another question

[whitey]

OK, I’m going back to my previous question, and expanding on it. Had a thought (look out!)

The 300/360 crate has a cam spec of 250/264 with .385/.401 lift roller cam. The 360 I built has a 268/276 with .429/.444 flat tappet. The crate has a 9:1 CR while mine has a 9.6:1 CR. MPP suggests a 750 CFM Holley for this crate engine. Both engines have the magnum heads-stock valves.

I went to Holley’s web site and used their carb selector. In the results for a 365 street engine, vacuum sec’s, electric choke, mildly modified, 6k rpm, the 770 St Avenger keeps coming up.

I am using a 3” x 14” dia. K&N with the x-stream top, a functional 440 scoop, Aluminum Radiator/shroud, B&M trans. cooler, 7 blade fan. A Crosswind ‘Airgap copy’ intake, TTI headers w/2.5 exhaust with an x-pipe. Holley blue electric fuel pump. It seems that I would be moving a lot of air into and around the engine, keeping it kind of cooler as well.

My question is, keeping in mind there is a ratio of air/fuel to go through the intake and a cooler engine, would it be better to go with the 670 Hooley and re-jet it higher or go with the 770 and re-jet it leaner?

 

[AdamR]

What gearing and trans/converter are you running ? If your running 323s or 355s and an auto the 670 would be better on the the low end but if its got 391s or 410s with a high stall or 4 speed Id go with the 770.

 

[whitey]

Hey Adam,
I have 3.73's in my 8.75. I don't have my converter yet, I was probably going to use the MPP 2000-2200. And 727 with a TF2 shift kit.

 

[AdamR]

Your kind of middle ground there. I would go with the 670 myself. It will give better low end, better throttle response and better fuel mileage.

 

[OldVart]

That sounds like a nice engine combo you have there. With the 3.73 rear gears I'd go with at least the MP 175K converter, and as Adam said, go with the 670 CFM carb.

 

[whitey]

and fatten the carb one notch?

 

[moper]

That's interesting..I did the same thing on the holley site. I find it interesting that they say 750 and 770 for a street car. A note Whitey, carb size has nothing to do with jet size. The entire engien and package does. SO every carb you buy will require some work to be perfect. Now, some guys dont need perfect, or dont know how good perfect can be. So in many cases, they say "it's perfect right out of the box". I tend to think nothing is perfect out of the box..lol. So in either size's case, I would bolt it on, and see what the engine tells you it wants. It may tell you you're too rich with either one, so you will need to lean it. Or, it may be what you consider "perfect". You dont know until it's on there and running.