302 misfire problem, need help! 302 misfire problem, need help! 302 misfire problem

Discussion in 'Classic Mustang Specific Tech' started by brennan carey, Dec 13, 2004.

  1. Hi guys, need some help. I have a recently rebuilt 302 (1500 miles) with edelbrock performer rpm carb 750cfm (electric choke) performer rpm intake and performer rpm cam. Cast iron heads with 1.9 intake and 1.6 valves. roller rockers etc. I had the car on the dyno did 300hp at 4900rpm. Rev any higher and it just went dead. timming was advanced but it did not help. We suspected a ignition/ distributer problem took the car to a distributer guy who replaced the module (stock ford distributer with ignitor electronic conversion) and he also replaced the coil. This did not help..

    I took th car to another mechanic who asked if I had replaced the valve springs when i did the engine. bingo... i did not! so he repaced the valve springs with Isky double springs for high RPM performance. I get the car back and now it revs to 6500rpm but at 2500rpm when "under load" it misfires. take your foot off and accelerate slowly and its fine. it only misfires at this rpm. need help as i dont know why this is now happening, as it was not an issue before.. I have taken it back to him and he has reset the tappets and is now blaming the distributer. I am going around in circles!
  2. I was gonna suggest you recheck the timing order, but after reading closely that could not be your problem. I dunno bro, that dont make sense to me, could not be a fuel delivery issue since it is fine at higher RPMs. You are getting 300rwhp out of a 302 so I cannot think of anything major being out of place. Possibly a delayed or sticking advance in the distro?
  3. I did an edelbrock swap on mine with a 600cfm elec. choke and performer 302 manifold. Also installed the ignitor and blaster coil because of the same gremlin you are describing.

    When accelerating to pass from a slow speed or rolling stop - BANG!!.

    I pushed the timing up to 12 deg. and used higher (read-expensive) gas and the problem seemed to disappear. I also suspected arcing between spark plug leads (ACCEL 8.8) and re-routed the passenger side as I noticed they were wedged between the heater/pcv hoses and the valve cover. I think the leads were probably fine.
  4. I took the car back to the Distributor guy and he had a look at it. He advised the conversion he had done is not the problem, leads,coil, ignitor etc is all 100%. He advised it is the carb that is lean. Anyhow I collected the car very frustrated, drove home andto my surprise there is no problem now at all.. Its the best job done that has never been done it seems!

    I guess he fixed it without knowing or was to shy to say he messed something up! we will never know...

    So i a off to the dyno again soon. With the "new life " above 5000rpm due to new valve springs I am hoping for an HP improvement in the 5000 to 6000rpm range?
  5. Glad you got it figured out.

    So, are you making 300hp to the rear wheels? What kind of tranny do you have?
  6. yeah so far so good, for now that is... lets hope the problem does not come back. I have a 4speed top loader with 9" diff.