Home1) What are those little boxes above the page tabs?
2) How do I enter the correct dome or dish size?
3) Why does the Valve Timing Calculator show 4º of advance when I installed the cam straight up?
4) What dome or dish size are my pistons? What is my valve relief size?
5) How far down the bores are my pistons?
6) What is the thickness and bore of my head gasket?
7) My cam specs say the intake valve closes at 30º. Why does the program say it closes at 66º?
8) I DLoaded the program but Excel or Word says it can't open it.
9) I DLoaded the program but Windows says a file is missing.
10) How do I open the archive (.ZIP) file?
11) Do I need to press the calculate button when I make a change?
12) How accurate are these calculations?
13) Why is the calculated Static CR with the DCR calculator different than what the mfg says.
14) Step by Step instructions for using the DCR Calculator
1) What are those little boxes above the page tabs?
Those are information boxes to remind you what duration and intake closing angle is in use. Early versions of the program do not have the feature. The first version that has this feature allowed the user to overwrite the display. However, anything written in these boxes by the user is ignore and will be overwritten by the program when the "calculate" button is pressed. Later versions have these boxes locked.
2) How do I enter the correct dome or dish or valve relief size?
Use the mfgs published volume. Some mfgs use a negative sign for domes, others use a positive sign. So, put it in the box as a positive number and select the proper type of piston ("Flat or Dish" or "Dome"). The program will assign the proper sign. If you have measured the piston volume, use that. It is likely to be more accurate than published figures. Remember to select the proper type of piston and use a positive number.
3) Why does the Valve Timing Calculator show 4º of advance when I installed the cam straight up?
Cam timing is always referenced to the crankshaft. That is, the installed intake centerline (ICL) is always in degrees after top dead center. Some cams are manufactured with some amount of advance built into them, 4º is very common. In this case, if the cam is installed with the timing gear marks lined up for "0" advance, the cam is actually installed with 4º of advance. While the timing set may say the cam is straight up, it is, in reality, installed with 4º of advance. The program (or engine, for that matter) doesn't know or care what the timing set is installed at, it only cares where the ICL is in relation to the crankshaft.
4) What dome or dish size are my pistons? What is my valve relief size?
I can't answer that. There are a great many different dish, dome, and relief sizes manufactured. You need to find this yourself. If you are using KB pistons, their site has very good information available. In most cases the CR stated are quite accurate (there are a few errors). KB uses .040" quench distance for all their calculations. Federal Mogul/Speed Pro has a horrible site with no information available. You need to find someone with a catalog. Their CR estimates are not reliable since they never spec what gasket thickness, deck height, or quench is used. Here are a few piston volumes. More will be added as I get them.
5) How far down the bores are my pistons?
It is essential to know this dimension. Stock deck height for SBC and BBC is .025". The pistons should be this distance if stock compression height pistons are used and the block has not been decked. This can vary a bit, say +-.005". If the block has been cut, the only way to know is to measure. In addition, the compression height of pistons should be mentioned. Most cast replacement pistons are made with the wrist pin .020" higher in the piston. This lowers the top of the piston this amount. This is done to lower the CR in stock rebuilt engines that have had the block surfaced. It is not desirable for a performance engine. Also, many high performance forged pistons are made for a 3.500" crank in a 350ci SBC. This lowers the top of the piston .010" below the stock height unless a 3.500" stroke is used. So, to know how far down the bores your pistons are, you need to either measure (the best way) or know if the compression height is the stock height and if the deck has been cut (and how much).
6) What is the thickness and bore of my head gasket?
This is something you'll need to research. It is usually printed on the packaging or the paper work supplied with the gasket. You can also, find some data at Summit or Jegs web sites and in their catalogs. As for Fel-Pro SBC gaskets, the composite gaskets of .039" and .041" thickness have 4.166" bores. The shims (.015" and .018") have 4.100" bores. Victor has .020" and .026" compressed thickness gaskets for the SBC, the bore is 4.100". I don't know any others.
7) My cam specs say the intake valve closes at 30º. Why does the program say it closes at 66º?
The program uses advertised duration for the calculations. Most mfgs don't give advertised duration cam timings anymore and only supply .050" timing. .050" valve timing events are totally useless to both humans and engines. When you enter the advertised duration, LSA, and the ICL in the Valve Timing Calculator, the program will calculate the timing events. These calculations are accurate and are the values needed to accurately calculate the DCR. That is why the Valve Timing Calculator is included. Since overlap is easy to calculate from the results, it is included for your information. It is not used in calculating the DCR.
8) I DLoaded the program but Excel or Word says it can't open it.
The program was archived with WinZip 7.0. Excel or Word are not the proper utilities for un-zipping the program. You can get a free demo of WinZip from WinZip's site.
9) I DLoaded the program but Windows says a file is missing.
You need to DLoad the larger version of the program. The DCR Calculator was written in Visual Basic 6 and need certain files to be on your system in order to run. These are called Visual Basic Runtime files. No version of Windows comes with these files, they must be installed. The larger version of the DCR calculator has these files bundled with it. You can also DLoad them from Microsoft's site.
10) How do I open the archive (.ZIP) file?
Use an un-zipping utility like WinZip. You can get a free demo of WinZip from WinZip's site. After Un-Zipping the archive, run "Setup.EXE" to install the DCR Calculator. You can Un-Install the calculator with Control Panel's "Add/Remove Programs" utility.
11) Do I need to press the calculate button when I make a change?
Yes. The computer has no way of knowing you want calculations made on any changes unless you tell it by hitting the "Calculate" button.
12) How accurate are these calculations?
Very accurate. The Valve Timing Calculator uses industry standard formulas for calculating the valve timing. The Dynamic Stroke Length Calculator (which is the heart of the DCR concept) uses a formula I developed used CADD drawings. It has been tested with a great many different intake closing times, rod lengths, and strokes. The results matched exactly with charts posted on Isky's web site. Unfortunately, the chart is no longer at the URL I have for it. When I was building my last engine and degreeing the cam, I measured the piston location at intake closing. It measured exactly to what the calculator predicted. The CR calculator is one I found on the net. I like it because it includes some items other calculator don't, like gasket bore and deck height. It does not include the space between the piston and the cylinder wall above the top ring. So it's not perfect but is very close.
13) Why is the calculated Static CR with the DCR calculator different than what the mfg says.
Most piston mfg do not spec the quench distance used. Speed Pro/TRW uses what they call industry standard gaskets for their calculation. I don't know what that means. Specifying the quench distance would eliminate any question of the accuracy of their spec. The only mfg I know of that specs the quench distance is KB pistons.
14) Step by Step instructions for using the DCR Calculator
Click the cam timing tab
Enter the adv dur for intake and exhaust
Enter the LSA and the intake center of the cam install
Click calculate
Click the stroke calculator tab
Enter the stroke
Enter the rod length
Click calculate
Click the Compression ratio calculator tab
Enter the number of cylinders and bore
Click the check box 2 times to transfer the stroke from the stroke calculator
Enter the cc of chamber and headgasket data
Enter the piston cc and click whether dished/flat or domed
Click calculate. This displays the Static CR.
Click the check box to make the check mark visible. This transfers the Dynamic Stroke Length.
Click calculate
Read the green number at the bottom of the page. This displays the DCR.NOTE: You can run multiple copies of the DCR Calculator to compare results for different combos.