Cam choice??

[daveismissing]

.... One is that alum heads need about 1 full point to be on par with iron....
[size=78%] [/size]

0.1  or 1.0 ?


Could someone elaborate on this phenomena? Why?

[motorhead]

.... One is that alum heads need about 1 full point to be on par with iron....

0.1  or 1.0 ?


Could someone elaborate on this phenomena? Why?

1 full point.

http://performancetrends.com/Definitions/Heads.htm
Material is typically either cast iron or aluminum.  Aluminum is lighter and easier to port and modify.  However aluminum can "suck" more heat out of the chamber due to it's higher thermal conductivity.  The aluminum head may run cooler, which helps pack more air into the chamber because the incoming cool air does not pick up as much heat.  Both of these aspects can help avoid detonation and improve volumetric efficiency. 
However, loosing heat to the coolant rather than keeping in the chamber to push on the top of the piston should reduce thermal efficiency.  This is typically insignificant to the other cooling benefits to aluminum.
Depending on the actual warm-up time and other aspects of the engine's running conditions (quick drag race vs road racing vs street driving), cast iron can actually run cooler than aluminum in some cases.

I love this site: http://speedtalk.com/forum/viewtopic.php?t=5973

http://www.popularhotrodding.com/tech/0311_phr_compression_ratio_tech/viewall.html

Tonnes more if you are interested: https://www.google.ca/#hl=en&safe=off&tbo=d&sclient=psy-ab&q=thermal+efficiency+aluminum+cylinder+heads&oq=thermal+efficiency+aluminum+cylinder+heads&gs_l=hp.3...538.14431.0.14590.46.45.0.1.1.0.235.4744.33j11j1.45.0.les%3B..0.0...1c.1.D4wwLApE66s&pbx=1&bav=on.2,or.r_gc.r_pw.r_qf.&bvm=bv.1355534169,d.aWc&fp=1585625df7f66034&bpcl=40096503&biw=1388&bih=912

[TWIN86GNS]

Earl,
 
Thanks for the video of checking the volume of the heads.  I think I will try that next week sometime.  I will see if I can find a large syringe or a turkey baster that will show ml.
 

[TWIN86GNS]

TWIN86GNS,

210/215 roller over hear from Mike at Full Throttle mated to 1:65 roller rockers in champion iron heads, 98% street car, lights up the tires at 55 mph in 3rd gear when you go WOT. Not scary, but you can hear them spinning.

Earl,

Thanks for this information above, good stuff!

Chuck

Chuck,
 
Thanks for the post.  Are you happy with your cam and if you had to do it all over again would you get the same cam again?  If not would you go bigger or smaller?

[84 BuickGNYorkPA]

Paul,


You know me, I'm not a racer but a daily driver(always drive to BPG and other events), so there are better combinations out there for the racing crowd then what I have.


But on the other hand for a street car, not sure what I would do different in the roller cam or the roller rocker department. I do have maybe a half second delay when I floor it before I'm in the boost, but once I'm at 1-2 lbs it seems to be instant 25#lbs boost from there.


I've noticed that some of the faster guys have the cam numbers switched, say a 218/210 grind instead of the 210/215 that I run.


Chuck

[earlbrown]

Chuck, if you've got the pushrods for it, you should slap a set of stock rockers on your car. There's a chance you'll pick up some gas mileage and throttle response without slowing down.

Any idea what the separation angle is on your cam? Is it wider than normal to offset the 1.65 rockers?

[84 BuickGNYorkPA]

Earl,


It was a new 210/215 off the shelf roller cam kit, the rockers, 1:65 new off the shelf also, at the time there where no 1:60 in stock. I was very perticular with the valve train set-up. I brought home my machinist tools from work and took my time, had to order special length push rods. Mike at Full Throttle Speed, was super to work with me on getting the new push rods. I was concerned about valve spring binding, but never a issue, also valve depth at full open to the pistons, I have plenty of clearance with the diamond pistons, that are notched.
I now where progressive glasses, and it's no fun to wrench anymore, especially being under the car looking up... so I probably won't go back in the motor until some type of failure occurs and we all know that it will, eventually. I see that Dr. Paul (pacecarta) is in the 9's with a 1:55 roller rocker.


Chuck

[earlbrown]

I was just thinking it might be more efficient without the extra overlap from the rockers.