My Oregon cam regrind came in yesterday.  It is grind #218, mild, I & E duration at .050 is 225 degrees, duration 260, lobe separation 108,intake centerline 108.

I need to settle on a target static compression.  Does this dynamic cranking compression sound right?  154 psi.  Here are the variables that I plugged in giving the calculated 154 figure..  Alt. 1330, bore 3.86, stroke 3.44, rod length 6.25, intake .020 before closing is at 58 degrees ABDC, static compression 9.7:1.  The 154 psi seems lower than expected so I would like someone else to have a go at the numbers. 

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

That sounds nice!



It'll probably increase with little ring break-in.....





You did do it with either the carb removed or the throttle plates full open?

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
1955 F-600/272/E4OD// Disclaimer: No animals were injured while test driving my F-600 except the ones I ran over intentionally!

---------------------
This post was created using OpenSuSE Linux x64 and Firefox

Rick it is in the machine shop.  I'm trying to decide upon what the static CR should be, with the resulting Dynamic Cranking compression.  My understanding is much above 170 psi cranking compression gets into the detonation area.  Given the mild cam I was surprised what the calculator showed on dynamic Comp.  Figured it would be higher, but maybe I am using the wrong calculator.  With gas expense as it is, sure wouldnt want to build this to run on premium.

I edited the first post.  Maybe it is clearer now. 

Also, I dont recall seeing the ceiling of cranking compression for running regular.  What is it, and would it be raised a little with E10?  Iron heads in use for all of this.

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

I don't think you should let gas prices alone influence this decision. Higher compression results in higher efficiency. Higher efficiency equals more distance per gallon. The part that is tough to determine is just how much more distance, and how does it actually compare to cost. I bet it at least breaks even, and is possibly cheaper.



Will you be using the same set of heads, milled, for the proposed increase or are you planing on another set? A mileage/actual cost of use experiment will be interesting.


Lawrenceville, GA

Point well taken.  OK how about the cranking compression ceiling on mid grade .

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

I'm not sure about mid grade pressure.



I just got to thinking, with my old engine, I got about 12mpg on the highway. With my new engine, I get 13.5mpg when not in overdrive. I just don't know if it can be considered apples to apples with the stroke increase, different intake, compression increase, and etc. Pretty much, the cam is the same and everything else is different. If it can be considered apples to apples for the compression increase argument, it means you should go about 1.125 times farther with every gallon. I don't pay attention to gas prices, premium is what, 20 cents more than mid grade, so lets say 3.40 vs 3.60, that's a 1.059 increase in cost for a 1.125 increase in economy. Even from regular to premium is only about 1.091. That's definitely better, and if only a compression increase can result in the same thing, it can be a very cost effective way to increase mileage.


Lawrenceville, GA

I've been thinking too.  My 9.2 CR 292 with Isky E-4 duration at .050 of 216 (I think), has a cranking pressure of 150+.  This cam has a longer duration at .050, more overlap I assume, therefore 154 psi with static CR of 9.7 may be pretty close.  I do fine on regular, so maybe bump things to 160 cranking pressure (which may be possible with cam advance).  Sounds like a plan until someone fills it with holes.

With Mummert's rods, popup pistons and their nice pin location, shooting for prescribed CR sure is a lot easier.

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

Mike

Since you seem to be playing with a computer program to predict the compression PSI rather that taking an actual real world measurement what would running a 10.5 to one compression ratio and using a much longer duration cam have on cranking PSI? Can you set up the computer program to forecast  PSI by changing all the variables? If not, which ones can you change?

I take it you already have the cam? If your worried about the cost of premium gas have you looked into a knock sensor  or just restrict ignition timing as gas mileage is really most effected by vacuum advance with the engine under almost no load while mechanical advance can occur under extreme load. Pete

Pete, here is the calculator http://www.wallaceracing.com/dynamic-cr.php .  The thing here that really has to be known is how many degrees ABDC does the cam close to within .020.  Like it will take a few seconds to figure Dynamci compression at 4 degrees afvance, but I am trying to keep my mind on assemblying this damn desk.  It has more parts than a carburetor.

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.

I've been going at this again this AM, even though the desk isnt together yet .  The figure of 58 degrees ABDC I was using is the intake valve closing event of this cam, not .020 off of closing.  Luckily the calculator calls for the actual closing.  Dont know where I came up with the .020 part.

With the cam advanced 4 degrees, and using the resulting 54 deg. ABDC in the calculator, and bumping up the target static CR to 9.8, a dynamic cranking pressure of 162 psi, with Dyn. comp ratio of 8.13 is the answer.  It looks to be a good objective.

With a comb. chamber of 70cc, piston dome vol. of 5cc, and piston to deck clearance of .004, the static CR works out to 9.82.  Cool.

Mike, located in the Siskiyou mountains, Southern, OR 292 powered 1946 Ford 1/2 ton, '62 Mercury Meteor, '55 Country Squire (parting out), '64 Falcon, '54 Ford 600 tractor.