Slant *        6        Forum
Home Home Home
The Place to Go for Slant Six Info!
Click here to help support the Slant Six Forum!
It is currently Thu Mar 28, 2024 10:54 pm

All times are UTC-07:00




Post new topic  Reply to topic  [ 13 posts ] 
Author Message
PostPosted: Sat Jun 23, 2018 12:56 pm 
Offline
1 BBL (New)

Joined: Tue Jun 20, 2017 12:37 pm
Posts: 4
Location: Flagstaff, AZ
Car Model: 1962 Dodge Lancer, 2dr post
Gentlemen (and Ladies)... I am designing an intake manifold for an all-out (nothing but) drag racer with a 225 c.i. engine. In order to build this manifold properly, I need to know the absolute MAX CFM's that a 225 can move. The manifold will have six single-barrel carbs, but I need to know how much air I can move through each carb. I have to be very careful to NOT over-carb this thing, so if anybody has some very accurate flow info, I would sincerely appreciate your sharing it with me. Thanks, Guys! 8)


Top
   
PostPosted: Sat Jun 23, 2018 1:21 pm 
Offline
Supercharged
User avatar

Joined: Sat Feb 16, 2008 1:25 pm
Posts: 5599
Location: Downeast Maine
Car Model:
Are you using a stock head, or modified head with oversized valves? What is the compression of engine, stock or some number above 7.9:1? How fast is this engine going to turn? Is cam shaft stock or performance?

Keep in mind an engine is nothing but an air pump, and depending on how it is built will dictate how much air it will move. Where you are planing on six carburetors, whatever the total engine CFM is, divide that by 6 and that is max flow one carb has to be able to deliver.

Holley has a carb sizing calculator here This CFM calculator may help. While on Wallace race page, click on "Other Caculators" for more design help.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Image


Top
   
PostPosted: Sat Jun 23, 2018 2:24 pm 
Offline
Board Sponsor
User avatar

Joined: Tue Oct 29, 2002 8:27 pm
Posts: 9760
Location: Salem, OR
Car Model:
x2...

Various head flow numbers have gotten into the 174-180 cfm per cylinder on the flow bench... as you would know actual flow may vary
depending on your porting, valve job, valve sizes and volumetric efficiency at certain rpm, etc...etc...

There are a few guys that run IR single barrel carbs on their engine with pretty good results, but have not seen one that has gone the
top end high compression NA path yet.

Is this going into a car or a rail?


Top
   
PostPosted: Sat Jun 23, 2018 2:28 pm 
Offline
Board Sponsor & SL6 Racer

Joined: Wed Oct 23, 2002 7:57 pm
Posts: 8284
Location: Waynesboro, Pa.
Car Model: 65 Valiant 2Dr Post
Quote:
I am designing an intake manifold for an all-out (nothing but) drag racer with a 225 c.i. engine.


Webers :?: :?:

And how big of an overbore are you doing?

_________________
2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!
Image
12.70 @ 104.6
Image


Top
   
PostPosted: Sat Jun 23, 2018 2:36 pm 
Offline
Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6291
Location: So California
Car Model: 64 Plymouth Valiant
You size each single barrel carb for the whole 6 cylinders.

Most of the time the carb isn't flowing anything, then it has a big pulse all at once.

The peak flow is approximately equivalent to flow requirements for the whole 6 cylinders.


I would consider using CV40 constant velocity side draft carbs that were used on Harleys.

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

8)


Top
   
PostPosted: Sun Jun 24, 2018 5:43 am 
Offline
Supercharged
User avatar

Joined: Sat Feb 16, 2008 1:25 pm
Posts: 5599
Location: Downeast Maine
Car Model:
emsvitil:
Quote:
You size each single barrel carb for the whole 6 cylinders.

Most of the time the carb isn't flowing anything, then it has a big pulse all at once.


What was I thinking, duh. One cylinder fill at a time takes a full gulp.

_________________
67' Dart GT Convertible; the old Chrysler Corp.

82' LeBaron Convertible; the new Chrysler Corp

07' 300 C AWD; Now by Fiat, the old new Chrysler LLC



Image


Top
   
PostPosted: Sun Jun 24, 2018 6:38 am 
Offline
Turbo EFI
User avatar

Joined: Mon Jan 12, 2015 5:55 am
Posts: 1387
Location: Brightwood, VA
Car Model: 1965 Plymouth Belvedere I
Quote:
I have to be very careful to NOT over-carb this thing


Are there really that many single barrel carb to choose from?

