I have an 88 RS that i put a 327 in. For a while it wasn't very street friendly. The motor has all forged internals, drag race cam, roller rockers, 462 heads, single plane intake.

Cam is 292/300, 256/264 @ .050, .545/.563 lift, 105 LSA
I have a procomp distributor with locked timing, 10.5mm wires, and non-resistor plugs (ngk r5670-6, 6 being the heat range).
It had a weiand single plane intake, and would go to 7000+ no problem.

To make it more friendly, i got a performer rpm air gap (dual plane), I changed the plugs to a hotter, resistor type plug (ngk xr5).

I now experience puttering and misfiring at 6000+ rpm. ???

My cam is 4200-7200 operating range, so now i am missing out on the rest of my powerband. I normally take it to 7000 just about every time i drive it, and it is becoming a little annoying... (and embarrassing)

What would cause it to do this at high rpm only???

I check my plugs often, and the ngk "5" heat range seams to be right, and my a/f is pretty close to perfect using a holley 650DP.

Weak spark?
problem with plugs? wires? dizzy? intake?

help appreciated.

Josh

 

If it ran 7000+ with the single plane before, it should still run the same rpm with the dual plane without misfiring, just making less power. Here's something to look at. The new intake manifold may have positioned the dizzy slightly higher. If the dizzy has too much up-and-down end play, it can cause spark chatter at higher rpms if it has room to move. The other thing to check is to make sure a sparkplug wire wasn't damaged during the work. I've seen me do it.
p.s. nothing sounds as sweet as a SBC turning above 6 grand...

 

Well... i don't think that the distributor height has changed, because i can feel the distributor set down in there just as far as with the single plane manifold. My wires are procomp 10.5mm, and i am paranoid about keeping them away from danger.

previous manifold - weiand single plane, 7546 excelerator
new manifold - Performer rpm air gap

Does anybody know if resistor spark plugs can limit spark energy at high rpm or are the resistors only for static suppression for radios??

I had open headers once and had that thing at 7200... yeah... SWEET.

 

i don't know much about the resistor spark plugs. running at high rpms like that it could be fouling out maybe to much fuel going in the carb. Possible but again just imo. Could also be the distributor cap needs replaced or the rotor. Check them out as well.

 

If the engine ran 7K+ before and you only changed the intake and the plugs, the problem should be only something that was disturbed from the work.
Put the old plugs back in if you have them and eliminate them from the picture.