Posted By: BradH
Is this combination 93-octane friendly??? - 02/04/10 08:21 PM
NOTE: This post picks up where my "C.R. / Quench / Cranking Pressure dilema" threads leaves off.
Let's talk real-world exprience and whether the following combination will be able to run on 93-octane fuel. I'm basing a purchase decision on it and have some concerns.
RB Short block:
4.360" x 3.75" --> 448 c.i.
Flat-top pistons at zero deck height
Heads:
Edelbrock Victor (heart-shaped chamber)
.040" quench
Calculated CR = 11.1:1
Cam:
Comp Xtreme solid street roller
298/304 at .015", 260/266 at .050", .627"(1.6)/.597" (1.5)
LSA 108, installed straight up
Lash spec = .016"
My Engine Analyzer Pro simulation program says this combination should crank 199 psi and will definitely be in the "detonation danger zone" running 93 octane.
My real world experience is that my 452 w/ 10.8:1 CR and a 298/298 at .020", 266/266 @ .050", 108 LSA solid flat-tappet cam installed on 106 ICL has been running OK on straight 93 octane. But the extra .3 in static compression AND the shorter cam duration could definitely change the dynamics of the situation. There's probably 15 psi difference in cranking pressure between the two.
Is my simulation program spouting bogus data in this situation? I don't place 100% faith in it, although it's given me valid data for trend analysis, etc., before. And if the cranking pressure estimate is accurate, does the rest of the combination still look "93 friendly" due to the chamber design, quench height, etc.?
Let's talk real-world exprience and whether the following combination will be able to run on 93-octane fuel. I'm basing a purchase decision on it and have some concerns.
RB Short block:
4.360" x 3.75" --> 448 c.i.
Flat-top pistons at zero deck height
Heads:
Edelbrock Victor (heart-shaped chamber)
.040" quench
Calculated CR = 11.1:1
Cam:
Comp Xtreme solid street roller
298/304 at .015", 260/266 at .050", .627"(1.6)/.597" (1.5)
LSA 108, installed straight up
Lash spec = .016"
My Engine Analyzer Pro simulation program says this combination should crank 199 psi and will definitely be in the "detonation danger zone" running 93 octane.
My real world experience is that my 452 w/ 10.8:1 CR and a 298/298 at .020", 266/266 @ .050", 108 LSA solid flat-tappet cam installed on 106 ICL has been running OK on straight 93 octane. But the extra .3 in static compression AND the shorter cam duration could definitely change the dynamics of the situation. There's probably 15 psi difference in cranking pressure between the two.
Is my simulation program spouting bogus data in this situation? I don't place 100% faith in it, although it's given me valid data for trend analysis, etc., before. And if the cranking pressure estimate is accurate, does the rest of the combination still look "93 friendly" due to the chamber design, quench height, etc.?