_________________
-MattMan
LEANED & MEAN
Image


Top
   
PostPosted: Sun Jun 24, 2018 8:11 am 
Offline
Board Sponsor
User avatar

Joined: Tue Oct 29, 2002 8:27 pm
Posts: 9760
Location: Salem, OR
Car Model:
Quote:
Are there really that many single barrel carb to choose from?


Yes, there are common options for today.. like Ed said the Harley motorcycle option is one...

Fopar on his six pack to go car and his rail runs 6 Mikuni carbs... although not a full pushing the envelope
build, he runs good 1/4 times with both.

I would also wonder if someone would be able to get 6- TBI units used on 80's Chevy 2.8L to work...
or 6- 44mm throttle bodies and properly sized injectors to work (although wiring up the sensors
would be a tinker toy project...)


Top
   
PostPosted: Sun Jun 24, 2018 9:03 am 
Offline
3 Deuce Weber
User avatar

Joined: Sat Jan 27, 2018 4:26 pm
Posts: 92
Location: Utah-Idaho border
Car Model: 1964 Dart 270
They are pricey but you can get Weber style throttle bodies to go on IR manifolds now. Jenvey has some that are meant to be lookalikes to the DCOE (hidden injectors and fuel rail on bottom). Only $1200 at current exchange lol. Considering the carbs run about $900 plus buying jets and all that it doesn't sound quite so terrible. Might end up cheaper after Brexit, who knows?

DCOE style throttle bodies are cheaper than the carbs nowadays if you don't want the retro Jenvey look. (I really like the Jenvey look but they are out of the budget).

I've also seen someone use snowmobile carbs on another site (HAMBY I think?). SU carbs would be good too.

Brandon

_________________
____________________________

https://www.flickr.com/photos/162600228@N03/


Top
   
PostPosted: Sun Jun 24, 2018 9:14 am 
Offline
Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3805
Location: Indianapolis
Car Model:
Quote:
You size each single barrel carb for the whole 6 cylinders.


you may be thinking it right but you are saying it wrong

when using individual carbs/TB, you set the size per the cylinder it is filling.

when using one carb/TB for multiple cylinders it needs to be larger because more than one intake valve may be flowing air
at some times. Also with a single carb/TB filling multiple cylinders the air flow path will be compromised, bends, turns, so the over all
flow needs to be larger to compensate for restrictions. With an individual carb/TB per cylinder the flow can be a straight shot to the
intake valve, less restrictions so can be better optimized to that cylinder it is filling.

and I agree, there should be a nice selection motorcycle or snowmoble carbs or TB's around.
would be cool to find something with a slide valve instead of a butterfly control.

_________________
Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8


Top
   
PostPosted: Sun Jun 24, 2018 11:20 am 
Offline
Turbo EFI
User avatar

Joined: Mon Aug 02, 2010 7:36 am
Posts: 1200
Location: Rome, GA
Car Model: 1963 Dart 270, 1980 D150
I like the Harley carb idea. The Keihin CV40 is an excellent carburetor with lots of tuning parts readily available. https://cv-performance.com/ is a good source.

_________________
“Buy the ticket, take the ride.”
― Hunter S. Thompson


Top
   
PostPosted: Sun Jun 24, 2018 10:01 pm 
Offline
Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6291
Location: So California
Car Model: 64 Plymouth Valiant
DadTruck wrote:
would be cool to find something with a slide valve instead of a butterfly control.


The CV40 is a constant velocity slide with a butterfly behind it.

Mikunis are slide valve and common replacements for CV40s (making CV40s cheap (at least they were, not sure now) on ebay)


See older threads for my reasoning on 6 cylinder sizing of carb:

viewtopic.php?f=19&t=47013&hilit=photobucket+flow

viewtopic.php?f=26&t=42828&hilit=photobucket+flow

viewtopic.php?f=26&t=30750&hilit=photobucket+flow

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

8)


Top
   
PostPosted: Mon Jun 25, 2018 7:06 pm 
Offline
Board Sponsor & Moderator
User avatar

Joined: Thu Oct 17, 2002 7:27 pm
Posts: 14119
Location: Park Forest, Illinoisy
Car Model: 68 Valiant
A really good flow number for an intake port done by a mortal human is around 185 cfm. I have seen higher, but that is very rare, and sometimes suspect.

_________________
Official Cookie and Mater Tormentor.


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 13 posts ] 

All times are UTC-07:00


Who is online

Users browsing this forum: No registered users and 71 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited