B&m 144, using an edelbrock 750 carb, I recently changed the metering rods, primary jets to .113 and secondary jets were already at .113. Now I took it for a road test today, it idles at 11.2 to 10.2, part throttle cruise with vacuum at 14-18, afr goes kinda lean @14-16. Part throttle acceleration it's around 13 and at WOT it's at 11.7 to 12.7. Gauge is real quick and I had a hard time keeping up while watching the road. Is that afr ok for cruise? I can always tune out the idle, but when I richened up the idle circuit it helped with the cruise afr. Before it was jumping to 17 at part throttle cruise. Should I go up one stage richer in the metering rod? Or the main primary jet? WOT looks to be alright, might go to .116 on the secondaries just in case.

Most setups run best between 14-15 at light cruise. Timing plays a roll here too. If you have surging/chugging at that AFR you might need to decrease your timing in that range. Mine runs great as lean as 15.5 AFR with around 40 degrees total timing at cruise.

Ok, so 14-15 idle/light cruise, 12-13 part throttle acceleration and 10-11 wot ok?

I was thinking about locking my distributor at 28 degrees advance and using my vac advance, how does that sound?

Most naturally aspirated cars I tune I go for this:

idle 12.5-15 (large cams need to be on the richer end, stock cams usually tolerate leaner)

light throttle cruise 14-15

1/4 throttle accel 13.5-14

1/2 throttle accel 13-13.5

WOT 12.5 - 13.0 usually makes the most power

Now with a boosted application, most people (including me) target AFR's under WOT anywhere from 11.0-12.0 to help suppress detonation. How much boost does it make?

By the way an Edelbrock 1406 is a 600 cfm carb.

Your timing curve should be set up first or else you will be chasing your tail when it comes time to recheck your carb settings.
Timing curve should resemble something like this:

idle: 12-20 degrees depending on what it likes and where it makes highest vacuum. Large cams generally like more idle timing.

mechanical advance: make sure it doesn't start advancing until a couple hundred rpm over your idle speed or it can cause stalling when put into gear at idle. I usually set them up to come "all in" between 2500 and 3000 rpm. Usually I run the softest springs I can where it doesn't interfere with idle timing.

Locking it out at 28 would probably work fine, if 28 is where you want to be. I would run less timing that 28 unless you are at 5 psi or less.
My car at 10 psi doesn't like more than 20 degrees on 91 octane. If you are around the 6-8 psi range I would start lower around 20-22 and increase slowly if you like, listening closely for detonation. You can also check the porcelain on the plugs for black specks. Specks are signs of detonation and usually if you have loud exhaust it might not be apparent to your ears.

If you have an adjustable vacuum advance canister you can start by cranking it up to provide the most vacuum advance and if you get surging at light cruise (with AFR's in the right range) then back it off till the surging stops. This should give you the highest engine vacuum cruising and the best milage. This is usually in the 40-45 degree range. I don't know why some people don't run vacuum advance, if you don't you are simply leaving a lot of milage on the table.

Sorry I haven't updated my Sig in a while. I'm running a 750 now with .116 primaries and .116 secondaries. I have to figure out how to get enough timing for it to idle good and then not so much for when I'm under boost. I'm only at 5-6 psi.I was thinking locking it out at about 20 and running vac advance. I think that would be ideal for idle,cruise and wot. What do you think? Haven't been able to do a test run after I changed jetting but I'll update as soon as I do. Thanks for the info! Really helps out Alot!

Ps. We have 110 octane cam2 out here, would that help out with suppressing detonation?

Watching...

I will be trying to tune an f1 powered 390 fed by a carb specialties 750, Intercooled.

I tried limiting my mechanical advance by installing a screw next to the plate that rotated right under the rotor. It sort of worked, but tended to drift and change as the head of the screw would wear. To be certain it stays consistent locking it out and using vacuum advance should work fine. You 'll be giving up some timing when you aren't making boost but with a blower I don't think it 'd be as big a deal as with a turbo. I 'm running a MSD 6al-2 programmable box that works great and allows full timing and then automatically backs down timing as boost comes on. It helps my spooling quite a bit but like I said, keeping it simple with locking it at 20 and using vac advance should work just fine.

These roots blowers like a lot of advance. If you set your advance to be all in by 2500-3000 RPM's, you're leaving a lot of power on the table. That's great for a NA car....

You don't need to worrying about "spooling"...boost is instant as soon as you go WOT. So that curve is to lazy for a roots car. Since yours doesn't have a bypass valve, locking the mechanical out might work good for you.

Your only going to have a few degrees of mechanical timing anyways if you are stopping in the low 20's. Just lock it out and let the vacuum canister add timing. Of course you don't have to worry about spooling. I'd be more concerned with IAT's with a blower with no intercooler or water/meth injection. If you ran a water/meth setup you could probably run quite a bit more timing and add a decent amount of power. And you wouldn't need to run it so rich under WOT since you no longer need the extra fuel to suppress detonation.

