Disclaimer: All of the following engine profiles cannot be guaranteed to work adequately right out of the box. In any of these engine profiles, jetting combinations were determined from similar running engine profiles previously analyzed with ProCalc. Spark plug readings and engine temperature measurements are needed from incremental runs to determine if jetting adjustments from these baseline profiles may be further needed for your particular setup. Incremental runs with spark plug readings (such as described in our books and other sources) and temperature checking in between runs are necessary. Appropriate adjustments to jetting or ignition advance are all needed before full power, full runs should be done. Adequate performance without engine failures is also dependent on appropriate engine assembly and parts selection not addressed by these descriptions. Additional qualified expert engine building / tuning skills and information is necessary. Power levels & specifications contained in this article were observed from similar engines but cannot be guaranteed.
Low Cost Blown Alcohol V-8 Description
The following is an example of a low cost combination for land or water racing. It also was applied very well to drag racing exhibition and grudge fest, starting with a low cost blown alcohol racing engine. Keys to low cost are the following:
- a standard opening small blower (not the more expensive delta lower opening)
- mechanical fuel injection hat with only hat nozzles (no port nozzles) for methanol fuel.
This is a ‘high power per dollar’ engine that is based on a low cost block/cylinder head platform: all cast iron small or big block GM, Ford, or Mopar V-8 with the following specs:
- engine platform: small or big block GM, 460 Ford, early 354 or 392 Hemi, or Late Model Hemi (such as low cost 16 bolt intake/cylinder head combo), 413, 426, 440
- engine RPM: not to exceed 8,000 RPM
- displacement: 327-460 (engines larger than 460 are unnecessary and not recommended)
- power output relatively independent of engine size for engines within this range
- crankshaft: aftermarket 4340 alloy crankshaft based on a low cost forging made by one of several manufacturers with good heat treating and machining resources
- rods: premium high strength steel or premium high strength aluminum (minimum strength level: 7075-T6 alloy or greater in aluminum rods) in new condition; NOT used with a lot of runs on them; also NOT new or used rods without a history record, such as from a swap meet or classifieds ad
- premium soft bearings: main clearance approx. 0.0035 inches, rod clearance approx. 0.0025 inches
- pistons: thick dome blower piston with mild compression ratio approx. 9 to 1 with piston-to-wall clearance as recommended by the piston manufacturer
- alloy steel top ring, cast iron 2nd, high tension oil ring
- piston pins: premium tool steel
- camshaft: roller tappet with less than 0.700 inch lift, less than 290 deg duration, lobe centers 109 to 112 for wedge / poly cylinder head, 113-116 for hemi head; cam index: straight up; do not run a cast camshaft core, only steel
- cylinder heads: hand ported cast iron or aluminum; if aluminum for non-highway use, solid castings recommended
- intake valves: stainless steel 2 to 2.25 inches
- exhaust valves: stainless steel 1.6 to 2 inches
- valve spring seat pressure: 300 pounds with premium valve retainers and keepers
- ignition: 2 to 6 amp magneto
- blower: low cost standard 6-71 or 8-71 without rotor seals
- new or well maintained blower roller bearings and shaft seals are a necessity
- fuel system: mechanical fuel injection hat style throttle body with 8 nozzles
- fuel pump: 12.5 to 13 GPM rating at 4,000 pump RPM running at 1/2 engine speed; new or rebuilt used from one of the reputable fuel injection suppliers
- blower manifold: low cost, standard blower location, cast manifold with burst panel
- headers: individual pipes where rules permit; otherwise, four-into-one collector should increase mid range power with a small reduction in top end power; low restriction mufflers could be added for reduced noise although a top end power reduction occurs.
This engine can be assembled for around $10,000 to $15,000 with mostly new and premium used parts. It would be street-able although it would have very high fuel consumption and not emissions compliant in many parts of the world.
Intake & Fuel System
Note the following setups generated from our data base and ProCalc:
(1) fuel injection methanol setup (ProCalc) for about 1,200 HP in 95% air density
- stock 6-71 blower at 25% overdrive
- hat nozzles: front 2 at 0.052″; next 2 at 0.050″; next 2 at 0.048″; rear 2 at 0.046″
- main bypass at 0.130 inches for air density around 95%
- air to fuel ratio: approx. 3.7 to 1
- fuel pressure at 5,000 launch RPM: approx. 57 psi
- fuel pressure at 8,000 RPM: approx. 145 psi
- spark advance: approximately 34 deg for 2 amp magneto; 30 deg. for 6 amp magneto
- spark plug gap for magneto: 0.016-0.020 inches
(2) fuel injection methanol setup (ProCalc) for about 1,500 HP in 95% air density
- stock 8-71 blower at 50% overdrive
- hat nozzles: front 2 at 0.060″; next 2 at 0.058″; next 2 at 0.056″; rear 2 at 0.054″
- main bypass at 0.104 inches for air density around 95%
- air to fuel ratio: approx. 3.6 to 1
- fuel pressure at 5,000 launch RPM: approx. 55 psi
- fuel pressure at 8,000 RPM: approx. 140 psi
- same ignition setup as above.
For either engine:
- for any Hemi head with a lot of camshaft timing, start out with smaller main bypass for a richer air to fuel ratio
- for higher compression ratio, start out with a smaller main bypass for a richer air to fuel ratio
- for lower compression ratio, start out with a larger main bypass for a less rich air to fuel ratio
- for higher air density, run a smaller main bypass to maintain the air to fuel ratio
- for lower air density, run a larger main bypass to maintain the same air to fuel ratio.
Ram Air Effects w/o High Speed Bypass
For racecars or boats exceed 150 MPH with forward mounted hat throttle bodies or air scoops facing the air flow, ram air will make up for air loss inefficiencies that may occur at higher blower speeds. More information about ram air gains is in our nitro & high HP tuning manuals. Ram air effects tend to negate the need for a high speed bypass. As a result, a high speed bypass is not suggested.
These combinations are all based on the lowest cost blowers, heads, and block selections. More expensive components can be substituted especially if you already own them. Our late model blown Chrysler Hemi was set up for drag racing to produce similar power levels. More details of our engine builds are featured in our books: Fuel Injection Racing Secrets, 5000 Horsepower on Methanol, and Blown Nitro Racing on a Budget. Videos of our engine drag racing with a funnycar body or an altered body are featured in the following link: http://racecarbook.com/about/blown-altered-funnycar-videos/