Firewalker

We know, or I know the sales pitch from the OEMs, on why the switch to injection.

But I had Chryslers with good mileage using carbs, and so did friends of mine. I also had them go over 100,000 miles on the original motor, and still be running fine when sold. On mileage about the same time they shifted to injection they also shifted to overdrives, smaller motors, and lighter cars that were more aerodynamic. Hmm

There have been carbs that were junk just as there is now, but that does not mean all carbs are junk.

Most people I have known that tried to race Olds have blown them up. Must be bad motors most would say and do. But I say, I never have blown up an Olds I have raced even over decades and constant daily use much of that time. Hmm

olds 307 and 403

I owned and drove a few carbed Dodge's, smooth running was not their strong points. The Carter carbs were pretty hokey in my books. The Thermoquad was a good carb but it's choke sucked ***. The BBD had a lot of issues and the lean burn ran like *** no matter which carb it was attached to. Of course my EFI 2000 Dodge Dakota forgets how to idle when the battery runs low, great programming there.

cutlassefi

That's because some of the older systems don't compensate for lower voltage. My 94 Intrepid did the same thing.
And any of you are that deny the advantages of EFI are living in another world.
I just did a back to back carb vs EFI build. With the carb it needed an air/fuel in the 12.2 range to make the best power. On EFI it turned out that around 12.7 made the best power . Same with cruise/light load, the EFI ran the same or better with an air/fuel about a half point leaner.

AZ520

Pulled the plugs this morning to see what they have to say about this, getting a bit on the lean side I would say!

olds 307 and 403

They are on the lean side but not terrible. I have had them white lean, not good. What kind of mileage are you pulling off?

AZ520

Since Im still swapping out rods and springs I haven't been keeping up with the mileage, but I would estimate 15-20. The needle is slow to move for sure! I just received 68x57 metering rod, going from 67x52, I think its going to be the "one" It should give me the 14 A/F high rpm cruise and clear up the 3/4 throttle rich spot I am getting.

jpc647

15-20 is high! Like really high.

Looking forward to your updates on the new rods. Hell, if it works out really well, I might have to put my 1406 back together and try your combination before having the Q-Jet rebuilt.

I'm hoping I come across my tuning chart with my notes, I'd like to compare my current setup to yours.

76olds

I'm following along here, I hope you know this will help so many of us Edelbrock guys running stock engines with just a few bolt on mods. I know it will help me out alot. I'm not concerned about the MPG myself, I don't drive the car enough to worry about it.
I really appreciate you taking the time to bring this thread to us.
Put-r-ther
Eric

AZ520

Well I think its going to be good with these rods, might be a little on lean side. Here's the final set-up:

.095 main
.092 secondary
68x57 little on the lean side, going back to 67x55
short throw pump shot

I have an hei distributor set at 20 degrees advance at idle, vac advance is not hooked up or used ever. WOT is perfect 12.8 A/F. Cruising 2500 rpm sees about 13-14 A/F. Running crisp and strong, no drama anywhere, till summer comes and its 115 out, lol

Out of the box it looks like the Edelbrock 1406 comes way to rich for a stock olds 350. This was an older Weber built unit from the 1990s I think. The new ones come set-up with:


600 CFM, ELECTRIC CHOKE
(CALIBRATED FOR FUEL ECONOMY)
Calibrated for maximum fuel economy. Includes timed vacuum ports, EGR and fuel vapor outlet. Not for computer-controlled engines. Comes with the following jets, rods and springs: Metering Jets - Primary .098, Secondary .095; Metering Rods - .073 x .047; Step-Up Spring - orange (5" Hg).

76olds

PUT-R-THER,

I copied and pasted this on the 73-77 olds site for the guys, I'm going to give it a try this spring.
I'm not running EGR, no fuel vapor outlet either so I hope I get good results. I have 2 of these carbs so one will be a test "n" tune.
I really appreciate your post here!!
Thanks
Eric

olds 307 and 403

Cool, great for the Edelbrock guys. Why aren't you running vacuum advance? You will get better mileage and drivability, Olds V8's love a lot of part throttle timing, you can probably run 60 degrees with your less than 8 to 1 compression without detonation. If you don't want the 30 degrees the factory canister gives you, make a limiter or get an adjustable canister. This isn't a Chevy, Olds like timing!