Don't the Edelbrock/Carter carbs have brass floats? I'm not sure what psi they can handle before being collapsed by boost.

Since it's a draw through application for the carb, not a pressurized blow through like a turbo or Procharger....don't worry about the floats.

Yep my bad. I forgot about the draw through setup.

No biggie...easy to miss. I'm getting a wide band O2 very soon myself to see if I can dial it in a bit leaner myself.

From everything I've read or have been told, 12-13:1 is a good number to shoot for under boost and a max of 13.5:1 while cruising part throttle. I'll keep it slightly far so I'm not draining pistons with my oil during my next change.

What would help the most is having boost referenced power pistons. I feel you are experiencing a higher than usual vacuum at part-throttle. You can somewhat help this by using the stiffest step-up spring you can find. Some people claim that the Carter/Edelbrock carbs do not need to have boost reference, but I disagree. It is entirely possible to be at part-throttle under boost, yet have relatively high vacuum on the carb.

I've got a 383 procharged (D1SC w/ intercooler) set up with a C&S carb along with MSD boost referenced box. I have the FAST air/fuel system in my car with sensors in both collectors. At idle I'm shooting for 14-15, going down the highway at 55 turning 2700 rpm im at 13.6, WOT I like to see high 11's, low 12's depending on the weather. Compression is at 8 to 1 and running 16-18 pounds of boost. With the MSD boost referenced box I currently have everything set for a 1 to 1 ratio, meaning for every 1 pound of boost the box is going to pull one degree of timing. Timing is currently at 34, but I have found best results at 32.

Not to get off topic, but my biggest issue has been trying to keep the car cool. I've got a BeCool alum. radiator with dual flex-o-lite fans that are suppose to pull 3000cfm. Drove the car last night when it was 70 degs and the car gets up to 210 pretty quick on the highway at 55 (3.73 rear end gear with TH400), I had a 180 themostat in it and decided to take that out and try those moroso restrictor plates with no luck so far. I'm going to try changing the crank pulley from stock (7 5/8 dia.) down to 5 3/4 in hopes of slow down the flow of the water pump. I think the water isn't staying in the radiator long enough to cool everything down. Maybe I'm going down the wrong road, but not sure on what else to try to get the car running cooler, I can't guess what it would for coolant temp on a hot day (85+).

I'm running the stock radiator and stock electric fans with an intercooler directly in front of it with no cooling issues, even on the road course in 80 degree temps. What are you running for an air dam? There is much shrouding that can be improved to make sure the air must go through the radiator and not around it. I focused on making sure air is forced through the intercooler/radiator and it works great.

I replaced the stock 1 pc. air dam with a 3 pc. air dam. I have the air "scoop" for the intercooler in place which is roughly 8 1/2" from bottom of the air "scoop" to the ground and the air dam for the the car is roughly 6" from ground. I thought about adding a piece of plastic to the bottom of the air dam to help catch more air, just not sure how much more to add to my current air dam with out worrying about it draging all of the time. You got any pics of your step up?
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11.13 @ 123.8 on pump gas (10lbs of boost), no transbrake - 5/18/12 @ Cordova, IL - Drag Radials

10.73 @ 129.5 on 104 race gas (15lbs of boost), no transbrake - 9/8/12 @ Byron, IL - Drag Radials

10.62 @ 127.6 on 112 race gas (16lbs boost), w/ transbrake - 5/23/14 @ Cordova, IL - Slicks

Not to stay too off topic lol but here are few pictures.There are gaps alongside the radiator in the last picture that I sealed up, and the plastic cover on top near the hood latch is important too. Mine is off a carburated car. My air dam is just a piece of lexan I bent and then chopped up a rubber mud flap for the bottom couple inches so it can flex if it hits the ground. I also made a score line on the lexan just above where the rubber attaches so if it ever hits anything major it will snap off instead of bending the hell out of my core support.
I added a second tranny cooler (passenger side with block off plate on it) for when I go to the track and the cooler on the drivers side is for engine oil. To prevent turbulence I added some plastic that follows the original contour of the stock plastic curved piece just behind the nose to direct the air smoothly into the coolers. My main tranny cooler is mounted on the front of the radiator, behind the intercooler. I also added a piece of screen that catches most bugs and crap that would otherwise plug the radiator because of the aggressive air dam. I think that's why the stock air dam is almost verticle, to keep junk from deflecting up onto the radiator.

What is the name of the piece of plastic that runs from the center of the underside of the GFX chin to the car? Is your stock? Mine has always been missing.

Your air managment looks great.

Thanks for the pics! Here is what I came up with to try and pull more air up to the radiator. Its threshold that I bought at the local hardware store for $10, I think has helped but car still gets up to 210-215 under normal in-town driving conditions.

