we just got a 65 mustang here and it has what appears to be a stock longblock with a streetmaster 289 intake, holley 3310 750cfm vac secondary carb, long tube headers and flowmasters, it has a solid flat camshaft from the sound of it, but it has the short valve covers(havent pulled them off to check) It has a 4speed and don't know the rear gear. What would be the best carb to use? I was thinking a 600 or 650 cfm double pumper?
what carb? 750 3310 too big right?
- Thread starter DarkoStoj
- Start date
i got a speed demon 650 cfm vacum secondary. Would that be a better choice than the 3310 holley?
RFMustangGT
Member
+1 for the 570 Street Avenger. I have one on my 62 T-bird with a 390 big block. Does great on gas (for a big block) and very easy to set up.
that woudl be a good carb to use, but you will likely have to jet it down considerably from box stock. Throw it on and see what happens. Definitely a better choice than the 750 on it.
3310 is perfect on a dual plane intake. I'd use a 650 on a single plane. I'm assuming this is for street use with a bit of fun, if for racing 750 or bigger. don't change jets in the 3310 change the vac. secondary spring to one that opens slower. Everyone seems to think little carbs are what is needed for 289/302 engines but the reality is that they respond well to larger carbs. The design on the smaller motorcraft carbs is better imho but the 3310 is a great carb also.
A 3310 is far too much carb for a 289. You will never get close to using even 600 cfm out of the 750 max. Figure your carb by this formula:
145cfm per 100 hp (at the crank)
most carbs under a hood without a very good cold air induction will flow only 80% or so of their rated capacity.
750x.8=600 cfm
600/145=413
does your 289 make 413 hp? I doubt it seeing as Ford and the Shelby engine people (actually Holeman-Moody) could only build around 375 reliable hp from a 289.
If you do the .8x600=480 you are right where you need to be for a 289. Go with a double-pumper for a solid/4-spd car.
You ever swapped from a 3310 to a 570 on a mild 302? The difference is night and day my freind. The 570 is far and away the better size for these motors.
This was on the roller 5.0 in my 89 Ranger. The accelleration increase wuth the 570 was fantastic over the 3310. This motor is what you can consider the equivalent of an Explorer 5.0 in build. Ported E7 heads, same cam, but with 1.7 Cobra rollers. Tri-Y headers.That carb sizing formula is very nearly useless in picking the optimum size carb. The measurement used in rating the carb is only 100% accurate if the carb you choose sees a 1.5"HG drop(on a 4bbl Holley) on it's under side on the motor you bolt it on. Chances are that's not going to be the case. What any motor actually pulls in cfm's can only be accurately measured on a dyno, that formula is also not realistic enough to use. Case in point: my 331 when I had it in my 89 Ranger would top in at 90 mph on just the center carb of it's 3x2 setup. This carb was rated at 250 cfms. According to that formula, the 331 was drawing about 365 cfms at the rpms it was turning at 90 mph (4500 rpms in 4th gear--1:1 ratio, 3.73 rear with 28" tall tires)
Car Craft did an intake/carb test on a 440 a bout 10 years ago, starting with a dual plane intake and 750 carb. Which was according to the formula, about the optimum size it needed. In the end, a Tunnel ram intake topped with TWO 750 DP's was the max the motor wanted, showing a 1" hg vacuum at WOT.
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