LOTSARED

Recommendations appreciated --
After pouring much $ into the rebuild of my L36 big block, it is now "pinging". Adding 2-3 gallons of 110 octane race gas to a tank cures the ping & makes it happy. BUT... too expensive and hard to find.
Do any of the octane boosters work? I've tried a couple of brands with poor results. Any recommendations much appreciated.

Background -- Original 427/390 was completely rebuilt by reputable builder. Milds mods, Edelbrock Performer RPM heads, Comp Cams "Thumpr" cam, 454 crank, stock intake, carb, & exh manifolds. I'm not sure of compression, but I believe it's around 10:1.

cottoneg

I had a 350/350 that had the heads taken down twice and used to ping on high test. When I rebuilt the motor, even though they were forged pistons, you could see the chips from detonation.

I never found an octane booster that worked and used to rely on racing gas. Now that I have a new motor, I did the same thing. Get the compression ratio down to be able to run pump gas.

Shark Racer

Have you tried pulling timing? With aluminum heads and a decent cam, 10:1 shouldn't be that bad at all.

Check to see what your max timing is at, it could be that you're going beyond what you need.

FYI, I looked at the cam cards - even for the weakest "thumpr" I could find, you shouldn't be pinging on that combo. (at 10:1)

billla

At 10:1, it's likely not an octane issue if you're runing premium unleaded.

I'd go back and find out FOR SURE what compression - and what quench - was attained for the build. I'm still surprised at the number of engine builders that don't provide a detailed "build book" for their engines...something I always do.

Otherwise, I agree that I'd start by looking at the timing curve before looking for an octane booster. The Thumpr in particular should help the situation as it has a ton of overlap at idle to give a "rumpty" sound.

Vette5.5

What you're doing adding racing fuel's, really the best way. Torco claims to be concentrated race fuel, but never acually tried it, and not cheap. Another biggie, is how longs the present gas been sitting in the tank, as loses octane rating over time, such as sitting for 4 months over winter.

69 Chevy

Not surprising as the Feds have regulated all the good stuff out of existence. I had good results using 104+ Octane Boost. But that was the old formula not found anymore. You could always try retarding your timing a smidgen.

billla

In the past, I've also tried using 100LL aviation gas without much affect.

The 104+ stuff gives a point, maybe, per tank - just not enough to make it worthwhile.

cv67

Listen to billa on this one

Canned stuff like hes talking about is junk.

Look into why its pinging not how to cover it up
Stiches>bandaids

bluedawg

I agree with timing being the suspect cause. I've never tried it but have heard taluline used in small doses boosts octaine, there's always e85.

fugawi

i used 100LL avgas in my stock motor with 11.1 compression. worked great. just add 1 gal per tank. less expensive than racing gas. 104+ is junk. it's just marketing bull.

Tim H

I have put a pint of lacquer thinner in 10 gallons of 93 octane gas before and it runs really well!

shmoky

GREAT question lotsared. I need to pack some octane boost with me so when I get to a gas stationa and HAVE to buy gas and they DON'T have premium I can add the boost. I usually buy the minimum amount of regular + boost to just get me to the next gas station so I CAN buy premium and then fill up to the top.

I have been using NOS Octane booster -- street formula. Says "Increases octane effect as much as 3 points"
Use all 355 ml (12oz) for a 60 litre (16 gal) tank of fuel.

Here's a picture of the can.



What does anyone else use?

shmoky

v2racing

I agree with finding out why it pings and fixing it. Octane boosters in general are a scam. I know people in that business. The points of octane increase they claim is not a full point such as raising from 91to 94, but in .1 points. If it says on the can it will raise the octane 3 points, you will go from 91 to 91.3. Xylene and toluene will work as boosters, but it takes a lot of either one to produce results. Boosters with MMT will work better, but the level that is allowed by the EPA for street use in not high enough to do much. There are race formulas with much higher levels of MMT, but they will eventually foul your plugs with a reddish deposit from the manganese,

dennis

AV 100 octane LL or max lead 2000 to sunoco ultra. Only 2 things my 11to 1 liked until I tweaked the heads and timing. Now just ultra works no ping

U17

Be careful with the 100LL ... I don't even run that in my plane... Several times the lead in it than mogas...

7t9l82

its timing related more than likely the chamber design is better in your new heads and needs less timing. you will find better performance when you get your curve right

corvette_maniac

As stated above, check the total timing ... at what RPM is ALL of the mechanical advance in? Are you having hot start issues? If the answer to those questions are unknown, you could just be putting a band aid on a tuning issue. Is the fuel mixture and APT adjustment right on that q-jet?

TheSkunkWorks

IMCO this might be worth a read...

http://volvospeed.com/Review/misc_pe...celerator.html

Manuel Azevedo

As most have said a timing issue most likely. But also check the jetting to be sure your not to lean, to lean will also have the same effect as to much timing.

Vette5.5

While never actually tried it, people on other forums, swear Lucas Real Octane Boost racing formula works. It's about $8 bucks for a 15 oz bottle though.