Added 470 CFM carb.

[Ortie666]

I wouldn't be so eager to get rid of the 390. The 470 is bogging when the sec. open because it's to big.You should find out why the 390 wasn't performing on the primaries,holleys aren't that complicated.I had a 390 on an Offy manifold with a 260 cam and it ran strong.Check the jets,air bleeds etc;etc on the 390. There's a reason why both offy and holley both recommend the 390, because it's the right carb.

Well we dont know that yet now do we, say the secondary jets actualy are too big, clearly he already has bought the bigger carb so why not give him useful information about tunning it.. Dont wanna sound like an ass, but im getting sick of people saying shit cant be done when they have really never tryed it themselfs.

[ezrollin]

Well, I don't won't to sound like an ass either but consider this,most 4 bbl 60's run the 390 with great success. CFM calculations say that the 390 is more than enough for a 2.8,hell you could use a 470 on a small block V8.He was having problems with the 390 that he didn't resolve, now he's having problems with the 470 ,more cfm doesn't solve the problem.

[Ortie666]

A 470cfm would starve any smallblock period. Im telling him how to do this bescause Ive already seen bigger carbs hit harder than 390's on 660s

[sir loin]

I wasn't having any problems with the 390, in fact it ran quite well on my 3.1L.

I went with the 470 for several reasons, but mainly cause I new it would work.

Right now as it sits, the truck climbs out of the hole and wants to rip the tires!!!! It's unbelievable the difference between the two carbs, the torque is what I've been looking for.

Now, could I have tune the 390 a little more, probably a 50cc and bigger jets maybe. But, I wanted the Truck Avenger for all of the advertised features plus it IS a 470.

Ortie666 you're hitting the nail on the head. I'm over-jetted, especially on the secondaries. Nothing a jet kit won't fix. Holley says, "if you have to go more than 8 jet sizes smaller or larger, you have the wrong application carb." I know for a fact that 4 sizes max should do the trick.

And one more thing, those CFM calculations are a "rule of thumb". Even calculating at 100% efficiency, it doesn't take into account cams, valve sizes, etc., etc., etc.

[sir loin]

A 470cfm would starve any smallblock period. Im telling him how to do this bescause Ive already seen bigger carbs hit harder than 390's on 660s

Another question for ya....what about timing and plug gap. Before the swap I was set at about 12 degrees initial and .050 on gap. This engine was obviously TBI and usually "fuel injected" engines run a fatter gap...so I didn't figure on a bigger gap even with more spark.

For timing, I have all Mallory components: Dist., 6AL box and coil.

Disconnected the PCV and brake booster to make certain of no vacuum leak. Just want to make sure I cover all my grounds before I re-jet.

Thanks for your help!!!

[Ortie666]

well the objective when you have aftermarket Ign.'s is to use the highest gap without blowing out the spark, so if .050 works keep it, but if u find it spuddering at topend, or under heavy acceleration gap down .005 at a time till it is crisp again.. As for timming 12 int. is good, I think thats what the cam recomends, I usraly run for about 30-32° all in..