I'd do whatever is outlined in the excellent tuning manual that came with the carb.

But we need to know the cam specs before any more advice can be offered.  Like miker said, 7" hg is either a huge cam or a vacuum leak, both of which have their own tuning issues.  If it is a huge cam, you probably are undercarbed.  If it's a vacuum leak, then there is no sense trying to tune anything until the leak is fixed.



Lawrenceville, GA

Sorry maybe I missed it above but what jets for primary and secondary would you recommend for my area? thanks

I just put on my 4-hole 2" spacer. Seems to run a tad bit smoother in take off but not a lot. barely noticeable. Its an isky cam slight lope good for street performance. I will have to look up the specs. I am smelling a lot of gas while driving too but i dont see leaks anywhere.

MIker. To my knowledge Edelbrock recommended the smaller jets because of my elevation here in Colorado which 4,984′. the jets the recommended and that I have in the carb now are 83 primary and 92 secondaries. I was told to leave the rods as the were which i believe are 6554. My vacuum at idle is around 7. I have had the best luck with the strongest ( silver ) springs. I have a completely rebuilt t-98 4 speed for trans. And the original dizzy however I did put the pertronix in place of the points. 

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

1", 2", maybe even your 3" will be ok, if you can fit it under the hood.



Lawrenceville, GA

I do have an extra 4 hole spacer however its really tall about 3" I think. Is that bad or good? I can hit napa tomorrow and get whatever height would be best in a 4 hole spacer. Thoughts? I am still also confused on what springs jets and metering rods I should be running.

Try a 4-hole or divided spacer.  Open is generally not the best choice for street use.



Lawrenceville, GA

Yes, but I read ref#24 as being a 86 jet, not the 83 you're running. It's a bit confusing as the first jet chart starts at 1404, but later charts list 1403/1404 as the same. On the surface, it appears Edelbrock has made a recommendation different from the tuning manual.

If you're running an 83 jet, and the rod change for altitude as shown in ref#24, you're lean. You also need to know what your vacumn reading are at part throttle cruise at speed. If your base setting is lean, then the natural color spring at 8" will be opening the power circuit and help compensate for it. But until you know the vacumn reading at idle, light cruise, and (call it) highway cruise, you don't know when your running on the enrichment circuit (power valve open in Holley terms).

I don't have enough high altitude experience to know the effect on timing, but that will be another area to explore. I've got an old friend who does a lot of bracket racing, and he has years of data for each engine combination he's run. Tuning for density altitude based on atmospheric pressure and temperature is really a black art in his league. Uncorked, no throttle stops, he runs mid 9's on a cool day at sea level. This is to run a 10.7 bracket at altitude on a 100+ degree day.

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