Hi guys,

Well, in the constant pursuit of improving my carīs performance I bought a spare used in good condition JDM Evo VI complete engine. I will start with the head, it is already stripped and will be mainly cleaning up the casting marks and softening any sharp edges in the cc and polishing it.

Iīm posting pictures of the before state, also this is not the first porting & polishing that Iīll be doing as last year I worked on 3 WRX/STi heads and 1 Evo VIII head. Only have some pictures of one of the Subaru heads.

By no means do I consider myself an expert, so Iīll take on this job very slowly and prudently, and will be posting pictures as I go along.

So far, after reading many threads here, I think some of the definite NOīs are:

• Donīt enlarge the port opening
• Donīt polish the intake side

Ah, by the way, the finished head will have GSC S2 cams with Kiggly springs. My car currently is still with the stock Evo V turbo (ported) and running about 27 psi peak, later down the road the plans would be to go for either A BBK Full or HTA Green, or something in that size range.

All comments and suggestions are welcome!

Ricardo

 

don't polish the exhaust side like that either..just to add to that. We don't go any finer then 120 grit.

Looks good.

 

Thanks for the tip! Dave? Iīll save some skin on my fingers! Is it ok though to polish the cc? Also do you use 120 grit on the intake side as well or something coarser?

I read through you post about "how a combustion chamber takes shape at Headgames" and find it inspiring. I would have sent you the head if I lived in the states, but being in Peru itīs just way too expensive to send and a paperwork nightmare with our import/export laws.

Thanks again,

Ricardo

 

lol..no problem Ricardo. Yes, it is Dave.

I wouldn't go any smoother then 120 on the chamber too. Just think about how when your shinning that stuff up and touch it right after your going over it and it's hot or warm...same thing is happening during combustion. We do 60 or 80 grit on the intake, no smoother then that.

glad to be a inspiration! let me know if you need any of the porting materials as I am sure it is not easy to get over there ..I also understand how it is hard to ship overseas. We do it quite frequently, but I think cartridge rolls and stuff wouldn't be so expensive and easily go thru customs. But it looks like you do good on your own.


the problem with mirror polishing is it only looks good. I have never seen one run good.

 

Hi Dave, thanks again for the pointers! Iīll pm you about porting materials. It makes sense now about not mirror finishing the chamber as the heat from combustion could get those surfaces hotter than when not morror finished.

I must admit I thought it was good practice to mirror finish the exhaust side, the "theory" being exhaust gases would move faster and carry more heat energy to spin the turbo. But your findings indicate that is not the case so Iīll follow your advice.

Another question, I know the EGR passage can be welded shut on the intake manifold side (like it is shown in one pic of your heads), but is it possible/safe to also weld shut (and then port) the EGR passage that is in the exhaust side of the head itself? I mean the one top right in this picture.

Cheers,

Ricardo

 

I have an Evolution 6 and it doesn't appear to have EGR or at least the inlet manifold stuff the 7 and later ones do . Would a 6 head casting even have that passage ?

Also from WSMs the 6 engine is supposed to have a revised water in out layout .

I'll look at the above mentioned Head Games thread too , cheers A .

 

I could be wrong, but the US spec stuff would probably be the only heads that have the EGR. I know the 2J is like that at least.

I am also not sure how or why you would want to port it. I would just leave that thing alone. It would be alot of effort for minimal gain.

 

From what Iīve seen, the Evo V, VI has EGR from factory and the oem exhaust manifold has the connections as well, it was one of the first mods I did to remove it. Here is a picture of my engine where the block oof plate can be seen, canīt post better resolution pics.

Regarding the EGR passage, I was refering to first closing it by welding and then just porting (smoothing) so that the side wall for that exhaust passage (right after the valve seat) would be like the rest of the exhaust passages are in the head, whithout the hole in there that is no longer in use. Maybe Iīm just having a hard time putting in words what Iīm thinking, and not naming things properly. Or maybe itīs just a dumb idea.

I thought by doing this maybe something could be gained for that particular cylinder, as it would then be like the others are.

Thanks for the comments,

Ricardo

 

nope, not a dumb question at all...we have done that on many different heads just the way you described it. On the 2J and D series honda we make a aluminum cylinder the size of the hole and weld it on one end and blend it into the port. It's alot farther down in the port then the 4G however. Either way if you find a way to plug it..go for it. It's just the end your trying to cover is not the best shape to easily do something with.

 

Ok, many thanks for the explanation Dave, Iīll see if my local welder can give it a shot sometime, using a pre-shape aluminum cylinder like you advise.

Here are some pics of what Iīve done so far, basically Iīve gotten rid of all casting marks and smoothed down the lump near the valve seat at the mirror position of where the EGR whole is on the other side. I think that "lump" has a particular name but canīt remmember what it was.

The divider still needs more smothing, and I havenīt changed the shape of anything either. Was thinking of narrowing the divider a little.

Cheers,

Ricardo