TripDeuces

Those plugs aren't lean at all, sheesh

jpc647

I have to say, Generally speaking this is not going to be the case. I had a 1406, bone stock, and it had an awful off-idle bog, it would almost stall on hills, my plugs were almost white.

I'm currently running a 1405, which is the "performance tuned" version of a 1406, and I'm at step 11. With 104 Jets and 73x42 rods. My car is bone stock rebuilt, and at the top of first gear wide open, I'm still running out of fuel. If I unbolted your 1406 in it's new combo and put it on my stock 72 350 with 7a heads, it would probably stall at WOT.

This is mind boggling that it's running that well for you.

Please confirm, you actually meant .093 secondary and not a .092. You're off the chart here(which is fine you have a wideband, but I'm looking though the book, and they don't even list the .093. I only see them in tapered nitrous style jets.

AZ520

typo, yes .092 I guess the high compression heads? I have the #8s. If I put your carb on my engine it would hydrolock,lol

cutlassefi

x2.

Firewalker

Correct on using the canister, and I and others like manifold vacuum to it for more torque off idle and cooler running engines. The common adjustable cannisters allow you to adjust the amount of timing in the canisters, with an allen wrench. Those plugs are not lean either I agree. With a cheap Holley carb, my ND plugs looked almost like they were still new they were so clean running around town.

72delta88

[QUOTE=olds 307 and 403;997402]Be happy you can get it to run worth a dam, most can't with the Edelbrock carb. Why did you remove the Qjet? They are more adaptable to get what you are after. This adapter?https://www.google.ca/url?sa=t&sourc...sv_Hv8zvHcPNdw Very interesting adapter.[/QUote

i see your point some cant get an edelbrock to run my car has an edelbrock 1406 and runs perfect it didnt run for spit with the holley 600 dual feed vaccuum secondary now itll spin tires at will

by the look of the plugs go up a jet size

mine likes it a little bit richer for idle

jpc647

neither 7a or #8 heads are high compression. I don't know the big differences between 7a and #8 heads except the #8 I thought were on the later 73+ cars.

I'm pretty sure if I ran your carb, on my car it would run so lean i'd burn a hole in a piston, but I have been looking for a decent used wideband. It might be worth it to measure my car currently and see what i'm running here.

I'd love to rent one, but that's apparently not a thing around here.

olds 307 and 403

The 7a chambers are 10cc smaller but the 71-72 motors have 10 cc bigger piston dish. The 73 and up were calibrated leaner due to EGR.

AZ520

Well I have hit too lean and am working back to a little richer. Its been above 90 here and the car does not like it. Took it on a hard highway runs and its getting hot with the 68x57 rods, plugs were much whiter than the previous pictures, tossed the 67x55 back in there. So I am waiting on a 65x52. The car ran good around town, but at 2500-3,000 rpm cruising its not happy.
I got this carb in the engine deal, no Q-jet came with it, but I have been eyeballing those composite street demon q-jet copy carbs, I might ditch this and get the edelbrock AVS 650, since I have 175.00 in jets and rods,lol.

As far as the vac advance goes I will play with that later, it runs best without it at this point. Thanks for the tips! I really dont know much about the heads except I have the worst ones and the pistons are dished. With the pan off I found 1740 stamped on the pistons, standard low comp pistons. The guy I got this from said it was a fuel pig and the plugs were carbon fouled bad. It had .098 primary, .095 sec. 074x047 rods, yellow springs.

I dont know why this particular engine in this part of the world runs best with these smaller jets and needle, but it does. I have tried about all the settings to stay within the "zone" on the edelbrock 1406 chart and have ended up here.

AZ520

[QUOTE=jpc647;999465]I have to say, Generally speaking this is not going to be the case. I had a 1406, bone stock, and it had an awful off-idle bog, it would almost stall on hills, my plugs were almost white.

I'm currently running a 1405, which is the "performance tuned" version of a 1406, and I'm at step 11. With 104 Jets and 73x42 rods. My car is bone stock rebuilt, and at the top of first gear wide open, I'm still running out of fuel. If I unbolted your 1406 in it's new combo and put it on my stock 72 350 with 7a heads, it would probably stall at WOT.

This is mind boggling that it's running that well for you.

