Failed Attempt: 6-Bolt Head Port & Polish

[TrippnTSi]

Let me start by saying I knew the risks involved with trying this myself.

I am someone that always wants to learn more about the processes involved in engine building. I started out as a young teenager, and only recently began working on a new project. One thing that I’ve never really learned about is Porting and Polishing a cylinder head. Since I am much more experienced and financially stable these days, I’m willing to do trial and error to learn more.

I did some pretty decent research on how to go about doing head work, but all the research in the world has nothing on real life experience. After gathering all the tools and digging into this new engine, I find myself with a beautiful hole in my 6-bolt exhaust port… I guess you live, you learn, and then you get Loves.

I have already begun search for a new head, but I wanted to share my experience with anyone else that might want to try these things for the first time. Always be prepared to pay for your mistakes. Everything should be taken with a grain of salt in these circumstances. I only hope to get better as I go!

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[curt-s]

With as much capability as either head has off the factory floor, I stopped trying to enlarge anything and simply just smoothed out casting marks and flashing.
You have to go pretty far all things considered to burn right through the casting and the gains above a stock head aren't worth the trouble/risk.

 

[biglady112]

With as much capability as either head has off the factory floor, I stopped trying to enlarge anything and simply just smoothed out casting marks and flashing.
You have to go pretty far all things considered to burn right through the casting and the gains above a stock head aren't worth the trouble/risk.

I have run 8 seconds with a stock, unported cylinder head. I agree, that the gains aren’t worth the risk. I also value cylinder heads as throw away parts and no longer really invest the money.

On my 3800 cylinder heads, I do some clean up on the intake side and clean up the bowl on the exhaust side. I do remove a lot of material at the exhaust port but, inside the runners I don’t do much.

 

[TrippnTSi]

With as much capability as either head has off the factory floor, I stopped trying to enlarge anything and simply just smoothed out casting marks and flashing.
You have to go pretty far all things considered to burn right through the casting and the gains above a stock head aren't worth the trouble/risk.

I will be doing just that on the next one. I appreciate your input!

 

[donniekak]

I have run 8 seconds with a stock, unported cylinder head. I agree, that the gains aren’t worth the risk. I also value cylinder heads as throw away parts and no longer really invest the money.

On my 3800 cylinder heads, I do some clean up on the intake side and clean up the bowl on the exhaust side. I do remove a lot of material at the exhaust port but, inside the runners I don’t do much.

I’ve tried telling people this. We ran 7.8@179 with a bone stock 1g head casting.

 

[1990TSIAWDTALON]

Leave the head alone. Gasket match if you need that extra 4 hp with a polish of the ports. Fk them up or bowl and under the valve work and it's just asking for issue's. PLEASE leave it alone, they work just fine as @donniekak has reported.

 

[biglady112]

I’ve tried telling people this. We ran 7.8@179 with a bone stock 1g head casting.

I am glad there are like minded folks out there. I can agree that there are gains to be had. But, it isn’t hundreds of horsepower. It might barely be tens of horsepower if people are lucky. And that would be on a big boy setup.

People forget their turbocharger dictates their power production and power curve. Especially on a little engine. There just simply not enough engine their to make a ton of N/A power. Let alone the early 4g63’s flow like dogshit compared to other comparably sized engines.

And as much as max effort cars chew threw parts these days, one’s money and effort could be better spent on other parts of the car to see actual gains.

 

[curt-s]

Like stickers and giant wings

 

[jed344]

Honestly from my experience it is easier to waste time or hurt flow with head porting if a person does not know what they are doing. I have done a few heads over the years and i would not even call them ported. I just clean up the chambers and polish them, Smooth out the runners and focus on behind the valves where runner meets the seat. The valve job angles can effect flow quite a lot too i have seen, call it good. The gains are likely small. My own head moves a ton of air, was done by head games. The stock heads on these cars already do ok, with my head vs a cleaned up head i have done on very comparable set ups the gains are almost nothing. Likely 10-20hp going off the log's.

 

[curt-s]

I think it's important to note that 10-20 may be reachable but only when you're at the high end of the hp range. It's the result of a percentage, not an absolute value. for those searching and finding this thread, if you're running 200hp, you're not going to suddenly get 220 by porting.
You might go from 200 to 201.
But 600 (random value) to 620 may be possible but it depends on many factors.
It's not linear.

 

[jed344]

I think it's important to note that 10-20 may be reachable but only when you're at the high end of the hp range. It's the result of a percentage, not an absolute value. for those searching and finding this thread, if you're running 200hp, you're not going to suddenly get 220 by porting.
You might go from 200 to 201.
But 600 (random value) to 620 may be possible but it depends on many factors.
It's not linear.

Yes thank you as i should have been more specific with my answer to this point. This is on set ups that are well north of 600. Though this head has moved the air to make 788whp on whalenspeeds dyno. The comparable results i said are now with a smaller turbo. This is more in the range of mid 600's that is the gain the data shows. To be also honest with the downsizing now i suspect i have hurt some midrange and no longer am moving the air needed to justify the small gain up top. Maybe with a less aggressive port, but if a just cleaned up head already in this range can be this close. The gains to cost and risk are not worth it and when they become worth it you will know kind of thing.

 

[TrippnTSi]

I appreciate the advice from everyone!! I’ve been fortunate enough to pick up two more head castings to replace the one that I messed up. I’ll be simply cleaning up the casting marks on them and letting it rip!!

I’ve been waiting on my machinist to finish my short block, so I have been a bit idle with my build. I got the call to pick it up today, so I’ll be shifting into gear to get the car running again.

 

[bastarddsm]

While I'll agree they run good as is, it's not hard to pick up 40cfm, and a bunch of power if you are not compressor limited.