rx7srbad

Does anyone have experience of a 4 barrel on a street ported engine?
What are the pros and cons of using a 4 barrel?

BLUE TII

iTrader: (9)

Just looked at the SCR 4 barrel intake manifold.

Looks like it is a rebranded $250 Speedmaster manifold which is a copy of long since discontinued Extreme Rotaries manifold.

I have (have not used) this Speedmaster manifold- nice piece.

Speedmaster has inexpensive 4150 4 barrel throttlebodies as well.

peejay

I've been running one on a bridge ported 13B since 2012. I also temporarily used one on a street ported six port engine. I run EFI and am using a Holley 750, modified for 1:1 throttle actuation, as a throttle body. Think of it as 4x42mm ITBs, because that is how it functions.


Pros: Throttle response is wonderful. Airflow is also wonderful.
Cons: If you are not getting a Racing Beat manifold, quality is shoddy. I have not seen an aftermarket throttle body that was not junk, which is why I added a TPS to a forty year old carburetor and did some minor work to clean up airflow and eliminate air leaks.

EFI is cheaper than a decent carburetor in 2022. A half decent four barrel carb is close to $1000 (in the US!) and that is before you buy hundreds in jets and embark on an educational journey in modifying all of the different circuits in a Holley style carburetor. i say Holley style, because anything worth using is not made by Holley, and the other types of four barrel carbs (AFB, etc) are garbage not worth considering.

mustanghammer

iTrader: (3)

And just like that, Edelbrock come out with this: https://www.edelbrock.com/vrs-4150-carburetors
Everything is adjustable - everything. There are some YouTube videos that break it down and frankly what can be adjusted and changed is almost over whelming. Pricing is under $750 for a 750CFM double pumper on Summit Racing

rx7srbad

https://turbo-spec.com/products/13b-...ake-93-95-twin

this is the kit i got as it was more easily available locally. Hope it does well.

BLUE TII

iTrader: (9)

Oh, thats 4 barrel manifild with large single throttle body.

You wont have the benifit of improved throttle response from ITB/4 barrel throttlebody.

That is for max flow drag applications.
. Will be interesting to see how it works on streetport.

Drive by wire would be the modern solution to airflow velocity stall when big single plate throttle body is opened too quickly.

peejay

...and it's a Holley 4150 clone, not a Carter AFB clone like Edelbrock traditionally made (Wow those were janky, horrible castings and worse metering circuits. They did work OK in some applications but few and far between)

Still, very interesting to know about, thank you. Looks like an interesting alternative to Quick Fuel for those of us who need to color outside the lines. QF carbs are brilliant but they do not make a rotary specific one...

KNONFS

iTrader: (14)

Been running one for almost 20 years, the only cons is the AFRs during throttle transition is finicky, experienced tuner is needed there. Its not terrible, but my OCD and lack of tuning knowledge gets to me. I am running a jay-tec (now pro-jay intake manifold, and a Pro-Jay TB; previous TB was crappy, had to drop the $$$ for a quality one. I've been told that I am loosing TQ down low on with this setup, can't confirm or deny.

For the TBs, you got multiple options:

Pro-Jay https://www.pro-jay.store/
https://www.pro-jay.store/products/8...-body-1360-cfm
https://www.pro-jay.store/products/1...-body-1360-cfm

E&J https://www.enjautoworks.com/
https://www.enjautoworks.com/product...rottle-body-2/

E&J TB could be made into a progressive one, Pro-Jay one does not offers the option, and its not possible to convert it to a progressive setup. Both brands are proven, most drag racers put over 50psi through these TBs, no leaks, no bent butterflies, no BS.

rx7srbad

Thanks for the response on this everyone.

I have zero exp with 4 barrel setups on the 13b.

Only reason i want to try it is because i dont care about low end tq below 5krpm, However, from 5k to 9krpm I want it to take off to space!
I may use the rx8 dwb tb if the one supplied with this is terrible for cruise/idle.
The E&J ones are no longer available which sucks but im not sure if i will work with the scr top hat anyways.

peejay

The throttle response with the 4 barrel is incredible compared to a plenum manifold.

Excellent torque below 3000, I could drive all day keeping revs below 2500 with the bridge port 4 port or street port 6 port engines. Even in competition, a lot of times I would just leave in 2nd gear to avoid having to upshift.


Street port 6 port, 4.44 gears, 25" tires, not using 1st gear

KNONFS

iTrader: (14)

I don't have back to back dyno charts or log files from when I was running OEM intake manifold/TB to the 4BBL. Here's a dyno of my stock ports 13B, T04S turbo, no boost controller (9psi springs) and the 4bbl setup:


Overlaying my setup with other similar dyno graphs, I don't visually see TQ loss down below, but I like to quantify things with logs or back to back dyno sheets on the same vehicle/dyno/day.


LOVE it! My map can be GREATLY improved in the non boost area, been meaning to do that, but my experience and lack of finding a dyno willing to rent it to me has been a show stopper.