Need some advice from 2-bbl iron intake experts

General engine tech -- Drag Racing to Circle Track

Moderator: Team

PackardV8
Guru
Guru
Posts: 7619
Joined: Sun Jul 30, 2006 2:03 pm
Location: Spokane, WA

Need some advice from 2-bbl iron intake experts

Post by PackardV8 »

We're building a full race 270" V8 which has to run with OEM iron intake and exhaust. The best available intake seems to be the older higher-rise 2-bbl. The later 4-bbl intakes are a lower profile.

Would something like the 600 CFM Quick Fuel 2-bbl on a theoretically better intake be a better choice than a 600 CFM Edelbrock on a lower profile intake? (I know OEM 2-bbls are rated at 3" and 4-bbls at 1.5", but are race carbs also rated that way?)

Yes, we hope to get both intakes on the flow bench in the near future.

Are there any other 2-bbls a better choice for road racing?
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
strokersix
Pro
Pro
Posts: 413
Joined: Sat Aug 23, 2008 7:12 am
Location:

Re: Need some advice from 2-bbl iron intake experts

Post by strokersix »

OT I've always wondered about using 69 396 big block chevy iron 2bbl intake for classes requiring this. Seems to me a big block chevy would dominate?
PackardV8
Guru
Guru
Posts: 7619
Joined: Sun Jul 30, 2006 2:03 pm
Location: Spokane, WA

Re: Need some advice from 2-bbl iron intake experts

Post by PackardV8 »

strokersix wrote: Sat Nov 17, 2018 7:07 pm OT I've always wondered about using 69 396 big block chevy iron 2bbl intake for classes requiring this. Seems to me a big block chevy would dominate?
Way OT, even for SpeedTalk, strokersix, but remember there are Olds and Pontiac 455" 2bbls and even the 430" MEL back in the day.

Most of the 2-bbl classes usually are all 350" SBCs. What else runs in 2-bbl classes?

As a reminder, there are 4-bbl intakes for the Studebaker, but for fifty years now, I've wondered if with the right porting and the right carb, the 2-bbl intake might prevail.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Keith Morganstein
Guru
Guru
Posts: 5566
Joined: Sun Feb 19, 2006 10:19 am
Location: MA

Re: Need some advice from 2-bbl iron intake experts

Post by Keith Morganstein »

PackardV8 wrote: Sat Nov 17, 2018 1:51 pm We're building a full race 270" V8 which has to run with OEM iron intake and exhaust. The best available intake seems to be the older higher-rise 2-bbl. The later 4-bbl intakes are a lower profile.

Would something like the 600 CFM Quick Fuel 2-bbl on a theoretically better intake be a better choice than a 600 CFM Edelbrock on a lower profile intake? (I know OEM 2-bbls are rated at 3" and 4-bbls at 1.5", but are race carbs also rated that way?)

Yes, we hope to get both intakes on the flow bench in the near future.

Are there any other 2-bbls a better choice for road racing?

Modify the 2bbl intake to accept a 4bbl.
Mill the carb mount surface flat.
Mill the plenum inlet to the larger throttle bore.
Mill the larger throttle bore profile down to the plenum floor.
Round off (radius) the intake plenum to manifold runners.
Possibly port match to the heads.
Drill and tap new carb stud holes.
Automotive Machining, cylinder head rebuilding, engine building. Can't seem to quit #-o
User avatar
midnightbluS10
Expert
Expert
Posts: 933
Joined: Sun Oct 20, 2013 8:41 am
Location: Shreveport, LA

Re: Need some advice from 2-bbl iron intake experts

Post by midnightbluS10 »

I've always been told multiply the cfm by .707 to find out what a 2bbl rated at 3" would theoretically pull at 1.5"

Personally, I don't ever remember hearing of anyone losing anything when going from a 2bbl to a 4bbl. But my profession isn't in engines specifically so I've not seen near what you all have.
JC -

bigjoe1 wrote:By the way, I had a long talk with Harold(Brookshire) last year at the PRI show. We met at the airport and he told me everything he knew about everything.It was a nice visit. JOE SHERMAN RACING
travis
Guru
Guru
Posts: 1611
Joined: Sun Mar 15, 2009 5:31 am
Location:

Re: Need some advice from 2-bbl iron intake experts

Post by travis »

I have seen on multiple occasions where going from a factory 2bbl iron intake/carb to a factory iron 4bbl intake/q-jet made absolutely 0 difference in performance. Granted, these were not “full race” or even “1/2 race” sbc’s (307’s and 350’s with stock exhaust manifolds and stock or small cams), but I was pretty surprised that going going from a tiny Rochester 2G or slightly larger 2GC to a 750 Q-jet made no difference in 1/4 mile times or top speed.

