600 CFM vs 750 CFM...

Guys - I received the 1405 on Monday. Monday evening I had it converted to the 1406 set up and set it on the intake. There was a crack in the rubber fuel line, so I stopped there and went and got another foot of fuel line. Tuesday I finished the line and finished the car install. When I pulled the filter off, all manner of nasty schmutz oozed back out the backside of the filter. It concerned me.

The 1405 came with a clear plastic filter. I was glad, in that way I could see if the fuel is real nasty, meaning the tank needs attention. Luckily the fuel looks very very clean going into the filter. The filter may have been 30 years old.

Tuesday night I took it for a quick spin. It idles nice, comes off idle very well. It was very lean (too lean) in Power Mode (accelerating) so I did not attempt WOT. Cruising AFR's seemed close. I figure (but may be wrong) I need 8% more fuel to accelerate, and keep the same fuel level for cruising. I'll figure out what to do about that after I see what effect the below has.

I had an interesting conversation with an Edelbrock technical rep today. I told him about the off-idle lean spike. I read on the internet that a lot of Edelbrock owners experience this. I had it with the 1407, and now with the 1405. It seems that at about 1.5 seconds after beginning a slow acceleration, the pump shot is consumed and it goes lean. Sometimes bad enough to stumble. It's as if the metering rod needs to come up quicker to deliver more fuel. He said that if I switched from total vacuum to timed vacuum that it should resolve that or reduce it. And either in the videos or in the manual, I do remember being instructed to use timed vacuum. I will try that ... maybe tonight.

Yesterday I checked vacuum. At a warm idle, it's pulling 17" of vacuum. The Edelbrock manual says to take half the vacuum and use that size spring (at least as a start). 17 / 2 = 8.5. So I took the 4" spring out of it, and put the largest available 8" spring in it. This tends to make sense as the stronger spring would pull the rod out of the jet quicker. Which should also help with the lean spike. I didn't get to drive it as it was raining last night.

7milesout