1966 Impala
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Whats Next - E85 Fuel Conversion
Updated Sep-15-2026
Synopsis | Compression Ratio | E85 Parts Store | Parts List | Services & References
The next big update for this Impala is converting it to run on E85 fuel. This page is all about that conversion - the parts, knowledge, and details needed to make it go smoothly.
Future update: convert the carb and the entire fuel system to run on E85. Including a new fuel pump, non-aluminum fuel lines, Viton gaskets, and 30% more fuel flow. EGTs will be set at around 0.80 to 0.85 Lambda for ethanol, or about 1550F EGT temps.
IMPORTANT NOTE: The engine's Dynamic Compression Ratio may be able to be fixed by using a 0.080" thick copper head gasket, or two 0.040" head gaskets stacked (but may need adjustment to the rocker arm length).
Compression Ratio (E85 reference numbers):
Calculated using the static and dynamic compression ratio calculator at GoFastMath and the dynamic compression calculator at Camshaft School (which uses a measured 0.006" lifter lift for its values):
Static Compression Ratio: 11.87:1 - Not 100% sure about the static number, but its close enough.
Dynamic Compression Ratio: 10.25:1 - This one seems pretty accurate.
Here are the values I used in the calculator:
| Compression Calculator Inputs | |
| Cylinder Bore (inches) | 4.040 |
| Stroke (inches) | 3.75 |
| Cylinder Head Chamber Volume (cc's) | 74cc used in calculator. Heads are Air Flow Research 195CC runner heads, AFR part number 1036 - in fact 75cc Straight Plug heads: AFR 195cc SBC Street Cylinder Head |
| Piston Dish/Dome (cc's) | -12cc's (negative value signifies a dome vs a dish) |
| Head Gasket Thickness (inches) | 0.040 (copper head gasket) |
| Head Gasket Bore (inches) | 4.060 assumed (due to bored engine and natural sizes of these) |
| Deck Clearance (inches) | 0.00 (block was decked completely flat to zero quench) |
| Connecting Rod Length (inches) | 6.0" rods |
| IVC at 0.050" | 38 degrees - Comp Cams Xtreme Energy 276 (XR276HR-10) cam grind, 224/230 at .050, 276/282 advertised duration. Closest match found: Summit Racing |
| IVC at 0.006" | 64 degrees ABDC - used with the Camshaft School dynamic compression calculator (measured 0.006" lifter lift) |
E85 Carb Conversion Parts Store:
E85Carbs Store - This store sells all the things required to convert carburetors to run on E85. Like the higher flowing Power Valves, and 4 barrel double pumper E85 kits with all the parts needed.
Carburetor: 750cfm Barry Grant Speed Demon, from before the Barry Grant brand was sold to Holley. Note for future reference: the Speed Demon uses the 4150 style Holley layout.
Carb Rebuild Kit: Summit Racing DEM-190004 - Carb rebuild kit for the Speed Demon carb (4150 style Holley layout).
AED Performance - A professional service for rebuilding carburetors, testing, and wet flowing them for customers. I may use this service to have them convert my carburetor and test it for E85.
Race One 85 - A reference for information on how to tune carburetors for E85 fuel.
Team Chevelle forum thread: E85 Carb Conversion Pics - More information on the E85 carb conversion.
