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Anonymous
Guest
what is the highest compression you can go with premium pump gas with out problems?
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Anonymous
Guest
You'll hate my answer..... "It Depends".
Static compression ratio is not the only governing factor. Your cam and the valve timing will also determine the dynamic compression ratio that is achieved. Altitude, ignition advance curve and carburetion etc are all going to determine the limit where detonation is a problem for the particular combination of engine components that your engine is composed of.
Also, what is "premium" gas? The octane ratings of premium gas varies from state to state, city to city, and station to station. It also varies by season in some location not to mention from year to year.
Static compression ratio is not the only governing factor. Your cam and the valve timing will also determine the dynamic compression ratio that is achieved. Altitude, ignition advance curve and carburetion etc are all going to determine the limit where detonation is a problem for the particular combination of engine components that your engine is composed of.
Also, what is "premium" gas? The octane ratings of premium gas varies from state to state, city to city, and station to station. It also varies by season in some location not to mention from year to year.
The "Rule of Thumb" that I have seen in various places is to move the decimal point one place from the octane rating to compression ratio. So a 93 Octane # could be used in a 9.3:1 engine.
I have never "verified" that rule, but maybe others on this board have.
Just remember, its way easier to raise compression (and cheaper) than it is to lower it e.g. milling a head is cheaper than new pistons.
tanx,
Mugsy
I have never "verified" that rule, but maybe others on this board have.
Just remember, its way easier to raise compression (and cheaper) than it is to lower it e.g. milling a head is cheaper than new pistons.
tanx,
Mugsy
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Anonymous
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Well the biggest factor is head design........ with the six the head design is a small inefficent wedge so I am guessing about 9.25:1 on the cheap stuff a little higher with the higher octane and then timing is a huge factor to. on a good set of aftermarket heads I have seen 10.5:1 on 89 octane with 12 initial and no pinging so.....
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Anonymous
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our premium is 91 octane california.
I will probably be running an Aussie 2v head, hooker headers, Holley 350 2 barrel, probably an Isky 204d cam, I value torque more than hp because this is going in a lifted scout 800.
I like compression but I also like lots of valve lift.
I will probably be running an Aussie 2v head, hooker headers, Holley 350 2 barrel, probably an Isky 204d cam, I value torque more than hp because this is going in a lifted scout 800.
I like compression but I also like lots of valve lift.
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Anonymous
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do you think that a 250 with an aussie 2v will hold its own aginst a stock 2 barrel 351 in the same type of car?
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Anonymous
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CAN YOU USE AN AMERICAN CAM WITH THE AUSSIE 2v head?
I have two graphs which I researched from David Vizards work. Absolutely neat stuff. He listed about 13 variables which alter octane sensitivity. Check some work we've been doing, http://fordsix.com/forum/viewtopic.php?t=12838&start=0&postdays=0&postorder=asc&highlight=
but don't got bogged down on the detail. A few graphs will clear it up!
Not getting to big on the details, do like the Ford Falcon six performance handbook says. This is the Talmud for small six performance!
1) Exhast heat stove MUST GO! It needs a port divider to reduce heat soak, that will allow 8 motor octane numbers less for a start according to Vizard.
2) 0 deck the block or use 255 pistons to get a perfect 0 deck. Take a lot of the later head, and get a compression ratio into the 9's. Use the Schendahls compression ratio device.
3) Follow Mark P's advice on the head gasket type, and the amount of decking and high energy Duraspark ignition set-up.
4) Improve the carb arrangement to something that suits YOU. Personalise your engine to how you want it, but do the first 3 things.
I'm pretty sure the Ford 200, 250, and 300 engines often have to run high test because of these 3 things being so amazingly wrong straight from the factory!
but don't got bogged down on the detail. A few graphs will clear it up!
Not getting to big on the details, do like the Ford Falcon six performance handbook says. This is the Talmud for small six performance!
1) Exhast heat stove MUST GO! It needs a port divider to reduce heat soak, that will allow 8 motor octane numbers less for a start according to Vizard.
2) 0 deck the block or use 255 pistons to get a perfect 0 deck. Take a lot of the later head, and get a compression ratio into the 9's. Use the Schendahls compression ratio device.
3) Follow Mark P's advice on the head gasket type, and the amount of decking and high energy Duraspark ignition set-up.
4) Improve the carb arrangement to something that suits YOU. Personalise your engine to how you want it, but do the first 3 things.
I'm pretty sure the Ford 200, 250, and 300 engines often have to run high test because of these 3 things being so amazingly wrong straight from the factory!
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Anonymous
Guest
does anybody think that an edlebrock 500 cfm 4 barrel would flood out a mildly built 250; aussie 2v head, dual outlet headers, 255 flat top pistons, 0 deck, Isky 202D cam 112 lobe center .45 lift, pertronix and flamethrower.
3.73 gears T-18B, 31" tires
DAily driver, fording, mudd, hills, mild performance
3.73 gears T-18B, 31" tires
DAily driver, fording, mudd, hills, mild performance
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Anonymous
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out run a 177 cid bronco2 which is a nice truck.
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Anonymous
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I got these through E-mails to Isky cams and Edlebrock performance:
I asked Isky what is the most you can run on a 250 ford six with their 256 cam
I asked Edlebeock if their 500 4 barrel is too big for a 250.
From Isky
You could run the 700 CFM Max
From Edlebrock
Yes it can be used. Do you have a 500 cfm?
I asked Isky what is the most you can run on a 250 ford six with their 256 cam
I asked Edlebeock if their 500 4 barrel is too big for a 250.
From Isky
You could run the 700 CFM Max
From Edlebrock
Yes it can be used. Do you have a 500 cfm?
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