DOHC ZC rebuild query

[stndrd]

My apologies, was supposed to write oversize bearings. Have edited my post accordingly

[cbauto]

No worries, thanks for the clarification.

My query still stands, why do people run oversized valves?

I know it is off topic but this knowledge will still be educational.

[Daveho1]

cause race car.

[dougie_504]

No worries, thanks for the clarification.

My query still stands, why do people run oversized valves?

I know it is off topic but this knowledge will still be educational.

I'm up in the air about this.

Endyn believe that oversized valves on the sohc VTEC motors helps make power, partially because the VTEC only increases intake duration.

And I'm using Jun oversized valves in my B16A head which Skunk2 believes will yield up to 10HP with their camshafts (got my mechanic to enquire with them as they don't recommend o/s valves due to valve-valve clearance but I've had the engine clayed).

[chez00]

Very simply oversized valves improve the potential power ceiling of an engine. Engines are an air pump. The more air in the more power out. Oversized valves (can) improve airflow into an engine and really improve performance if the valves are the restriction in the whole equation of filling the cylinders quickly and efficiently. There is of course much more to it (air velocity, fuel atomization, squish, flame travel, opening events, exhaust back pressure and pulse widths etc) but in simplistic terms larger valves=more air:fuel=more power.

I saw a 7% power increase on my Peugeot 205 GTi (8v) going to a 1.5mm O/S inlet valve with no other modifications. Power improvement was pretty much from 3000 onwards, too.

Hondas would never see that kind of improvement as their combustion chamber design is pretty much the best on the planet and without a lot of R&D, these kind of mods often set a tuner back.

[RackCity]

Im guessing the best upgrade from a stock block would be conrods, what would a good aftermarket set for a DOHC ZC?

Also if I make harness odb0 to odb1, do i still use the pm7?

[carayan]

Im guessing the best upgrade from a stock block would be conrods, what would a good aftermarket set for a DOHC ZC?

Also if I make harness odb0 to odb1, do i still use the pm7?

no, you'd use an obd1 p28 for example, sohc vtec ecu and get a s300 to match

[RackCity]

so i can use a sohc vtec ecu on a non vtec dohc?

[carayan]

so i can use a sohc vtec ecu on a non vtec dohc?

its not desirable, but yes it's an option.

read here for a better idea:
http://www.hondata.com/engines.html

[stndrd]

For what you plan on doing for your ZC turbo build I would recommend a Haltech computer over a Hondata. Easier to find a tuner, more tuning parameters and just a better unit in general.

cbauto, with the oversize valves, its just another step in the equation to allowing the engine to breath better. Some setups may only require oversize intake valves, some may only require oversize exhaust (more turbocharged engines) and some may require both (heavily built high comp n/a engines).

[RackCity]

Ok thats good, because the local tuner JEM supplies Haltech, do these piggyback on to the ecu?

[stndrd]

Haltech is a full stand alone engine management. You will need to get a Sprint and wire it in