Polishing head chambers. I didn't do it. What can happen?

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Re: Polishing head chambers. I didn't do it. What can happen?

Post by groberts101 » Wed Jun 06, 2018 9:09 pm

statsystems wrote:
Wed Jun 06, 2018 8:25 pm
groberts101 wrote:
Wed Jun 06, 2018 8:19 pm
So I have a question for the guys who prefer burred chambers.

Does this texture remain or maintain the same surface profile over time?


I've never left a burr finish in the chamber because I can't do it well enough, so I don't know about the burr finish.

But I can tell you I've seen chambers that were CNC finished and eventual they smooth up.


BTW, there isn't much difference between an as cast chamber and a burr finished chamber. If the OP has an as cast finish in the chamber he should run it. If he has a smooth finish he should run it.

The OP is making a continent out of a flea turd.
That's exactly why I asked. Never chattered a full chamber but I have fully polished just about every single chamber on my own personal stuff.. and several others who would actually pay for the extra time and consumables.. for about the last 20 years or more. But years ago when closely following Larry Meaux's texture work I did 2 sets, SBF and SBC, with burred finishes around the intake throats leading right up to the seat and also around the chamber walls and also inside the intake valve relief of the piston. My motor came apart 2 years later for more aggressive port work with manifold change and didn't see the chevy for 5 years for a refresh. Both had very slight buildup in some area's of the choke due to slight reversion and all chatter finish in the chamber/valve notch was nearly indistinguishible from the surrounding fully polished surfaces due to layer of carbon.

Can't say for certian if that finish helped power at all initially.. but the only thing that I can say for sure is that the fully polished area's certainly were much easier to clean.

I only spend the time to do it because I think there's slight merit to reducing surface area, poor mans TBC, and it has proven itself at reducing heavy accumulations and is easier to clean off later on. Some area's can be scratched off with a fingernail. Same reason I fully polish uncoated pistons and valves as well.

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Re: Polishing head chambers. I didn't do it. What can happen?

Post by BOOT » Wed Jun 06, 2018 11:06 pm

I think head design, fuel type and use would be factors for chamber finish. LT1 I'd think rough would work better(aside from the reverse cooling). If you wanted to polish it all you'd need would be two new/used dummy valves to protect the VJ and then tape the deck. Also make sure to not get grit where it can do harm.
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Re: Polishing head chambers. I didn't do it. What can happen?

Post by modok » Thu Jun 07, 2018 3:43 am

A lot of surfaces end up wanting a similar surface finish, because they all use similar motor oil.

Since we run on similar air..... our air bearing surfaces might end up similar.

that is, unless we don't
The big roots blowers guys, and high boost guys, what they DO to the air, it might actually qualify as different!!
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Re: Polishing head chambers. I didn't do it. What can happen?

Post by cjperformance » Thu Jun 07, 2018 8:37 am

Definetly polish the exhaust half of the chamber and leave the intake half rough
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Re: Polishing head chambers. I didn't do it. What can happen?

Post by rebelrouser » Thu Jun 07, 2018 8:57 am

I mainly worry about the ridges in the combustion chamber created when they machine the head for the seats, I blend in those and burr finish any sharp edges around the spark plug threads. I have never seen any back to back studies or dyno tests on chamber finish. so I just do what common sense tells me about eliminating hot spots and improving flow of the head. I have run cnc finish, bur finish, and just as they came out of the box, mainly depends what the customer wants and is willing to pay for. My personal engines I burr finish. Carbon buildup in the chamber on refresh seems to me to have more to do how the customer takes care of his carb tuning and how long he runs it before deciding it needs work. But again I have no hard scientific evidence to prove I should do any of this, just what I have read and seen others talk about.

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Re: Polishing head chambers. I didn't do it. What can happen?

Post by cardo0 » Thu Jun 07, 2018 11:30 am

Not trying to make a big issue out this but the chambers came cleaned out and rough like sandpaper - not like rough cut
carbide cutter marks at all but more like sharp/clean sanpaper. If anything is a particulate in the chamber this surface will grab it. After seeing the chamber as it was all choked up I don't even need common sense to figure out it's gonna come right back.

I've driven the car with those heads using low octane regular fuel and it bucks and bogs on acceleration as it pulls timing back. So anything that can reduce the knock counts is better for any type driving out here in desert temps. I didn't have a good enough rotory tool at the time and dropped the heads off before I needed to thinking they were gonna smooth out the chambers along with unshrouding the chambers for the new/larger valves. Oops, they didn't do any unshrouding so the chambers just a very nice cleaning. To be fair to the shop I can't blame them as the work they did do was great and I wouldn't take my heads anywhere else here in Vegas. And I'm sure they would have needed to charge a lot more for unshrouding the valves and polishing the chambers. But I made the common mistake of not getting it written down.

