BBC intake flow
08-02-2025 | 06:57 PM
#51
Thread Starter
Registered
Joined: Jul 2025
Posts: 28
Likes: 10
From: Buenos Aires, Argentina
Thats a really good question that i DONT have definitive answer for. I can say this, I used a 2000 cfm throttle body on my street car, a 11.4-1 pontiac 461 with mefi4 ecm. I made roughly 580/590 hp on dyno and similar tq, it made 95% power at like 5/8 throttle too. I was able to tune any bog out of it with AE so even a really fast stab does NOT cause it to bog, it comes alive instantly. I was having a discussion about this intake and since the whole ports NOT big, IDK what it will really do on something its not appropriate for like a mild 509. It has a 5.31 CSA at entry and tapers / funnels down to a somewhat normal bbc opening , I wouldnt put it on a 454 unless it was gonna turn some serious rpms, like 7500/8000 BUT it WOULD be interesting to see what it does on like a stock 500 efi. Since a stock 500 efi is as cam restricted as intake restricted my guess would be it would give up 30/40 ft lbs tq sub 3000, 20-30 ft lbs tq 3000 to 4500 then gain 20/30 hp on top and 200 rpms based on shorter runner length and other intake experiments Ive done BUT you really DONT know until I pull lever on the dyno. Im gonna cast a mold of one of the ports to map/ measure size of csa top to bottom
08-04-2025 | 08:44 AM
#52
Registered
Joined: Jan 2003
Posts: 6,017
Likes: 1,518
From: Grand Rapids, MI
08-04-2025 | 08:16 PM
#53
Platinum Member
Joined: Jun 2004
Posts: 7,317
Likes: 1,032
From: frankenmuth michigan
Was in that place they call "ohio" tuning a twin engine efi whippled boat near Marblehead today. Shear line winds took a large portion of metal roof of the main shop in May, the guys finishing the new dyno room are the same guys Im waiting on to replace the roof first otherwise Id be close to done and moving new dyno in. I m wrapping up a afr 300 headed 496 for a customer, its next on the dyno. Just dynoed a F2R procharged 572, 2 8.8 liter whippled gen 7 bbc's and a roots blown LS, gonna get back on my own 548s for my boat when it slows down, Smitty
08-05-2025 | 12:13 AM
#54
Registered
Joined: Jan 2003
Posts: 6,017
Likes: 1,518
From: Grand Rapids, MI
Was in that place they call "ohio" tuning a twin engine efi whippled boat near Marblehead today. Shear line winds took a large portion of metal roof of the main shop in May, the guys finishing the new dyno room are the same guys Im waiting on to replace the roof first otherwise Id be close to done and moving new dyno in. I m wrapping up a afr 300 headed 496 for a customer, its next on the dyno. Just dynoed a F2R procharged 572, 2 8.8 liter whippled gen 7 bbc's and a roots blown LS, gonna get back on my own 548s for my boat when it slows down, Smitty
Just helped my friends kid with a blown LS with a GT500 blower in a Foxbody with that Ace's EFI. Fun car!
I'm epoxying up the floors of my Pro-Flow and will hopefully have it on in the next couple of weeks for a performance comparison in the boat. A lot of custom stuff to make it work. I 3D printed the velocity stack and 5° gasket to direct it above thermostat.
Last edited by Rookie; 08-05-2025 at 12:18 AM.
08-05-2025 | 06:34 AM
#55
Platinum Member
Joined: Jun 2004
Posts: 7,317
Likes: 1,032
From: frankenmuth michigan
[QUOTE=Rookie;4932036]S#it, that's not good.
Just helped my friends kid with a blown LS with a GT500 blower in a Foxbody with that Ace's EFI. Fun car!
I'm epoxying up the floors of my Pro-Flow and will hopefully have it on in the next couple of weeks for a performance comparison in the boat. A lot of custom stuff to make it work. I 3D printed the velocity stack and 5° gasket to direct it above thermostat.[/QUOTE
post pics of the epoxy work on proflow. If I ever get my own 548s assembled, its gonna be on my dyno for eternity testing intakes. So now test is up to:
1. stock 500 efi / stock tb
2. extreme modded 500 efi upper/lower (previously carried to a higher hp in testing on my low compression 548 then Ive ever seen or heard of before and had DISMAL tq from the mods)
3. proflow w modded tb w air horn (already know the mods give it its best power from previous dyno test)
4. box stock holley track warrior
5. Scott Foxwell modded Holley track warrior
6. this new tunnel ram/ fron tb efi intake I just got
Just helped my friends kid with a blown LS with a GT500 blower in a Foxbody with that Ace's EFI. Fun car!
