Here are some before and after pics of my port and polish job on EA71 Heads.

 

More to come as I progress.

 

Just been on the phone to Kelford Cams. The guy was really nice. He can fix me up with a suitable grind for about $150 NZ

 

The only thing is he did hint that there is more to porting than meets the eye.

 

It seems that you can make the engine run worse than before if you take off too much material in the wrong places.

 

I couldn't really take up too much of his time by trying to explain what I have done. So I wonder If any of you can point me in the right direction for these heads.

 

Cheers

 

Dirk

As a starter, the intake side should have texture (ie not be mirror finish) as this helps the fuel and air mix.

Yes I have heard this. It seems to be a fiercely debated topic.

 

But I believe those that say the fuel is vapourised in the carb long before it reaches the intake ports.

Essentally you want to try maintain a similar cross sectional area along the runners. Concentrate more on smoothing out where the intake meets the heads -- I have found this area leaves much to be desired. You'll need to cut the intake gaskets to match -- again, these are terrible as standard.

 

Areas of larger cross section encourage the fuel to condensate out of the air -- not good. Best to leave things similar to factory unless you have a very good reason not to....

Cool. Thanks Ross

 

Comments/advice welcome.

 

Cheers

 

Dirk

I'm an older bloke 58yo and never seen the results of port and polishing. thanks for the thread. its making sense.

Thanks.

 

Just remember........ I dont have the first clue into what I'm doing.

 

Hopefully someone will chime in with some technical feedback.  ( best advice I have had so far is to spend money on a good valve grind)

 

With best regards

 

Dirk

I am far from an expert on porting, but here is my 2 cents. Unless you plan to make your engine "breathe" better, through bigger carbs, racy cam, and large exhaust (read increase the RPM's), porting will may little if any difference to a stockish engine. You would probably get better results doing a simple port match and cleaning and deburring and a nice 3 to 5 angle valve job. There are other tricks like larger valves and cut down guides etc, but once again, you would only see results at higher revs.

 

Mark