Howdy folks,

Well I finally have my truck running after a full engine rebuild. Its a 59 292 bored.060 with a mummert aluminum intake and headers. It has a mild cam. 
My question is I had it over carbed I think with a 625 street demon carb. So the engine builder recommended a edelbrock 1403 500cfm carb with a 1" open plenum spacer. I live in Longmont CO and we are 4,984 feet above sea level. Anyone out there live in co and tune this carb for a y-block. I have tried every different spring and the strongest ones ( silver ) seem to work best. For the jets Edelbrock recommended 83 jet for primary and 92 for secondary. I tried several different metering rods and the stocks 6552 seem to be ok. The truck seems to have a small bit of lag when you really get into it. Its not a stumble but the pick up i not instantaneous. Any other tuning hits would help tons. Thanks folks.

Here's some background from Ted's site. Big motor,but the principles apply. See what clears the hood, and mind Edelbrocks warnings about air cleaner sizes and clearances. It's in the tuning manual.

http://www.eatonbalancing.com/blog/2012/09/29/carburetor-spacer-testing/

I'll stand by my comments about you needing to know the vacumn readings.

The Mummert manifold and headers would normally like a little richer mixture than stock. That's a generic comment about any engine with those upgrades.



That said, you need to sort out why you've got the smaller jets (how did Edelbrock recommend those?) than the base carb info and tuning chart show. If you didn't start stock, I'd be inclined to install the stock jets, rods, and springs in the primary. Since you don't mention the secondary's I'll assume they haven't changed. My experience with these carbs is on almost any moderate street motor, they're close out of the box. Tuning is relatively minor for drivability or max power. Then check the float settings. From your description, I don't think you've got a fuel pressure problem, but that's also a possibility. Check the timing, vacumn advance disconnected and plugged. Most of these motors like more initial than the book, up around 10 degrees initial, with 25-30 all in by 2500 or so. I'm assuming you've got the stock distributor, and someone didn't put a Loadomatic in it. They won't work at all with that carb. We could go on about a PCV system and the right valve, etc. but you seem too close for that.

From there, I'd tune for drivability, and follow the chart. You're at 5000 ft, so you're not going to move all the way to ref#24, just part of it. Maybe, depending on the cam, not at all. One change at a time. Watch the ambient temperature if you have big swings. A result in the morning at 50 degrees may not translate to late afternoon at 90. Keep looking at the tuning manual till you really understand it. I've been wrenching on cars for 50 years. Most of my dead ends were from not reading the instructions. Not just cars, either.

miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