Blake's Truck UPDATE

Blakewilder said:
Sounds good...Mike calls it SUBLIMATION!
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My wife is a chemist and loves the reference!

I learn so much from this site.
 
Prof said:
Can someone help me with the head flow issue??? With the assumption that an engine is just an air pump, what goes in needs to come out...what happens to the 58 cfm between intake and exhaust?

Still trying to learn.
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I would have to guess that you are burning off some of the O2 in the air along with the fuel. But what do I know?? LOL
 
Prof said:
Can someone help me with the head flow issue??? With the assumption that an engine is just an air pump, what goes in needs to come out...what happens to the 58 cfm between intake and exhaust?

Still trying to learn.
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Okay, where do I start.

Intake ports will always flow more than exhaust ports. You will also notice that the intake valves are always larger than the exhaust. Now as to why.

The only flow through the intake is a result of the suction created when the piston is on the down stroke. (Please note I'm only talking about a N/A motor and I'm not going to get into the effect that cam lobe overlap and header scavanging has.) On the exhaust stroke the piston is forcing the exhaust out the port. Make sense so far?

Where did that 58 CFM go? It's magic. Okay, not really. The flow of the exhaust is considerably more than the intake for a couple reasons. But first I want to remind you that the flow on the flow bench is measured at a specific vacuum level. In this case I believe it was 28 inches of water. So if you disconnected one sparkplug where that cylinder was not firing, the flow would be the same between the intake and the exhaust because the volume of air would be the same going in as going out. Still with me? Okay, now why is the volume so much greater when the cylinder is firing? Because when the sparkplug ignites the air/fuel mixture you have an explosion. These expanding gases are what drives the piston down for the power stroke. Well when the piston reaches BDC (Bottom Dead Center) those expanding gases are still wanting to expand further. Even if the piston did not go up on the exhaust stroke, if you were to open the exhaust valve the gases would go out the exhaust valve until the pressure equalized.

I hope that helps. If you still have any questions, let me know and I will try again.
 
Blakewilder said:
Yeah they are painting the block today and they are emailing me pics...Ill post em up. SD??
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SD as in San Diego :D ... redram he's not here yet, in a few weeks :D ... or sooner :dontknow: :D
 
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