The Stovebolt Site Forums The Shop Area Engine Shop sparkplugs for 235

Hi guys,

What sparkplugs & heat ranges is everybody running in their warmed-over 235s? Mine is gonna have the Holley 390, clifford, fentons, shaved '54 head, HEI, Howard M4F cam, flattops punched .060" over.

How about jets? I was running 54 jets and a 6.5" power valve in my Holley 390.

thanks,

chiphead

Hello? Anybody awake today? C'mon guys, I don't want to detonate or run lean. Then you guys would have to listen to me b*tch even more....

All I know is you need six, sorry.

I think the AC plugs for that engine with a normal ignition system was an R45. These plugs are the same plugs that were in my old 68 Chevelle with a 307 which had a 9-1 compression ratio so they should do OK in the 235. If you plan to run at full throttle a lot you may wnat to go to a colder plug but you would have to be pulling alot or running really hard to damage the plugs or bet preignition. You said you shaved the heads but you didn't say if you did it to increase comp ratio or just true them up. If your at 8.5-1 comp ratio or less you'll probably be OK. I don't know if these old plugs will stand up to the higher voltages of HEI or not but your local speed shop should be able to help you there The bigest problem with taking an old engine to HEI is the original style spark plugs are set up to have the gap set at about .030 inches and are manufactured so that the ground bar on the tip parallell with the flat portion of the electrode tip. HEI gaps are usually .045 to .060 which gives a much higher voltage and higher energy spark but an old plug set at this gap will not be parallel with the electrode so it won't work as well. A speed shop could probably help you wit this especially if you can find one that has an old timer at the counter that used to run the old Chevey's. Remember chevy had a 302 in the Z28 Camaro that was rated at 290HP at about 3200 RPM (because if it was rated at 300 + HP the insurance would be outragious) with a redline of 7500RPM. The true HP from factory I heard was somewher over 400HP and this was with a points type distributor. Of course that was when they had Ethyl fuel and a 12.5 - 1 comp ratio.

IN MY 5-4 THIS SUMMER I WILL STIL USE THE SAME AC 45 PLUGS THAT WERE IN IN WHEN I INSTALL MY HEI. I PLAN ON GAPING THEM AT .060IN. AND WILL SEE WHAT HAPPENS THEN. ALWAYS LIKE USING NON-RESISTERED PLUGS IN THE OLD STUFF (SNOWMOBILES INCL. ), JUST SO PEOPLES T.V.S AND RADIOS GET A LITTLE STATIC. WHEN I DRIVE BY

My '54 head is shaved about .030". I was running R45s, but the insulator was bone white. I went from 51 to 55 primary jets, and used different heat ranges and plug types. The plug color didn't change. Always whiter than a sheet of typing paper. My exhaust pipes were black though. Its hard to tell if I was lean or rich, or if the plugs were too hot or OK.

When I pulled the head for the rebuild, the exhaust valves were between black and chocolate. Piston crowns were sooty/flaky, but not pitted or anything. Engine had 10 K miles on it when thrust bearing pounded out.

Would the plugs for an early-model 250 with HEI work in a 235 head? I ask because it would be nice to get the same heatrange with a stock gap of .045".

Thanks
chip