darkmage

i just bought a new engine and i was wondering what size and/or modle carb will work best for my app.
cid: 350 .30 over
cam: valve lift .468 intake .480 exaust, sae duration 304 deg. int. and 287 deg. exaust. lift at cam is .312 int. and .320 exau. duration @.050" cam lift is 220 deg. int. and 231 deg. exau.
rockers: crane stud mounted energizer 1.5-1 rollers
10-1 compression
intake is edelbrock proformer
and if it matters i'll be shifting at 6500 RPM
thanks for your help

five7kid

iTrader: (14)

1st, need to know if this is a daily driver that you'll race occasionally, or a race car that you'll drive on the street occasionally.

2nd, I don't think your shift point is realistic. For one thing, that intake manifold dies at 5500, so the last thousand RPMs will be on the downslope of the torque & power curves. For another, that amount of cam duration would only have power above 6000 RPMs if the LSA is very tight (what is the LSA?). You might want to reconsider that combination.

Finally, more information would be helpful with regard to heads, transmission (auto/manual, stall, etc.), rear gears, and the like.

F-BIRD'88

A 750cfm carb is the best size of 4 barrel carb for a performance 350ci motor.
You have a choice of different secondary control mechanism and brand of carb. All will work well.
A vacuum secondary carb is perfered if you'll be using a basicly stock or near stock torque converter and modest rear gearing. You can use a double pumper if you have a high stall converter and higher ratio rear gearing.
If you'd like to pick up about 15 to 20hp over the performer, change over to a Performer RPM intake manifold. They work very well.
6500rpm is going to be too high of a shift point.
When you get to take 'er to the track, try different shift points and let the et slips tell you what the motor likes for RPM. It will be around 5000 to 6000rpm.

IHI

iTrader: (1)

In MUCH agreement your shift point is waay to high for that intake, and cam. From experience you should feel the car start to literally nose over at 5500. If intake is'nt bought yet, step up to the performer rpm at a minimum, or at least a vic jr. I used to run the performer rpm on a lower compression 355 with 232 actual duration .480 lift and it ran hard with a borrowed 830DP and same et/mph when I bought my 950HP holley. Now you now why I said 5500 it will be all done. I got a vic jr. for almost free and threw it on the motor, I noticed literally no difference in low rpm's from what the performer rpm had to offer, but it pulled the car easily to 6200rpm ere I finally shifted it, but felt like it wanted more. Even a torker II would'nt be a bad choice. With any of the intakes at a minimum get a 1" 4 hole spacer to help pull even more lower rpm grunt out of it.

This based on mostly "straight line" performance. For a daily driven car you wont go wrong with a 750 VS Holley. Personally never ran an edelbrock, but have been there when 3 were installed new on motors-all different motors nonf them ran worth a darn out of the box. Never had any intrest in them either so never learned how to tune them, but I've personally never seen a holley not out run a q-jet, and we've never experienced problems out of the box with them either. Just MY experiences with carbs.

darkmage

well the intake is one i had around, but im willing to buy a new one. the car will see some street driving like cruzing every now and then and and track but i would like to keep it streetable the heads are chevy 76cc pocket ported 202, 160 valves the trans is auto the gears are going to be 410s im not shure what LSA means and i could use alittle help on stall speed

IHI

iTrader: (1)

LSA is lobe serparation angle. This nukber determines where your power will be, a cam ground on a 106 LSA will make more hp at higher rpms at the sacrifice of lower rpm torque and usually requires a bit more compression. A good street/strip cam is usually ground on a 108 LSA to utilize a broad mid-range power band. Then 110-114 LSA is where alot of stock cams are usually ground.

4.10 gears with that cam is going to be overkill, your gonna wind it out too quickly and wont be utilizing the torqueof the cam. A 3.73 gear would be the best choice given the smaller cam specs, should put your 1/4mi. trap rpm where it needs to be for maiximum grunt. A 3.42 is a wise choice as well.

darkmage

the lobe seperation is 110.

five7kid

iTrader: (14)

That's "high" for top end power, so again, doubt it will pull to 6500 RPMs.

What are the casting #'s on the heads? End in "882"? If so, that's a big power restriction right there.

Any idea of your torque converter stall? It needs to be at least as high as the lower end of the cam/intake powerband.

pwmin

if youre at high elevation, you might want to go with the performer rpm air gap. when i was choosing my intake, i was told that they're not worth the extra money, but from my experience, i wish i had gotten one cause they allow for more air into the carb (sim to a spacer, but easier). you might have clearance issues though. i don't have experience with the air gap specifically, so if anyone disagrees, let it be known.

IHI

iTrader: (1)

I'm thinking a good 9" 3000 stall would be a good double duty choice convertor for street/strip. It'd really like a 35-3600 for max effort though.

One things for sure the quoted rpm band in most speed catalogs are never accurate, most cams only have about a true 3000 rpm band where they're making the most usuable power. And depeding on like 5seven said, some of the componets in the motor will have a tendency to shift the power band up or down. Even with that said your cam is not a high rpm cam.

darkmage

i did a computer dyno on it and w/ single plane intake it said 431 hp @ 6500 thats why i said 6500 as shift point but i dont know how accurate the desktop dyno is though! dont rember on what carb size was though a local auto shop did the dyno. i will check the casting # tommaro

IHI

iTrader: (1)

The only wat to get "close" on the ddyno is to have the actual head flow numbers from the heads you will be running and the exact cam opening/closing sequence numbers then the rest is pretty basic. I took all my info when I was putting my motor together and came up around 591hp on ddyno, and according to the weight of my car and mph it's pretty darn close. But without having exact data to enter it's still a vague guessing game at best.

darkmage

what other info do u need other than cast #

darkmage

the casting # 387349(or 8)3 not shure casting worn a little

nsimmons

3973493....71-72...400..........76cc chamber

darkmage

thats correct

RB83L69

2-barrel early smog heads..... eeeewwwwwwww.....

You won't be shifting at any 6500 RPM; or if you are, you'll be slowing the car down dramatically by doing so.

In addition to those heads not supporting such a thing, the cam and intake you have aren't appropriate for that either.

With that combo, I'd go with a 650 spreadbore; and shift it where it stops making any more power. No point in just holding it in low gear and listening to the engine tach out very slowly withoug accelerating the car. Should be around 5000-5200 RPM. A chassis dyno will tell the tale; the car will go fastest when shifted at the RPM where peak HP occurs. That means, the transmission shifts then, not the driver moves the gearshift when he sees that RPM go by on the tach.

darkmage

the cam is degreed @ 107 if thats makes any diff.

darkmage

i also have a holly street dominatre Sq. bore intake that i just picked up for 50$
just wondering if that will work better

waldershrek

Well, I was going to post a new thread asking almost the same question, but I guess i'll just add to this one. My motor is a 383 stroker, 2.02/1.90 heads, 76cc combustion chambers, Performer RPM cam, Performer RPM intake manifold 700r4 tranny, 2000 stall coverter and 3.23 gears and I need to decide what carb would be best for me. I am not sure of the compression though. It is a daily driver that I take to the track on weekends. I would be willing to sacrifice some gas mileage for power, although obviously I would like to get the biggest compromise from both.

The other problem is is that car is actually Super Rammed FI right now, and I want to switch it over to carbed mainly because I do not have the computer for this setup (it is just the stock computer) and it is not letting the motor run right. I am also needing to know what will need to bechanged over from FI to carb. I have been told that I can use my same HEI distributor along with the in tank fuel pump, however i would have to put a pressure regulator before the carb. My tranny is also electronic lock-up so how would I have to deal with this? All your help is appreciated.