bustoff Posted June 17, 2015 Share Posted June 17, 2015 72 monte 402 headers air gap manifold 750 street demon carb hei ignition stumbles off idle tried everything any suggestions would help Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted June 17, 2015 Share Posted June 17, 2015 Larger squirters on the primary side Quote Link to comment Share on other sites More sharing options...
Bluemalibu Posted June 18, 2015 Share Posted June 18, 2015 Larger squirters on the primary side ...And by all means, replace the accelerator pump. Having it fall on its nose off of an idle is a classic symptom of the butterflies opening without a shot of fuel from the Acc/P. Doug Quote Link to comment Share on other sites More sharing options...
stangeba Posted June 18, 2015 Share Posted June 18, 2015 Or the pump / outlet is clogged with debris. New fuel lines / fuel pump / gas tank work, can lead to a bit of junk stuck in the accelerator pump passages. Do you have a good fuel filter? How old is it? Good luck! Bruce Quote Link to comment Share on other sites More sharing options...
bustoff Posted June 20, 2015 Author Share Posted June 20, 2015 fuel lines and filter are brand new anybody know off hand what size nozzles came stock on a #1903 street demon carb? I want to step it up a few sizes but don't want to buy all 10 sets hope it cures this issue Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted June 20, 2015 Share Posted June 20, 2015 the size should be stamped on it, only one screw to remove it, take it off and take a look Quote Link to comment Share on other sites More sharing options...
bustoff Posted June 22, 2015 Author Share Posted June 22, 2015 new nozzles and jets on the way will keep posted 1 Quote Link to comment Share on other sites More sharing options...
bustoff Posted June 25, 2015 Author Share Posted June 25, 2015 there was 40 nozzle on the carb the demon instruction manual said it had a 31 W.T.F put on a 35 runs much better need to adjust trans 1st gear shifts too soon raining out will try to adjust module tomorrow will post updates Quote Link to comment Share on other sites More sharing options...
bustoff Posted June 27, 2015 Author Share Posted June 27, 2015 today same stumble just wondering if this intake carb combo is too much for stock cam try something different tomorrow go to a 28 nozzle and cross my fingers Quote Link to comment Share on other sites More sharing options...
bustoff Posted August 22, 2015 Author Share Posted August 22, 2015 installed a quick fuel 680 vac sec carb today same stumble does anybody know if the rpm air gap manifold is too much for this engine? (402 headers streetfire ignition) its making me crazy cant figure it out. ANY IDEAS? Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted August 22, 2015 Share Posted August 22, 2015 so you went from a 35 down to a 28? here's a video on basic squirter and cam tuning Quote Link to comment Share on other sites More sharing options...
bustoff Posted August 22, 2015 Author Share Posted August 22, 2015 thanks I did most of that on both carbs jets squirters cam timing base timing total timing changed distributer advance with a 373 gear this car wont even spin the tires the so called experts are saying too much manifold for smog motor with peanut ports car ran much better stock Quote Link to comment Share on other sites More sharing options...
Sam (Bones) Posted August 22, 2015 Share Posted August 22, 2015 I don't believe that make sure there is no slop between the pump arm and adjustment rod, that can cause a stumble no matter what squirter you have look down the carb as you push the throttle plates, you should have the accelerator discharge as soon as you move the throttle, also try opening your mixture screws another 1/8-1/4 turn Quote Link to comment Share on other sites More sharing options...
72 LS5 Posted August 24, 2015 Share Posted August 24, 2015 I suspect that you need to get the accelerator pump cam kit along with a large squirter. Then you can pick a pump cam with the steepest ramp just off idle. You may have to mess with the number 1 or number 2 screw positions for the cam. When installing a new cam, be sure to take any slack out of the pump arm so it barely rests on the cam (with the adjustment nut over the spring of the arm). Have a look at this pic with the cams all lined up and the difference in profiles. BUT, before that, be sure your initial timing is set properly. Many an engine has stumbled or been sluggish with not enough initial timing. I used to run about 12-14 initial and about 36 total on my 454. Vacuum advance helps off idle as well. That manifold should run well with the peanut port, as long as its made for the peanut port heads and not 0val ports? Can't imagine why there's not torque. Check firing order, vacuum leaks, and basic stuff - sometimes something gets overlooked. Quote Link to comment Share on other sites More sharing options...
badddoin Posted August 25, 2015 Share Posted August 25, 2015 I was having similar issues, along with idle issues. My problem was junk getting past the filter. I thought it was rust from my 40 year oldtank, but when I dropped the tank and removed the sending unit, it wasn't rusty inside at all. The problem was my 40 year old pre filter (sock) was falling apart. It was black, and when I fetched a piece of it out, it would turn into a gazillion fibers in my hand. I cleaned it all outta there with a contraption I made to attach a piece of steel fuel line to my shop vac - pat. pend. I also got one of those groovy scopes from Harbor Freight, so I could see all around in there. If you have an old tank, you might consider taking your bowls off and seeing if anything is getting in there. Quote Link to comment Share on other sites More sharing options...
bustoff Posted August 27, 2015 Author Share Posted August 27, 2015 going to drop the fuel tank and see what it looks like in there, everything is set where it should be and car is not performing if that don't help motor comes out next weekend Quote Link to comment Share on other sites More sharing options...
BigDan Posted September 26, 2015 Share Posted September 26, 2015 Does it still stubble at low speed's like 10-15mph when you go WOT? I had THE WROST time trying to tune my carb to deliver max power when I wanted it. The only way I got around my ussue was to zip tie the secondary linkage to my primary linkage so all 4 barrels fully opened or fully closed when the throttle was pressed. I took it to tons of race shops and nobody could improve on my zip tie trick, even tried all the secondary springs and still fely like a like a 150 hp 2 bbl instead of a ZZ4/ Quote Link to comment Share on other sites More sharing options...
bustoff Posted October 10, 2015 Author Share Posted October 10, 2015 I pulled the motor timing chain was VERY LOOSE 5 degrees on crank about 12 degrees on cam that explaines why the it was so eratic anyway that motor is under the work bench and the 468 gets put in next weekend cant wait will post pics soon thanks for the help Quote Link to comment Share on other sites More sharing options...
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