port + polish

how much hp could i expect from a decent port and polish. also, how much approximately does it cost cause i got an estimate of 800 to 1500 cdn for a 4 banger 16 valve. seems kinda steep?

it depends on the engine and how small the stock ports are.

Those prices sound right, it takes a decent amount of equipment, and a lot of skill and time.

uhh...im guessing close to 30 to 40 hp at the wheels...?? dont see your engine?

It depends on how big you go and if you use the stock cams. the purpose of having four valves per cyclinder is to decrease individual port size,therefore increasing velocity. its called a venturi effect. although most engines can benifit from some airing out, for maximum results the correct cam selection is very important. and will be easier to determine with more details on your motor. i.e. displacement, compression ratio, forced induction, cam grind and so on. on a stock motor, depending on type, with no other modifications you would be lucky to gain 10 hp. gains go up exponentialy with other modifications.

From what you have told us there is no way to determine gains. However, assuming everything else is stock, porting and polishing (and hopefully port matching) will provide very little HP. Possibly in the 4 to 5% area. And then it will only provide the additional HP at the higher RPM's. You will probably never feel any "seat of the pants" HP with this alone. We have ported some engines where the port match was significantly off. In those cases you might see a bit more.

BTW, You can do port matching at home in a couple hours and get most of the above gains. Actual porting though, requires a Flowbench and correct adapters.

Again for a street car, I would never recommend the work. Mainly because usually aftermarket products are available for much cheaper that give as much gain. In some race venues, where the stock pieces HAVE to be used and you are always running at high RPM, porting makes sense.

Jim
SR Racing

and polishing on the intake side is a worthless cause :)
porting and polishing will only help if it is the heads which are restricing the engines power...otherwise you are simply reduceing velocity, but a little polishing on the exaust side will never hurt.

Must be an import or a Saturn. As others have said, with stock cam and valve train, probably little to be gained. But... If you're trying to spin 'er up, and have the valve train to back it up, no other modification will net you as much power as a good porting job. And contrary to popular belief, a turbocharged or supercharged engine will gain an even higher percentage with a good porting job.
With the 4-valve/multi-port heads, we modifiy one port for "swirl" and the other for "tumble". The end result is a very effective power curve.
As for polishing the intake ports? Old school is to never do it. With today's port-injected engines, it has no negative effect, as the port isn't really carrying "mixture", but just air. The atomization from turbulence in a carburetted engine is different than that of a modern engine.
In truth, for high RPM applications, we seldom concern ourselves with turbulence. When modifying the port, if you maintain the original shape, and keep the cross-sectional area consistent, velocity will also be maintained. Velocity at low engine speed is the key to street performance. Volume at high engine speed is the key to power production.

Jim

FI or NA? 2 different answers.