Internal Body Aerodynamics

69427

The Artist formerly known as Turbo84
Joined
Mar 30, 2008
Messages
2,942
Location
Clinging to my guns and religion in KCMO.
Mike:
if you are same gent who's seeking (on another forum) OE valve spring info for your 12363392 bowtie heads, I actually have the real specs but cannot post on that forum.

To begin with, the specs below are found within the 2006 GM Perfomance Parts catalog:
12363392 head's spring seat diameter is 1.550" (Not the spring OD)
dual valve spring is GM pn 12462970
spring OD = 1.514"
installed height 1.940"
pressure (aka seat) at 1.940" = 140 psi
solid height = 1.200"
average spring rate = 325 psi

head x390 (cousin to your x392) is virtually same head but has larger (heavier) 2.25" OD intake valve (your x392 are 2.19" OD).
Those x970 springs are OE in both 390 & 392 heads. And, those x970 springs are OE in Both ZZ454 and ZZ502 heads and both of those motors have OE Roller Cams & OE Roller Lifters. However, as you know, GM OE roller lifters have No link bars; thus are lighter than retrofit rollers with link bars.

lastly some of those leading "experts" on that other forum are FOS and are faking lots of it and have successfully snowed an army of sycophants. Not a thing wrong with contacting PAC, but I'd first ask your cam manufacturer what its spring recommendation is. No surprise the know it alls couldn't come up with any real, correct data. BTW, I note B2B hasn't posted on that other forum in about a year; is he OK? pray he is.

Jack, yes, I'm that guy (gent might be a bit of a stretch :giggle:).

That is exactly the info I am looking for! If I understand things correctly, Chevrolet appears to have kept the same springs/specs from the initial introduction of those heads up through the introduction of the ZZ series of big block crate motors, which use the same cam and lifters I'm currently installing in my engine.

I haven't heard from B2B in quite some time, but I semi-regularly correspond with a mutual friend out in California. I'll inquire about B2B's welfare.

Thank you (profusely!) for this information. This issue has been stalling my effort to get the engine put together and thrown back in the car. Please do me a favor, and keep in touch. I'd like to buy you a beer or lunch sometime if the opportunity arises.

(VM guys: Please excuse the momentary topic drift here. I have been looking for the information that Jack provided and have been failing in the process. Jack's help is enabling me to get the car back together in time for this spring's events.

I now return you to your regularly scheduled topic.)
 

phantomjock

Well-known member
Joined
Sep 2, 2009
Messages
1,580
Location
Retired Again!
The "German 'Vette" a couple of posts back :
1648848531013

Is using flush mounted headlamps. Also note the splitter is something like SuperBuickGuy is fabricating on his fantastic2.
The radiator ducting on the splitter has some nice features including built-in brake ducts. Nice.

But, the image brings up the topic of Headlamps!

Here is an interesting video well worthy of you viewing time:



Has good coverage of the first 6 generations of the corvette and the C2 - C5 with headlamps up and down.

Cheers - Jim
 

69427

The Artist formerly known as Turbo84
Joined
Mar 30, 2008
Messages
2,942
Location
Clinging to my guns and religion in KCMO.
The "German 'Vette" a couple of posts back :
View attachment 53569

Is using flush mounted headlamps. .........................................

Cheers - Jim
I've been kicking around doing a similar thing on my car, but with removable body colored covers. I've got a set of late 80's Oldsmobile (Cutlass?) small headlights and brackets, and it's easy enough to fabricate some aluminum covers, but I haven't come up with a design yet that will look 100% stock, while also allowing the covers to be removed quickly without any tools (and won't accidentally release due to bumps or chatter on the track).
 

phantomjock

Well-known member
Joined
Sep 2, 2009
Messages
1,580
Location
Retired Again!
A Water Channel/Tunnel is like a Wind Tunnel, but using water. Then, it uses an electric current to generate a bubble stream in lieu of smoke. Advantages; smaller, less power required, can reduce the size and speed of the run and still hit the same Reynolds Number (Re). This means a smaller model can represent a full size vehicle at "affordable" speeds. Here is a quick example of how speed and size in water vs air can help reduce costs:

Example(1) Air 100 mph 10' length > Re = 8672882
Example(2) Water 20 mph 1.8' length > Re = 8858375

Not an exact comparison, but should help -- I hope!

