Take 2: Second Head Under the Knife

[flat_black]

New info in post #3!

 

[PR5Matt]

Well, no pictures this time, but a little bit of information that I forgot to post. =)

Firstly, I have some volumes for you all. Stock head specs are as follows:

Stock Head Gasket Thickness: .040" (1mm)
Deck Height: .060" (1.5mm)
Combustion Chamber Volume: 44cc (1cc max variance Low: 43.5, High: 44.5)
Piston Displacement Height: 4cc for stock 9.1:1, -4.7cc (Domed) for 10.4:1

I'll be ordering a new head gasket at .027" thickness, and the head is getting milled .010", which should bring me up to JUST shy of 11:1 compression, when all is said and done, and welding up the quench should put me around 40-41cc chamber volume, which puts me right where I want to be, at around 11.5:1 CR. =)

Please get that head flowed at some time so we can get an idea of what we have to work with. Your porting is so mild that an after flow job would be okay for my uses.

 

[flat_black]

Wow... Big font. The exhaust ports are 50mm wide, and intake are 52mm, that's a widening over over 3mm via porting, so it won't be accurate. For that matter, I've done extensive bowl work, and the valves are now swirl polished, the intake and exhaust ports are coated, as is the combustion chamber, so... It might be a bit off.

However, I do have a stock head (Three total, now), and I can get that flowed at some point. The issue with that is that unless you get the flow measured on the same machine, or same style machine, it won't be accurate. I intend to get the stock one flowed at some point, just to compare my results, but I don't think the flow numbers on this one will be too useful to you.

 

[chooch]

Well, no pictures this time, but a little bit of information that I forgot to post. =)

Firstly, I have some volumes for you all. Stock head specs are as follows:

Stock Head Gasket Thickness: .040" (1mm)
Deck Height: .060" (1.5mm)
Combustion Chamber Volume: 44cc (1cc max variance Low: 43.5, High: 44.5)
Piston Displacement Height: 4cc for stock 9.1:1, -4.7cc (Domed) for 10.4:1

I'll be ordering a new head gasket at .027" thickness, and the head is getting milled .010", which should bring me up to JUST shy of 11:1 compression, when all is said and done, and welding up the quench should put me around 40-41cc chamber volume, which puts me right where I want to be, at around 11.5:1 CR. =)

Just wondering where this info came from... it's way different from what I measured. I just double checked and measured a stock head gasket and it's 0.026". I cc'd the chambers a while back using an acrylic cover and syringe (burettes are expensive) and the variance could not have been more than 2cc off. I measured 36cc.

Stock piston 9.1:1: -18cc dished
10.4:1 piston: -9cc dished (I have a set here)
Deck clearance: 0.015" block has not been decked. #1 cyl at TDC measured with a digital caliper.

http://www.wiseco.com/PDFs/Catalogs/SC06_HyundaiMazdaMCooper.pdf

Wiseco actually has this information in their catalog. I would hope they are more accurate than me but I'm not too far off from the spec's they have.

 

[flat_black]

This was also cfrom ccing the chamber, lexan cover, burette, and so on. The headgasket thickness was from a stock, unused headgasket. Dished should be measured in positive volume (4cc), and domed should be negative (-4cc.) This does not include deck height, of course. I can try it again, but I'm pretty sure the results are pretty accurate, as the comes out comes out to aproximately right.

Doing it with your results of 0.026" gasket, .015" deck, and 9cc piston dish displacement, according to:

[(3.27 2)2 x 3.14 x 0.026 x 16.387064] + [(3.27 2)2 x 3.14 x 0.015 x 16.387064] + 36 = Vc (Compressed Volume)

[(3.27 2)2 x 3.14 x 3.62 x 16.387] + Vc = Vu (Uncompressed Volume)

Rc (Compression Ratio) = Vu / Vc

This ends up being 10.83:1 CR on the 10.4:1 pistons, and 9.35:1 CR on the stock 9.1:1 pistons.

I'm not sure exactly where the variances would occour in the measuring, but I can have DPR check the volumes and CR for me to make sure once I send them the stock head I have for flow testing, if you think they're way off. =)

 

[chooch]

This was also cfrom ccing the chamber, lexan cover, burette, and so on. The headgasket thickness was from a stock, unused headgasket. Dished should be measured in positive volume (4cc), and domed should be negative (-4cc.) This does not include deck height, of course. I can try it again, but I'm pretty sure the results are pretty accurate, as the comes out comes out to aproximately right.

Doing it with your results of 0.026" gasket, .015" deck, and 9cc piston dish displacement, according to:

[(3.27 2)2 x 3.14 x 0.026 x 16.387064] + [(3.27 2)2 x 3.14 x 0.015 x 16.387064] + 36 = Vc (Compressed Volume)

[(3.27 2)2 x 3.14 x 3.62 x 16.387] + Vc = Vu (Uncompressed Volume)

Rc (Compression Ratio) = Vu / Vc

This ends up being 10.83:1 CR on the 10.4:1 pistons, and 9.35:1 CR on the stock 9.1:1 pistons.

I'm not sure exactly where the variances would occour in the measuring, but I can have DPR check the volumes and CR for me to make sure once I send them the stock head I have for flow testing, if you think they're way off. =)

I get approx. the same number with compression ratio calculators but the high numbers from calculations could very well be from a 2cc measurement error. If you look at the Wiseco catalog, they list the piston as -16.5cc. No way it could be a 16cc domed piston. Also, if you use any online CR caculators, dished is negative.

I know my volume measurements aren't 100% accurate, maybe not even 90% accurate but I am sure about this:
9.1:1 piston is dished more than 4cc
10.4:1 piston is not domed
My used head gasket is 0.026" so you should be using this value or less for CR calculation. It will actually be slightly less than 0.026" compressed.
Piston to deck clearance is between 0.015-0.020"

What's your view on your volume measurements vs Wiseco's?

I'm not trying to be difficult or to discredit you. If I'm doing something wrong, I would like to know because I just sent my head out to be milled 0.030". I've been working with Wiseco's volume numbers, since my measurements "apparently" came pretty close, and punching number's through CR caculators that tell me it will put me at ~11.1:1. My chambers have been opened up to a full 83mm and I have factored it in.

 

[PR5Matt]

Wow... Big font. The exhaust ports are 50mm wide, and intake are 52mm, that's a widening over over 3mm via porting, so it won't be accurate. For that matter, I've done extensive bowl work, and the valves are now swirl polished, the intake and exhaust ports are coated, as is the combustion chamber, so... It might be a bit off.

However, I do have a stock head (Three total, now), and I can get that flowed at some point. The issue with that is that unless you get the flow measured on the same machine, or same style machine, it won't be accurate. I intend to get the stock one flowed at some point, just to compare my results, but I don't think the flow numbers on this one will be too useful to you.

Anything is useful. Either what we have to work with (stock) or what is possible (your head).

 

[shabaka]

this is an oldie but....sub'n
pay no attention to me...nothing to see here

 

[Crazee D]

Funny I just subd yesterday

 

[shabaka]

yeah i have a head dying on me right now
it's like having oil squirters on the wrong side of the piston
...grab'd this for a good resource

 

[Thekid760]

Bump, Flatblack, have you got this head back yet? Has it been flow benched yet?