Here is a good read....

Just one example:
The FRPP aluminum SCJ's will flow about a MAXIMUM of 360 CFM @ about .650" valve lift on the intake side with only a "bowl port" job.
The Trick-Flow streets will flow a MAXIMUM of about 375 CFM @ around .750" valve lift with the same kind of simple "bowl port" job.

There is no contest if the maximum flow numbers are the only criteria.

The SCJ's flow about 315 CFM @ .400" valve lift and those STREET's will flow about 275 CFM @ .400" valve lift.
At overlap the SCJ's intake valves are minimally hampered by a valve notch in the piston where the STREET's intake valves are deep into an intake notch which hampers flow from the intake; until the piston is out of the way.
The SCJ's intakes empty into the cylinder right near the bore centerline where the bore is widest and the STREET's empty near the exhaust side of the bore which is not a prime location. The exhaust valve locations have similar values.
The SCJ's use about 5° less ignition timing than the STREET's in order to make maximum cylinder pressure.

NOW ... the choice between cylinder heads has a whole new meaning than simply maximum flow numbers.
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Last edited by rmcomprandy; 12-01-2009 at 07:25 PM.

I guess the area under the curve at all cam lift values is most important. The peak flow is nice but one needs to look at the whole picture, not just the peak numbers.

Bill

Very good read, indeed!

that right there is what puts flow numbers in perspective ................ Great read Lem

Thanks Lem.









Doug...

...Thank Randy he wrote it

Now do a max effort port on both heads and really see the SCJ's shine.

even with a simple port bowl blend a set of Streets can build 800+ hp. in essence thats still pretty impressive...


Randy

This thread is about what to think about ....not which is best ....tfs/scj/p51...we are very lucky these days...aint NO wrong cyl. head...just the one that is best for ones needs/budget .

I agree Lem if Fords were like Chevies we would have 27000 different heads to choose from...I am just happy we have the great choice we have....


Randy

the Coug wrote:I agree Lem if Fords were like Chevies we would have 27000 different heads to choose from...I am just happy we have the great choice we have....


Randy

Are Procomps included on this list of great heads???

couldnt resist.

We have come along way w/bbf heads in the last few years,but I think we have a long way to go yet. I think the GM stuff is still ahead of us in R&D and also in selection and low prices. I would like to see more companies step in like DART and Merlin. IDT has some really nice Selections for A head BBF's right now. If I was building a Big inch A head I would seriously look at going w/them. JMO