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what plugs for BB ?

1531 Views 11 Replies 6 Participants Last post by  SWHEATON
I'm running Delco R44T plugs @ .45 gap in my street only BB and have for years. Iron heads, HEI ignition. Time to replace plugs and wondering if anyone has a suggestion for any other brand or gap or am I ok with what I'm using ?
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If the motor is stock or stock build with 10.25.comp pistons going from r44t to r44ts /newer extended tip design is a better choice for sure as Shurkey already stated.

I have used the newer design extended tip r44ts taperd seat design plugs (R44XLS for older heads with longer gasketed 13/16" design )for yrs in the 396 & 402 with 325-330-350-360hp along with 427 low perf(330hp?) and 390hp and 454-365hp motors all being the 10.25.1 comp motors with smaller domed slugs.

The r44t & r44ts are same exact heat range,on diff is non vs extended tip,that's it.

But the extended tip design plugs may be an issue with larger domed 11.0 comp pistons in the stock higher perf 396-375-425hp (65 vette ) ,427-425 & 435 hp & L88,and 454-ls6 450hp bbc's to name a few bbc's so keep that in mind. But if you look up the plug application for the hotter 11.0 comp bbc in a newer ac delco plug cat if it lists the extendedtip design as a plug to use for that application it should be ok,just treying to error on the safe side here with the larger domes hi perf 11.0 comp bbc's when it comes to the extended tip plugs.

But if your not sure of the pistons/comp then i would stay with the r44t plugs since they have been working well for you.

BTW,these older pt# plugs are a hard to come by ut i get them all the time from summit as they still get them from somewhere. I have not had as good as luck with the rapid fires in these 40 yr old design motors so dont waste you time with them for this application,for todays motors that they are designed for they are very good.

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To reclarify,i have been installing the r44ts extended tip plugs in the stock bbc's i already mentioned above running the lower domed 10.25.1 pistons for many yrs with never 1 issue because clearance isnt an issue.

Its the larger domed 11.0 comp setups that i have not tried the extended tip plugs on.

If the mid to late 70's ac delco plug catalogs list the extended tip plugs as service rep then they are fine for that app.

But if GM/AC Delco plug catalog doesnt list the extended tip plugs for any of the the higher perf/higher domed 11.0 comp bbcs (but stilll lists them for the lower perf 10.25.1 comp bbc's ) then in that case i would think the extended tip clearance is an issue with the higher 11.0 comp motors with the higher domes and i would not run them.

Thats quick way to get a bead on if the extended tips were ok for that hiigher perf app .Thats because i think GM would have listed the newer extended tip plugs (for 11.0 comp motors) that were specifically designed with tip more centered in comb chamber/ flame to run a little hotter staying cleaner in traffic . But on the other hand they also run a little cooler when under load (EPS @ WOT) with the additonal fuel & air coming in to cool the tip of the plug too. Its a win win situation eps for a perf motor with more cam etc that typically run's a little dirty/less efficient in stop/go traffic being moreliable to load the plugs up a bit.

Again, i am talking bone stock motors as deliever by gm back in the day ,not motors that have been rblt 1x-2x-3x with who knows what pistons in them

I know the extended tips are also fine with the replacment speedpro L2240NF30 .182 domed pistons that are approx 9.6-9.7 comp in a 396-402 with 063 heads/R44XLS long reach 13/16" & 290 heads with R44TS 5/8" tapered seat & same pistons.

I run the r44xls in my motor with those speedpro pistons and 063's and my friends same setup/pistons in his 396 with 290 heads,both the heads are lrg oval port with small closed chamber design with very roughly 100-101 cc chambers + - few cc for mfg variation which was substantial at times. But these are slightly lower comp/lower domed pistons then stock gm 10.25.1 comp bbc motors had fro factory.

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HI Jim,agree with Schurkey,.045" for plugs.

As far as the ext tip plugs go,the pistons" L2242 .060" i dont see listed in summit as an avail pt# so what size dome are they or compare they supposed to be with the larger chamber 820 heads?

Jim,all i can suggest is that with approx 10.6comp with 109 cc heads i would think that would require larger domed pistons which your seem to be from specs you gave but i dont know that for 100% sure.

So in that case you could buy 1 extended tip plug to test out.

Remove all plugs from the motor,then install the ext teip plug in cyl # 1 ,then spin the motor over very slowly/very gently by hand to if #1 psiton contacts the ect tip plug.

If there is no contact then you are likely ok. But if the std non extended tip AC plugs have worked ok in the past with your setup then maybe to be safe you should stick with them,i believe summit still stocks/sells those too.

But for the bone stock bbcs with stock smaller domed 10.25.1 comp pistons i know the extended tip plugs are ok to run,i have been doing that for yrs now with no issues.

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