HICKL Posted September 18, 2006 Share Posted September 18, 2006 What exactly does it do when you try to exceed that rpm range, does it start missing, stumbling or just sound normal? Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted September 18, 2006 Share Posted September 18, 2006 I feel your pain, same for me too. I did a compression check, all was good. Did a leakdown test all was good, so I switched out all of my electronics, I have replaced the msd unit, coil, dizzy, and plugs. Have not tried it yet but if this does not fix it maybe it is my fuel. I am at witts end. Good luck in finding your problem, just wanted to let you know you were not alone. John I just found out the carb was bought is for a 402' date=' and jetted as such. They jet the carbs for a small or big blocks... This one is the small calibration. It should feed up to 385 hp.. Im looking at more like maybe 300 hp. So it should be plenty of fuel... I did a compression check and it ranged from 163psi-170psi, so all is good with that. Someone told me it could be the valve lash adjustment is to tight. Could this be true? The engine was originally a TBI set up. Do you think that I have the wrong intake manifold (edelbrock proformer for vortec heads) to mach the cam? could that be why I cant rev past 4000 rpm in first? It isnt as noticeable in 2nd or 3rd gear. The engine was a stock replacement for a truck, could the cam be set up for towing? Iv gone through my entire HEI distributor, wires, plugs, coil, capasitor, ecu, and fuel delivery... Im at my wits end and have been struggeling with this problem for over a month... If anyone has any input, it would be greatly appreciated. Iv tried everything else...[/quote'] Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted September 19, 2006 Author Share Posted September 19, 2006 When I hit 4000 rpm it just sits there. It doesent miss, doesn't stumble, it gains very little rpm after that, if any... If it was the fuel it would still accelerate after 4000rpm but slower right? Iv done the fuel system already and everyone has told me its enough psi. Could it be too much?(8psi at the carb, @ 97gph with 5/16 lines... The car runs norlam and good at all times. When it hits that mark it just sits there. Quote Link to comment Share on other sites More sharing options...
HICKL Posted September 19, 2006 Share Posted September 19, 2006 I only have 5 psi at the carb and have never had a problem. When I have had fuel or timing advance problems, It would almost stall, fall on it's face. Are you absolutely sure you are getting wide open throttle, it seems like the only logical thing. Motor would most likely rev under no load but would level out like you say going down the road. Any weird/incorrect spacers or anything under that carb that would limit the butterfly's from opening? Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted September 19, 2006 Share Posted September 19, 2006 You know HickL could be right, if you are not getting full throttle this would explain your issue. It would not hurt to check this out. John Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted September 19, 2006 Author Share Posted September 19, 2006 I have a 1/4" spacer between the carb and the manifold. Iv already checked if it was snagging the "throttle plate"---its not. My linkage is pulling back all the way and im getting full throttle. Could it be cam timing? or to tight on the valve lash adjustment? Q-jet carbs have that funny "flap" above the secondaries, when I nail the throttle the "flap" opens up only about a 1/2". Is this normal? I was told that the flap allowes only as much air to enter the carb as the engine draws (this avoids flooding, as a 750cfm carb is too much for a sbc) Could it be starving my secondaries? If so, how do I remidee this? Quote Link to comment Share on other sites More sharing options...
HICKL Posted September 20, 2006 Share Posted September 20, 2006 You got any buddies with another carb you could slap on there? That would for sure rule out the carb if the problem stays. Quote Link to comment Share on other sites More sharing options...
280zwitha383 Posted September 21, 2006 Share Posted September 21, 2006 Yesterday I installed a new fuel filter and problem solved, it really came alive. I even lose traction after 5k. Quote Link to comment Share on other sites More sharing options...
Nealio240z Posted September 22, 2006 Author Share Posted September 22, 2006 Im going to look into valve adjustments this week end... Maybe that will help. This is the second carb that iv put on this motor... PROBLEM IS STILL THERE... Quote Link to comment Share on other sites More sharing options...
jnjdragracing Posted September 22, 2006 Share Posted September 22, 2006 You don't think you could be floating out your valves due to weak valve springs. It could be possible. On valve adjustment, the looser they are the more bottom end you get. I don't know if they are hydraulic, solid. If you had some to tight you have a miss in the engine.... John Quote Link to comment Share on other sites More sharing options...
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