I am not planning on anything immediately, but I am curious as to hp, cubic inch, and cam duration limitations of the CC carb and distributor set-up?

Thank you in advance for your thoughts.

 

Keep making more HP until something fails. That's the limit.

 

The carb flows about 750 CFM. The more cubic inches, the better, as you can use a milder cam and keep the O2 sensor from confusing the ECM.

Some calculations:

The "standard" formula for carb CFM is (cubic inch x RPM)/3456. Let's plug in a 400 cubic inch engine and solve for RPM: (750 CFM x 3456)/400 = 6480 RPM.

Now, the formula for horsepower is torque x RPM/5252. Assuming a 400 cid engine can make 400 ft-lbs of torque at 6480 RPM, the result would be 400 x 6480/5252 = 493 HP.

Is that possible? Perhaps. A 400 cid small block with good heads, RPM Performer Spreadbore intake, and a cam with a powerband up to 6500 RPM might be able to do it.

Let's take another example: How many cid will a 750 support? Back to the formula, CFM x 3456/RPM=ci. Let's assume 5500 RPMs (a nice, easy to support number without too much cam overlap): 750x3456/5500= 471 cid. Okay, let's take the typical .060"-over 454, 468 cid. A cam with a 5500 RPM powerband, Performer Spreadbore intake, decent heads, should be able to easily produce 450 ft-lbs. Same HP formula, 450x5500/5252=471. Swizzle those numbers around, you could probably get into the 490-500 hp range. (Yes, this would work - the distributor will fit in a standard deck BBC, all you'd need to add to keep the ECM happy is O2 and coolant temp sensors.)

That give you an idea?

 

Thank you very much for your well thought out reply. I'm of the understanding that the primary of the E4 carb utilizes solenoids to meter the fuel much like fuel injection. I'm curious as to the limitations of the ecm/ carb combination in part throttle as well as wot. Honestly, I find it really interesting......just curious.

 

After a fashion. A solenoid pulses a needle/jet setup to control primary mixture. It's mostly an issue in open loop operation, as the pulses are pre-determined, not based on O2 feedback. There are different jets, but to the best of my knowledge, the biggest were used on 350s, so that may take some tweaking. Normally you shoot for 50% duty cycle in closed loop idle, as that will give you the best open loop operation per the programming. Might be able to fuss with the programming if you're up for that.

At WOT, the primary mixture goes open loop full rich, but the secondaries overwhelm the overall fuel/air ratio.

 

Very interesting. I am not arguing with you, but if the O2 sensor doesn't control afr what does it do?

 

O2 sensor is narrow band and only controls idle and part throttle lean cruise because that's all it CAN do being a barrow band sensor. Once you go away from idling or cruising the O2 sensor is not used at all and the carb reverts to mechanical operation. Because under any condition other than those, the computer is blind.

The sensor can ONLY read 14.7:1 AFR. Or rather it can ONLY tell the computer if it is leaner or richer than 14.7. It does not work at all for any other mixture. Therefore it cannot function in any meaningful way when at WOT, where your mixtures are probably in the 12.5 range.

GD

 

Makes total sense now. Thanks to all for your time.

 

Its more of a idle vacuum limitation on these setups than anything. I have run one with a GM 847 cam in a 383 Vortec. As long as it gets atleast 15 in/hg of vacuum at idle you can make it run acceptably. Also the advance curve in the LG4 chip is very weak. Run a L69 or ZZ3/ZZ4 chip instead. The stock electric/mechanical fuel pump setup also struggles with much more than stock. I would use a TPI pump in the tank with an external bypass regulator mounted close to the carb with an insulated fuel line to the carb. Keeps the fuel circulating and cool, avoiding vapor lock. I used the same setup on my old 1983 G20 van for a while. Had no problem fueling a 400 HP 350 with a stock Q-Jet that had been tweaked. The van already had DR rods on a F-hanger. Just modified the air door to open to 90° for more flow and used the high flow big block needle and seat. The air door limiter choked some of these carbs down to the 500-600 cfm range.

 

Excellent information thank you Sir. I am pleasantly suprised, because the GM 847 is no slouch in 383. I did install a Hypertech chip along with the aforementioned heads and cam. I checked air door on this carburetor and the air door seemly opens all the way.

 

http://www.jegs.com/i/Carter/180/M6626/10002/-1

Replace your fuel pump with this first. Yours is 32 years old.
You wouldn't believe the low GPH rating on the stock pump.

 

Done deal! I will order it in the AM