I'll add - just clearance the block. Give yourself .100" clearance and move on. Ive done probably 20 over the years. Some making 1.7hp/inch with the nitrous. The bottoms of the cylinders are not what one worries about.
Thank you very much... that's the experience that is priceless and is very much appreciated. I'm going with SCAT or Eagle rods anyway so that will help lessen the interference.
FWIW, I did run across this on the gels and substitutes; the source link is included.
"The stuff we use (ECHOTRACE 9000) is water based so it is easier to clean up. Generally speaking most silicone oils & gels, greases, Vaseline (pariffin) and even some hair gels etc can be used if the temperature is not sufficient to make it run out from under the transducers and or be workable in overhead applications. I have found that good quality high temp wheel bearing grease is usually a suitable alternative. Glycerin can give a few extra dB of coupling (it can sometimes help obtain useful readings when there seems to be no reason why it won't work) as it's acoustic impedance is similar to plastics, but it can cause corrosion and or rusting so it must be completely removed." Ultrasonic or Acoustic Couplants and Alternatives - wiki
