Posted by Charlie (IP: 152.163.201.179) on January 31, 2000 at 21:02:40:
In Reply to: Drivability problem posted by Erik on January 31, 2000 at 18:48:04:
Sounds like your mileage is due to the carb. Holleys are great carbs but the 390 is wrong for your application (probably overjetted), and possibly worn-out. The secondarys won't open unless the car is under a load, so don't watch for that to happen in park. It is almost impossible to open the secondaries without driving the car.
I think you should get a new carb, not necessarily an Edelbrock. Edelbrocks are good carbs, but I think they are overrated. Lots of hotrodders are getting tired of their worn-out Holleys and trading them in for new Edelbrocks, and saying how fantastic the difference is. I think they would see the same improvements with a new Holley. I did. Holleys are the best performance carb, and Edelbrocks are based on the GM carter design.
Whichever carb you choose, you'll probably be happy though.
(I get 15/19 mpg with my new Holley 600 DP)-CP
: I know what you are thinking if you have read my previous posts, damn that guys car is piece of junk.I posted these question last nite I think but the MB was changed so it got lost I guess.Anyhow , my problem is my car doesn't seem to be running at full potential and it gets bad gas milage.My engine now has about 700 miles on it since the rebuild and I would think it should be freeing up a little and getting good milage by now, but it only get on an average 13.5 miles per gallon between city/highway.Now I am not sure why this is happening so please tell me if there is something wrong with my set-up and let me know if my assumption is correct.Rearend is 3.00:1 , C4 trans., 302 (stock bore/stroke), cam: DUR. 260 int. , 270 exh., Valve lift:.424 int., .448 exh., I am running headers and Edlebrock performer intake.Now here is where I think my problem is , I am using a 600 cfm Holley from a 75 F250 that had a 390.The carb. is running really rich and I have leaned it out as much as I can ,but it is still rich(If I lean it too much it won't idle smooth)possibly the jets are too big? I am also babying the car and still no luck with MPG.Also , the carb. throttle shaft doesn't have the pin for the A/T kick down , so I am running it without , any problems with that?And final question , my secondaries don't seem to be opening (at least not when floored from stop, haven't taken speed high enough to see if they open at high speed)what could be causing this?Should I just junk this carb. in favor of an Edlebrock?