I guess the biggest thing is going to be where the biggest restrictions are. How good are the exhaust manifolds on whatever it is your building? What kind of power will these things make? Is porting allowed?
Geoff2
Guru
Guru
Posts: 1980
Joined: Mon Nov 09, 2015 4:36 pm
Location: Australia

Re: Need some advice from 2-bbl iron intake experts

Post by Geoff2 »

Yes, for road racing a Weber 44 IDF would be great on a 270" engine.
PackardV8
Guru
Guru
Posts: 7619
Joined: Sun Jul 30, 2006 2:03 pm
Location: Spokane, WA

Re: Need some advice from 2-bbl iron intake experts

Post by PackardV8 »

Geoff2 wrote: Sun Nov 18, 2018 3:53 am Yes, for road racing a Weber 44 IDF would be great on a 270" engine.
Yes, Geoff, that thought had actually occurred to me. However, the reason the 4-bbl intake was made lower profile is hood and air filter clearance. The vintage saloon classes aren't allowed to run hood scoops and the Weber stands too tall on the high rise 2-bbl intake.
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
pamotorman
Guru
Guru
Posts: 2802
Joined: Thu Mar 06, 2014 11:55 pm
Location:

Re: Need some advice from 2-bbl iron intake experts

Post by pamotorman »

if you are allowed an adapter between the carb and manifold why not use a curved adapter with the weber carb horizonal
Walter R. Malik
Guru
Guru
Posts: 6353
Joined: Tue Jul 24, 2012 11:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: Need some advice from 2-bbl iron intake experts

Post by Walter R. Malik »

PackardV8 wrote: Sat Nov 17, 2018 1:51 pm We're building a full race 270" V8 which has to run with OEM iron intake and exhaust. The best available intake seems to be the older higher-rise 2-bbl. The later 4-bbl intakes are a lower profile.

Would something like the 600 CFM Quick Fuel 2-bbl on a theoretically better intake be a better choice than a 600 CFM Edelbrock on a lower profile intake? (I know OEM 2-bbls are rated at 3" and 4-bbls at 1.5", but are race carbs also rated that way?)

Yes, we hope to get both intakes on the flow bench in the near future.

Are there any other 2-bbls a better choice for road racing?
Some 30 years ago we stop watch, track tested a bunch of different factory cast iron intakes for both best lap time and driveability on a 1/2 mile flat oval track we rented for the day.

The best we had, (and we ran about 10 different ones), was an intake from a 340 HP Corvette engine which originally had a Carter AFB carb. I don't think it has been available new since the early 90's.
It is easy to spot as the front and rear runners are slanted not straight across.

Since then ... the Z-28 aluminum 4 brl. intake manifold was produced in cast iron mainly as a marine offering; it is still out there.
http://www.rmcompetition.com
Specialty engine building at its finest.
User avatar
midnightbluS10
Expert
Expert
Posts: 933
Joined: Sun Oct 20, 2013 8:41 am
Location: Shreveport, LA

Re: Need some advice from 2-bbl iron intake experts

Post by midnightbluS10 »

travis wrote: Sun Nov 18, 2018 2:17 am I have seen on multiple occasions where going from a factory 2bbl iron intake/carb to a factory iron 4bbl intake/q-jet made absolutely 0 difference in performance. Granted, these were not “full race” or even “1/2 race” sbc’s (307’s and 350’s with stock exhaust manifolds and stock or small cams), but I was pretty surprised that going going from a tiny Rochester 2G or slightly larger 2GC to a 750 Q-jet made no difference in 1/4 mile times or top speed.

