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06-07-2014, 10:12 AM | #1 |
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Location: Cincinnati, OH
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What's the best compression ratio for everyday driving
Trying to choose between installing a 5.2 or 7:1 head. Anybody use a 7:1 for 'normal' driving? What are the pros and cons in your experience?
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06-07-2014, 10:55 AM | #2 |
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Location: Temecula, CA
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Re: What's the best compression ratio for everyday driving
it depends on the combustion chamber design. i ran a cyclone head at 7.4:1 for years, with no problems. do not let it detonate (ping) as that is hard on rod bearings.
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06-07-2014, 10:57 AM | #3 |
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Re: What's the best compression ratio for everyday driving
A 7-1 head is totally unnecessary for "normal" driving. The full benefit of that ratio cannot be realized anyway unless other modifications are made as well. There is just no reason for it. IMHO.
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06-07-2014, 11:16 AM | #4 |
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Re: What's the best compression ratio for everyday driving
I do fine with my stock head, but at some point I will install a 5.5 head to see if it helps mileage.
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06-07-2014, 12:40 PM | #5 |
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Re: What's the best compression ratio for everyday driving
If you're not going fast, the lower compression-
if you want to cruise highways, the higher compression with other modifications as well. |
06-07-2014, 01:36 PM | #6 |
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Re: What's the best compression ratio for everyday driving
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06-07-2014, 01:37 PM | #7 |
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Re: What's the best compression ratio for everyday driving
Thought this was interesting...check out the ad from Pierre Bertrand (top right) in the May 15, 1937 Muroc speed trials program;
"Winfield flat head job with Bertrand cam and 6:1 compression ratio holds the record here at the Lakes; 121.62 M.P.H.". Pretty surprising given that Winfield did, at that time, offer a 7:1 head as well; not to mention the Cragar and Riley heads that were popular at the time as well... I suspect that cars with higher CR heads or OHVs were not configured in such a way to take advantage of their 'superior' designs, at least on that day. As has been mentioned, I think the 7.0 head is probably overkill on a typical touring engine. |
06-07-2014, 02:46 PM | #8 |
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Re: What's the best compression ratio for everyday driving
Any head works fine for everyday driving. The original Ford head would give you the 60 MPH.
The real need for an everyday driver is all the rotating parts being well balanced. You also need a great condition cam with properly adjusted valves. Many cars are no wheres near Ford factory specs and this will have substantial effect on how well the car runs and drives. Mix in any of the mellow modern chamber heads and you will have a sweet driver good for 50,000 miles of hard running. |
06-07-2014, 03:25 PM | #9 | |
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Re: What's the best compression ratio for everyday driving
Quote:
I agree.
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06-07-2014, 03:47 PM | #10 |
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Re: What's the best compression ratio for everyday driving
Remember, raising the compression makes it go faster, but it also raises bearing load. I believe in moderation. I went with a Snyder's 5.5 on my T.S. and on my coupe, the head was cut down about .090, for what that's worth (4.6/7?). A 40 HP ain't never going to match that 2013, V12 vomit comet your neighbor has in his driveway. All you can do is make it run a little better.
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06-07-2014, 03:57 PM | #11 |
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Re: What's the best compression ratio for everyday driving
"The higher compression makes cold starts much easier and the plugs do not carbon foul at low speeds."
I never had any problems with cold starts or plug fouling with a standard head. Easiest car I ever had to start at 30 below zero, and that was with the 6 volt system. |
06-07-2014, 04:44 PM | #12 |
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Re: What's the best compression ratio for everyday driving
I think it also somewhat depends on what you are driving. The 4 doors, such as the Town Sedan, weigh significantly more than say a 2 door Coupe or Roadster. The increased power of a 5.5 HC head will help acceleration and hill climbing both in these heavier cars.0
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