Adjusting webber 38

mwalls54

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i just resently slaped a webber 38 on my 74 fj40 and was wondering how many adjusting screws are on it? right now i have a slight hesitation at low rpms but its strong after i get past that. out of gear it revs ok and every now and then it will have a exhaust back fire. any one have any ideas
 

73lndcrsr

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How is the mixture? Take a look at your plugs. There are 2 idle air screws on the base. One for each throat.
 
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Check the timing, advance it a bit, then do the valves. Hook a vac gauge to it and run both mix screws all the way in. Back both out 1.5 turns then run it. Go in and out with the screws until you reach max vac.You want the screws to be equal. SHould end up 18-22 lbs. Make sure you have a steady vac reading. it is very common for Webbers to leak vac around the baseplate. You also might need a fuel pressure regulator. Most 2F/F motors with a webber do best around 3lbs of fuel pressure although I dont think that would cause the issues you described.
 

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Mwalls:

As stated above, verify that you do not have a vacuum leak at the baseplate/mounting area for the carb, as this would give you symtoms that you are describing. Warm it up so that it is idleing well, and then spray some gummout carb cleaner, or equivelent, at the base mounting area. If the RPM's increase, you have found a leak!!

Good luck!

-Steve
 

mwalls54

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[quote author=dd113 link=board=1;threadid=8937;start=msg77819#msg77819 date=1071851879]
Check the timing, advance it a bit, then do the valves. Hook a vac gauge to it and run both mix screws all the way in. Back both out 1.5 turns then run it. Go in and out with the screws until you reach max vac.You want the screws to be equal. SHould end up 18-22 lbs. Make sure you have a steady vac reading. it is very common for Webbers to leak vac around the baseplate. You also might need a fuel pressure regulator. Most 2F/F motors with a webber do best around 3lbs of fuel pressure although I dont think that would cause the issues you described.
[/quote]

is the 18-22lbs of vac at idle? i only have around 6 to 9. if i adjust it have more vac the idle is way too high.
 

mwalls54

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[quote author=IDave link=board=1;threadid=8937;start=msg80807#msg80807 date=1072536934]
If your vacuum is truly 6-9 lbs, something is very wrong.
[/quote]

thats all the pressure i have at idle. when i give it throttle it pickes up. let me ask this. i only have one vac line and its going from the carb to the dist. and i also have one coming off the intake for the brakes. does this sound right
 
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Does sound right. I have a very tight engine and my engine pulls 23 lbs now that everything is right. A more worn engine might pull 15-20, but anything lower means something is significantly not right. First question, I guess, is, is the vacuum steady at idle?
 
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I had a very similar problem when installing my weber 38. The guys here gave me a couple of helpful hints to help fix vac leaks and I discovered acouple of things as I went as well. First off, use a vacuum pump to check for line leaks.. I checked my brake booster thinking it might have a leak, but it was fine. One of my leaks was actually from the vacuum line to the distributor. The vac port on the carb is huge while the vac port on the distributor was very small. The first size line I used to try to fit on the carb was too big for the distributor and I got a leak there. The next leaks came from the crappy weber base plates themselves. The hex screws included in the kit are too long and bottom out against the first plate essentially prying them apart.. mine was leaking horribly from there. I ground down the bolts and they now fit snug. Also make sure your intake manifold itself is sealing properly to the head.. Good luck.. jsut go through everything methodically and you will eventually beat it.

Mike
 

mwalls54

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well the carb has no leaks. so i guess i am down to the intake manafold. :'( i would be safe to say that it has never been off. i guess some good pb blaster will help come out
 

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