I've been dreaming of Carbs

90WT

90WT

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Looking for a local support group to talk about how to get the most from carburetors. I'm talking air & fuel, all mixed together in a perfect (explosive) harmony.

After years of sub-par performance out of my V8 rebuild, I realize I failed to adequately tune it well. The truck runs "meh". And I want "oh yeah". And after a bit of reading, I'm convinced that instead of just fiddling with the carb, I gotta take a whole new approach and start from scratch.

My build (Warning Not Toyota Specific):
Ford 352 V8 with 4bbl Edelbrock 600 CFM electric choke - Naturally aspirated, ol' skool points ignition.

Here's my plan. (Tell me if I'm crazy). I'm starting with a wideband O2 sensor install to get an initial read on my Air/Fuel mixture. Then I'm going to go back through the timing, check the vacuum lines, install a fuel pressure gauge, a fuel pressure regulator, maybe an electronic fuel pump, and maybe a fuel return line to the tank, all to make sure my carb is getting stable fuel supply at a constant pressure. Then, I'm going back through the carb to fine tune jets/needles/springs/float height. I'm optimistic it will yield better results. Like massive results.

I keep mulling over this stuff in my head.

Anybody having trouble with their carbs? Shoddy performance? What did you do wrong / what did you do right?

Anybody drop their rig on a dyno before and after a tune? Is there a dyno in the valley? How much does it cost? Was it worth it?

Should you bail on the points ignition and go electronic ignition?

Should we all go with fuel injection?

Oooh, how bout Holley vs Edelbrock?

Is tuning an engine becoming a lost art?
 
pigmony

pigmony

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Anybody having trouble with their carbs? Shoddy performance?
I got mine working pretty good for the moment, but it needs attention whenever I go up for down more than a couple thousand feet in elevation and it needs some fine tuning about every 2-3 months of driving.
What did you do wrong / what did you do right?
I found a manual online and actually read it. That was a turning point for getting mine to behave.
Anybody drop their rig on a dyno before and after a tune? Is there a dyno in the valley? How much does it cost? Was it worth it?
I haven't felt the need to do so, but it would be interesting. There is one at Mike's Offroad/Altitude Tuning. There might be more. I'm pretty sure @wizmariefa has used a local one recently.
Should you bail on the points ignition and go electronic ignition?
Probably. If for no other reason than simply for the improved maintenance interval.
Should we all go with fuel injection?
Yes. The latest generations of engine management systems allow for tremendous control and tuning, or you can simply set some starting parameters and let it tune itself. The Sniper systems are really amazing.
Oooh, how bout Holley vs Edelbrock?
I've had both and spent a lot less time messing with Holley carbs. Both can make an engine run. Holley costs significantly more, in general.
Is tuning an engine becoming a lost art?
Nope, it just looks different. Owning a laptop doesn't make you an engine tuner. You still need to have an understanding of what's happening in the engine, why it's happening the way it is, what the variables are, which variables you can control, and what those variables do to the whole system. Engine management systems can kick out tons of information and pretty graphs, but all the graphs in the world wont help you if you don't understand how to use the information.

Tuning carbureted engines might be becoming a lost art. They're becoming more and more rare, so there are fewer opportunities for getting experience with them. I'm not sure that's a bad thing either. Progress for the sake of progress is one thing, but fuel injection is objectively better in every way except for system cost and susceptibility to EMP (which hasn't been as big of a problem as it was expected to be post 1945).
 
REZARF

REZARF

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Carbs... I like donuts! But I digress.

Dyno Jet is made here in town... not sure if you can hop on one. I bet Dark horse has someone they use or have their own.

Your plan sounds solid Matt. I’ve had a bit of experience with the edelbrock carbs, they tune pretty easy. Keep them clean, set the mixture and Hit the gas!


What Brand/CFM do you have now? Have you already tried a good basic tune up? Timing, new plugs, valve adjustment... vacuum leak test. Even a good compression test and leak down test to make sure your foundation is solid?

I find it’s easier to add a loud muffler than actually gain performance. Both make me smile! YMMV :D

You know this, but adding HP is a slippery slope that has no finish line.

Torque > Raw
 
90WT

90WT

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@pigmony Good feedback. What engine, ignition,carb setup are you running now? Would you say its a good combo for what want out of it?

