Scott,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.
Would the extended tip plugs work with my 396 with "820" heads and closed chamber L2242 .060 pistons?
I'm also unsure about the gap...running an MSD dist, box, and coil.