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Old 09-04-2013, 08:58 AM   #1
Dragsinger
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Default gasoline vs Methanol combination specific

It has been suggested that with this particular combination [SBC with 2.0 + horse per cubic inch with carburetor] gasoline may be a better choice than Methanol. This is a 420 CI SBC, Brodix aluminum block, drag race package making about 860 - 870 horse and operating between about 6800 - 8300 RPM with about 15:1 compression.

Let me hear about your experience.
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Old 09-06-2013, 01:13 AM   #2
Greenlight
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Default Re: gasoline vs Methanol combination specific

I will give you my opinion, based on what others have told me. I have never personally run an alcohol vs. gas test.

To make 870 HP you need about 1200 cfm carburetor dry flow when running on gasoline (give or take a little). To make 870 HP on alcohol you need about 1320 cfm dry flow.

I think the reason many people experience really good low and mid range torque (and therefore quicker 60' ET) with alcohol, but claim less 1/4 mile MPH (and perhaps slower 1/4 mile ET) is because the single 4 bbl. carb. that they are using is too small for alcohol. This is especially true with your specific combination of a 420 cid engine making 870 HP with a single 4 bbl. carburetor. You simply can't find a carburetor big enough (that meters and atomizes the alcohol correctly). On a single 4 bbl. manifold the excess fuel (alcohol vs. gas) can't turn the sharp corners as well and comes out of suspension. It's generally harder to get good mixture distributions (even exhaust temps.) with alcohol on a single 4 bbl. manifold.

When alcohol vs. gasoline is used on a properly sized IR system the alcohol with make ~ 8% to 10% more torque and HP throughout the RPM range. It is quite easy to get even exhaust temperatures. I have seen similar results when two 4 bbl. carbs. are used.

Many claim that the intake port must be properly sized for alcohol (usually about 5 to 10% more cross section area). So, if the head is properly sized for gasoline it may not be optimized for alcohol.

I have seen NHRA Comp. Elim. A/ND and B/ND run quicker with gasoline (they are allowed to run alcohol) than alcohol. However, in each case the racer was eventually able to run quicker with alcohol once the entire combination of port size and camshaft were worked out.

In summary, if the alcohol combination is optimized it will be quicker. If you switch from gasoline to alcohol without making any changes, the gasoline combination may very well make more power.
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Old 09-06-2013, 03:46 PM   #3
Dragsinger
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Default Re: gasoline vs Methanol combination specific

Thank You
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