Maybe your have a fuel restriction? Carb Floats out of spec? Clogged fuel tank? Fuel filter? Weak fuel pump?

olds 307 and 403

As I said, run vacuum advance. That composite Street Demon is basically an improved 3 barrel version of the Thermoquad, a much better carb to begin with and they eliminated nearly all the problem areas. Other than adjustable secondaries do you gain anything over your AFB?

Firewalker

220 bucks for a refurbished Demon and one left

http://www.ebay.com/itm/Factory-Refu...hWSmE8&vxp=mtr

jpc647

Where are you getting these jet/rod recomendations? They are not common sizes, and what I mean by that is they aren't perfect sizes on the edelbrock chart.

But from what I can deduce, with the 68x55 rods you were somewhere near step 15 but a little bit leaner on power mode, so approx. 14%leaner than stock under power, and 12% lean under cruise.

This car is already 2% leaner than a 1405.

So with the new rods on the way, you're still somewhere in the 10-12% lean area. That's amazing.

Two very similar engines, running vastly different amounts of fuel. I'm wondering if I'm doing something wrong, I'm on the richer side of the scale at +8/12% to get my car to not bog and hesitate.

Hell, I might just have to invest in the wideband.

It could be a fuel pump issue, it's certainly an old fuel pump. I've checked the floats, and at edelbrocks advice adjusted them a little bit to add a tad bit more fuel into the bowls, to no avail. Fuel filter gets changed 1 or 2 a year, depending on use. Usually at the oil change.

I've tested it a few times, and it seems to hold steady. But even taping it on the windshield and driving is more of a reasonable guesstimate. It's possible I miss quick or spiky fluctuations.


Already sold out. :/ Not sure i'd recommend that at this point for the OP. If it doesn't work out of the box, he's looking at buying a calibration kit for them, and at another $90, seems like if he can dial in the edelbrock, he might be better off. But I do like the idea of the composite fuel bowl to prevent percolation. No idea if any of the metering rods etc would fit/cross over. I'd suspect not.

Firewalker

Jets they say are Holley on the Demons. The rods, I would guess, pretty much probably change out between the AFBs, AV, and Thermoquads and them, except some are two steps and some 3 steps. The Demons seem to run good for people out of the box, but some tuning probably is usually needed to get closer to perfection on the springs and rods mostly, and the secondary flapper, plus idle screws and choke settings.

Hope you get the one you have you get to where its running good.

AZ520

Where are you getting these jet/rod recomendations? They are not common sizes, and what I mean by that is they aren't perfect sizes on the edelbrock chart.

The recommendations are coming from the Wideband, also by feel and the plug reading of coarse. The wideband is an awesome tool to have. I had 2 fuel injected 1980s Porsche 944s that would not pass emissions and was able to use my wideband to figure out and make sure they would pass, I know the wideband works and is accurate. One thing I have read about carb tuning is every engine is different, even if they have the same specs.




It could be a fuel pump issue, it's certainly an old fuel pump. I've checked the floats, and at edelbrocks advice adjusted them a little bit to add a tad bit more fuel into the bowls, to no avail. Fuel filter gets changed 1 or 2 a year, depending on use. Usually at the oil change.

I would hook up a fuel pressure tester and see where you are at. Edelbrock recommends 5-6 psi. I have a mr. gasket regulator set at 5, stock pump was 8-10. I verified before and after psi to make certain I had it right. I wound also make sure all the passages and ports are free of debris. You may also have a vacuum leak sucking in more air. Another consideration is I have 2 insulating carb spacers, one is 1 inch think with a composite insert and adapts to the q-jet pattern and the other is 1/4 inch think edelbrock spacer gasket.


https://www.spectreperformance.com/s...aspx?prod=5765


http://www.jegs.com/i/Edelbrock/350/9266/10002/-1

jpc647

I meant like the rods themselves, the numbers. For example, where did you find out that there is is a 68x55 rod? It's not listed anywhere on the Edelbrock chart for the 1406.

True, all engines are different, mine is just using 20% more fuel under WOT than yours. And they are very similar.


I rented a fuel pressure tester from autozone a year ago, and I screwed in a smaller range gauge (0-10psi) because the one from autozone was meant for fuel injection. It maintained 5-6psi. It would drop to like 4.5/4.75psi if I blipped it fast and high in park, but didn't seem to do that on the road. Even so, I thought that was close enough to 5psi.

