Cam lobe wear

[hemiken]

According to spec it should be +5, you add combustionchambers volume by the reliefs. Domepistons is minus.

Enter Bore/Stroke Designation Type
1 = Inches 2 = Millimeters     
Enter Cylinder Bore Size                                                                    4.360
Enter Piston Stroke Length                                                                3.750
Enter Head Gasket Bore Diameter                                                        4.500
Enter Compressed Head Gasket Thickness                                             .038
Enter Combustion Chamber Volume In CCs                                             78
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-')       -5
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') :                 0

Calculated Engine Compression Ratio                10.875566027694876

This is what i calculated as your pistons are a flat top with zero deck hieght so they have to be -5cc for the valve reliefs.  If your pistons hung out of the bore it would give you more compression and a dome would give you a + reading.

[Belgium Cuda]

I meassured the piston to deck beeing 0,022 so that's already a help. I don't agree with you about the 5cc for my pistons, the reliefs take away compression since your combustion chamber gets bigger. A dome piston is higher and reduce volume and increase compression so according to
my opinion it should be +5cc.

[hemiken]

I meassured the piston to deck beeing 0,022 so that's already a help. I don't agree with you about the 5cc for my pistons, the reliefs take away compression since your combustion chamber gets bigger. A dome piston is higher and reduce volume and increase compression so according to
my opinion it should be +5cc.

Hi BC,

If a piston has no reliefs it is Zero........right   -   Flat Top
If a piston has a dish it is classed as negative........... right    - Dish Top
So anything below a flat top such as valve reliefs is classed as a negative and in this case it is -5cc.

But all is cool buddy, i just hope you can run it on pump gas like you want to. just trying to help.

Have a look back at the link for the calculator it has this same written line as below
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-')
this means you are taking away cc's from the total cylinder volume and your valve reliefs are 5cc.

[422STROKER]

Static Compression Ratio Calculator
Bore    inches    Diameter of cylinder
Stroke    inches    Distance piston moves
Head Gasket
thickness    inches    Measure your head gasket tthickness. It's usually 0.040", but not always...for example, on K1200 BMWs it is 0.070". On 113/135" ORCA motors it is 0.00 because they use metal seals and no head gaskets.
Deck Height    inches    Move piston to TDC, and measure the distance between the flat top surface of the piston (not the top of a dome or the bottom of a valve relief) and the top of the cylinder. Enter a negative number if the piston's flat surface sticks up past the top of the cylinder. At TDC the piston will "rock" so be careful in your measurements. ORCAs are .035".
Piston top
volume    cc's    You'll have to calculate this value the hard way i.e. do it yourself or call the piston manufacturer. Enter a negative number for a domed piston. Enter a positive number for a dished or dimpled piston. If you have a flat piston with no valve reliefs enter 0.00.
Combustion
Chamber    cc's    Get out your 100ml burette, your light, non-nasty grease, your handy dandy plexiglass or lexan sheet, your Marvel Mystery Oil and a six pack and get ready to party. Don't forget to cc the combustion chamber.
Static Compression Ratio:

Pretty much the opposite of this calculator.

It's all moot anyways since it comes to 10.91 at +5cc's anyways.  Your going to have to maybe polish the chambers and use a thicker head gasket to get it down a bit.

Tom

http://www.rbracing-rsr.com/compstaticcalc.html

[hemiken]

Hi Tom,
just wondering why you would use a BMW calculator as it is up side down with its comment and calculations old mate. there calculator does work when you use it the way they tell you to though.
Anything under Zero deck is a Negative and anything over is Posative, same goes for the Earth, anything under the Equator is South or Negative and any thing above the Equator is North or Posative.
I can not see were it has gasket volume anywhere ? as in bore size.  I just cc'd a pair of heads and lumpy top pistons for a 383 just three days ago and had to work everything out the old fashioned way with measurments and burette and hand calculator through a number of different formulas as they were big lumpy tops.  General rule of thumb and a quick measurement of Felpro head gasket measured at .044 new with a 4.5 hole and this comes in at around 8cc's.  And these Felpro do crush to .038 thick.

Just thought i would try wean you off that BMW stuff buddy

[422STROKER]

It was the first one I found.LOL

Here is another one though for you.

http://www.kb-silvolite.com/calc.php?action=comp

Same thing but adds bore of gasket as well, still comes out a bit high at 10.85 or so to 1 

BG maybe with some time polishing the chambers and a slightly thicker gasket you can do it.

Tom

BTW that was a Motorcycle site and they do turbos for Harleys too.

Think of the + and- this way.   If you fill the valve reliefs with fluid with your little burette thingy what do you get?  +CC's right?  Or take his pistons and take the valve reliefs and add them to the chamber volume, in this case 5cc's and now you have 83cc's.

[hemiken]

Hey Tom,

Different strokes for different blokes old mate .  I will stick to the way i know how as it works for me.
If i change things up now i will get myself in all kinds of problems

 

[422STROKER]

Do toilets flush in the opposite direction down there?

Tom

BG with a Felpro Z1105 you can get it at 10.47-1 and if you polish a bit of volume in get it a little lower to help.  Or run the 440 Source ones they are 84cc?   With your gasket and the 440 source heads you get 10.2-1.

[hemiken]

Think of the + and- this way.   If you fill the valve reliefs with fluid with your little burette thingy what do you get?  +CC's right?  Or take his pistons and take the valve reliefs and add them to the chamber volume, in this case 5cc's and now you have 83cc's.

Hey Tom, in answer to your question, it takes 5cc's to fill a -5cc relief in a piston. That is minus 5 out of a 100cc burette. if you add 5cc to a 5cc hole you get Zero simple math 101..........

Do toilets flush in the opposite direction down there?
Tom

And our toilets do run backward when flushed compared to yours of course..........

[422STROKER]

   I'm totally confused here.

Tom

I always thought that the toilet thing was a joke.

So if I drill a big hole in the piston say a 20 cc hole, according to your way I get over 14-1 compression using a -number in the calculation.  Doesn't make sense.  Shouldn't it be a lower compression ratio if there is a bigger hole(valve relief vs none for example)?

0 for piston head volume = 11.48
-5  "                            = 12.11
+5  "                           = 10.91

[422STROKER]

Ken not trying to be a pest but now I see another site asking for it as a "-" number.  Holy smokes way to confusing.


http://users.erols.com/srweiss/calccr.htm

Tom

It could be how the individual calculators work,

[hemiken]

Hey Tom, try this one i posted on the last page


http://www.csgnetwork.com/compcalc.html

same deal.

and the toilets really do cycle in reverse to your toilets here in Australia buddy

Maybe you should start using the new calculator you found as it is the right way of thinking.
Drilling a hole in a piston would make the compression less for sure.  and drilling would be taking away material, that is a minus "-" , Minus = less.  End of lesson 101

[422STROKER]

I got you, what if you made the chamber bigger would that be minus too?

Tom

Belgium Cuda what you going to do?

[Belgium Cuda]

Calculating it my way, +5, I will go for a Felpro 1039 gasket which will lower the comp to approx 9,8. That way I can use the heads.

No offense hemiken 

[hemiken]

Calculating it my way, +5, I will go for a Felpro 1039 gasket which will lower the comp to approx 9,8. That way I can use the heads.

No offense hemiken 

Hey BC, water off a ducks back buddy. Nothing sticks there.  All in the individuals perception. Your way works for you, and thats that i am cool with it.

let us know what thickness Felpro gasket you decide to get