Guest Posted May 9, 2002 Share Posted May 9, 2002 Would anybody know the gap to use for a set of world big block grumpy jenkins cast iron heads using champion 670 plugs. Thanks Link to comment Share on other sites More sharing options...
Guest Posted May 9, 2002 Share Posted May 9, 2002 Even if you are using a MSD type IGN system keep the gap at .035". In the late 80's GM sent out T.S.B.'s instructing all dealers to change plug gaps from .045" back to .035", IT took them 15 years to figure out what racers have known for years, IT'S NOT THE SIZE OF THE SPARK KERNEL, IT'S THE INTENSITY OF THE KERNEL THAT COUNTS. When we speak of a hotter spark it means more intense not just bigger. Also the higher the compression the harder the mixture is to ignite, thats why blower motors run gaps as small as .020". Don Link to comment Share on other sites More sharing options...
Guest Posted May 10, 2002 Share Posted May 10, 2002 Thanks ------------------ Jason's 1971 Monte chicagorodfathers.tripod.com Link to comment Share on other sites More sharing options...
wallaby Posted May 10, 2002 Share Posted May 10, 2002 Agreed. There was a period when specs called for gaps as large as .060 with HEI systems, but it was found that the increased amperage required to fire the plug was destroying the cap, rotor, and wires. It was not uncommon for the .060 gap to widen as the plug aged, and the spark found it easier to travel straight down through the rotor, to ground on the distributor shaft. There are still spark plugs listed for these aplications that are " extended gap". The plugs come with a gap of about .060 right from the box, and I was told that it was not a good idea to close them down too much, because the ground electrode gets too bent in the process. Instead, use a different plug that starts with the gap you want. Link to comment Share on other sites More sharing options...
wallaby Posted May 10, 2002 Share Posted May 10, 2002 By the way, I have the same heads on mine and had some bad experience with them. I have it sorted out now, but did it all the hard way. Link to comment Share on other sites More sharing options...
Guest Posted May 10, 2002 Share Posted May 10, 2002 Thanks for the info What problems are you talking about, I have not installed mine yet will do so next weekend. I will be grateful for any assistance advice you can give. ------------------ Jason's 1971 Monte chicagorodfathers.tripod.com Link to comment Share on other sites More sharing options...
astrochimp Posted May 10, 2002 Share Posted May 10, 2002 Anybody else thinking that he shouldn't be use CHAMPION plugs? I have never heard a good thing about them in my entire LIFE Link to comment Share on other sites More sharing options...
wallaby Posted May 10, 2002 Share Posted May 10, 2002 I run autolite. Are we talking about World Products merlin cyl heads? I have them, and the initial build quality was poor. They were still loaded with casting sand, and the valve to stem clearance was tight in some, and excessive in others. I had bought them assembled, and just figured I could bolt them on and go. First day, I was towed home with a bent pushrod, and a broken rocker arm. I got that fixed, but soon after I began to burn LOTS of oil. The car would put out a thick cloud of smoke while I waited for a stoplight. I was too embarassed to run it that way, so I tore it down for new valve seals. ( the heads came with umbrella seals....not too good). The guides had to be honed to size, then diamond knurled, and teflon positive valve seals installed. The machinist said this is a common problem with World Products heads because their quality control is not good. He also said the cylinder heads make good power, but it is best to buy the heads bare, and have someone reputable assemble them. Link to comment Share on other sites More sharing options...
Guest Posted May 14, 2002 Share Posted May 14, 2002 The best plug I've used in years are the v power NGK's. I have seen these fire when soaked in raw fuel!! Even in high copmression race engines they last a lot longer than any others even the $4.95 each champion race plug's!! NAPA auto stores sell the NGK's hear at about $1.98 each, remember the heat range #'s on the ngk's is different, their number would be like r5764-3 the -3 is the heat range 1 is hottest and 10 is coldest. start out with a 3 and work fom there. Don [This message has been edited by Rice Racing1 (edited 05-14-2002).] Link to comment Share on other sites More sharing options...
kc8oye Posted June 15, 2002 Share Posted June 15, 2002 Quote: <font face="Verdana, Arial" size="2">Originally posted by wallaby:Agreed. There was a period when specs called for gaps as large as .060 with HEI systems, but it was found that the increased amperage required to fire the plug was destroying the cap, rotor, and wires. </font> hehe, my '94 oldsmobile runs .090 gaps. (DIS Tho) Link to comment Share on other sites More sharing options...
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