Weekly Fun Question for 1-01-2011 - Test Your 71-73 Mustang Knowledge

Good Day All,

First of all, I wish each of you a very Happy New Year!

As we TRY to do every Saturday, this thread is designed to post the "Weekly Fun Question." The first non-VIP Forum access member to provide the correct response to the question via PM to "rocketfoot" and me will be declared the "winner" and will receive a nice #1 Icon. As a reminder, any non-VIP Forum access member who provides the correct response to three (3) different "Fun Questions" will have his/her membership upgraded to VIP status.

The question this week has to do with a member who has a 1972 351C (bored .030 oversize) motivated Mustang. The engine has a Competition Cam XE274H and has been dynoed to reflect a volumetric efficiency of 90%. The specific question is:

Based on the dyno results and the specifications of the camshaft, what size (CFM rating) carburetor would be optimum for this application? A two (2) part question, the correct response MUST include an explanation as to how the response was developed.




Again, responses are to be sent via PM to "rocketfoot" and "cobra3073." Results will be posted to this thread on Monday, January 3, 2011 at approximately 7:00 PM (CST).

Please note that VIP members may also respond to the question for "bragging rights" - - within their ranks. As with the non-VIP Forum members, responses from the VIP members should be forwarded via PM to "rocketfoot" and me. Those results will be posted on the VIP Forum on Monday, January 3, 2011 at approximately 7:00 PM (CST).

Again, Happy New Year and Good Luck on your response to this week's question!

BT

Well, we do have a WINNER - - david020278!

To recap, the scenario for this week's "Fun Question" had to do with a member who has a '72 Mustang with a 351C bored .030 over sized. The motor has a Competition Cams XE274H camshaft and has been dynoed with a volumetric efficiency (VE) rate of 90 percent.

It should be noted that typical VE for "street engines" is usually about 75 - 80 percent. Please keep this in mind when considering your own carburetor requirements. The engine in question obviously has some improvements.

The specific question for this week was:

Based on the dyno results and the specifications of the camshaft, what size (CFM rating) carburetor would be optimum for this application? A two (2) part question, the correct response MUST include an explanation as to how the response was developed.




To reach the desired response, there are three "issues" to be addressed. The range of the camshaft (2000 - 6000 Per Comp Cams), the size of the engine (351 has a 4.00" bore + .030" = 4.030") and finally the size of the carburetor. Please note the 351C has a stroke of 3.50". One way to correctly determine engine size is by using the formula:

Bore X Bore X .7854 X Stroke X the number of cylinders. For this case:

4.030 X 4.030 X .7854 X 3.50 X 8 = 357.1568

Armed with this information, one can now use another formula to determine desired CFM.

VE X Engine Size X Maximum RPM : 3456 = Desired Carburetor CFM

.90 X 357.1568 X 6000 : 3456 = 558.05 CFM

 


For this situation, a 600 CFM carburetor should be fine.

We only had one response (from the general membership) and that response (which was correct) was submitted by david0202787.

GREAT job, David!

BT

Congrats, David! Your award has been issued! Keep up the great work!

Congrats, David! Your award has been issued! Keep up the great work!

Click to expand...

Congratulations, David! Good work!

Doc

::goodjob:: and way to go

Alright David!

Great! Thank you....