Cylinder Head Flow Numbers

We can agree that this head with bigger than stock valves and port work of whatever quality you want to say, is an improvement in flow compared to a stock head. Flowing somewhere between stock and 300cfm intake and 180cfm exhaust, and leave it at that.

All at 0.500 lift-

211cfm Intake/141cfm Exhaust - stock head 1.91"I/1.50"E
261cfm Intake/166cfm Exhaust - Clearwater aftermarket BV head with 2.02"I/1.60"E no porting
237cfm Intake/182cfm Exhaust - Dr. J's ported stock 1.91"I/1.50E" -By one of the top porters out there
???cfm Intake/???cfm Exhaust - Actual 505 Perf BV Stage 3 ported head 2.00"I/1.57"E
300cfm Intake/180cfm Exhaust - Claimed 505 Perf BV Stage 3 ported head 2.00"I/1.57"E

What I would really want is a Clearwater aftermarket BV head (+50cfm Intake/+25cfm Exhaust) that has been sent to and ported by Dr J's (+26cfm Intake/+41cfm Exhaust), but that doubles the price, but if additive, would be a thicker aftermarket new head, big valve, ported that flows 287cfm Intake and 207cfm Exhaust.
 
CobraMarty said:
We can agree that this head with bigger than stock valves and port work of whatever quality you want to say, is an improvement in flow compared to a stock head. Flowing somewhere between stock and 300cfm intake and 180cfm exhaust, and leave it at that.
Click to expand...

There is no agreement here. The work on that head is unprofessional and less than amateur. Sunken valves never help flow, unless they are covering up some other disaster. And that isn't even slightly sunken, its like Titanic sunken.
 
Talyn said:
And that isn't even slightly sunken, its like Titanic sunken.
Click to expand...

this and the rust in the water jackets are the two big red flags I saw... then i got to the half ass polish job on the combustion chambers. :bs: whoever made the comment about the monkey with a die grinder was spot on, and i'd be on the phone with them saying the same thing.
 
Talyn said:
There is no agreement here. The work on that head is unprofessional and less than amateur. Sunken valves never help flow, unless they are covering up some other disaster. And that isn't even slightly sunken, its like Titanic sunken.
Click to expand...

Not defending 505's work one bit, but there are times where sinking valves will help flow. Going as extreme as 505 probably hurt the flow.

If whoever owns that head wants it put on a flowbench send me a PM. We may be able to work something out.

~Alex
 
Soon I'll post a pic of the 2nd head I spent 20-25+ hrs porting and polishing that will get put on my brother's 4.9l with the 505 roller-cam setup.
 
Sweet. 20-25 hours, Ouch! Roller cam, Nice.
 
One thing many seem to be forgetting is the effect of intake manifold runner airflow. Unless that can match or exceed the airflow in the intake ports of the cylinder head, it's a waste of time and money going for big head flow numbers unless you're using either forced induction or a custom intake manifold. The runners of the stock intake manifolds (log type and especially the smaller cross-section horseshoe) don't have the necessary flow capability and would require extensive modification.
 
Dr. Dyno said:
One thing many seem to be forgetting is the effect of intake manifold runner airflow. Unless that can match or exceed the airflow in the intake ports of the cylinder head, it's a waste of time and money going for big head flow numbers unless you're using either forced induction or a custom intake manifold. The runners of the stock intake manifolds (log type and especially the smaller cross-section horseshoe) don't have the necessary flow capability and would require extensive modification.
Click to expand...

Exactly, That is why I am using FI/SC and Sprintex 3" short runner, large plenum intake manifold.

Why would anyone run a ported or big valve head and choke it off with a stock log or horseshoe intake manifold, even if 'port' matched. Maybe if the runners were fully ported, which is nearly impossible due to their shape, unless maybe extrudehoned.

It is a 'system' all the way from the air filter inlet to the cylinder. Only as good as the worst flowing link.
 
Don't forget about acid porting. It works very quickly with aluminum.
 
Dr. Dyno said:
Yeah, and extrude honing isn't exactly cheap either.
Click to expand...
And uncontrolled.

alex22 said:
Don't forget about acid porting. It works very quickly with aluminum.
Click to expand...
I haven't heard of acid used to actually port, but to cover up porting work and leave a cast like finish. Cheating.
 
Talyn said:
I haven't heard of acid used to actually port, but to cover up porting work and leave a cast like finish. Cheating.
Click to expand...

You haven't spent much time with roundy round engines then.

A year or so ago I acid ported an aluminum "snail scroll" type manifold for a buddy's turbo 5 cyl Volvo along with a heavily ported head and modified euro exhaust manifold. He said it maintained boost to higher RPMs than any other Volvo he's seen dyno graphs of with an OEM manifold.

~Alex
 
In the 70' in the 'stock' class VW desert buggies they would 'acid' port the intake manifold with slight increase in performance. Looks fairly normal/stock to the eye.
Cheating at it's best.
 
rmx250cfl said:
Aint no body got time for that, tell alex to cut it in multiple pieces, port it and weld it back together. Hes a pro at it.
Click to expand...

Yea, like I have the extra hundred or so hours...
 
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