Edelbrock 4bbl on a 225 V6

I'd asked a lot of questions a couple of months ago, then dropped off for a while (first for a wheeling trip, then for cancer surgery - on me, the jeep bodywork comes next ;-) )

Thought it might be of use to someone to relate my experiences setting up an Edelbrock 4bbl carb on my V6-225 – warning, long…

Background: In bringing my ’66 back from a long sleep, it became clear an engine re-man was in the cards (145K miles, valves acting up on un-leaded gas, etc.). I had the engine sent off to Jasper (magnafluxed the block, .040 over, RV cam, etc.). Unfortunately the original intake manifold was apparently warped. Even after a light pass at a machine shop, we couldn’t get it to seal up, and could not find a replacement 2bbl manifold. So, I ended up with an Offenhauser 4 bbl. intake manifold (dual port, dual plane). The smallest carb we could find was the Holley 390 cfm, but after 2-3 months of messing with it, including 2 pro 4x4 shops here in northern Colorado, I could not get it running well. I swapped the Holley back out for an Edelbrock (model EPS 1404, 500 cfm, elec. choke), which out-of-the box ran better than we ever got the Holley.

I live at about 5000’, and mostly go up from there, so no surprise that even though the engine ran pretty smoothly, it was way rich. Edelbrock carbs (http://www.edelbrock.com/automotive/index.html) use both metering rod and jet changes as needed to calibrate. I had a big trip coming up (a week of wheeling in the Colorado high country!) very shortly after getting the carb in, so we took a guess at 3 steps lean (we would be above 12,000’ on at least a couple of trails). Incidentally, Edelbrock recommends 1 step (4%) change in mix with every 3000’ elevation change.

Stock setup (sealevel) for the carb is .086 main jets, .065 (cruise) x .052 (power) metering rods, and .095 secondary jets, and typically a bigger engine. From Edelbrock’s chart (see above site, owner’s manual) we tried .083 main jets, .067x.055 rods, and .089 secondaries, and hoped for the best. I also put in the ‘off road’ kit, PN 1465, and a 1” phenolic spacer under it (heat was ‘boiling’ gas in the bowl). This got me through the trip, but with considerable difficulty keeping it running under higher power, higher elevations (seemed pretty rich). Gas mileage for 500 miles was not much over 8 mpg!

By then, I’d had enough of trying to get someone else to set up the carb right, and with this elevation range in my ‘back yard’ I decided I’d best get this beast figured out myself. I got with Larry at Edelbrock tech support (found them <very> helpful, by the way). I bought the calibration kit, PN 1486, and got a few more sizes of rods along the way.

Knowing I didn’t know much about tuning a 4bbl carb, I also sprung for an O2 (air/fuel) exhaust sensor, and a dash mount meter (http://www.summitracing.com, PN SUM-G2989 and Cyberdyne digital (LED)). This really made the difference! I could finally measure the mixture, not guess (even though metering is <too> sensitive, one has to do kind of a visual running average). It turned out I was running way lean at cruise <and> way rich at power, even before compounding this with the elevation change.

Since then, I’ve tried quite a number of metering rods and jets. I won’t bore you further with all the combinations (send me a note if you’re curious), but here’s what I’ve ended up with as the best I can find for my rig, YMMV:

.083 main jets, .065x.057 rods, .089 secondary jets. At 5000’ this combo sets me a bit lean on cruise (as I like), and a bit rich on power (I’d rather be nearer neutral, but they don’t make the ‘perfect’ rod, my guess is ideal would be about .065x.059, since I’m more likely to go up than down in elevation). Mileage now runs more like 12–13 mpg around town, and in one run up to 10,000’ and back I got nearly 16. Big improvement! Sounds and feels much happier, too.

I also will carry .068x.057 rods (likely about right for cruise at 9-10,000’) and .070x.057 rods (for higher elevation cruise). Unfortunately, there aren’t any rods available that lean out the power side in this range. I could go to a still smaller jet (.080 and .077 are available), but then I’d be way lean on the cruise side. If I get a chance sometime, I will experiment with the .080 jets and .065x.057 rods at higher elevations, though swapping out jets requires opening the carb body, not something I’m excited about doing on the trail. Note that changing the rods is a breeze, accessible right under the air cleaner.

Whew, way longer than I’d have liked, hope this helps someone!

 

Nice write up Van!

 

it was way over my head at times, but this is osmething i will keep, i just cut and pasted it into my jeep info folder.thanks

 

Re Dan: I wish you live at sea level, i could use the rod numbers you use to tune the carb.

