Edelbrock 750 #1407

[hunt2elk]

Is anybody familiar with the jet - metering rod combinations for this carb.? I want to lean the primary, but leave the secondary and power mode as is. I am confused by the chart in the manual which runs mostly diagonal. I am debating either #22 or #23 in the chart. Will the #22 combination cause me to lose any power after cruise mode?

 

[IQ52]

I can't tell you what it will do to your engine, but I can give you my recent experience with those settings.

I have a 383 with a mild hydraulic cam upgrade, a DP4B manifold, headers and about 9:1 compression with iron heads in my 4x4 truck.

I live at 5,280' elevation and made the trip to the NATS in Columbus, OH. Before I left for the NATS, I set my 1407 up with the 4% lean 104 jet in the secondary and went to the #22 setting in the primary. With 87-88 octane, when I got under 3000' elevation, I got a lean stumble on takeoff from a start. When I crossed the Mississippi River I started noticing some pinging when I rolled the throttle into the primary power mode. I switched to premium fuel and the pinging went away.

Later at the motel in OH, I changed to the #23 combination in the primary circuit and switched back to (the cheaper) 87-88 octane and had no more pinging. I never lost the lean stumble until I got back to higher elevations.

Will you loose power with the #22 after cruise? You'll just have to try and see. Best part is that it is an easy metering rod change you can make in a few minutes.

 

[Meep-Meep]

I'm running the same carb on a mild 440 and it runs right to 6000 RPM. I did have to go 4% richer on the secondaries to cure a slight stumble when I slammed it open, but otherwise it's at the factory baseline setting. I'm not surprised that you experienced pinging as you got closer to sea level and it was most likely caused by a lean mixture. If you have a mild to stock 383 I would say the 750 might be a tad big - at least near sea level that may be the case. Air moves through a carb much easier than fuel so that's why it's important to size the carb correctly for the application to maintain proper air velocity. Your setup might work great at a mile high, where you need all the air you can get, but near sea level it's another story. Edelbrock suggests 2% leaner per 1500 ft and I'm sure that rule applies to a carb that was properly selected for the engine. Also the fuel at high altitude is different than we sea level folks get and that might be a factor too. Just throwing some stuff out there.

 

[IQ52]

Thanks for the thrown stuff. I had to do some bobbing and weaving but I suffered no serious injury.

Well lesse', my only carburetor choices for that run were:

950 cfm Quick Fuel
850 cfm Mighty Demon
1050 cfm RS Race Demon
1090 cfm King Demon
1150 cfm Pro-Systems Dominator
800 cfm Edelbrock Performer
750 cfm Edelbrock Performer

See my conundrum?

Everything else smaller (500-650cfm) I had given to the kids and grandkids for their 318, 383, 400 & 440 powered cars.

Seems like I only get the leftovers.

I brought 100+ needles and 200+ jets with me on the trip to adjust the fuel mixture for the best economy. It was afterall a 4000 mile round trip. It got hot and I got lazy. 12.3 mpg seemed good enough until the pinging irritated me so I only made the one change AFTER the engine cooled down all night.

 

[hunt2elk]

I know the 750 is a little big, but I have tried a 650 Edelbrock Thunder for the past couple of months. I was happy with the idle and low end, but the top end doesn't even come close to the power of the 750. I even went 2 steps richer on the secondaries of the 650. So I have decided to go back to the 750 and fine tune the idle and cruise modes. My only complaints are raw gas smell from exhaust when idling and about 3 mpg poorer milage compared to the 650. I have only 9.5-10" vacuum at idle (because of my cam) and am also going to try a weeker spring on the metering rods.