4 barrel set up higher than 390cfm

[Datsun#1]

Hey,

I thought Id write this up due to the mis conception about the 4 barrel set up. I have ad ztheropy su carbs,tripple mikunies and the holley set up.all are great set ups,each having there benefits.

 

The common issue I see is people saying that a 600+ cfm carb on,a 2.8l engine wont work well..WRONG.

And size carb will work from 390-1000cfm! If you step away from the typical su carbs and tripples and actually take the time to learn how to properly tune a 4 barrel carburetor,you will see that a 650cfm dubble pumper can be ran effectively on our engines! Its all about booster signals,jets,air bleeds,power valves and patients. There are many guys out there who run the holly set up.the ones who dont like it,dont understand carburetor tuning.I honestly like the 4 barrel set up over the tripples.there cost vs performance is so close ya cant beat it.try to find a triple carb set up for less than $500 USD.so all you guys out there bashing the 4 barrel set up,give it a try and have someone who knows 4 barrels set it up.its a much cheaper option than tripples.As far as #1-#6 cylinders running lean,instal annular boosters to get better fuel atomization.I have yet to see proof that there is a lean condition. Btw,love this site! Donating next month!

Cheers.

[Roanz]

Tell me more about the annular boosters.  thanks

[Rob L]

I run a 450cfm on my 2.6l without issue ....but ditching that once my stroker is done just because i hate the look.....love the look and sound of triples.

[McGruber21]

I own a 1978 280z, Installed the Arizona z car 4 barrel conversion kit and have regretted it ever since. it is a great quality product but 390cfm is too big for a stock N47 2.8l ( 165-170psi compression on all cylinders). It is too inconsistent, some times the fuel mixture is too rich and others its too lean. Just a stock holley 390cfm was installed with 48 main jets (5psi fuel pressure), was too rich you could smell it in the engine bay, the exhaust tips and also the spark plugs, and timing didnt help nor did the fuel to air mixture screws. so i installed size 40 jets, that was TOO LEAN, until you go full throttle and then the mixture seems about right, but anything under full throttle was too lean and the engine performance suffered. I then installed size 44 main jets, reset the timing (about 5 degrees advanced), gaped and installed new spark plugs, and hooked up a vacuum gauge and set the mixture screws, finally i have something that kinda works. at times it can be a bit too lean or a bit too rich but overall the power curve has smoothed out. Also note that this is a hot set up and I would highly recommend an exhaust heat shield between the manifolds. but if you want to install this on your stock l28 DONT, do some slight mods to your engine before strapping on this carb.

~McGruber