port matching... any benefit?

[markey b]

as per title. my engine is in bits and noticed how inlet, exhaust and head is all smaller than the gasket. is it worth opening them up to all match?

[James5]

as per title. my engine is in bits and noticed how inlet, exhaust and head is all smaller than the gasket. is it worth opening them up to all match?

Defo worth opening up those inlet ports at least to match the gasket size:D

[Os8472]

as per title. my engine is in bits and noticed how inlet, exhaust and head is all smaller than the gasket. is it worth opening them up to all match?

Tis usually an N/A tuning thing but it doesnt hurt to do it

Make sure the lent manifold is slightly smaller than the gastket and the inlet ports match the gasket, the exhaust ports slightly smaller than the gasket then the exhaust manifold mayn't he'd to the gasket if that makes sense

[Scoff]

The exhaust ports are supposed to be smaller than the manifold and you should leave it that way.

[andybond]

Not doubting your judgement Chris . Just trying to understand why. Why leave them smaller?

[Matt Cole]

Not doubting your judgement Chris . Just trying to understand why. Why leave them smaller?

Gas velocity and reversion!:D

[andybond]

Cheers matt. Tell me more. The smaller diameter of the exhaust manifold means th gas is under more pressure therefore moving faster ? As opposed to the inlet mani which should be bigger so you can cram more air in ?

[Matt Cole]

Cheers matt. Tell me more. The smaller diameter of the exhaust manifold means th gas is under more pressure therefore moving faster ? As opposed to the inlet mani which should be bigger so you can cram more air in ?


I did write a load more gumf but for some reason the websiye keeps throwing up errors on long essays!:(

To cut it short, the exh ports are smaller to help prevent reversion.

[andybond]

I'll google that last word. Thanks for your time Matt :)

[TNT ANDY]

I did write a load more gumf but for some reason the websiye keeps throwing up errors on long essays!:(

To cut it short, the exh ports are smaller to help prevent reversion.

For a given application.

I think for cars pushing 100% more power than originally designed this would be a worthwhile investment would it not? or do other bigger BHP cars still retain standard exhaust valves, head ways, ports, valve and exhaust once modified?. I used to tune mini's (N/A) and was always avised to increase port size in accordance to the state of tune, ie minor mods needed nothing, and full race engines needed a lot, but the key was that it would not produce power on it's own but would assist in benefiting other mods done.

In short if it is to be done, I think some serious thinking needs to go into this.

[Scoff]

Andy, yes, but when you increase the port by X % you should increase the manifold runners by the same %.

Reversion becomes more of an issue the more you push the engine so if anything it gets more important to do whatever you can to reduce it.

Truth be told that step probably isn't worth a toss on these engines but smoothing it won't do anything so I'd leave it in.

[TNT ANDY]

That's another waste of money then LOL:)

[Woznaldo]

Andy, yes, but when you increase the port by X % you should increase the manifold runners by the same %.

Reversion becomes more of an issue the more you push the engine so if anything it gets more important to do whatever you can to reduce it.

Truth be told that step probably isn't worth a toss on these engines but smoothing it won't do anything so I'd leave it in.

Surely having no step has to better than a step? Maybe not noticeable on it's own but better none the less?

[Trevhib]

I thought the area that needs attention here is the gasket itself, in that the holes in it don't line up properly with the head port or either manifold ports, and that dremelling (sic) the gasket is beneficial in a very small way for the sake of flow?

[Matt Cole]

Surely having no step has to better than a step? Maybe not noticeable on it's own but better none the less?

No, not in limiting reversion. You want the gas to go out and not have an easy path back in especially if running wild overlap. If you port match the whole lot (gasket, manifild port etc) then you may need to consider some sort of anti-reversion method. I guess the gas velocity at the port exit is greater than at the entrance of the manifold runners which would see a decrease in velocity and, hense, an effect of negative pressure right at the port mouth.

My thoughts porobably incorrect!;)

[markey b]

ok so leave exhaust alone, what about inlet?

[danielmk323]

can you make the valves bigger or there is no point in doing so or cant be done ?

[Trevhib]

I thought the area that needs attention here is the gasket itself, in that the holes in it don't line up properly with the head port or either manifold ports, and that dremelling (sic) the gasket is beneficial in a very small way for the sake of flow?

Scratch what I've said, I've misunderstood which bits affect this reversion thing. I assume matching the gasket to inlet manifold ports is ok still.