How Much Horsepower Should my Kit Car Have ?
First Question : How much HP is enough and How much is Too much ?
200 – 300 – 400 – 500 + HP ? What is right for you ?
This comes down to driving Style. Broken down into different categories.
Stage 1 : Daily driver, Smooth Idle Factory to slightly Modified Engine. 200–275 HP Range
Stage 2 : Cruiser, More Aggressive Idle, More added Punch & Torque 275-350 HP Range
Stage 3: More Lopy ,Racier sounding idle, Increased Low to Midrange HP and Torque, Striking a balance between streetability and Power. We deal with most guys who fall into this category. Anywhere from 350 to 450 HP Range.
Stage 4 : Choppy Idle, Street / Strip use, Big Camshaft and High Compression. A Headturner. Highly Modified Engine. This would be more around the 500+ HP Range.
Many of these cars are very lightweight. Around 2000 lbs. overall. So they will be very responsive to Even mild enhancements. to give them a launching effect.
You can actually lose power in many cases. The important thing is to find a happy medium to stay within the Power band you are driving in most. A lot can be achieved out an engine without going with a Huge camshaft or Carburetor.
Type of Fuel Big Compression Engines have no place for running on the street. To run pump gas in your engine it’s wise to keep compression within 9 to at the most 10.5 to 1 Ratio. Compression beyond this can cause the engine to start running Hotter and cause preignition or worse detonation problems.
Radiators and Oil Coolers Engines need to run cool to perform at their best. Even the best Water pump in the world is not going to make up for a restricted or defective Radiator. The bigger and more potent the engine the More important it is to have an efficient Cooling system. The Radiator is something not to Skimp on. Oil Coolers are popular setup for some of the big Block engines it can be helpful otherwise the smaller engines can do fine without them.
Domino Affect Whenever you start climbing up in Horsepower / Torque keep in mind that the rest of the car needs be setup to handle this. The Rear End, Transmission, Clutch, Suspension, Braking, Cooling System. Etch. Everything needs to work in Harmony. Otherwise the weakest link can be exposed and break.
Engine Selection
Small Block V-8 Ford or Chevy engines deliver the most bang for the buck. Light weight , Plentiful and most of the manufacturers setup their cars to easily drop them into place. Plus you can get all the power you need out of them.
302 Ford
The 302 is a nice motor to start with. With a steel Roller Cam in it. You can wind it up quickly and is very quick from 0 to 60 MPH. The stock engine with about 225 HP is excellent for a daily driver and the Factory Transmission and Gearing.
It can be built up extensively more HP with a Hotter Cam, Aluminum Heads, and a efficient Flowing Induction System. Obtaining 350 HP is a good goal to obtain without sacrificing reliability. When you want to get more out of the 302 stroking it out to a 331 or 347 would be the best way to go when going beyond the 400 + HP Mark. Those of you who may not be familiar with what is called a stroker engine, Basically from the outside of the engine is the same. The connecting rod length or Crankshaft index has changed giving it more cubic inches. For Example the 302 stock Rod length is 3.0 inch changing it out to 3.40 inches to become a 347 when bored .030 oversized. With Forged components like the connecting Rods and Pistons and a Cast Steel Crankshaft it’s a proven performer ! A lot of people feel that a Cast crankshaft can’t handle higher strains. The Scat Cast Crankshafts are Designed to handle up to 500 HP .Same goes for connecting Rods. H Beam Connecting Rods are nice insurance but when using the Factory Rods with some ARP Retaining bolts they hold really strong.
351 Windsor Engine
This is our best selling Ford Engine. Lots of advantages with using this motor.
1. Same Engine Mount and Transmission Bellhousing pattern.
2. Close to the same weight as the 302 maybe 70 lbs. more
3. Has Thicker webbing block & larger Main Cap & Connecting Rod Bolts and also larger Cylinder Head Bolts for added strength
4. It is close in the same price as the 302 too.
The 351w is a great engine to give you the seat of the pants Grunt power more so than the 302.. This motor can develop huge torque similar to the Big Block engines. Especially when its built as a stroker engine. Some of the sizes available are the 377, 393, 408w, 418w, 427w and the 454.
Whenever you have a choice of going with a 302 or 351w Stroked engine your better off with a 351w being that it is a stronger beefier block.
The Rod angle is said to be too much when you go beyond the 427 stroke. So that is why the 393 and the 408w are a good way of going for longevity.
Not unusual for these to go from 0 to 60 in 3.5 seconds. The 302 are capable of doing it in about 4.5 seconds. These engines can easily get 450+ HP and develop 500lbs of Torque. The car can really launch with this setup. Again matching it up with the right Transmission and Clutch among other upgrades is a must.
390, 427 or the 428 FE Engines
These engines are used for those who want to have the vintage look under the hood.
The 390 to 427 and 428 can belt out a ton of torque. They are within the same engine family and if your car is setup to take a FE Big block then anyone of them could fit into the chassis. They weigh about 85lbs. more than the 351w and 150 more Pounds than the 302. But the biggest problem is the availability of them especially the 427 Side Oilers which you pay a premium price for and then your taking a chance whether it’s good or not. From the outside the 390 appear just like the 427 and deliver just as much power when setup properly . There are some companies coming out with the new bare 427 side oiler engine blocks which require a big investment in parts and machining for everything to come together.
This a rarely seen in the Ford Replicas or other Kit Cars. Due to the weight increase of about 250 lbs. more than a Small Block Engine it can compromise the handling of the car. The Kit company would need to be notified if you intend on putting in a 460 Big block thats being fitted to go into Rolling Chassis of the car. So the proper mounts are supplied and hood clearance is checked to prevent any problems
Here are some basics on gaining power.
Fuel Delivery system.
Don’t need a lot of Carb. when you have a smaller engine in the car. As the efficiency of the engine increases or you have a bigger engine then a bigger carb. would be beneficial.
Same thing applies with a Throttle Body. 600 to 650 cfm for the 302s. The 350 chevys and the 351w can handle a 750-800 cfm. The more efficient the engine is the more Air and Fuel can be pumped into it and therefore a bigger Carb. or Injector Size
Dual Plane for low to mid range speed. Power Range from 1500 to 6500 RPMs.
Single plane design more for mid to top end Power. 2500 to 6500 RPMs
If you were going to pick one bolt on that would get you the most power .. Cylinder Heads would probably be it. The time you get involved with Porting and Polishing Cast Iron Heads you can buy better flowing and lighter Aluminum Cylinder Heads. Much larger Intake and Exhaust Runners and bigger Valves. Using the proper Matching Camshaft can easily add 100 HP.
Factory internal parts will be fine for slightly modified engines. Once HP figures start climbing up then more attention needs to go to beefing it up the bottom end.
ENGINE FACTORY INC. copyright 2005
1-800-704-5385
See our Customized Cobra Engine Build