Now that I think about it, LSA would play a part at bleeding off cylinder pressures as well..... Not sure where to get a good dcr calculator from. The KB seems to be the popular one here on the board.

Best best would be to get ahold of Brett (sstrokerace) or Llyod (nighttrain66) and see what they could do for you by way of custom grind or parts , etc. I gave Llyod the specs and Brett designed the cam.

 

I am not sure what the deal is with the KB calculator...but it is weird.

A couple of things to keep in mind.

1. Cylinder head information is not calculated into the mix. Are they assuming a standardized VE for all motors...
2. You cannot use DCR as a fits all number.
3. In order to do this correctly, you MUST check the volume of YOUR cylinder heads.

I can say one thing, I have been around atleast 10 motors, identical to this, and they did not have a problem with detonation.

I would also second calling bret.

Dennis

 

Im getting the deck 0 decked and I cc'd the heads at 53.5 CC's earlier today. So, I should be around 11:1 SCR and 8.2 DCR. If someone thinks I should go with the -5's and still get a quench inbetween .039 and.045 and still be able to run on pump gas, I will. But I need some more info, and going with -16's will give me a large margin for error. Im open to ANY siggestions though. My engine builder needs to know before Tuesday at 9am though.

 

Hello....McFly.

 

Another semi-off topics question...

Which spark plugs should I run? And at what gap? Im not sure how much colder I should run...

NGK TR55, TR6, 4091, something else??

 

The fact that his question annoys you is a red flag that you should consider it more carefully. It is afterall a reasonable question.

Why is it a reasonable question?

Because if these "old school" builders you mention cannot explain why such a large quench is desirable then you may not want them building your engine.


FWIW, a quench of .060 is so big that I question if it can really do it's job in a naturally aspirated engine. Quench, by violently "shoving" the combustion mix to one side, homogenizes the mix for a better burn and makes the "burn field" (I just made that word up) smaller, leaving less room for secondary ignition.

These two actions do much to suppress detonation, and the larger the piston crown surface area the more important it becomes.

 

Was it not your intent to point out that he SHOULD have asked the followup question?

I realize that we disagree on the issue of Quench, but that's a seperate issue.