My 40 Dodge Truck Build - Maybe a 41 LOL

Rat Rods Rule

Help Support Rat Rods Rule:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
WOW!
Spending the money that was spent the 1st time all over again sucks, but its really good all that crap was caught before it killed the good parts.
I too would be concerned about those 11:1 pistons. Maybe his definition of "pump gas" isn't the same as mine. Racing fuel does come out of a pump, its just not the pump I'd want to have to buy my gas out of.
Yah Bud.....sucks. I didn't pay to have it rebuilt, I bought it in supposedly rebuilt condition but was far from done right. Looking back I suppose the right thing woulda been to open it up but buying from a motor shop I thought I was safe and wouldn't have know good from bad unless it was a crack or something very obvious. I'll be looking into the pump gas.....from the corner gas station that is
 
I just remembered something, isn't the heads on that engine aluminum? If so it most likely can handle the 11:1
The cast iron headed engines cannot run 91 pump gas at 11:1
 
E85 requires a new carb metered for the alcohol
My 392 is 10:1 with iron heads. At 30 degrees of timing I run 87 octane at 36 degrees I run 91
 
I see.... that stuff is all greek to me!
The total timing on a Mopar is deemed to provide the best performance at 36 degrees total advance. If the motor pings at that 36 degrees of total advance, you either add higher octane fuel, or you reduce the total timing until the pinging quits. Reducing the timing generally reduces the maximum performance.

To get those total ignition timing degrees of advance, you start with the degrees of advance the distributor is set at, then add the number of degrees the distributor mechanical advance adds (which is determined by the weights in the distributor), and then add any advance and vacuum advance might add (by pulling the plate inside of the distributor). Generally, the number of degrees of mechanical advance, and the number of degrees of vacuum advance are not adjustable, but they may be delayed or the vacuum can be eliminated (a completely different story). That means the difference in the total timing is usually set by the degrees of the distributor rotation in the block.

His 392 Hemi has 10 to 1 compression and the motor has iron heads. Generally, aluminum heads run cooler in the combustion chamber, so you can get away with more total timing on lower octane fuel.

87 Octane is the level of the cheapest pump gas and his motor does not ping on the 87 octane if the total timing is set at 30 degrees instead of at 36 degrees. He is giving up a bit of top performance, but can buy his gas at any gas station across the country.

91 Octane is the rating of most premium gas available at most gas stations. Some gas stations do not carry 91 octane gas, if they do, its generally 30 to 50 cents per gallon higher priced. His motor does not ping on 91 Octane gas with the total timing set at 36 degrees advanced. He is not giving up any power at that level.

If the "pump gas" the motor builder says the motor will run on is 93 octane, that means the motor will run without pinging on that 93 Octane at 36 degrees total advance. Generally 93 Octane is not available at most gas stations, it is often labeled as racing fuel and carries a much higher cost per gallon, when you do find it. You may be able to reduce the timing enough to get rid of the pinging if you run 91 octane gas, but at how much power reduction? There will probably not be any way you could run the 87 octane gas without some pinging going on, but every motor is different.
 
Thanks.
I've spend a lot of years translating automotive and heavy machine operation functions to people without an understanding of how those functions work.

I often get accused of writing books because most of those translations get wordy. Blame that 12 grade writing comprehension class teacher. She told me I should write stuff as though the people reading it had no idea what I was saying. I've been doing it ever sense.

It really helped when we had to explain to the factory president why a machine he wanted to have running was down.
 

Latest posts

Back
Top