I started with an engine rebuild and slapped on new Edelbrock carb. Setting up the carb for high altitude and lean/rich was pretty straightforward using their charts in the Edelbrock manual. I had figured that the performance kit with lots of needles/jets/etc was the end all adustment. But now I'm seeing where folks are re-jetting in much smaller increments than what was in the kit I bought. In addition, the carb wants a steady fuel pressure, which I can't guarantee from the mechanical fuel pump. Adjusting secondaries is a whole another task. For this reason, I'm installing the wideband O2 sensor. I want to see the A/F mix ratio at idle, when the secondaries open, and WOT. I think what I'm going to find out, is that the current carb setup, although ok, is far from good.

Anybody else have an O2 sensor on a carbureted engine, reading A/F mix in real time?

While initially tuning, I figured my timing was off, and ended up advancing it way beyond what my original owner's manual calls for. I could hear the engine running better after many little adjustments. Never would have thought to do this. I just recently I found out my timing light is initial timing only. And there's this thing called total timing!? So I ordered up another timing light that will adjust for total timing. My guess is that I'm still 5-10 degrees off from having the total timing right for this engine/carb combo. That in turn has me thinking about a significant amount of horsepower i'm wasting, which is why the dyno thing seemed intersting.

I like the idea of adding electronic ignition. I don't know what it costs, but I'm guessing it's worth the investment to have one less variable in the equation. Is there a problem with points at higher RPMs where they become ineffective? Since it is a mechanical separation between the contacts of the points, it would seem at some magic RPM the spring can't accurately keep up. Is that a thing? I will say though, that points are a 5 minute adjustment, and extremely cheap compared to other maintenance costs.

So, what does the modern engine tuner look like? Ol skool tuners seemed to listen to everything. With their ear and a long pipe, they were engine whisperers.
 
90WT

90WT

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What Brand/CFM do you have now? Have you already tried a good basic tune up? Timing, new plugs, valve adjustment... vacuum leak test. Even a good compression test and leak down test to make sure your foundation is solid?

Edelbrock 1406 (600 cfm with electric choke)

I'm kinda starting from the beginning I guess. No compression test, or valve adjustment though. I started this recent tune with new plugs, wires, distributor cap, rotor, points, condenser. The plugs were fairly fouled, which is no surprise given the engine tune isn't where it needs to be. Everything looks to me like the A/F mix is too rich.

I ordered up a timing light that reads total timing. I have a timing light that does initial timing only, which I recall to be set at maybe 8-9 degrees before TDC.

Vacuum and fuel pressure gauge showed up this week. Haven't had a chance to play with it yet. I ordered up a bunch of diagnostic guages and tools that have random delivery times over the next two weeks. Gonna have to race Mrs 90WT to the mailbox every day for a while. 😜
 
elkun1

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check your fuel flow before putting on an electric pump, should provide plenty as is. do you have your points adjusted proper, they should be fine we used them forever. how do your plugs look, that will let you know how the carb is set. lots of guys used to change timing based on elevation, whats a timing light. seems like carbs are much more sensitive to getting gummed up by old fuel. i believe edelbrock has an off camber float kit but it's been a few years. a well adjusted carb works wonderfully, i'm down to 1 vehicle with a carb and i'm about ready to sell it, doubt i'll ever have another. i don't remember which injection system we put on sam's 55 but it works well. will lift the front end off until things go boom. if you want i can find out what's the latest and greatest system as he's into that and i'm not. almost forgot, is the choke shutting entirely off
 
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pigmony

pigmony

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I'm running an LS-9 5.7 with an HEI distributor and an Edelbrock 650 cfm (can't remember what model right now). What I want out of it is the ability to drive at MT highway speeds in a 40, fuel economy numbers that don't hinder my ability to go exploring (ie can I carry enough fuel to get from station to station), a useful powerband for my skill level, and reliability. Not necessarily in that order.

With my current setup I can achieve and maintain MT highway and interstate speeds. Low speed cooling has been an issue, but I think I finally have that sorted out. I get 13.26 mpg as a true average including highway/interstate, low-speed trails, and commuting miles. Fuel economy is not as good as I would like. The engine makes adequate and useful power. I've never felt like engine power was holding me back. In fact, with sticky tires on dry warm pavement, it has sufficient power to lift the front tires off the ground. Which is terrifying and not something I want to repeat. Then there's reliability.

