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Compression Ratio on the Street

April 22 2012 at 3:56 PM
Rob  (Login Robenstein45)

So I am getting ready to put my 390 together and am going to sit down and order parts soon. Being this is my first FE motor I was wondering what compression ratio I can get away with on the street using 89 octane gas. Im using Fairlaine 390 GT heads on this motor. Now in the past on my Chevy motors I usually could get away with 10:1 compression but I thought I read somewhere that FE motors are a little more prone to detonation.

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(Login x4rdtech)

Re: Compression Ratio on the Street

April 22 2012, 4:58 PM 

If you are going to run more than 9.5 then you will need 93 or what you can get in your area.jmho of course.

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Wes Adams Ford428CJ
(Select Login ford428cj)

You should be fine~

April 22 2012, 9:20 PM 

I ran 11to1 in a 4x4 (About 5,000lbs) with a 4spd. Ran pump premium.... JMHO

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(Login TorinoBP88)

In a fairlane? What cam? What intake?

April 22 2012, 9:35 PM 

With proper ignition timing and cam timing, you should be fine.

Make sure you intake valves are not sunk into the head too far, that will make them run hot and ping.

Here in california, gas is bad, so i would recommend 9.1 to 9.8 for a driver, 9,75 to 10.2 with a hotter cam, over that you have to be very careful or have a reduculus cam for a driver.

1964 Galaxie 4Dr Sedan, 289, 3spd (re-installing OD soon), a Texas Sargent's Personal Car
1967 416 GT engine, BIBO Wide R TL
1968 428 'C', '69 SCJ heads, Gal Wide R TL

Oh and a Bicycle daily driver.

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(Login Robenstein45)

Re: In a fairlane? What cam? What intake?

April 24 2012, 2:57 AM 

No its going in a Model A coupe street rod in front of a C6. Cam is going to be an Isky 264 Mega hydraulic cam and it will have a dual quad Edelbrock intake with two 500 cfm AVS carbs unless I come up with the extra scratch to get a factory tri power setup between now and then.

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(Login 65pony)

Compression Ratio and Gas

April 23 2012, 4:56 AM 

To hijack the thread, what brand gas do you guys prefer? National brand or regional brand? Any additives you run with higher compression?

I am working toward a Fairlane with 427 and my brother is looking at a 66 Cyclone GT like he had new, 390 and C6. The 390 specifications says 10.1 compression and the 427 calculates to 10.5.

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(Login Noble1Tech)

Re: Compression Ratio and Gas

April 23 2012, 10:00 AM 

My S code 390 in a 68 Torino liked Sunoco 93.5 back in the early 90's. I see the local 66 station's premium is 93 vs 91 most everywhere else in central Ia.
I'd have to look again, but I believe the owner's manual says use 100 minimum.

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(Login Robenstein45)

Re: Compression Ratio on the Street

April 23 2012, 8:35 PM 

Well around here 91 and some 92 is available. Usually I use Shell or CP gas in my cars locally. The valves will have a good valve job with new hardened seats and stainless valves.

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(Login chris401)

Central Texas daily driver

April 24 2012, 11:09 PM 

My FEs have done well with 9.5 to 10.1 using Cheveron 93. Others are good too but they dint like the Fina for some reason.

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