Rule of Thumb for Cams Compression?

[relxn88]

With all the different specs on all the different cams, is there a rule of thumb for the correct compression to be used on any particular cam. Example: Andrews 37 (intake close @42) seems to run best with 9.8/1 compression. Did somebody determine 9.8 was correct by a formula? Or is there a general rule like, anything under intake closing of 40 degrees is less than 10/1 and anything under intake closing of 45 degrees is 10.5/1 and so on. Just curious how
builders determine what the correct compression is for their specific build.
my winter build:
2002 dresser
axtell 107 jugs/ stock 4" crank
S.E. P/P heads/1.94int-1.625ex/rollerrockers/comp rel
Woods Tw-6hg cam
DakotaKid 48mm bored stock t/b
ProPipe (trying both BP and PP muffler on BP header to see difference)
3.37 gearing

[Hillside]

Originally Posted by relxn88

With all the different specs on all the different cams, is there a rule of thumb for the correct compression to be used on any particular cam. Example: Andrews 37 (intake close @42) seems to run best with 9.8/1 compression. Did somebody determine 9.8 was correct by a formula? Or is there a general rule like, anything under intake closing of 40 degrees is less than 10/1 and anything under intake closing of 45 degrees is 10.5/1 and so on. Just curious how
builders determine what the correct compression is for their specific build.
my winter build:
2002 dresser
axtell 107 jugs/ stock 4" crank
S.E. P/P heads/1.94int-1.625ex/rollerrockers/comp rel
Woods Tw-6hg cam
DakotaKid 48mm bored stock t/b
ProPipe (trying both BP and PP muffler on BP header to see difference)
3.37 gearing

There is a dedicated engine building formula to determine where you need to set the static.
Scott

[HRLYDeuce]

Scott,

After researching all of this crap about cams, engine builds, etc, and going all the way back in the forums since it's inception, how about a formula?

I posted in another thread, when reading back in the archives, you were considering a custom cam grind, one with around 545 lift, unsure of the duration, but believe it was back around 2006. Did you ever come up with anything on this?

[HRLYDeuce]

Bump, Bump!

[nw_guy4_fun]

Big Boyz has a calculator use it
If you stay under 9.1/1 CORRECTED FOR CAMSHAFT compression ratio you will be fine with todays gas provided 91 octane is available. Some may run more but this number leaves a little wiggle room.
Tight squish and a proper tune are prerequisites.

[relxn88]

Originally Posted by nw_guy4_fun

Big Boyz has a calculator use it
If you stay under 9.1/1 CORRECTED FOR CAMSHAFT compression ratio you will be fine with todays gas provided 91 octane is available. Some may run more but this number leaves a little wiggle room.
Tight squish and a proper tune are prerequisites.

Finally had a chance to go on-line and see about my question. I too was hoping for a formula. I'm not a builder, just curious.
I understand nw_guy4_fun says stay under 9.1 dynamic, but that seems to general and we have 93 octane here. I had read somewhere(Doc,or Grock I think) said that ballpark was 9.0 to 9.5 for most builds. For example, I run a Andrews 67hg with 10.5 static. This gives a 9.3 corrected compression, and it actually could use a higher static, which would give me a higher dynamic.
I guess what I'm saying is, a general statement such as nw_guy4 stated seems to be just too general.
The formula for determining the proper dynamic compression for a particular cam is probably more than I want to know. Most of this stuff goes over my head.

[arealinvestor]

People never go by corrected.It's static that people always talk about!!!You can run well into the 13's static comp.Of corse this would mean your corrected would be lower because of cam choice.How do I know this because I'm running 13.5 to 1 on my sports bike(water cooled).Of corse you need higher octane gas.I run mine on 92 and it runs fine.You will never run an HD(air cooled) at 13.5 on the street the motor wouldn't hold up.So it's not the gas you have to worry about.Most parts of the country you can still buy 92 octane.California I don't know about,but certainly most other places.The comp & cam work closely together.Your riding style also plays a big part in this,as well as,weather in your area.I say run as much comp as you can reasonably with reliability.

[BVBOB]

Example: Andrews 37 (intake close @42)

The 37 cams are actually 38 degree closing, some published specs have them at 42, set yourself up at no more than 190 ccp and you should be fine with your setup. If it really worries you, install comp releases, better to have them and not need them than need them and not have them.