I talked my carb guy (Roger @ C&S out of missouri) and suggested trying a mechical fan, rather than my dual electric fans. He thinks that the mechical fans will pull more air. He indicated that he has had guys in the past with my same problem and in ever case that fixed the cooling issue. At the this point in the game I'm willing to try anything to get the car to run alittle cooler even if it cost me 12-15 horsepower.

I'm not sure what the plastic "air smoother" deal is called but I bet it makes a big difference. I would try to find one.

So it looks like you have a scoop in front of the radiator one? Is that for your intercooler? I can tell just by looking at the threshold you added that it's not nearly as large as mine with the rubber mudflap on it. I would try extending it further down. You should be able to get away with a few more inches. (That's what she said.) Unless your car is lowered. Mine is stock height.
Also I bet the intercooler scoop is disrupting whatever air would deflect off the radiator scoop. Does it run hot on the road (cruising speeds)or just when sitting in traffic?

The "air smoother" that you are referring to is just a rubber flap. It came like that and thought I would just leave it how it came. Yes that scoop is for my intercooler, which is why I thought I should try and find something else to help pull some more air to the radiator. Without adding another piece of aluminium, I have it down as far as possible.

I did a test the other day sitting in the driveway, I thought I would start it cold and just see how hot it gets at a idle. It got close to 210, it was also mid 80's so I did have a fan in front of the car to help move some air. Last night I took the 5/8 restrictor plate out and put the 180 thermostat back in. It was mid 60's last night and it still got to 210 going down at the highway at 55 (2700 rpm to 2800 rpm).

I really dont think my flex-o-lite electric fans are able to pull enough air through the radiator. I ordered a mechanical fan (17in-reverse rotation) and a shroud yesterday for a 82-85 firebird. I'm sure that I will have to modify the shroud with having the procharger set up. I'll post results.

If it's getting hot at idle AND on the highway I wonder if there is something else going on. I'm running a 180 T-stat with stock pulleys, water pump and radiator. It runs right at 180 with no fans as long as I'm moving over 30mph. At idle, one fan will maintain about 190-200 pretty much forever, and both will keep it at 180. How thick is that radiator? I seem to think the thick ones have so much air restriction that it counteracts the added internal coolant surface area and they don't cool as well as the thin stock ones. What is your ignition timing at idle and cruising? I know if I retard my idle timing back to like 10 degrees it makes much more heat than when it's at 20-25 degrees. I'm sure it's no different cruising.

i have a d1sc procharged 388 stroker 1985 camro with 14 -15 psi devils own meth inject i had an intercooler but it blocked too much air flow to the radiator took it out and now the temps are way down from 210 all the time to 180- 190 in the 85-95 degree summer heat it only touches 210 now if im at stop signs romping on it on slow roads. Over 50 mph with 373 gears temps at 190. the a/f is at like 12.8-13.8 cruising 13.4 hot idle and im real rich so it drops to 10.0 bottoms out the gauge at WOT. spraying alot of meth 275psi with 2 nozzles a #14 and #3 devils own running pump gas with some octane boost
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jegs radiator running #67 jet in secondary

The radiator is a BeCool (2" thick), timing is set at 30 degrees. Maybe I need to bump that up to 34 or 36 degrees. I previously had it at 34 degrees and didnt seem to make much difference in the cooling department.

I talked to BeCool today and explained my current situation and they said at a idle I should have a 3/8 to 1/2 stream of coolant flow, instead mine is probably closer to 3/4 or 1. The tech I talked to also didn't like the fact that I've got a tranny cooler in front of the radiator. He sugguested relocating the tranny cooler some where else. I'm hoping by putting a smaller crank pulley on (going from 7 5/8 to 5 3/4) will help slow the pump down (not so much at a idle, but more for going down the highway at 55). I've got the car up to 80 mph and put the tranny and neutral to let it coast at at idle and I can physically watch the temp come down, which kind of helps my theory about the pump spinning too fast. If that doesnt do the trick then I'm going with the mechanical fan setup.

I wouldn't think changing timing a few degrees would make much difference in the heat department. 2" is a pretty thick radiator considering the stock one is about 5/8". Are you running vacuum advance or is it just locked at 30 always? I forgot what you said above but you must be pulling timing under boost below 30. My timing is up in the lower 40's at high vacuum (over 15") cruising down the highway which definitely adds efficiency. It makes quite a bit more engine vacuum with the extra timing and gets way better milage, so you know it's burning less fuel which creates less heat.
And most guys run a tranny cooler in front of the radiator, but if it's possible to move it somewhere else obviously it couldn't hurt.

No vaccum advance pod, its locked at 30. I have a MSD boost referenced box, currently it is pulling 1 degree of timing for every 1 pound of boost (up to 15 degrees total). I do have a advance pod, just never put it in.