445 Stroker Build Help

[plovett]

It's amazing how many people, even professional engine builders, don't understand what DCR is.  The crappy name is the biggest issue.  It sounds like what you would call cylinder pressure in a running engine.

If we could rename it that would help immensely.  Valves Closed Compression Ratio (VCCR)?  Or Cam Adjusted Compression Ratio (CACR)?

I think anybody who understands what it is, also understands it's limitations.   It's just one of many tools.  The tool is only as good as the one using it.   

JMO,

paulie

[scott foxwell]

It's amazing how many people, even professional engine builders, don't understand what DCR is.  The crappy name is the biggest issue.  It sounds like what you would call cylinder pressure in a running engine.

If we could rename it that would help immensely.  Valves Closed Compression Ratio (VCCR)?  Or Cam Adjusted Compression Ratio (CACR)?

I think anybody who understands what it is, also understands it's limitations.   It's just one of many tools.  The tool is only as good as the one using it.   

JMO,

paulie

I think calling it a ratio of any kind is the mistake. It's simply the result of the valve events. Not a design criteria or goal.

[plovett]

DCR is indeed a ratio.  It is the ratio of the volume in the cylinder and combustion chamber when the valve closes to the volume in the cylinder and combustion chamber when the piston is at TDC.

I agree it may be difficult to very accurately determine the volume when the valve closes.  No argument there.  But it's still a ratio.

JMO,

paulie

[scott foxwell]

DCR is indeed a ratio.  It is the ratio of the volume in the cylinder and combustion chamber when the valve closes to the volume in the cylinder and combustion chamber when the piston is at TDC.

I agree it may be difficult to very accurately determine the volume when the valve closes.  No argument there.  But it's still a ratio.

JMO,

paulie

Imaginary number that represents nothing useful other than to generate amusing internet discussions. Again, IMO.

[plovett]

Well not imaginary.  ANY number is only as good as your measuring tools.  No event anywhere in the world can be measured absolutely correctly.  There is always some error.  But just because there is error (lack of accuracy) doesn't mean the number is meaningless.  ALL measurements are inaccurate.  It's just a matter of how much.

JMO,

paulie

[Thumperbird]

This thread had turned into a DCR discussion but one other aspect I am looking to reserect a bit is the nitrous piece.
Since I finally got the dual carbs where I want them last summer it is time to finish the plumbing and prepare the nitrous system.  I think the engine is near the 500HP goal that was planned and the nitrous is a theoretical 200HP shot. 

Reminder there is a plate under each carb sitting on top of the offset spacers, it is a dual plane setup which I know may present some challenge/risk.  I have Edelbrock wet plates, can someone tell me if the orifice hole size # published is just the orifice id or is there some translation?

The sum of area of the bar holes (6 per bar) seems less than the area of the restrictor orifice upstream, this confuses me, seems like spray holes themselves are more restrictive.  Does anyone know what size the bar holes are supposed to be for an edelbrock square bore plate in their 250hp kit?

Was testing the system with compressed air on the car, not "hearing" the flow I think I should out of the spray bars, dumb me did not flush all that plumbing prior to assembly, off come the carbs again here some time to check and clean everything up.

May find some 50hp orifices for a total of 100hp to start with, nervous about 200 all in at once if it actually does what it is supposed to, car is plenty to manage as is being a boat and all.

[blykins]

700-750 hp on a factory block?

I’ve got spares when you split yours in half.