Hmmm, a 3000 mile road trip?? Nahh, too wet down there ;-)

One way to look at it would be to take my base setup, and try to guess back the other way. Unfortunately, the combo I ended up with isn't on their chart, but a first rough guess would be to try their chart ref. #4 (http://www.edelbrock.com/automotive/index.html, find calibration chart for 1404), which would be .065x.057 rod with your stock .086 jets. I'd probably drop one level on the secondaries, too, not that they get opened much. If my guessing here is right, you're currently not running to badly at a steady cruise, but acting rich as soon as you get on it some?

Luck!

 

Well, I got lucky and got my $$$ back for the Holley (still on warranty), so no trade stock here. If yours has the manual choke I wish I had it. Mine's actually the 1403, auto. choke, which was not what I wanted.

BTW, howdy 'neighbor', I'm just north of Fort Collins!

Van

 

Same issues with the carb on my M715. Had the original (as far as I know) motorcraft 2150 on it. I tried putting a remanned motorcraft 2150 from Partsamerica on it. After a lot of work and many weeks, I got the auto choke system on it working but still only got 7.5 mpg.

Finally gave up and put a Holley 2300 2V 350CFM on it. Manual choke is WAY better than that auto crappola. Runs better now than I've ever had it run. I'm at 5000' too and need to re-jet and drop the #61s down to #57s but even at that it looks like it's getting 9 mpg right out of the box. Doesn't sound great but after 7.5 mpg for months it's a big improvement!

Stan

 

Just to tie back to what I experimented with, Warlock lists the same set of jets and rods I had on when I left for my wheeling trip. It sounded good (to my not very well calibrated, 60 yr young ears), and drove pretty well here. Where I ran into trouble was flooding at higher elevations, plus getting rougher running at low power also.

This is also the setup that the fancy crutch (meter) says runs lean on cruise (pegs the meter low) and rich on power (pegs the meter high). Changing to the 65x57 rods gave me a little more fuel on cruise (.065 vs .067, .002 smaller pin in the jet => less hole blocked). On the power step, changing from .055 to .057, .002 larger rod, blocks more of the hole in the jet thus isn't quite as rich on power.

HTH, Van

 

Mtntinker:

What is your opinion of the Offenhauser dual port dual plane manifold. I'm especially interested in low rpm preformance for rock crawling (550 to 650 rpm)?

 

Whitelighting: Someone on here in CA put one on and he was happy with it. Maybe he'll chime in.

 

I'm certainly happy with what I see so far. I'd seen lots of warnings about 4bbls having poor response at low rpm, but have no complaints myself. But, I have plenty of gears to choose from, too. Haven't run any others 4bbl intakes to compare to, tho.

 

After 15 years running an Offy360 with every 4bbl in the book, I found that the stock cast iron manifold with the old 2gc preformed the best(under 1500RRPM).Stock gearing and a sane throttle foot could net 25mpg hwy miles and no offroad troubles. HOWEVER, when it comes time to "slap the horses rump", to clear the tires, or sand ect..... the four bbl combo really makes the difference, especialy when the rpm's begin to climb. BTW, I've run a Motorcraft 2300, Holley 2350,4150,and Economaster,and Carter AFB(which I had good luck with). Belive it or not, I'm currently running a Q-jet and am quite happy with it. Look for S-A Design Books manual #ISSBN 0-931472-11-3, or Fedral Mogul form #3703A. These are older tunning manuals, but if you can find one, they are a wealth of information on tunning Carter AFB's(Edelbrocks)In conclusion, I believe for "turn key" fun at low RPM's, the stock set up will run as good or better than any 4bbl set up.

 

A little more for the record - another way of looking at the setup options, and an experiment:

As mentioned in the first post, I'm reasonably satisfied with where I got for home, 5000', but not satisfied with the power side options at higher elevations. After writing the main post, I got to looking at the Edelbrock options (jets and rods) one more time, and figured that what I really needed was as little difference between cruise and power on the metering rods as I could get. So, I made myself a list of all the available rods that would have .008 or less difference between the two steps. This turns out to be a pretty short list - most rods have a bigger difference. Then, I looked at the available jets to see what was nearest the same opening (jet size - cruise step on rod) to I'd already found worked (.083 jet - .065 rod = .018 difference in diameter).

The new discovery from this is that if I use a .077 jet, I can use a .060 x .052 rod, and get very close to the same performance as .083 with .065 x .057 (just based on the numbers). .077 jet - .060 rod = .017 difference. When I put this in my rig, I found it is actually better for me. I'm just a little leaner than before, and get actually a better burn at power than I did. Sure satisfying when reality confirms the numbers!

What's even better, is that now I can carry a set of .065 x .057 rods (thus going .005 leaner on both cruise and power settings), and have what I think will be a great setup for the high country (9,000 - 13,000') with only a rod change. Rod changes are VERY easy on the Edelbrock.

Looks like a big win for me - YMMV of course.

The more general conclusion seems to me to be that for a 4 bbl. to work well on these smaller engines, we want a fairly small difference between the cruise and power settings.