Thursday, August 11, 2011

Correct spark plugs for AFR Big Block Chevy heads.

I've been battling this mystery miss with this engine since my Camaro hit the road last fall. While I've managed to tune the carb many times, often getting better results each time, I have never been able to rid myself of the annoying miss. That all should change in a few days.

Dumbfounded, I questioned what is left to try? In my mind, the spark plugs were one of the few, if not THE only variable left that could be causing the problem. I turned to the net, to see just what was recommended for my AFR heads. The first site that came up was from AFR's FAQ page for big block Chevy heads. Considering I've been battling this miss since last year, it should come as no surprise that one of the last variables I'm down to appears to be the solution.

The first line regarding spark plugs states "All AFR BBC heads accept spark plugs with a flat gasket seat and washer (not the tapered seat style) and a .750 long reach." Having bought a second set off the shorty Accel plugs, I didn't even have to remove one from the engine to confirm my suspicions, as the Accel plugs were in fact tapered.

Without a proper seat, these plugs likely have been causing numerous problems. A lean condition, the occasional backfire at idle, caused by an exhaust leak, not from the headers, but from the plugs, something I hadn't considered. The engine miss going down the road is almost without a doubt caused by these incorrect plugs. During my couple test drives today, with everything else seemingly spot on, I had already raised an eyebrow at the plugs...it only took me a year!

I called the local parts store, though doubted they would have the plugs in stock, since they are a race plug. I wanted to pull the guy through the phone when he asked "what year car is it for?" I had already gave him the part number I was inquiring about, and when he found it, they would have to come from the warehouse and it would be on Saturday. Saturday would be fine, though I figured I may as well order a set of header gaskets, since I've removed the passenger side header just enough to remove the plug a few times now. I'm pressing my luck, and the last thing I want to listen to is a header leak ticking away.

I logged into Jeg's, found the Autolite AR-3935 plugs that AFR recommended, a set of AFR header gaskets, and checked out. The parts will likely get here on Saturday, and by the end of the weekend or early next week, my car should be running better than ever, and engine miss free!


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