Another jetting question

You have answered your first question correctly. The fatter ( leaner ) F36 needs one step up on the mains compared to an F24.
A 200 air with the 55 idle and the 47/48 mm float height would get you close with the 130 main you are currently using. The smaller air corrector does tend to bring in the main circuit earlier with the submerged emulsion tube holes in the F36 tube.

Cheers

 

you have rebuild them, so these came of the car. Was the problem allready allways there before rebuild?
If he was running ok before there is no reason the jetting is wrong after rebuild.
Personally I hate fumbling with jets without putting the car on the dyno...If it is running lean in the high revs you only know its wrong when you can rebuild your engine also.

 

I have run the 50/130/220 with the F24 and just had the low speed/tip in flat spot noticed by many. I currently run a 125/200 F24 (mod) which is too rich 12.4 AFR but runs well.

If you can't get onto the main circuit, ie full throttle rolling second gear, then something else such as is likely to be at play.

You do need to know your front and rear bank ignition advance timing and have some idea of fuel delivery such as plug color and/or AFR readings. Super clean plugs?

Performance Oriented a very good overview on the selection of the idle jet size and main jet tuning/ emulsion tubes.

I would try some fine wire occluders in the air correctors ( as in the DCNF progression tuning thread)
to pull the ac down to the 170/180 mark to see if that helps the main part of the circuit response before doing full throttle work.

Good luck

 

Do check all your electrical earthing. That is coils, engine block, and battery connections. They can lead to miss fire/ power loss gremlins which look a lot like carburettor problems.

 

Always thought these bad boys would be good for diagnostic tuning but takes some time to flow test back to fixed weber jet sizes.
Weber Adjustable Idle Fuel JET DCD IMB 24 26 28 32 34 36 NEW | eBay

Seriously though, you will have to try some 55 idles from one of the other cars or buy some to try.

 

That is indeed stock jet size. I have had very good success bumping the main jets to a 140 and using a 190 air corrector. The larger main brings the main circuit in a bit sooner and the smaller air corrector reduces air more specifically about 5000rpm which is really when these engines lean out as that is about when the cams come on power. The F24 tubes dump a huge amount of fuel during the transition circuit so I stopped using them. F24s can be controlled with somewhat careful throttle movements, but I've found it easier to just continue with the F36 tubes.

 

+1

My 308 didn't have an engine earth. A battery jumper lead from chassis to engine fixed lean spikes on my AFR trace at cruise and a miss fire under heavy acceleration. Hit a pot hole at speed and the car became undrivable, until I tightened the +ve battery terminal ! I have added an earth connection as a permanent solution. More of an issue with electronic ignition triggers, igniters and control units etc.

 

OEM jetting is shown in the Owner's Manual for your car.

Is the gas/fuel you use the same as when the car was new? In the USA, the addition of up to 10% ethanol will cause the engine to run leaner, all else being the same. I found this most noticeable in the transition zone, under light load.

Bill

 

Yep, go up on the idle size

 

Switching to ethanol free gas has resulted in a huge improvement in my car. The change was evident from the first tank and the flat spot/stumble continues to improve to the point where it's almost gone.

 

An idea what the stock NEEDLE VALVE size is? I'm looking at the rebuild kits, and they offer several.

 

175 ( 1.75 nominal mm )

 

DUDE,

If I commit the unpardonable crime of using "NON-ALCOHOL" gas in my beloved car, (at$5.50/gal). The Schwartz/brown will excommunicate me. I have to sign in blood that the alcohol free gas I buy for my mower/weedeater/chain saw/generator, will NEVER be used on the highways, lest I defile them with a better running car.

Coincidently, the saw shop that I take my yard equipment to says that "OVER 50% of their shop work is repairing damage done by alcohol".

It is more polluting to produce, gets worse mileage, drives up the price of food, F**Ks up our cars - this is looking more like a not win- not win.

clearly, I need another beer.
best,
chris

 

Florida has no such restrictions. Ethanol free gas is sold as "Recreational" fuel at many stations. 3.99/Gal today.
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