I guess there's no way now to tell what I'm missing with polishing the chambers but it reads like nothing destructive is gonna happen. Thx again for all the support. :)

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Re: Polishing head chambers. I didn't do it. What can happen?

Post by BOOT » Thu Jun 07, 2018 12:57 pm

cjperformance wrote:
Thu Jun 07, 2018 8:37 am
Definetly polish the exhaust half of the chamber and leave the intake half rough
LOL I just had a sim idea and started a thread, should of read this 1st I guess.
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Re: Polishing head chambers. I didn't do it. What can happen?

Post by John Haskell » Sat Jun 09, 2018 12:43 pm

Some tid bits to pass on from my time in racing & what I saw.

I would say the most I learned came from the Stock, Super Stock & Modified Production classes in Drag Racing. This covered a lot of 'can't do, can do' areas of combinations & over the time frame of the 60's /current & is usable today.

To shorten it up, chamber finish did not have an effect with on track performance.

These results have been pleasing to me due to the fact of simplicity in completing heads & manifolds. I spend the hours porting on changes that get results rather than wasting on pretty.

I have a 'Steel Grit' I describe as #2 gravel. On aluminum, it creates avery aggressive finish on everything. Much more course than the roughest casting you have seen. Cast iron, not so much.

I came to this conclusion from no Dyno development, just watching what happens on the track. In my case, it has worked for me.

Where I first noticed chamber problems came from the exhaust side of the wall & this a long, long time ago. The more fuel/air an engine used, the more went out the exhaust. Now remember, some of these classes would not allow modifications to work on this so you watched, worked & adjusted where you could while noting the trends.

Where welding could be done it was but remember, those days no one used a dyno or could afford one. It was called 'Work'. You did it yourself & kept a small group to work between. Not so today. Racers today, it's called "1-800 send me one". if they don't have something computerized to tell them what to do or can't buy it, might be lost. Years of experience are the real teacher, no free lunch in my generation.

I did not have anyone teach me, lead me or show me the way (Save Bob Mullen). I was born a self starter, took a 10 yr. SAE home study course & learned more than I would have with out them. David Vizard is my blood. If you think like him, you think like me. The other top shelf boys on here know who they are & where they come from but,

Be at peace with you combustion chamber finish.

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Re: Polishing head chambers. I didn't do it. What can happen?

Post by cardo0 » Sat Jun 09, 2018 7:39 pm

John Haskell wrote:
Sat Jun 09, 2018 12:43 pm
Some tid bits to pass on from my time in racing & what I saw.

I would say the most I learned came from the Stock, Super Stock & Modified Production classes in Drag Racing. This covered a lot of 'can't do, can do' areas of combinations & over the time frame of the 60's /current & is usable today.

To shorten it up, chamber finish did not have an effect with on track performance.

These results have been pleasing to me due to the fact of simplicity in completing heads & manifolds. I spend the hours porting on changes that get results rather than wasting on pretty.

I have a 'Steel Grit' I describe as #2 gravel. On aluminum, it creates avery aggressive finish on everything. Much more course than the roughest casting you have seen. Cast iron, not so much.

I came to this conclusion from no Dyno development, just watching what happens on the track. In my case, it has worked for me.

Where I first noticed chamber problems came from the exhaust side of the wall & this a long, long time ago. The more fuel/air an engine used, the more went out the exhaust. Now remember, some of these classes would not allow modifications to work on this so you watched, worked & adjusted where you could while noting the trends.

Where welding could be done it was but remember, those days no one used a dyno or could afford one. It was called 'Work'. You did it yourself & kept a small group to work between. Not so today. Racers today, it's called "1-800 send me one". if they don't have something computerized to tell them what to do or can't buy it, might be lost. Years of experience are the real teacher, no free lunch in my generation.

I did not have anyone teach me, lead me or show me the way (Save Bob Mullen). I was born a self starter, took a 10 yr. SAE home study course & learned more than I would have with out them. David Vizard is my blood. If you think like him, you think like me. The other top shelf boys on here know who they are & where they come from but,

Be at peace with you combustion chamber finish.
Thx for sharing, hearing your experience is what I needed whether good or bad. It's surface is rougher and even kinda sharper that I expected so it was bothering me as I do know most owners will smooth any sharp edges from the chambers and piston tops. But I really trust/like my machine shop and I expect they wouldn't let anything that would hurt performance go out the door as word get around.
BTW I think I own nearly every D. Vizard book and read most of them at least twice.

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Re: Polishing head chambers. I didn't do it. What can happen?

Post by DrillDawg » Sat Jun 09, 2018 11:10 pm

With all that information at your hands, why do you have to ask about polishing your head's chambers?
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Re: Polishing head chambers. I didn't do it. What can happen?

Post by user-23911 » Sun Jun 10, 2018 3:24 am

David Redszus wrote:
Tue Jun 05, 2018 8:16 pm



And when the smooth surface becomes coated with carbon, what then?

Carbon sticks to everything.
In that case it's not tuned right.

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