I'm epoxying up the floors of my Pro-Flow and will hopefully have it on in the next couple of weeks for a performance comparison in the boat. A lot of custom stuff to make it work. I 3D printed the velocity stack and 5° gasket to direct it above thermostat.[/QUOTE
post pics of the epoxy work on proflow. If I ever get my own 548s assembled, its gonna be on my dyno for eternity testing intakes. So now test is up to:
1. stock 500 efi / stock tb
2. extreme modded 500 efi upper/lower (previously carried to a higher hp in testing on my low compression 548 then Ive ever seen or heard of before and had DISMAL tq from the mods)
3. proflow w modded tb w air horn (already know the mods give it its best power from previous dyno test)
4. box stock holley track warrior
5. Scott Foxwell modded Holley track warrior
6. this new tunnel ram/ fron tb efi intake I just got
08-05-2025 | 06:57 PM
#56
Registered
Joined: Jan 2003
Posts: 6,017
Likes: 1,518
From: Grand Rapids, MI
Mismatch
1.900" fill
Prototype Dart Pro1 head
Last edited by Rookie; 08-05-2025 at 07:00 PM.
03-24-2026 | 04:31 AM
#57
Registered
Joined: Jul 2009
Posts: 215
Likes: 8
From: Cedar Springs,MI
Sorry not to hijack this thread and I know this is a boating site but there is usually better info here than on car site about motors…Are there any other front entry style intakes for BBC other than the crazy expensive stuff? I was thinking of using a Pro Flo XT on my 70 GTO with 540 BBC but I think the top of the Throttle body will hit my hood. I want to use the Holley HP efi have left over from an old boat motor but don’t like the looks of the regular Holley intake with 4150 TB and fuel rails
Last edited by lucky cat; 03-24-2026 at 04:34 AM.
03-24-2026 | 01:10 PM
#58
Registered
Joined: Jul 2009
Posts: 215
Likes: 8
From: Cedar Springs,MI
Hello
I was looking for information about marine EFI intake manifolds and found on the forum that there are two designs: the 502 MPI and the 500/525 EFI.
I want to install them on a 454 BBC on my '68 Chevelle. I'm looking to achieve flat low- and mid-range torque and maximum hp at 5800-6000 rpm.
Several people on the forum said the designs were restrictive, perhaps they are restrictive for 502-525ci and but sufficient for a 454.
Do you have flow rates for these intakes?
thanks
I was looking for information about marine EFI intake manifolds and found on the forum that there are two designs: the 502 MPI and the 500/525 EFI.
I want to install them on a 454 BBC on my '68 Chevelle. I'm looking to achieve flat low- and mid-range torque and maximum hp at 5800-6000 rpm.
Several people on the forum said the designs were restrictive, perhaps they are restrictive for 502-525ci and but sufficient for a 454.
Do you have flow rates for these intakes?
thanks
03-24-2026 | 05:47 PM
#59
Registered
Joined: Aug 2019
Posts: 1,201
Likes: 411
From: BC
My floors are raised so port height is 2.100". Jim only raises the floors and does not touch the port ceiling. I add enough epoxy so the port height is about 1.900" and blended about 2.500" up the runner. I just try to give a nice transition to enter Jim's head port.
Mismatch
1.900" fill
Prototype Dart Pro1 head
Mismatch
1.900" fill
Prototype Dart Pro1 head
I think a small shear line at the bottom where the head a a bit higher won't hurt flow that much, if at all...but the fuel droplets get a shear point to atomize and get into the airstream for the short side to draw them into the valve venturi. Are you using Splash Zone?
Nice work by the way.
03-24-2026 | 07:25 PM
#60
Registered
Joined: Jan 2003
Posts: 6,017
Likes: 1,518
From: Grand Rapids, MI
