VP RACING FUEL

[Marc N.]

Good Morning,

anyone out there every use a product by VP Racing fuel/octane power booster...sold in califoria stores / long black bottle. says it contains "petroleum distillate methyl cyclo prntadenyl manganese tricarbonl (MMT).....advise if you know this product. thanks, marc

[Duke W.]

Re: VP RACING FUEL

MMT is an octane enhancer, but the amount in a 12 or 16 oz. can is probably not enough to create a meaningful increase in the octane number of 20 gallons of fuel.

The best what to increase octane, if your engine pings on the best available pump gas, is to blend in some high octane race gas or 100 LL avgas. Through experimentation you will find the minimum quantity.

Many SHP 327s are detonation free on pump premium, but SHP BBs have a bigger octane appetite because of their larger bore.

Duke

[Gary Wilkerson]

Re: VP RACING FUEL

My L76 has later model heads which I belive ended up putting me at about 9-9.5-1 CR.
Will a stock L76 with 11-1 run on todays pump gas without pinging?

Gary

[Duke W.]

Re: VP RACING FUEL

Based on owner reports, it appears that most will. A L-76 with the Duntov cam may have a bit more tendency to ping due to its earlier closing inlet valve/higher dynamic compression ratio. The L-79 dynamic CR is about the same.

The 30-30 or LT-1 cams yield a lower dynamic CR because of their later closing inlet valves so they will be a little more detonation resistance at the same CR.

When rebuilding an engine is is very important to manage the build to achieve a target CR of no more than 10.5:1 for a SHP SB and about 10:1 for a medium performance version. This is usually no problem with the OE type replacement pistons and a composition head gasket, but you need to take all the relevent measurements such as block deck to piston crown clearance, and this should be done at DISASSEMBLY, so you can start working the CR issue. If you use the OE replacement pistons, the deck heights on the reassembled engine will be about the same, so you select a gasket to achieve the target CR.

The decks are usually "straight" i.e. parallel to the crankshaft centerline, so measured clearance should be fairly consistent down each bank, and any lack of parallelism will be evident. It's not uncommon to have a few thou difference between the banks. If the LH side is high you can mill it down to equal the RH side. Of course, you don't want to touch the RH side if the original data stampings are still there, so if the RH side is high, you can use a slightly thinner gasket.

With no more than the above specified true CRs for a small block, any detonation can usually be tuned out with minor ignition map changes.

Duke

[Joe C.]

Re: VP RACING FUEL

Gary:

Here is my testimonial:

1. I live in NJ, so the hi-test that I use is probably "better" than some others, i.e. California. I use no additives, and use run-of-the-mill premium, like Getty/Hess/Raceway. I don't bother using the 93/94 octane brands like Sunoco, nor do I need to. Of coures, I do most of my driving at sea level. My engine does not detonate, even if I try to initiate it.

2. When I built my engine, I carefully measured everything, including chamber volume, ring land volume, deck clearance + COMPRESSED head gasket volume, and piston dome volume. I used these numbers to calculate C/R for each cylinder. The actual compression came up around 10.6:1 +/- .1 .

3. I installed the 30-30 cam, which is reproduced by Federal Mogul. I installed Federal Mogul forged aluminum "11:1" pistons.

4. When Chevrolet marketted these engines, they tended to exaggerate the C/R, as well as the horsepower/torque. The "as advertised" C/R of 11:1 was actually more like 10.75:1.

5. Additionally, I am running a stock "069" distributor, which I rebuilt with the stock vac can, and a stock timing curve (which I checked against the spec sheet). I currently run 14 degrees static timing, which is four degrees ahead of the L76 spec, and two degrees ahead of the L84 spec.

Hope this helps. This is just my experience. Others may not have been so lucky and/or careful.

Joe

[Gary Wilkerson]

Thanks Joe! Clears up my misunderstanding! *NM*