concerned about compression ratio
Fleet Mechanic
Joined: Sep 2003
Posts: 1,716
Likes: 15
93 here. Your octane rating method may be different in the land down under (oh no, now I'm humming that song!). IIRC, the present US Octane rating system is Reseach + Motor, divided by 2. In other words, average the numbers that the two methods give.
Didn't oz have monkey troubles?
Didn't oz have monkey troubles?
Freshman User
Joined: May 2003
Posts: 42
Likes: 0
From: sydney,australia
Oz is "the land down under"or as my friends call it "god's country" australia.
So torky you've heard about the politicians in australia then. lol
I'm pretty sure we run the same formula for octane as the US.(not 100% sure though)
Aaron,
So torky you've heard about the politicians in australia then. lol
I'm pretty sure we run the same formula for octane as the US.(not 100% sure though)
Aaron,
Elder User
Joined: Nov 2002
Posts: 526
Likes: 0
From: Spokane WA
I am running 9.5 cr with mild port, polish and gasket match, stock exhaust and Motorcraft carb. I have been able to run on 87 Octane but had to retard a fair amount to only get slight pinging when lugged down.
Running on premium(91 Octane) it difinately runs very smooth and strong.
I can only break the tires loose in 2nd gear(A 4 spd NP with 4:10s)
I am getting a back fire(I think through the carb not the tail pipe) and will be putting in new points and setting the dwell next weekend. This backfire occurs sometimes when the foot goes to the floor and the secondaries kick in. The secondaries don't always kick in smooth, sometimes faulter alot, once in a while a backfire.
Any thoughts here?
Running on premium(91 Octane) it difinately runs very smooth and strong.
I can only break the tires loose in 2nd gear(A 4 spd NP with 4:10s)
I am getting a back fire(I think through the carb not the tail pipe) and will be putting in new points and setting the dwell next weekend. This backfire occurs sometimes when the foot goes to the floor and the secondaries kick in. The secondaries don't always kick in smooth, sometimes faulter alot, once in a while a backfire.
Any thoughts here?
Senior User
Joined: Jan 2002
Posts: 492
Likes: 0
From: Spokane WA, USA
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Cargo Master
Joined: May 2001
Posts: 3,208
Likes: 13
You need to figure your altitude in to this deal also. At sea level a 10.5 to 1 engine will have problems with detonation on 91/93 octane fuel at 4000 ft or higher it will run on 87 octane no knock. I don't know the exact formula but for every so many feet of altitude you lose 1/2 point of effective compression. As for lead substitue. If an engine has ever had leaded fuel ran in it. The residual lead will protect the valve seats indefinitely. If an engine is not constantly ran under heavy load it will take a long long time before any valve seat damage to show up. And any Ford engine built in 1972 or later was designed to run on low/no lead fuel IE: harden valve seats
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