For those of you running dual Weber 38s...

TodB

TodB

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I've read the historical posts and threads on Weber 38s which were helpful but I'd like to know from those of you running later M30 motors, either 3.3 or 3.5Ls, what specifically are you running for jets, emulsion tubes, etc. and what engine mods do you have, i.e. cams, headers, head porting, etc.? Do you run the stock air filter housing or do you have top mounted K/Ns? Location and elevation would also be helpful.

2013 will be the year I finally get dialed in correctly...

Many thanks in advance.
 
Yep, the car will go on the Dyno for fine tuning the AFRs but I was curious to hear what others had for jets as a starting point and a comparison to what I have now.

Right now, I am way to rich down low even with the air filter housing off.
 
I have them on a tired M30 3.5. No cams, headers or anything to boost HP.
Car was new to me almost a year ago and the list of repairs is very long.

Needless to say the engine does not idle well and I just haven't gotten serious about the problems until just recently.
As far as I know the jets are stock.
Runs rich particularly at idle.
Just happen to be looking in the throat of the back one and noticed fuel all over the top of the closed butterfly. Engine was running.
Did some reading and heard that the power valve in the bottom of the float bowl can stick and cause this problem with too much gas.
A friend had an extra 38 which was working fine when removed and he loaned me the carb to try. Much better and not all this gas smell although I'm still suspicious that it is still rich.
I have also rebuilt the distributor and added Petronics.
Each time I do something it runs some better.
Did a compression test last night and not bad. Low of 135 to high of 148.
I knew I shouldn't do this but also did a leak down and confirmed my suspicion's that this head needs a rebuild.

So not much help on jetting but I sure want to hear what you find out?

There is some tuning info on the redline weber site. Just Google it.
 
I've done to the googling and research, I was just looking for what folks here were running for jets for real world experience. I know you are out there!
 
Webber Jetting

My car was a dual webber 38 downdraft on a 3.5litre, 9:1CR with 282 cam when I bought it and ran very well at sea level. I live and play between 2000' and 7500' which means between 10 -15% less air density so the jetting formula below will be lean unless you live in the mountains as well. Hope this helps. If I find more post in add them in here.

Doug



38/38 Weber Mixture Screws
Can't find my Weber manual so I'll have to ask for advice. If you set up the idle circut according to the Weber "lean best idle" proceedure you are adjusting the idle speed and mixture screws to get the proper idle jet size and idle settings for best low input (round town) throttle response - right? So the question is, does the adjustment of the mixture screws also effect the fuel/air ratio of the main jets and air corrector jets? I leaned out the idle circut (it is still a little rich but good) and there was a significant change in the colour to a very light tan/grey (lean) of my plugs after an hour of moderate to hard driving.

I'm close enough on the idle circut now so I'm going to reduce the air corrector one size at a time and see what the plugs show. Make sense?

The answer is the mixture screws have no effect on the mains and air jets.

In case anyone is interested in settings at 4500' here they are:

Idle jets 50
Idle screw 5/8ths of a turn at 700rpm
Mixture screws at 1 1/8th
Main Jets 135
Air Jets 220 (soon to be 215 or 210)
30-32 degrees total advance ( higher for altitude)
12 degrees at 700 rpm "
 
Primary - 135
Air Corrector - 185
Idle - 60
Mixture Screws - 1 1/2 turns

Ethanol free gas has gottten rid of the flat spot, but gas mileage is poor. I'm incline to go to a small air corrector jet to make the mains kick in earlier, and then lean out the mains.
 
Thanks for these posts.

I'm also interested to hear what you are using for air filters, i.e. OEM housing with stock filters, top mount K/Ns, etc. I ask because I am wondering if the OEM housing will be to restrictive.
 
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