wassup everybody. i been trying to tune webers and stuff and i just wanted to know what you think of the setup i have now. the problems im encountering is my truck stumbles or hesitat from 1000rpm to like 1500 rpm after that it clears out. i dunno if its because the power band on the cam is 1500rpm to 5000 rpm current jettings weber DCOE 40mm: main jet:135 air corrector: 190 emulsion tube: f16 idle jet: 50f9 choke: sorry i dont know at the moment pump jet unknown mods: msd 6al msd 8.5mm wires blaster coil 268s comp cam(valve lash set at stock settings but on the cam card it says to set the valve lash at .010 on the intake and the exhaust) and timing set at 10 degrees advance without vacuum advance spark plug gap at .38 magna flow muffler with 2 1/4 tail pipe do you think i should set the valves to what the cam card says yes or no? do you think i need more advance? thanks for the help guys
Always follow the cam specs for lash. Albeit, it's only a small difference, but go with what they say. If you don't already have it, get a book about weber carbs. And depending on how bad the stumble is, you may or may not get it better without other sacrifices (bottom end power, mileage, ect).
Are the carbs synchronized? More advance should also help. My base timing is about 15 degrees advanced.
i found one problem well its a problem to me it seems like one carb sits higher than the other carb. ill try and get a pic of it. i gotta double check if the carbs are sync, ill get back to this one
ill just redo the valve lash and set it to the cam card than. well the stumble aint that bad but you can feel it. but after that it clears up.
I forgot to mention i have a 20r canon intake manifold fitted on to my 22r head. maybe the flow from the manifold to the head is restricted or has a junk flow what do you guys think
First and formost, i'd check if the carbs are synced. Your gonna have to buy a syncrometer from redline (or other retailer) and sync those carbs up. That should have been the first thing you do after getting the engine to run and after you get your a/f figured out. If this wasn't done, expect the stumble. Don't worry too much if one carb sits higher than the other...Keep in mind that with these sidedrafts, you have one primary for each cylinder. If you wanna fix it though, you might wanna "true" your manifold (google it). Meaning that the mating surface is flat, or..."true". I taped a piece of sandpaper to my garage floor and went back and forth with my manifold to get a flat surface...kinda getto, but it works.
I would think the 50 idles are a bit on the fat side, but the 20r intake on a 22r head has me wondering how well its sealing, possibly its leaking causing a lean stumble.
yesterday i took the carbs apart and cleaned the the passage ways with a blower, cleaned all the jets. adjusted the floats to the rec. setting. but the spring for the accelarator pump seems weak. in the book it says that if the lever is depressed to full throttle the gas should squirt atleast 3ft. but it doesnt even get near that it only squirts at 1feet. so i gotta get that changed. but other that when i put the carbs back on to the manifold i synce'd the carbs, and the surging went a way. but now its time for the tuning
ill get the idle jet changed ill try and go down to a 45f9 and see how that feels like. the manifold is not leaking at all i checked for vacuum leaks and there wasnt any. the idle doesnt fluctuate or anyting.
Change your air jet to 185, stay with current idle jet, choke size should be 34 and sinc. carbs. Set timing at 30-32 degrees total with timing all in about 2000-2200 RPM. Set idle between 900-1100 RPM. Install spark plug (close to stock spec) and gap at 31. Turn your Idle jet screws all in and back out 3 turns. Start and warm up motor to normal temp. Adjust for smooth idle. Check exhaust outlet temp. of each cylinder with an infrared thermometer-temperature of cylinders should be within 25-30 degrees of each other. Adjust idle jet screws in to increase that cylinders exhaust temperature or out to decrease that cylinders exhaust temperature. Drive vehicle down the road for awhile, stop and pull spark plugs; check for rich or lean mixture. Do this a number of times until all plugs look about the same. Make idle jet and main jet corrections as required.
I forgot and this is extremely important DO NOT EXCEED 1 PSI FUEL PRESSURE AT THE CARBS other wise your carbs will flood.
Im with nook id be checking for a vacuum leak. Take some carb cleaner and spray around the base of the carbs and all around the intake, propain works well to ive heard, if it stumbles or dies you've got a vacuum leak. I fought with a vacuum leak on my truck forever. still runs like poo poo but atleast i know its now vacuum leaks.
