A Little Carb vs EFI info
Gold Member
12-03-2014, 07:07 PM
#5
Registered
iTrader: (1)
I would like to see them run a pair of T/B's on the same top plenum they used for the dual carbs and see how it acts.
I still like EFI though.
I also want to know if thats a typo or how the fock they get an LS6 block (5.7 liter) to 468". Biggest I knew about was 441 or something close to that after some serious re-sleeving and even those are known for being time bombs.
On a side note, that thing does look bad azz with those 2 carbs sitting on top doesnt it?
BUP, thank you sir for posting this up!
I still like EFI though.
I also want to know if thats a typo or how the fock they get an LS6 block (5.7 liter) to 468". Biggest I knew about was 441 or something close to that after some serious re-sleeving and even those are known for being time bombs.
On a side note, that thing does look bad azz with those 2 carbs sitting on top doesnt it?
BUP, thank you sir for posting this up!
Last edited by TooLateVTEC; 12-03-2014 at 07:09 PM. Reason: added info
12-03-2014, 09:14 PM
#6
Registered
Join Date: Jul 2014
Location: Northern Indiana
Posts: 376
Likes: 0
Received 0 Likes
on
0 Posts
What they left out was a port style efi will ensure you don't get lean cylinders. You can also enrichen detonation prone cylinders and even out cylinder to cylinder combustion temperatures by adjusting the individual cylinders fuel rate. If you want to run an engine on the ragged edge, I'll trade 10hp for reliability all day, odds are though, you'll gain that right back with the proper tune.
Platinum Member
12-04-2014, 08:28 AM
#9
Have built a lot of engines with dual quads as well as fuel injected. Back in the day 50s 60s dual quads were used in some production engines and aftermarket as well as other multible carb setups. This was because of the size availibilty back then. They often produced amazing power over a wide power band. My duall quad 312 ford 375HP+. Why they out perform a EFI setup is having 8 smaller throats compaired to 1 or 2 large throats. Just think if a carb only had a single throat 750 CFM. Thats a similar comparison to to a HP SEFI system today. So you nail the throttle on a typ SEFI system air speed dropps sgnificantly compaired to 8 venturies. To make up for the SEFIs big drop it quickly nails the A/F ratio from 14.7ish to 12.5ish to cover the big hole that just opened up. Carbs on the other hand open up from 14.7ish and rather slowly in compairison AF would go to 14 to 13 to 12.7 as engine speed increases and need for fuel increases. So think about 1bbl 750 or 4 bbl 750 or 8 bbl 750.
So my last engine build was based on this. A 302 with ported DOOE (1969 351W heads) 235 CFM @ .500 lift, dual quad intake ported to flow 215 CFM bolted to the head, 2 small 4 bbl carbs modified to flow a total of 1040 compaired to a Victor 5.0 with a 75 mm TB. A mild 220 @.050 .500 lift cam. The SEFI set up took 6 months or so to realy data log and tune. Sent the carbs to Nickerson for stage 5 mods which could be done myself but wanted to make the carbs exactly matched in flow fuel and air. The dual quads out performed the SEFI including MPG 20 SEFI, 24 dual quads.
I would consider a SEFI set up with 8 stracks such as HILBORN would out perform the dual quad set up though.
So my last engine build was based on this. A 302 with ported DOOE (1969 351W heads) 235 CFM @ .500 lift, dual quad intake ported to flow 215 CFM bolted to the head, 2 small 4 bbl carbs modified to flow a total of 1040 compaired to a Victor 5.0 with a 75 mm TB. A mild 220 @.050 .500 lift cam. The SEFI set up took 6 months or so to realy data log and tune. Sent the carbs to Nickerson for stage 5 mods which could be done myself but wanted to make the carbs exactly matched in flow fuel and air. The dual quads out performed the SEFI including MPG 20 SEFI, 24 dual quads.
I would consider a SEFI set up with 8 stracks such as HILBORN would out perform the dual quad set up though.
Last edited by turbo2256b; 12-04-2014 at 03:26 PM.