I guess the biggest thing is going to be where the biggest restrictions are. How good are the exhaust manifolds on whatever it is your building? What kind of power will these things make? Is porting allowed?
Thanks for sharing. I truly appreciate it.
JC -

bigjoe1 wrote:By the way, I had a long talk with Harold(Brookshire) last year at the PRI show. We met at the airport and he told me everything he knew about everything.It was a nice visit. JOE SHERMAN RACING
novadude
Guru
Guru
Posts: 1500
Joined: Thu Oct 11, 2007 3:24 pm
Location: Shippensburg, PA

Re: Need some advice from 2-bbl iron intake experts

Post by novadude »

Walter R. Malik wrote: Sun Nov 18, 2018 12:54 pm
The best we had, (and we ran about 10 different ones), was an intake from a 340 HP Corvette engine which originally had a Carter AFB carb.
I'm trying to picture what intake this might be? The actual 62-63 Corvette 340 hp 327 had an aluminum intake. 300 hp 327 used a iron manifold.
Walter R. Malik
Guru
Guru
Posts: 6353
Joined: Tue Jul 24, 2012 11:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: Need some advice from 2-bbl iron intake experts

Post by Walter R. Malik »

novadude wrote: Mon Nov 19, 2018 2:49 pm
Walter R. Malik wrote: Sun Nov 18, 2018 12:54 pm
The best we had, (and we ran about 10 different ones), was an intake from a 340 HP Corvette engine which originally had a Carter AFB carb.
I'm trying to picture what intake this might be? The actual 62-63 Corvette 340 hp 327 had an aluminum intake. 300 hp 327 used a iron manifold.
It is cast iron... it might have been a different horsepower but, that is what I was told.
In the 90's, new ones were still available from the dealer and we bought several. It used a Carter AFB 4 barrel carb with the smaller AFB bolt pattern and exhaust ran around the underside, front of the carb at the manifold carb pad. we plugged those exhaust access holes.

EDIT: I looked-up some of my real old invoices and the part number was #03852569.
EDIT: This appears to be an iron exhaust manifold we bought, oh well.
Last edited by Walter R. Malik on Mon Nov 19, 2018 4:05 pm, edited 2 times in total.
http://www.rmcompetition.com
Specialty engine building at its finest.
Carnut1
Guru
Guru
Posts: 4659
Joined: Tue Jun 11, 2013 6:32 pm
Location: Melbourne fl.

Re: Need some advice from 2-bbl iron intake experts

Post by Carnut1 »

l79.jpg
Walter R. Malik wrote: Mon Nov 19, 2018 3:43 pm
novadude wrote: Mon Nov 19, 2018 2:49 pm
Walter R. Malik wrote: Sun Nov 18, 2018 12:54 pm
The best we had, (and we ran about 10 different ones), was an intake from a 340 HP Corvette engine which originally had a Carter AFB carb.
I'm trying to picture what intake this might be? The actual 62-63 Corvette 340 hp 327 had an aluminum intake. 300 hp 327 used a iron manifold.
It is cast iron... it might have been a different horsepower but, that is what I was told.
In the 90's, new ones were available from the dealer and we bought several. It used a Carter AFB 4 barrel carb with the smaller AFB bolt pattern and exhaust ran around the underside, front of the carb at the manifold carb pad. we plugged those exhaust access holes.
Aluminum 340-350 hp manny. L79 design usually had 585 cfm Carter, different years had t-stat in different location.
You do not have the required permissions to view the files attached to this post.
Servedio Cylinder Head Development
631-816-4911
9:00am - 9:00pm EST
Walter R. Malik
Guru
Guru
Posts: 6353
Joined: Tue Jul 24, 2012 11:15 am
Location: Roseville, Michigan (just north of Detroit)
Contact:

Re: Need some advice from 2-bbl iron intake experts

Post by Walter R. Malik »

novadude wrote: Mon Nov 19, 2018 2:49 pm
Walter R. Malik wrote: Sun Nov 18, 2018 12:54 pm
The best we had, (and we ran about 10 different ones), was an intake from a 340 HP Corvette engine which originally had a Carter AFB carb.
I'm trying to picture what intake this might be? The actual 62-63 Corvette 340 hp 327 had an aluminum intake. 300 hp 327 used a iron manifold.
This iron manifold was Genera Motors part number #03852569. I'll keep looking as this appears to be an exhaust manifold we bought.
Last edited by Walter R. Malik on Mon Nov 19, 2018 3:59 pm, edited 1 time in total.
http://www.rmcompetition.com
Specialty engine building at its finest.
Post Reply