When I was working as a manufacturing engineer, my job was to make automated assembly lines work better. The ultimate goal was for the end product to be consistently within tolerance, but that really means that you want each dimension to be within a tolerance of the tolerance. So, cut the acceptable tolerance in half and operate within that range (if possible). By doing this you end up catching problems before they would cause issues down the line. You also want the lines to be faster. The quicker the machine can spit out good parts, the more money the company makes. Downtime kills that average. So, reduce downtime. What makes downtime? Breakage and wear make huge downtime, so engineer everything to be just enough overbuilt that it doesn't break and eliminate wear points and/or engineer them to be easily serviceable. Now, you're down to service and tuning adjustments. You've already engineered your wear parts to have a long service life and be easily serviceable, but what about tuning adjustments? You want to tune the machine to run at its' best, but you don't want to slow the machine down to make adjustments all the time. You want the adjustments that you do make to be as permanent as possible. You don't want to spend the first 3 hours of your day getting all your machines running properly. You want things to just work.

I want the same thing for my engine. I don't care if it can rev to 8,000. I don't need that. I don't care if it can make 500 hp. I don't need that. I want it to start every time I turn the key and I want it to perform "within tolerance" whether I'm in Bozeman or Missoula or at the top of the Beartooth Highway or at sea level. I don't want to have to open the hood to make adjustments when the elevation changes more than about 2,000 feet. I'm not a good enough driver to have another thing to mess with and worry about.

So, yeah, reliability and CONSISTENCY is something I think my current setup is lacking. There is something to be said for being able to fix most issues with a few hand tools, but I don't want to have issues to fix in the first place.

Now lets say that I take my 40 to a dyno shop in Bozeman (4800 ft -ish of elevation) and they've got somebody who really knows how to tune a carb. Maybe they even have the ability to make their own jets and needles to really fine tune things. Maybe they are even able to get my Edelbrock to keep the adjustments, which would be really quaint. I'd leave that shop with a really well running truck...until I drive to Big Sky (7,200 ft -ish) or Missoula (3,200 ft -ish) or Polson (2,900 ft -ish) or Seattle (200 ft -ish). Then it wouldn't run quite as well and I'd be disappointed.

One of the things that I find most appealing about the systems like the Sniper are that they have maps to deal with changes in air density and they can adjust in real time. Yes, you'll still notice a difference in peak performance between high and low altitude, but you probably wont notice a difference in idle or low-power situations. The system makes the adjustments and the engine just works. That's really appealing to me.

Circling back to your earlier comments -
There used to be a race shop across the street from the place my dad worked back in Michigan. They built engines for dirt track racers. I remember when they got an engine dyno because the exhaust faced the place my dad worked and it made impressive noises. Before they had the dyno, they would put engines into a test chassis and test on the dirt drive behind the shop. They tuned the WOT throttle stuff purely by seat of the pants feel. I don't have a calibrated butt, so I would never be able to tune secondaries or WOT as well as guys like that. A dyno and calibration gauges are the best bet there, unless you happen to have a calibrated butt.

Messing with mechanical advance and initial vs total timing is another area where the modern engine management systems are superior. They just give you so much more control over those things. Not to say that you can't achieve the same results with proper tuning and the right equipment, but it can be done via laptop so easily.

I'm curious, what do you want out of your setup? Are your needs/wants significantly different from mine? Are you skilled enough that you are outdriving the abilities of your vehicle and it's powertrain?

(edited engine code LT-9 to LS-9)
 
90WT

90WT

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@elkun1 What's a timing light? LOL. Are you one of those engine whisperers? When I rebuilt my motor I set the timing with a timing light to 6 deg BTDC per the manual like a good boy. The poor thing ran so bad. Definitely needed advanced.

I'll re-check the choke fully opening when warm. that could be an issue.

I've heard, and maybe it's a rumor, that too much fuel pressure, from an over zealous mechanical fuel pump at high RPM can overpower the carb. Basically the carb can't resist the fuel pressure and runs too rich. ??
 
pigmony

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I've heard, and maybe it's a rumor, that too much fuel pressure, from an over zealous mechanical fuel pump at high RPM can overpower the carb. Basically the carb can't resist the fuel pressure and runs too rich. ??
There's definitely something to that. I'm not sure exactly how that issue presents itself. Years ago I converted from TBI to a big 4 barrel on a GMC pickup. I didn't know that you needed a regulator. I ended up with a lot of fire in the wrong places. and that's the story of how my dad's shop ended up with TWO fire extinguishers.
 
90WT

90WT

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@pigmony it has sufficient power to lift the front tires off the ground. Holy Smokes! And hell yeah!

