Thread: Domed pistons and quench?

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Have any of you people got a link where I can read up on Dave Vizards new thinking ?

http://www.compcams.com/Community/Ar...ID=-2026144213

What?? No comments yet??

Some more Vizard:
http://www.babcox.com/editorial/ar/eb90252.htm

And a lively discussion from another forum:
http://forums.performanceyears.com/f...d.php?t=479323

I read quite a bit of it last night and to be honest,,,I am having trouble accepting that overlap and LCA are more important than lift and duration.And wish he would have wrote it so a country boy could easily understand it
Did anyone notice that the LCA determination chart is a little off from what factory HI-PO motors are? But of course the major mfr's.had to keep driveability in mind.
I'm still reading and will check out the other two links,,,very interesting. Give me a month or two,,,,

WHEW ???? thats a big read tech, just got to think about it. Then go back and read it some more.

There are a couple of things that have come up in all this reading that I'd like to pass on.

First, lifter clearance in the bore. Performance motors should be set up with 0.0015" to 0.0025" clearance. You want the lifter loose enough in its bore that the cam lobe will rotate it, but not so loose that you begin to lose oil pressure. Oil pressure problems would begin around 0.004" to 0.005" clearance. If the lifter is too tight in the bore and the lobe can't rotate it easily, the lobe will tend to wipe off the lube at the lobe/lifter interface and you know what happens then.

Armored lifters: Compcams has developed a lifter that has a stellite coating on the face of the lifter that supposedly will make the lifter more scuff-resistant.

Beehive springs: This looks like a real good idea. The wire used to wind these springs is shorter in vertical section (oval) than a conventional round wire spring. This will allow more lift with the same setup. Also, the retainer used with these springs is smaller in diameter. It is therefore lighter than a conventional straight spring retainer and also will allow more clearance between the rocker arm and the retainer when using higher lift cams.

Lift: Vizard recommends all the lift that can be bolted into the motor. That would have me thinking that it would be a good idea to use 1.6 rockers on every small block Chevy I build from now on.

Just something for you guys and gals to chew on.

A novice or newby builder may be making a bigger mistake in cam selection than they usually would if they choose a cam based on overlap and LDA. Because,,,unless I'm wrong,,,he is making this suggestion based upon the presumption that the intake and exhaust sides of the entire motor are properly designed. If they are, then I can see his reasoning and learning from it. Think back to your teeny-bopper days if you chose your first cam with a tighter LDA and higher overlap then you'd made the same goof-up I made But his suggestions are 'seemingly' for a race motor with 'proper designed intake and exhaust systems',,,,,everything balanced proper. How many motors aren't???
A small valved,short stroked motor with a full and restrictive exhaust system may not like the overlap that the chart suggests?

Then there is the hollow stemmed stainless steel valves that are lighter than the convential solid valves. They are lighter so their float revs are higher 8000rpm up on a solids 7600 rpm. Also the beehive springs by thier design help prevent spring surge, so not so much mass of the spring is needed to control surge as in a conventional paralle spring, so the spring seat and open pressures can be lighter, thus cutting sown on cam and lifter wear.

Sorry to resurrect an old thread but I have been digging for info. since this and can't find an answer either in books or on the internet.
My question concerns octane and high CR's.
What is the deal with octane limitations but race motors are running high CR's?
I have heard/read that race motors can run a DCR as high as 9.1:1 on race gas without problems,,,now does this mean that a race engine running 13:1 or even 16:1 has to design the motor to produce 9.1:1 DCR???
Is there really a DCR limit if using race gas???

Originally Posted by FAYLUR

Sorry to resurrect an old thread but I have been digging for info. since this and can't find an answer either in books or on the internet.
My question concerns octane and high CR's.
What is the deal with octane limitations but race motors are running high CR's?
I have heard/read that race motors can run a DCR as high as 9.1:1 on race gas without problems,,,now does this mean that a race engine running 13:1 or even 16:1 has to design the motor to produce 9.1:1 DCR???
Is there really a DCR limit if using race gas???

What we have been doing on gas is 13.5 to1 or less 112 octane over 13.5 to 1 we use 116 octane.
If you run the higher octane gas with the low comp. engine I doubt you will see any hp gains.