Login    Forum    Search    FAQ

Board index » Racing Forum » Fuel Systems




Post new topic Reply to topic  [ 8 posts ] 
Author Message
 Post Posted: Thu Apr 19, 2012 9:49 am 
Offline

Joined: Tue Apr 01, 2008 10:56 pm
Posts: 110
Location: Kilgore Tx [North East Tx]
Every time the subject comes up I regain interest in experimenting with two carbs on a tunnel ram.

My Firebird with 408 SBC weighs 3050 with driver and runs 6.18 @ 112 MPH in the 1/8th mile. [about a 9.75 1/4 mile]

Also, it has conventional 23* heads and judging by the performance it makes about 650 or so horsepower.

If I want to experiment with dual carbs what manifold and carbs will be a good choice?

Thank You.

_________________
Larry Woodfin, builder of Kinetic Art.


Top 
 Profile  
 
 Post Posted: Thu Apr 19, 2012 10:09 am 
Offline
Site Admin
User avatar

Joined: Tue Apr 18, 2006 6:38 am
Posts: 11804
Location: Coming At Ya!
I've been fooling with TR intakes now since back in the 1990s and I can tell you that they are more often a pain in the ass and not worth the trouble of running them when you consider the amount of performance gain you get in return. I've got a sheetmetal intake on my engine now that will likely be off that engine by June and I'll be back to a single Dominator.

So what I'm telling you is that I've run single and dual carbs on my 23* engine and seen little if any difference in performance. I've also run both single and dual carbs on my 18* engine and seen very little if any difference.

I can tell you however that dual carbs require TWICE as much of anything you do carb wise, ie, MABs = 8, IABs+8, MJs = 8 etc so anything you do with them costs twice as much and takes twice as much effort!

So unless you just want to throw money away for something to "play" with, I'd put that money somewhere else, say in a good pro port job on your heads and intake that will net you more performance gain than the addition of another carb!

And as usual, your mileage may vary! ;-)

_________________
Big Boyz Toyz!

Image

Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.

William Pitt, British Prime-Minister (1759-1806)


Top 
 Profile  
 
 Post Posted: Thu Apr 19, 2012 10:32 am 
Offline

Joined: Tue Apr 01, 2008 10:56 pm
Posts: 110
Location: Kilgore Tx [North East Tx]
Ken, your experience sounds reasonable from the stand point of money/time invested vs increased performance. If I was working on a larger engine, higher RPM, more power the story might be different.

Maybe I should experiment with a 1050 Dominator.

_________________
Larry Woodfin, builder of Kinetic Art.


Top 
 Profile  
 
 Post Posted: Thu Apr 19, 2012 4:04 pm 
Offline
User avatar

Joined: Sat Feb 07, 2009 4:12 pm
Posts: 1215
Location: Adelaide Australia
There is no point playing with a tunnel ram when the real issue with a engine is the porting design. A 400 cuber with 23 degree heads making 650ish is a recipe for porting issues like turbulence and chokes and fuel seperation across a short turn. A tunnel ram wont fix those issue. it will amplify them. Experimenting in the areas that are the actual cause of your problems is more worth while. 23 degree heads are not for efficiency at the higher RPM range typical of racing.


Top 
 Profile  
 
 Post Posted: Thu Apr 19, 2012 4:20 pm 
Offline

Joined: Tue Apr 01, 2008 10:56 pm
Posts: 110
Location: Kilgore Tx [North East Tx]
Shrinker, Thank You for the note. It is not that I have a problem, the combination runs good. However, I think you are correct that I am near the reasonable expectation for a 23* 408 CI package at 3050 pounds. I like learning, tuning, experimenting but even more, I like winning. It is a good consistent package and increasing the performance slightly will not matter for "shoe polish" ET bracket racing :)

_________________
Larry Woodfin, builder of Kinetic Art.


Top 
 Profile  
 
 Post Posted: Thu Apr 19, 2012 4:49 pm 
Offline
User avatar

Joined: Sat Feb 07, 2009 4:12 pm
Posts: 1215
Location: Adelaide Australia
Well if thats what you like to do then get a data logger with O2's on each cylinder and start fixing distribution issues. Then you can make the combo more consistent and learn a lot of stuff. EGT's per cylinder a is a lot cheaper to do but EGT;s are much less information than AFR. They simply react way to slow and are not relevant in some situations.


Top 
 Profile  
 
 Post Posted: Thu Apr 19, 2012 6:45 pm 
Offline
Site Admin
User avatar

Joined: Tue Apr 18, 2006 6:38 am
Posts: 11804
Location: Coming At Ya!
I'll add some stuff to what shrinker has posted. I've run EGTs in all 8 and now I'm on O2s reading all 8 in 4 passes and the shiete is still confusing to a point!! I'm not doing the EGTs at this point but I can tell you that even a sheetmetal tunnel ram with 2 carbs is NOT consistent as far as AFRs are concerned!! I'm just as far out in left field with O2 readings now as I was with EGTs last year!! [-(

Having said that, and if you'd want to play around with something, I'd go with O2s in as many locations as possible, ie, ONE IN EACH HEADER TUBE ABOUT 12 TO 14 INCHES DOWN FROM THE HEAD! I've got an LC-1 O2 setup on each side of the car that will reach all 4 cylinders on each side so in 4 passes I can record O2 data from all 8. Ask me how that's working our for me?? [-( O:)

_________________
Big Boyz Toyz!

Image

Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.

William Pitt, British Prime-Minister (1759-1806)


Top 
 Profile  
 
 Post Posted: Thu Apr 19, 2012 11:17 pm 
Offline

Joined: Wed Jan 12, 2011 1:28 am
Posts: 140
Location: N.W.
I still like the old set-up of 2 660s sideways with dominator bowls like I ran about 15 years ago when I was running a small block. It was a great combo!


Top 
 Profile  
 
Display posts from previous:  Sort by  
 
Post new topic Reply to topic  [ 8 posts ] 

Board index » Racing Forum » Fuel Systems


Who is online

Users browsing this forum: Bing [Bot], Google [Bot] and 1 guest

 
 

 
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

Search for:
Jump to:  
cron