Hi folks,
didn't find any significant answer on the web so i'm writing here what's going on my engine.
Freshly rebuilt GM 350 first gen, Alu heads with 70 CC chambers, mild cam(Edelbrock 2102) and same performer alu intake, forged flat top pistons, headers, that's pretty much it, i'm using a TBI by Howell wich is made by genuine GM components except for a custom Prom.
Engine is running great but i'm experiencing problem with a random misfire when cold, usually when the engine is warm it runs perfectly, sometime the misfire disappear after just a few minutes after the start up sometime it needs a little more to dissappear but i would say it has no problems when warm, i can't figure out what is causing this issue, wires seem to be ok, i tested them with a multimeter, distributor rotor and HEI cap are fairly new and with no oxide, coil and module even better, spark plugs are brand new (NGK BPR6EFS), i know they're cheap but they are the only ones i can use due the clearance problem i have with the headers.
Problems seems to pops out more often if i leave the car alone for weeks, i'm just trying to figure out if better plugs like irudium or platinum would solve this or maybe i'm using a wrong heat range but i've seen a couple of spark plugs interchange charts and those i'm using should be very close to the CHAMPION RN12YC recommended by Edelbrock.
i'm wondering if the problem could be fuel related because of my "aftermarket" TBI wich is not perfectly tuned when cold ,the fuel mixture ratio is ok when engine is warm, i checked that with a gauge but i'm not sure is too rich when cold causing fouling or flooding plugs...
I also read that the plugs heat range is related to the compression ratio too, the more the CR the colder must be the plug, mine should be in between 9,5 to 10:1, however using aluminum heads wich use to run colder the their cast iron sisters i believe plugs should be slightly hotter? just wondering, engine is on a Jeep so it is spending 70% of its life under the 2000 RPM, don't know if this matter or not but i'm pretty sure high RPM engines call colder plugs wich is not my case.
Recently i took off all the plugs and checked them out, they were all good except one tat had a weird spark so i replced it with a new one, engine started great and till today i thought problem went away then today again with that stupid misfire, i can clearly hear the engine running on 7 cylinders, so i grab the infrared pyrometer to see which header's pipe was cold and found the #1 cold, replaced the plug and engine runs great now but i have no idea how much will last.
Any suggestion will be appreciated, thank you.
didn't find any significant answer on the web so i'm writing here what's going on my engine.
Freshly rebuilt GM 350 first gen, Alu heads with 70 CC chambers, mild cam(Edelbrock 2102) and same performer alu intake, forged flat top pistons, headers, that's pretty much it, i'm using a TBI by Howell wich is made by genuine GM components except for a custom Prom.
Engine is running great but i'm experiencing problem with a random misfire when cold, usually when the engine is warm it runs perfectly, sometime the misfire disappear after just a few minutes after the start up sometime it needs a little more to dissappear but i would say it has no problems when warm, i can't figure out what is causing this issue, wires seem to be ok, i tested them with a multimeter, distributor rotor and HEI cap are fairly new and with no oxide, coil and module even better, spark plugs are brand new (NGK BPR6EFS), i know they're cheap but they are the only ones i can use due the clearance problem i have with the headers.
Problems seems to pops out more often if i leave the car alone for weeks, i'm just trying to figure out if better plugs like irudium or platinum would solve this or maybe i'm using a wrong heat range but i've seen a couple of spark plugs interchange charts and those i'm using should be very close to the CHAMPION RN12YC recommended by Edelbrock.
i'm wondering if the problem could be fuel related because of my "aftermarket" TBI wich is not perfectly tuned when cold ,the fuel mixture ratio is ok when engine is warm, i checked that with a gauge but i'm not sure is too rich when cold causing fouling or flooding plugs...
I also read that the plugs heat range is related to the compression ratio too, the more the CR the colder must be the plug, mine should be in between 9,5 to 10:1, however using aluminum heads wich use to run colder the their cast iron sisters i believe plugs should be slightly hotter? just wondering, engine is on a Jeep so it is spending 70% of its life under the 2000 RPM, don't know if this matter or not but i'm pretty sure high RPM engines call colder plugs wich is not my case.
Recently i took off all the plugs and checked them out, they were all good except one tat had a weird spark so i replced it with a new one, engine started great and till today i thought problem went away then today again with that stupid misfire, i can clearly hear the engine running on 7 cylinders, so i grab the infrared pyrometer to see which header's pipe was cold and found the #1 cold, replaced the plug and engine runs great now but i have no idea how much will last.
Any suggestion will be appreciated, thank you.