Totally valid comment on what you want from your motor. I'm with you where reliability and consistency trumps big horsepower. I chase kids/dogs/cats/Mrs 90WT around all day. Doesn't leave much time for car adjustments before every drive. My classic old ride needs to be driveable. I drive around town with very few trips outside of town anymore. I enjoy hearing all 4bbls open up between stop lights. And absolutely love slow speed 3rd gear drifting when the roads are snow covered. I have no use for a beautiful auto that is always garaged and never driven.

For my case, Henry Ford says the stock FE 352 is in the range of 210 hp. It's been completely machined and rebuilt with a few performance parts thrown in. I'm hoping that it is capable of 300 hp. I'm totally guessing. (I have no calibrated butt :rofl:). I'm not buying more parts for the engine, just trying to tune what i have. Still interested in playing on a dyno to see where it's at now, versus a few weeks from now when I'm done messing with it. Part of me wants to know if I'm spending too much time and money chasing 10 hp or if I've gained 50 hp somewhere.

That Sniper fuel injection is super cool. I'd never seen that before. 1k for the Sniper seems like a lot, but not if you're already looking at $350 for a new carb... Anybody in the club have one of those?
 
pigmony

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It's not really 1k though. You need a fuel pump and all the lines, adjustments your wire harness to power the system and remove any redundancies, and either modify the intake to be able to monitor the air density going in or use a wideband in the exhaust to monitor air/fuel. Either way, you have to modify the exhaust for some type of oxygen sensor. Adding a fuel pump can get pricey depending on the route you go with. Fuel lines can add up quickly, again, depending on the route you go with. I think it would be pretty easy to get to 1500-2000 to do the conversion.

A guy I used to work with back in Michigan has been using the Sniper system on 5 iterations of his Jeep build. It's currently running a compound turbo setup on a remarkably stock Charger motor and making 900+ horsepower to the wheels. He's able to swap tunes for drag racing, autocross, or just cruising. He ran it at Drag Week a couple years back when it was a single turbo making 700-something to the wheels, and it got mid/high 20's for fuel economy during the event. On the cruise tune, it starts up and drives with good manners and no stupid race car noises.

Here's a couple older links about it:


After watching him build that Jeep and seeing how well the system works, I'm convinced that I need a Sniper system. ....but I also need new tires and to fix my rust and to redo my wire harness and add sound deadening/insulation. So, in the mean time, I keep messing with my carb.
 
elkun1

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@elkun1 What's a timing light? LOL. Are you one of those engine whisperers? When I rebuilt my motor I set the timing with a timing light to 6 deg BTDC per the manual like a good boy. The poor thing ran so bad. Definitely needed advanced.

I'll re-check the choke fully opening when warm. that could be an issue.

I've heard, and maybe it's a rumor, that too much fuel pressure, from an over zealous mechanical fuel pump at high RPM can overpower the carb. Basically the carb can't resist the fuel pressure and runs too rich. ??
i'll look around the shop, i've probably got a fuel regulator that the price would be right on
 
wizmariefa

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I did use a dyno recently! I plopped my slow old Lexus up there and it performed..... as expected.
Powertrain plus in Belgrade has a 4wd one, can’t recommend them enough either. They were more excited the dyno night than we were, and that‘s saying something!
 
pigmony

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Did you just get baseline data or did you do some tuning while it was there? What does it cost?
 
MontanaLax

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Dark Horse definitely has an in-house Dyno, and I believe it is four wheel drive capable.

I've used Dynojet's in house Dyno, but It was tuning a bike with a buddy that worked there. I don't know that they offer tuning for the general public.
 
90WT

90WT

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Well. No real forward progress yet for me.

I attached a vacuum gauge on the manifold side of the carb. Vacuum bounces all around at idle (575 rpm). But smoothes out quickly when the rpm is increased. I'm hoping that the bouncing vacuum at idle is due to the Comp cam shaft I have. I'm gonna try to dig up the receipt to figure out what cam I put in there and research a bit. Hope it's not an indicator of valve problems.

Should I be reading baseline manifold vacuum at a higher rpm, say 800 or 900?

Later this week, I will be checking to see if the vacuum advance can is working (once I get another vacuum line adapter to hook up the gauge). And will pick up a compression tester to rule that out. O2 sensor should drop in this weekend.

If we do a club event at dyno night, or get our own dyno night, every one that participates should chip in an extra 5 or 10 bucks to go to the dude (dudette) with the lowest horsepower run. :cool:
 

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