following engine setup:

Stock displacement
Euro Pistons
8.3:1 Compression
9550 Camshaft and valve train etc

Ignition is a Mallory Dizzy from Chris with wires
and the Mallory Ignition box is not installed yet.

Fuel,
Weber Carburators new 40 IDF
28 Ventures
55 idle
115 Emulsifier
(not looking for a discussion about the 9550 with carbs)

Timing now 25 degrees adv
I set the car at 2500 feet above see level with 27 degree timing and 93 octane fuel.

I drove the car cross country to CA and trough different altitudes and then with 91 octane, so my heads started getting too hot, actually never too hot, so I had to go down to 25 degrees, with the consequents of power loss.

Lately I have even more power loss and the car is loud and misfiring.


So here my question,
what would be the best carb set up for that engine
and how can I tune it right, to the power it should have?

Thank you guys!

I would have to say first off, you need an O2 sensor and gauge. Everyone here can make stabs at what jetting you should have, but your motor will tell you what it wants if you install the gauge.

You didn't say what main jets you have, but I bet that if you fattened them up a bit your temps would go down.

The mains are F22, if that even makes sense...

And I wasn't planing on putting an O2 sensor on it for a while but it's my daily driver...

What throughs me of is that the timing is of so far...

F22 sounds like the emulsion tube. I have 44idf's and it is probably a bit different and I am far from expert. The main jets and air jets I thought should be a three digit number. Make sure you have the numbers straight because there are a lot of folks here who will be able to help.

You jetting can cause the heat. Retarding the timing will not help poor jetting.

You need to get the timing set to where it should be, then start looking at the O2 sensor.

I agree that i need to start with the timing:

TIMING:
What is the magic number?
FI was 27 and carbs should be 32 or 34 right?
Over 30 I get predetinations…
So I'm sure someone is running a 9550 with 40 carbs and a Mallory dizzy
on only 91 octane with ethanol…
What is your number??????

Then back to Jetting:
On the mains I have these three numbers: see pics

If it is 20 or 22, that seems awfully small for a 2 liter engine,
for the little I know about carbs.
I heard though that the F series is not chronological…

Anybody?

How are the stacks/towers/chimney on the top of the carbs called?
What would be the right size for my carbs? With the red line filters?


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Stock weber setup is:

Main jets: 115
Air correctors: 200
Emulsion tubes: F11
Idles Jets: 50
Pump jet: 50

Have you cleaned the idle jets since it started running poorly?

Valve adjustment?
Valve to tight will do this.

Timing should be 27 degrees at 3500 rpm,s

Cornelius.......The carburetors that were installed when your engine was new had the following as standard new 40 IDF carburetors:
AIR CORRECTION 200
EMULSION TUBE F-11
MAIN JET 115
PUMP JET 50
IDLE JET 50
VENTURII 28mm
I would bet that you have been running a bit lean for quite sometime. I hope the integrity of your new rebuild hasn't been compromised after all this time and all those miles.

Jerry

thank you rich and jerry!

the idle jets are 55… always where….

So what would be the next sizes of main jets?
When I change those, what do I have to do to the other jets in relation?

Which would be the right velocity stacks?

What is the exact adjustment for the floats?

I did adjust my valves and I did clean my idle jets since the power went down.

Next up would be 1.20 get 4 of them...if you happen to get used ones, or even new ones for that matter, always check that the number matches the actual measurment. Main jets are available from 1.00 to 2.55 mm

A Picture is worth 1000 Words.

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The 27º adv at 3500 is too much at for the mallory Distributor.
Too much predatination.

We ended up setting the timing at idle with the "0" mark.
At "0" in idle it is 16º adv at 3500 rpm
So we set it at 4º, which was not quiet enough and 7º was too much (each time at idle),
so I'm gonna try 5º tomorrow and adjust the carbs after finding the timing sweet spot.

When reading the Haynes manual the 5º at idle have something to do with the adv at 27º at 3500 rpm with the original distributor, but I have the feeling, that that does not work with the mallory set up.

Mallory has different advance curve springs, but if you bought it from foley, I believe he sets them up with the gray weights which are damn close to correct.

Seems like something else is wrong.

Rich

Has the distributor been removed since the original install ? If so I would suggest that the ignition shaft got moved from the correct position. I believe it may be off by only a little, (A tooth or so) but you must get it back to where we had it when we first fired up that engine (It was perfect at that time). Unless you do this you will not be able to use the red 27 degree timing mark at 3500 RPM. Let me know if you need to know a good way to do this.

Having the distributor gear drive off does not invalidate the timing marks.

It just means your cyl#1 does not point in the usual direction.

Stu

Setting it at 5 degrees adv at idle is close to 27 degrees adv at 3500 rpm according to the Haynes manual. I just wonder why I can set it up better at idle...

The distributor was never removed.

Now next question:
Why do you set the valves at 0 clearance with the 9550 cam and the tabu valve train?
I get the point with the 911 svival heads,
But the valves are still going to expand under heat...
I'm asking because I have power loss once the engine really warmed up...
I'm asking because the 911 has a 004 clearance...

I've always run the Mallory Unilite at 28 total advance, 12 initial, with the grey springs, like everyone else does.

It has nothing to do with the cam.
It is the pushrods.

Since you mention 9550 & swivel feet, I assume you have Jakes cam kit and you cut your own pushrods.

If that is the case, then you have Jakes chromolly pushrods.
They get set to zero lash because they will expand/contract differently from the stock rods as the engine heats.

Stu

Sorry for just getting back to the topic, I wasn't able to do anything due to very busy days. Tomorrow I will do some more work. I did set the car at 5º idle though and it runs a lot better. Maybe I have to find a fault that could cause the timing set procedure to vary so much… Any ideas?

I understand that the chrome molly pushrods have a much lower expansion rate then the factory aluminum push rods.
But the temperature at the push rods is a lot lower then on the valves and the valve stems. that should not change the gap to zero, so you are driving with non closing valves. I understand though, that everybody with that valve train is running zero clearance, I just try to understand, especially, because I have a power loss after the car warmed up.

Tomorrow I'm gonna check the floats (finally) and maybe a buddy is going to come by with a wide band for the tail pipe.

I also received my velocity stacks, I figured while setting up the car, I might as well set it with them…

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Work on my crabs today.

The floats on both sides where at 3mm shut off and at 20mm on the open, so I adjusted them to 10mm and open 32mm.

W also hooked up a wide band at the tailpipe and it was reading 14.4 under constant load. But between 10 and 11 at constant idle while driving (no pulsating)…
I have 55 idle jets? And adjusting the screews didnt really make a mixture diffrence at thge reading of the wide band.

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I also checked the gas screens in the carbs, they where/are ok!

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