Cheers - Jim
 
Last edited:

rtj

Well-known member
Joined
Nov 5, 2011
Messages
2,431
All the splitter talk/discussion made me do a quick search. Thought this was good.

 

phantomjock

Well-known member
Joined
Sep 2, 2009
Messages
1,580
Location
Retired Again!
86 inches wide- WOW! I'm a piker - been working at 78 inches! (But then again - it was a '78!) And I'm looking for a trailer that won't brealk the bank.

Didn't see/hear mentioned the added efficiency you can gain from adding the diffuser/tunnel on the splitters. [Maybe missed it]
These additions can add significant downforce and can help reduce overhang to limits (when needed).
If you check out their performance curves - they show the results. In fact, their splitters have very low overhang - good to have the tunnels.

Good find on the videos rtj!

SBG - Those links could be useful for your splitter if you want to forgo building those - but pricey I'd say.

Cheers - Jim
 

rtj

Well-known member
Joined
Nov 5, 2011
Messages
2,431
The young guy with the beard in the first splitter vid goes into the splitter diffuser. He describes it as a Venturi effect.

He keeps most of the wind tunnel data to himself. :)

 

phantomjock

Well-known member
Joined
Sep 2, 2009
Messages
1,580
Location
Retired Again!
Staying with the discussion of Tunnel/Diffusers on splitters. I've mentioned previously, that the added efficiency can result in using less surface area.
Even though RHR keeps their wind tunnel data "close," they have let out some very useful information.

Here I have used that (intel) to drive home the point:

SplitterTunnel Downforce

Adding rake to the body also increases downforce for the same reasons a diffuser creates downforce. And, rake rotates the lift vector contribution from the hood slightly forward. Suggesting an ever so slight propulsive force, but there is no free lunch!

Cheers - Jim
 

SuperBuickGuy

Well-known member
Joined
Jul 16, 2012
Messages
3,279
Location
Seattle, WA
86 inches wide- WOW! I'm a piker - been working at 78 inches! (But then again - it was a '78!) And I'm looking for a trailer that won't brealk the bank.

Didn't see/hear mentioned the added efficiency you can gain from adding the diffuser/tunnel on the splitters. [Maybe missed it]
These additions can add significant downforce and can help reduce overhang to limits (when needed).
If you check out their performance curves - they show the results. In fact, their splitters have very low overhang - good to have the tunnels.

Good find on the videos rtj!

SBG - Those links could be useful for your splitter if you want to forgo building those - but pricey I'd say.

Cheers - Jim
when I finalize the design of my front spoiler - I'm seriously considering sending it to be made in carbon fiber....

the other thing I'm considering is putting another air dam between the front wheels ala IROC Camaros. make it of mud-flap material so it can freely give if hit but it would comply with the rules and even help more with controlling lift.... OR
putting something similar between the rear wheels to channel air to the brakes (rather then running ducts)
 

phantomjock

Well-known member
Joined
Sep 2, 2009
Messages
1,580
Location
Retired Again!
Kinda' like this:
1649113604812

Here is a "prettier version:"
1649113578625

Add a curve - or angular section to the wheel wells? Sounds like a plan. Makes a Mix-and-Match with the splitter.

Cheers - Jim
 

rtj

Well-known member
Joined
Nov 5, 2011
Messages
2,431
His cad drawings:


He has the wide tires installed at 27 min.
 

BBShark

Garage Monkey
Staff member
Joined
Mar 5, 2008
Messages
4,544
Location
Right here
Did the guy explain what his objective is? Seems like if you were going to drive the car with it that low you would want to move the suspension points and also (moving the suspension) would allow you to lose those wheel spacers.
 

rtj

Well-known member
Joined
Nov 5, 2011
Messages
2,431
BBShark, I skipped through it pretty fast, but I kind of thought he was winging it. :)

His cad looked interesting, so figured l’d share the link.

C4 corvettes are the last budget corvette.

Edit:
Watching it again made me think he didn’t do the cad.
 

rtj

Well-known member
Joined
Nov 5, 2011
Messages
2,431
The Block tribute car has much more radical aero, rules are probably minimal on PP.

 
Top