Recently I decided to go back to AC Delco plugs. I have a 91 305 tbi, and i bought the rapidfires which come factory gapped at .40. Now i realize that my gap is in the manual as.35, but everyone i asked said it would be OK. Now, here is my problem...i am recently finding a bit of hesitation high in my power band, as if the engine is working, but the car isn't going anywhere. i get great takeoff, then it dies a bit. its not drastic, but noticable. I wrote about it here the other day, and all the suggestions (which i appreciate) came up nill. so now i am wondering if it could be the "excessive gap" on my plugs. I have recently replaced the plugs and wires, cap and rotor, along with my coil which is an accel. my plug wires however are 7mm. anybody have this problem, should i go back to .35 or get bigger wires? thank you in advance.

 

somebody...anybody....some input, even if you dont have rapid fires. could the high gap have a negative effect on my car??

 

i figure a plug is a plug,but when i tried the rapid fires...well,i noticed the same thing.So i went back to using the regular ac delco plugs and the car was fine.I really don't think your plug wires have anything to do with it though.Unless you have a ripped wire.hope this helps ya out.

 

I have the AC Delco Rapid Fire Plugs, and I really seem to like them. I can't really say that I notice a huge amount of power from them, but the car runs great (Idleing, and full throttle).
Take care
Mike

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Gran Turismo Americano "The Ultimate Firebird"
Smokin 1989 GTA- Bone stock except for exhaust. (no catalytic-stainless pipe into Flowmaster 2 chamber) & AC Delco Rapid Fire Plugs; Removed Smog Pump and all other Smog related parts.

 

The rapid fires have a much lower resistance as compared to the regualr ones. THis is what allows you to run the extra gap because there is more power left over at the electrode. Maybe what is happening at high RPMS is that you are not getting a clean fire and since it take so little to get the Rapifires to fire you are getting some false spark creating knock?
I had mine with a MSD and Hypertech coil with MSD wires and Rapid fires and routinely took my 355 up into the 5300rpm range. This was after the 58mm TB and full intake porting to match the SLP runners, but worked great for me. Oh and I open my gap up to .050

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89 Trans Am Turbo 3.8L All stock 43,000 miles #1053 of 1555

Past Thirdgen:
86 Trans Am w/ built 355TPI with SLP goodies and too much other stuff to List. One sweet *** car, wish I would have had a good enough Job to pay insurance on three cars so I could keep it, but for a 89 Turbo Trans Am w/ Low miles, I think I made the right choice!

 

When I tried rapidfires my motor just didnt run right. I have a mallory dist, jacobs ultra coil, and a msd box. I read somewhere that rapidfires are designed only for stock ignitions. I took the plugs out put autolites in and runs good again. I put the same set of rapidfires in my chevelle with stock ignition and they run fine there. Dont know what the problem is...just had the same experience.