Octane and lubricant question for drag engine

[Motv18]

Sounds good would you try 108 or think it’s to low?

[Jay Smith]

IMO it would be according to the compression, timing , altitude , load , distance of pass and rpms engine turning during load applied ... When I was racing I made a pass durning tuning session I’d make the pass kill it clean , roll # 5 to bottom dead. center and with a bend o light look at the vapor wash at intake side of piston if it’s dry it’s lean , it the vapor moisture travel across that piston the distances of a dime it pretty close if it’s the distance is a half dollar or half way across piston the motor is loosing power by being too rich ... That the way I tune my engines ( multi time World and high point champion 1400 modified class winner )

Jay @ JSRE

[99fxst99]

​Interesting thread! Kudos to Jay Smith for his forthcoming transparency with the information he shares.

[Jay Smith]

I don’t mind sharing any knowledge I’ve gained building these things and will admit some of the knowledge gained is by failures , back in those days a piston was $65.00 and plenty of blocks and parts now you can’t find good blocks that’s not tampered with or full of welds , problem with tons of welds is the line bore straightness gets out of wack and that motor will NEVER be competitive...

Jay @ JSRE

[nitro_rat]

​Interesting thread! Kudos to Jay Smith for his forthcoming transparency with the information he shares.

Jay has shared tons of good information over the years! If you search his posts you will find that he has in fact shared almost everything you need to know about building a merc 2.5!!!

[Chaz]

I recon someone needs to break the bad news to all them ProGas and Outlaw World Champion's with moved port motors by way of weld and epoxy, that they will never be competitive ...

Chaz = thinking, so many machines ... so few welders

[Jay Smith]

No problem folks thanks , I’ll help anyone anytime I think that’s been apparent over the years of near 12,000 posts for 20 + years I’m as close as your phone , and if I don’t know how to fix issues I have an arsenal of folks I can call on for informational help ...

God bless all ,
Jay @ JSRE