burgerburnerjr

i have a 80 pickup 4wd 20r desmogged w weber 32/36 its idles perfect and revs up fine while sitting there but under a load it starts to break up and miss usually around 3000 rpm and never gets better until i let out the gas. i was just wanting to know what jets i should be running in the carb i live right on the beach i just need some where to start i dont want to start just guessing and get nowhere. thanks in advance for any help.

gillesdetrail

iTrader: (1)

Check out the weber tuning how-to, that explains how to find out if you have the correct size jets. Checking your spark plug colour also gives you an indication of your air/fuel ratio. Is your timing set correctly?

burgerburnerjr

Timing is set at 10* I've narrowed it down to either fuel or fire I was just wondering if anyone could tell me what jets they were running in a 20r so I could put those in and run the truck to see if I need to go into troubleshooting the ignition because she idiles perfect and will turn up without load but take it on the road and it breaks up after about 3000

gillesdetrail

iTrader: (1)

Isnt 10 deg too much? I thought it was supposed to be 5.

kawazx636

iTrader: (3)

Check your manifold advance - one of two things is probably happening. Either the timing isn't advancing with the RPMs (could be a vacuum leak going to the distributor or bad advance mechanism in the distributor) causing you to get late spark. Or your timing is too far advanced (I believe it is 5* on the 20R as well - I know it is on the 22R) causing you to get an early spark. Webers are jetted at sea level from the factory so jetting shouldn't be your issue.

burgerburnerjr

Thanks guys I'll try this when I get home i had the advance turned up because of the weber instructions said 12-14* but I was worried to go that high so maybe I can get it figured

gillesdetrail

iTrader: (1)

Keep us updated!

kawazx636

iTrader: (3)

The Weber controls fuel delivery, not spark. The timing shouldn't even be listed on the Weber instructions, in my opinion - it should simply say, "set timing to factory specs." The timing may vary due to the increased atomization of the Weber, but not by 5-7* more. The reason you advance your timing is so that the spark can "catch up" and burn the fuel at the appropriate time according to the position of the piston. Simply put, fuel takes X amount of time to ignite and burn regardless of the speed of the engine so in order to achieve a complete burn the mixture would need to be ignited earlier when engine is running at higher RPMs thus the advance. If you advance too far forward then your mixture will be burning too soon during the compression stroke (essentially slowing the engine on the upstroke) and would be basically fighting itself throughout the four strokes that each cylinder is simultaneously trying to complete. Thus causing studdering, stalling and poor performance.

burgerburnerjr

got home put it on 5* idile speed screw set at 1/2 turn in mixture screw set at 1 1/4 turns out. idles fine purrs like a kitten hit the gas twice and it backfires out the tailpipe. jets are: mains 140 accelerator double pump jet 55 primary idle 60 secondary idle 50 air correctors are 160 primary 170 secondary. it does it while sitting there or trying to drive it down the road. it also has a sync link installed on the weber if that makes a difference. been trying to get this truck down the road for about a month now and just cant get it to go

double pump jet
55
160 170
60 50


140 140

burgerburnerjr

i tried to make a diagram of the jets but it didnt work thats what all those numbers at the bottom were haha

gillesdetrail

iTrader: (1)

When was the last time you changed your fuel filter and what do your spark plug look like? whitish grey?

burgerburnerjr

the plugs are black the smallest mains i have are 140 i have a jet kit for low altitude but everything in the kit is bigger than what i have in the carb. so black plugs mean its rich now but i dont no how to correct it thanks for any ideas

burgerburnerjr

fuel filter is brand new along w pump and lines all the way from the tank to the carb and my pump is mounted at the rear also

kawazx636

iTrader: (3)

Black plugs could also mean that they are fouled with oil. Any blow by issues or compression loss? Also, you need to disconnect the vacuum advance when setting the timing to 5*

burgerburnerjr

well she backfired so hard that it blew my adapter plate gaskets out so now i have an air leak that wont let the motor idle down but on to bigger problems now i was having trouble with air in the coolant system and found the culprit when i got the truck from the PO he said he has ran it around the block a few times but that was it and was selling it because his girlfriend was pregnant. i got it home to find out it had no water and 1qt of oil in the pan. over the last month while running the truck it would overflow and then over heat. well a leak down test confirmed it today with #2 cylinder under pressure you can hear bubbles in the rad so i pulled the head off and saw that the PO had poured block filler in it to try and stop it. SO my new gasket will be here in the morning and i am going to get the vacuum leak fixed and ill repost with my results. YOU NEVER KNOW WHAT YOUR GOING TO GET

Yoda38052

Hey guys I also have a new weber 32/36 that runs great on the driveway but put it in the road and hit 4th gear and it starts to load up and backfire. Then it begins to buck after I back off the gas and reapply. I don't have a fuel regulator so I thought it was maybe getting to much fuel? Does that make sense? Not trying to hack the thread just trying to get a solution. Thanks

83

20R or 22R? Or more specifically mechanical or electric fuel pump? Supposedly you only "need" the pressure regulator with mechanical fuel pumps, and most 20Rs actually have electric pumps.

Aside from all that, though, I put a pressure regulator on with my Weber, even though I've got an electric pump.

Yoda38052

My truck has a 20r with mechanical pump. I'm thinking maybe it's getting to much fuel..

JonnyBoy

Yoda38052 I installed a Weber on a buddy's Dodge D50 that did that until we got a regulator on it, so I'd try that. It also made it empty the fuel bowl until we blocked off the fuel return to the tank, though. How does it run up until 4th gear? And what are your mixture and idle screws set at?

To Burgerburnerjr, yes it does make a difference that you're running a sync-link. Even though you have different diameter venturi, the primary and secondary idle and main jets need to be the same, or else you'll get some strange part-throttle behavior. I was at high elevation and had a 22r, but those might even out and you might have good luck with my jet setup or something close. Take a look at my old thread here for some of the things I ran into while running the sync-link.
https://www.yotatech.com/forums/f114...talled-225236/

Yoda38052

Ok guys I was having issues with my Weber 32/36 last time I was on here. I am glad to report that it is running a lot better since I had a moment. I was adjusting my carb when I looked down and seen a shadow in my clear fuel line right in front of my fuel filter. I reached down and pulled the fuel line apart and out came a big piece of paper towel. My son was helping me clean a plastic tank to use as gas tank and I guess a piece of it tore and got sucked up in the fuel line.. I removed it and there is no more issues at the moment.. LoL thanks for all the help and remember,,,, sometimes it is the simplest things that we over look.