What holley truck avenger with amc 360?

[mkzmomo]

Hi,

I will buy a new holley truck avenger carb this week for the freshly rebuilt amc 360. The engine as... pro comp cam 268H cam, roller rockers, ported head, edelbrock perf intake, stock manifold. 3" single exhaust.

Now my question is should I use the 670cfm or the 470cfm? The engine will go in my CJ8, 5" lift, 35" tires. 50/50 on and off road use.

thank you
Mike

[tufcj]

What gear are you running in the axles? If it revs higher the 470 won't be enough. I'd go with the 670. Since it's a vacuum secondary carb, you really can't over carb.

Bob
tufcj

[mkzmomo]

the gear in the axles are 3.73 for street and off road with the t18a it's fine for now

so 670cfm would be my choice then

[juggernaught]

I have done quite a bit of web surfing and calls to holly because I have the same delima. I have been running a m/c 2100 with very good off road results, but with moderate success on the pavement.
I did the engine/carb. calculator and it says that a 470 is ok for a stock 360 at 80% effeciency. Some guys have run a 470 on there ford 351 with good(?) results. I did not want to "over- carb" my motor and since my m/c was a 289 cfm carb I figured a 470 would fit the bill.
Then I talked to Holly....they say that the have not had good success with 470's on amc 360 size engines. Part of the reason is that with a 470 you are running on less than 1/2 the cfm of the carb before the secondaries cut in. Part of the reason I was leaning towards the 470 was to keep my vacuum high at low idle. I understand with the 470/670 setup, that there design keeps the vacuum high at lower rpm on both carbs.
I have still not seen a definative thread that shows a heads up test. From all I have read I have decided to go with the 670 since I have some head work, 9.0:1 pistons and a mild cam. But, I am still loooking for more input from someone who has run both the 470 and the 670 on the same v-8.
I run a t-18 with 4.10 diff and 33" tires.Hope thi helps.

[mkzmomo]

thanks for the answer juggernault.

this looks like I really need a 670... I should of keep my 470 to try it on first, but needed the money . I'll buy the 670 and try to find a 470 from a friend and try them both when I get the engine running

[Dusty]

ran a 470 on a 360 for high vaccum in offroad application. holley is correct the carb works fine idling and decent when on the street but performance was mixed at anything over 20 mph lol. took the 470 off my 360 and put it on my 304. perfect match. stuck the 670 onto my 360 and the motor came alive, offroad driving was fine. street performance was good too. ultimately stumbled into a new Rochester and liked that even better but good luck finding a virgin these days.