What do you think about porting and polishing? Mainly polishing combustion chambers and piston tops, as porting and polishing the intake is known for success.

Any gains from polishing combustion chambers and piston tops? Or is it just for looks?

 

You don't need to go down that road ., the advantages of polished combustin chambers is to reduce spikes in combustion temps on the surface of the cylinder head .via a smooth surface unable to create hot spots This is highly effective in endurance motors or high compression motors . That see constant high rpm high temp conditions were pre ignition could cost major bucks . If you wanna mess around with the combustion chamber on your head for cheap take some steel wool to it and give it a polish smooth it out ..the effects are minimal to none existent on a street motor but its damn cheap

 

oooohhhhh, this could turn into a he said/she said convo easily....

like every mod done to your engine, it has its pro's and con's. it all depends on what you're doing and what application you are going to use it for.

 

You need to be around 12.5 to one on 112 gas to experience .hot spot detonation .. You won't be able to achieve that on a street motor without killing the valves if the heads off scuff it up with wool but you wanna focus more on the valves than the combustion chamber .. Theses are long stroke motors none revers .. Piston temps and cc don't get hot enough . To fully utilize a professional CC polish

 

I have a 20r head, and it's just sitting waiting for a short block to be built for it (haven't decided if I will use my .020 over 20r block or if I'm gonna get a 22r block.).. I've already started with the intake runners, but it will be a while til its needed which is why I asked about the combustion chamber..

Scrub88. So your saying I should just smooth the chambers a little but don't waste my time on getting a mirror finish? Just trying to fully understand what your saying..

Litneon. Ive read quite a few articles as well as talked to people who have done this stuff, but none of them really said anything about the combustion chamber, maybe I should ask about it.. I've already started working on the casting flash and just smoothing everything out on the intake runners

 

Porting intake exhaust chambers yea go for that .. But paying to have you combustion chamber polished out . Wouldn't be a good purchase .. The benefits don't outlay the cost However you can use steal wool and what not to polish it out a bit

Ported heads and intake plenuims can make some decent power increases .. But polished cc chambers aren't really a power mode more insurance and endurance mode for motors runing on the edge all the time ...

 

I wouldn't pay for it to be done, was thinking more of wet sanding it to be smoother.. Good to know that it won't benefit much if anything!

 

Yea if u wanna just smooth it out to take some ruffness of it then nuttin wrong with that . I thought you were gonna pay to have it done . They look like a mirror when done . But the money could also go elsewhere ... But a few types of sand paper and some steel whool can knock down some of the ruff areas carful not to damage valve seats. A Dremel can make some decent intake and exhaust porting with some quality bits to

 

I'm using a die grinder with a carbide but bit for the big stuff like casting leftovers and sandpaper flap wheels I smooth it out.. There's no way I'd pay to have polishing done.. I'd use the money elsewhere like a header or bigger valves

 

Post some pics as you go.

 

Well here is a pic of how it is currently. Nothing special, just popped the valves out and a little port work, mainly gasket matching.


I also did a little bit of calculating and comparing the valves out of this head(20r) and valves out of a late model 22r or re, and this is what i found.

Intake valves:
20r is 43mm diameter and 115.5mm long
22r is 45mm diameter and 113.4mm long

Exhaust valves
20r is 36mm diameter and 113.4 mm long
22r is 37.5mm diameter and 112.3mm long

I measured from bottom to top, not valve seat to the locking ring thing.. Can I use the late 22r valves in my 20r head? or do the 1 or 2 millimeters shorter in length make them unusable? I twould be awesome if they could be used since i already have them and since the intakes are 2mm bigger and the exhausts are 1.5mm bigger!

 

Without getting too into the details I would think you wanna match the springs to the valves. The 22R springs should be equally shorter. That's not taking base height and keeper hat thicknesses into account. Somebody will chime in on that detail. I'm not sure. Valve to piston clearance might be an issue with a domed 22R piston underneath and a big cam. Stock valves and a 465" cam work on stock 20r valves with a 22r block tho.

 

I'm not using a 22r block, I have a 20r block with the flat tops..
It doesn't matter if I can't use a BIG cam, but I want a decent one. Maybe like .440" or .450" something in that area..

I can't quite remember for sure but was it the rocker arm assembly off a late model 22r that messes up the geometry stuff when put on a 20r head?

After a quick measurement it looks like the 22r valve springs are a little shorter..

 

I have the late model aluminum rockers on my 20r head with no problems. Ran that way for years. I've heard that sometimes the valve guides wear out faster tho.

 

I figured out what I was thinking.. Toysport mentions that too high lift affects the geometry, not what I was thinking..

Now I just need to figure out if I can use the valves from the late 22r.. I'll probably ask my machinist as he's done a few Toyota motors..

 

if you're building for more top end power, might as well shorten those intake runners.

 

22 r valves will work on a 20r head but will have to be cut and machined valve seats will need work .The simple tried and true methods will work . The rocker arms can only handle so much lift before bind comes a factor .. A set plan on what this motor is for will largely dictate cam choice and cam choice falls on compression ratio .. .if your n the 430 lift up range and the bottom end isn't built to aid aggressive cams it won't be optimal performance . .if the motor is going to stock internals with the exception of porting .. The engnbldr 270 cam would be prime .. Works well with the r series stock rev limit

 

I made a final decision on what I want. I'm going for a solid and reliable as well as decent top end power, not something that starts dieing out at 4000rpm. Starting with a .020 over 20r block, stock style pistons, then shaving some off for higher compression. Lightened and balanced everything, and ported and polished and bigger valves.

To me this sounds like a good setup, less moving mass from the smaller pistons and balanced so it won't self destruct at higher rpm. The only problem I see is getting it to breathe enough.

With that said, what is the highest rpm you have done with your setup while it still pulling?

 

6500 rpm mine starts to nose over. Shift at 7 thousand.

I blame my stock manifold for choking it.

But if you want to see some 20r head work, search my build thread.