RMC List - Octane boost question

Tue Apr 28 16:18:47 EDT 2026

Dieseling is usually the result of a timing issue in relation to the octane
fuel you are running.

While not on my Corvair, I had this issue with an old pushrod Volvo that
had a real flame flower engine under the hot.  Hotter cam, bigger pistons,
etc...

If I adjusted the timing to avoid dieseling, it would ping from time to
time under heavy load.

Ultimately I adjusted the timing to avoid pinging, yield the best power,
and just learned to slip the clutch when turning the car off.  (I'd put the
car in 2nd gear, slowing let off the clutch while also stepping on the
brake while turning off the ignition.)

Perhaps not the most eloquent solution, but it worked.  I suspect it would
also work on the Corvair.

All this goes out the window if you have a Powerglide though.

Kindest regards,
--
Dylan Berichon
IHeartMedia Denver <https://www.iheartmedia.com/>
Oregon State Beavers Broadcasting <https://osubeavers.com/>
Learfield <https://www.learfield.com/>
(503) 427-8305

On Tue, Apr 28, 2026 at 5:05 AM Garrie Fox via RMC-List <
rmc-list at corvair.org> wrote:

> Interesting!
>
> I owned a '65 180 convertible Turbo which I sold at the Flagstaff National.
>
> I never had a detonation problem after I added a Dale Mfg Turbo
> retard/advance  unit.
>
> I ran colorado base fuel Octane.
>
> There is a long uphill run on HWY 94 east of the Springs. I always used it
> to check Turbo Boost.
>
> If it was running well, the gauge indicated 14 +or more.
>
> I bought Marlyn Lyles. PPCC member, 66 Aztec Bronze 180 Turbo for the
> storage fees owed in the 90s
> He stated that the Corvair Blew Away the Big Mustangs going west our of
> Denver to the Continental Divide.
>
> I will admit to using aircraft 100 octane aircraft fuel. But only once.
> It was available with  credit card at a El Paso County airport.
>
> It was for a Binion FI car that I still have.
>
> I also determined on that runway at night that a Binion FI Corvair red
> lined at 119 MPH. The '66 Sports Sedan had a 3:27 diff ratio.
>
>
>
>
> Regards,
>
> Garrie Fox
> 719.338.5051
> (texting not available)
>
>
> On Monday, April 27, 2026 at 11:00:33 AM MDT, Eric Schakel via RMC-List <
> rmc-list at corvair.org> wrote:
>
>
> Michael,
>
>
>
> I’m curious about the rpm and load where your Spyder detonates. I had a
> couple of 180 turbo Corsas in my youth, and recall that even with the 98
> octane leaded ‘Hi-Test’ of the era, there was always a little buzz of
> detonation on throttle tip-in. I initially addressed it by opening the
> passage to increase the accelerator pump shot.
>
>
>
> Turbos are an awesome secret weapon. Linae’s Mazda CX-5 has a turbo 2.6
> four, and the thing runs a quarter-mile as quick as my 1971 455 Pontiac
> Trans Am!
>
>
>
> Eric
>
>
>
>
>
>
>
> *From:* Michael Brittan <mibrittan at gmail.com>
> *Sent:* Monday, April 27, 2026 9:17 AM
> *To:* gearhead066 at gmail.com
> *Cc:* Rick Beets via RMC-List <rmc-list at corvair.org>
> *Subject:* Re: RMC List - Octane boost question
>
>
>
> Hi Eric,
>
> Now you're talking!  A 140 with 10.4:1 compression and a turbo.  In the
> interests of Corvair science though, you'll have to run the experiment on
> two cars - one with fuel with ethanol and one without.
>
> FYI, a can of VP Racing Octane Booster (purchased at Walmart) added to a
> full tank of ethanol-free 87 gas took care of the detonation on my Spyder.
> This can was the cheaper of the VP options so I'm not sure if it contained
> alcohols.  The can blurb did not provide the ingredients.
>
> Best,
>
> Michael
>
> Michael
>
>
>
> On Sun, Apr 26, 2026, 10:22 PM <gearhead066 at gmail.com> wrote:
>
> Michael, for what it’s worth, I’ve ignored all warnings and online threads
> talking about detonation and engine wear and simply used standard Tier 1 91
> octane pump premium with ethanol at Denver’s altitude for years. I dislike
> the hassle (and occasional clothing disaster) of diddling with octane
> boosters and fuel additives. Even in engines with cylinder heads milled to
> raise compression to a true 10.4:1 range, detonation and wear have not been
> issues. I can’t comment on a turbo engine at this point, but I’m thinking
> of tossing a turbo onto a set of 10.4:1 compression 140 big-valve heads to
> see how long it takes to melt the piston tops. If I do that and ethanol
> helps with piston top life, I’ll let you know!
>
>
>
> Eric S.
>
>
>
>
>
> *From:* RMC-List <rmc-list-bounces at corvair.org> *On Behalf Of *Michael
> Brittan via RMC-List
> *Sent:* Friday, April 24, 2026 1:47 PM
> *To:* rmc-list at corvair.org
> *Subject:* RMC List - Octane boost question
>
>
>
> Hello All,
>
>
>
> I like to use only non-ethanol gas in my cars (Spyder and 2x164/110
> Monzas).  87 non-ethanol is available in my area of SE Denver at a
> reasonable price.  Preferred 91 octane non-ethanol is available at the
> Mobil station in Lakewood, but at a huge price premium and a 30-mile
> round-trip (+- 2 gals of gas consumption right there) from my home.
>
>
>
> I can eliminate the pre-ignition with expensive octane booster containing
> MMT.  Cheaper brands contain alcohols, so defeat the purpose of using
> no-ethanol gas and don't raise the octane as much per ounce of dosage.
>
>
>
> I'd welcome members' views on using such octane boosters and whether they
> may have preferred brands.  Could any harmful side-effects be experienced
> with our trusty Corvair engines using these boosters?  What do members feel
> about using standard pump 91 octane containing ethanol?
>
>
>
> Best,
>
> Michael
>
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