Originally Posted by BuzzLOL
.. Ignore the red hot headers for now, since they're wrapped/insulated, of course they're going to run hotter than bare ones that can loose heat/energy/power...
.. Sounds like you have a severe lean misfire at high RPMs... and plugs verify it... those look like old used plugs that were sooted up a bit, then you put them back in the new engine build and they're burning white/lean/too hot on the ground strap/outer electrode end...
.. As others noted, is the timing advancing as the RPMs go up... are all the EFI sensors good?
.. What did you do to make a 355"? Was it a 350/355 to start with? Was the EFI/TBI for a 350/355 or for a 305?
.. Is this an edelbrock 2-bbl. TBI intake or a 4-bbl. one with a 2bbl. adapter? Are the cylinders sealed/separated 4 and 4 from each other under the TBI, or is there some common plenum opening feeding all 8 cylinders? If there is common plenum for all 8 cylinders, it usually requires a richer TBI or carb. secondaries to avoid going too lean at WOT...
First of all, thank you for helping me out, so, the EFI is brand new and comes in a kit made by Howell-EFI using GM 2BBL throttle body and ECM, sensors are new too, there's also a new fuel pump that i mounted below fuel tank, i gave to Howell all the specs of the engine and they made a custom prom for me.
Engine is a common 350 first gen bored over .030 with alu heads, a mild cam, Edelbrock performer intake and Hedman headers.
I noticed today looking at the spark plug wires that one of the caps was seriously cracked by beeing too close to the headers and i'm thinking that the misfire may be caused by this problem.
The spark plugs are new too, i put them after the rebuilt so they are like 2 hours old.
I found here on the forum shortys like the Accel i'm using made by Champion, NGK and others so i will tru to put a new set soon, the only thing i'm not sure about is the heat range, the ones i'm using are the hottest available, when cold the engine shakes a little but just for a minute than runs pretty good, don't know if a colder plug would be a good idea.
I'd like to try Champion RV92YC, looks like they are supershort like Accell but cheaper, hope the quality isn't cheaper too.
About the timing, this is a bit more complicated because of the water pump clearance i have in my motor, is really hard to see the mark on the damper, i found on the net that the ground strap shows the advance too, mine is about in the strap curve, closer to the thread means it is more advanced, any experience on this?
My only concern is to damage pistons running too lean but the plug "circle" is quite dark...
I'll keep you on the loop.