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#21
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Steve is correct Jim McFarland wrote a lot in Circle Track about using them on heads chambers. He also worked at Edelbrock and told me he helped designed the Pontiac Torker original for Q jets.
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Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
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#22
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It sounds like the dimples have some straightening effect, but the main purpose is to reduce wake and make the ball fly farther. That article says a golf ball with dimples will fly twice as far as one without. That’s pretty nuts. Again, no relevance to automotive applications (unless you’re dimpling your body panels like Sirrotica suggested), but still nuts.
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1976 Trans Am Buccaneer Red 468ci, 10.5:1 CR, 87 CC RPM CNC e-heads, HR 282/288, 230/236, 561/.573 lift, Johnson Lifters & HS 1.65 Rockers |
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#23
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Don’t go into ports often, but when I do, dimples are there….
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1963 Cat SD Clone (old school) streeter 1964 GTO post coupe, tripower, 4speed (build) 1965 GTO 389 tripower, 4 speed, driver 1966 GTO dragcar 1966 GTO Ragtop 1969 Tempest ET clone street/strip 1969 GTO Judge RA lll, auto 1969 GTO limelight Conv. 4speed go and show (sold) 1970 GP SSJ 1970 GTO barn find..TLB…390 horse?….yeh, 390 1972 GTO 455 HO, 4 speed, (build) 1973 Grand Safari wagon, 700hp stoplight sleeper 525ci DCI & 609ci LM V head builds |
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#24
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Obviously someone believes there's an advantage to pock marks in the port, that's a lot of effort, for no return on investment..........
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#25
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Quote:
So the ball goes farther. Not sure what any of this has to head porting though. Hard to believe the juice is worth the squeeze. Maybe it is, who knows ? |
#26
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We did a lot of Cylinder Head flow testing on accurate Engine dynos with top notch Emissions equipment and never saw
the "bang for the buck" ANYPLACE. We monitored Tumble and Swirl, did lots of flow testing and head design testing, and the number of valves, size of valves, and valve lift all had a lot of different effects depending on the engine design, so generic statements are fine but not really helpful for lots of combinations that do not fit the model. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#27
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If the dimple are coated, then the fuel will vaporize. Maybe a NiB magnet in each dimple. Yea.
So, back to the basics: 4-Cycle the straightest intake port with best port/head angle and valve/head angle wins the optimal VE. Wheter direct-port FI or carb'd the only diff will be mixture richness to compensate for chamber fuel dropout. Time the Exhaust lobe/valve closing to define EGR effect at cruise, scrub compression to mitigate ping, and time the overlap boost at higher rpm. Time the exhaust reflection to enhance the EGR effect at cruise, yet the reflection magnitude kept low to remain insufficient to cause reversion and mitigate reversion at idle to cruise, enhance reversion magnitude (timing about the same mechanically, but not thermally!) to enhance overlap boost at desired rpm( converter initial stall rpm!). Or run open exhaust at the Collector peak pressure zone to promote overlap boost. 2-Cycle: consult an expert. Carb throat CSA, length, crankcase volume&shape, crank shape, port windows (big strategy there), slug dome shape, Head mini-dome shape, proper mix vs pre-mix , and every subtlty you can imagine to keep the slug from burning a hole just when the max boogie is reached. Shape and time the exhaust reflection for desired powerband vs rpm, or run 1.5" long open exhaust, of near equal CSA as the exhaust port, no flare. |
#28
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Even with a EFI calibration you still get some "wetting" of the runners prior to the intake valves.
The Calibration guys do the following: A Throttle blade change, read by the TPS sensor, tells the calibrator whether to add or decrease the pulse width to the injectors for that event. If fuel is pulled from the runner walls or plenum, the calibrator has the injector reduce the pulse width for that series of combustion cycles, until the HEGO says the air/fuel is where it needs to be for Stoich operation again. The Government requires running at stoich all the time. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. Last edited by Tom Vaught; 06-26-2022 at 02:32 PM. |
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#29
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https://www.speedofair.com/
Mostly Diesel-intensive, but supposedly "proven" on gasoline, CNG, swamp gas, etc. Any piston that UEM makes can be dimpled, if your credit card is Nomex. |
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