Team Camaro Tech banner
Cancel
Create thread New Garage Forums

CD vs Stock Coil - What Plug to use?

Jump to Latest
1 - 7 of 7 Posts
S

smiller

· Registered
Joined
·
165 Posts
Discussion starter · #1 ·
I just switched out my stock 327 coil for a new CD coil and ignition box from Summit and runs good at high RPM but get intermittent backfiring out the pipes at about 2000-2500 RPM. Do I need different plugs for the hotter coil and ignition box? I didnt change the distributor which is a MSD magnetic 'ready to run' without points. Any clues on whether to advance or retard to eliminate the backfiring would be appreciated.
Many thanks
Steve
 
#4 ·
try opening the gap up a little...hotter spark means you can run more gap and get a more complete burn...but i`m thinking you need to fatten up the idle circuit...the idle circuit in a holley is a large part of the drivability portion of it...also check out the pv...could be too tight...might need a softer one...
 
Discussion starter · #5 ·
Thanks Mike.
Sounds like I would keep the same plug spec and just give it more gap with the hotter spark? I'll do some more fiddling with the timing and carb idle/air adjustment to eliminate the backfire. Seems like its from unconbusted fuel vapors in the exhaust that ignite on the way out.
Steve
 
#6 ·
if so, then you dont have enough timing...retarded timing will cause excessive heat in the exh...try total at 34-36 for a start, and see if it pings...you can prolly run a 35-40 thou gap without a prob...read the plugs to see if you need a hotter plug...prolly stick with what you have for now...popping in the exh can be interpreted several ways...there are lean pops, and rich fuel in the muffler pops...lol...sounds now like you`re describing the latter...see if more timing helps and post back...
 
Discussion starter · #7 ·
MIke
I advanced the timing to 40* and still get some pops, and yes it sounds like detonation in the muffler, not loud bangs, just puts and just once every 30 seconds or so at about 2200 rpm with foot on the gas. Less timing seemed to be worse on the backfiring. I didnt have the problem with my old stock coil, this just started with addition of a CD ignition. I could lean the carb a bit more. Plugs except one cylinder were looking hot, with redish brown tinge on the ceramic. definitley not rich. Any more thoughts appreciated.
Many thanks
Steve
 
1 - 7 of 7 Posts
About this Discussion
6 Replies
2 Participants
Last post:
smiller
Team Camaro Tech
posts
2.4M
members
90K
Since
1998
A forum community dedicated to 1st generation Chevy Camaros owners and enthusiasts. Come join the discussion about performance, builds, restoration, modifications, classifieds, troubleshooting, reviews, and more!
Full Forum Listing
Explore Our Forums
Bench Racing Engine Body Shop Performance Brakes, Suspension & Steering