The carb has been cleaned, I've taken the mixture screws out and blown carb cleaner through them. The booster nozzles I cleaned to make sure. The carb is less than two years old.

I suppose I could test the fuel pressure again when the weather breaks. Is your regulator one of the mr. gasket dial ones? I tried one a while back and it leaked all the time. I ended up returning it.

Ive got an edelbrock spacer as well. It's one of the dual plane ones, like your heat insulator so that if two cylinders use slightly more on one bank than the others, they can pull slightly more fuel.

AZ520

Here is the listing for jets and rods:

Scroll down


http://www.edelbrock.com/automotive/...ibration.shtml


I'm now running a 65 x52 it's a safer rod, seeing 13 at cruise and 12s at wot. Engine runs cooler on the hwy. I'll pull the plugs after a few drives and see.

Firewalker

Engine will run cooler, if you get that vacuum advanced hooked back up like it needs to be, and on manifold vacuum.

Firewalker

http://www.carburetor-parts.com/Cart...Rod_p_258.html

AZ520

Dang, I should have shopped around more, I was paying 15.00 per pair. I am now trying it with manifold vacuum, thanks for the tip!

What do you think about the timing at 20 degrees with Hei distributor?

Firewalker

20 degrees sounds fine with them, or maybe even more, but if you hear any ping on slow/light acceleration in high gear back it down a few degrees.

jpc647

That's 6.98 a piece, not for a set, don't panic! ha.

Firewalker

Now panic LOL

http://www.ebay.com/itm/Carter-16P-7...hWkhEb&vxp=mtr

JamesRiot

A Street Demon was what I ended up with after trying to tune a Edelbrock that was bolted to a mild 350 when I got my Cutlass. It's not perfect - there is still some fine tuning to do - but it's a night/day difference over that Edelbrock. At least I can drive the car now

JohnTN

I installed a new Street Demon 625 on my mild Olds 350 last year and it started and ran smoothly right out of the box. However, my average mileage was only 14 mpg versus 18 mpg I had been getting on a leaky reman QJet. After some study, I bought and put in leaner primary rods and jets that should have reduced the fuel flow by about 22%. After this change my mileage is about 18 mpg and performance improved a little - better than the QJet I think.

I've gotten 21-22 mpg on the interstate at 60-65 mph.

The plugs are medium to ark ashen gray.

So, the stock SD 625 is set up for a high performance small block. Out of the box was too rich for my mild 350 (stock 8:1 compression, 204/214 cam, auto transmission, 3.42 rear gear).

John

jpc647

How much tuning did you do on the edelbrock? Did you buy a calibration kit and try different rods and springs? Mine certainly runs okay with the edelbrock, and needs fine tuning, but edelbrock is less than helpful in that process.


Wow. That's a big percentage to drop! Do you notice any changes, like hesitations, or bogs, or jitteryness when hitting the accelerator quick?

Firewalker

Let me throw this one in real quick. The float height can also effect how they all run, just like with Holley's. The higher the fuel levels in the bowls the richer, and the lower the leaner, to some extent.

olds 307 and 403

This makes perfect sense, most people will be running 9 to 1+ compression and something larger than a 204/214 cam on their hotrod. Another reason to run and slightly tweak the stock Qjet accordingly if it salvageable, GM put a lot of effort into matching carb to combo. GM's just plain ran better than Ford or Dodge's thanks to the reliable HEI and Quadrajet.

JohnTN

I am not experiencing any driveability issues with the leaner setup of the Street Demon carb on a mild Olds 350 engine (1971 engine with 146K miles).

Here is my story: After experiencing worse fuel mileage with the stock SD 625 I called the Tech line (long wait). Their only comment was that the SD was set up for performance and I might have to do some tuning for a mild engine, but the tech did not offer any suggestions on changes to make.

My research was to compare the Calibration Reference Charts in the Edelbrock manual for the 1405 ("Performance") and 1406 ("Economy") carbs. From what I could find out the only differences between the two carbs was the primary metering rods and jets, and electric choke (there might be other differences but I could not find any documentation in the manual or on discussion boards).

Based on the flow area between the primary rods and jets, the 1405 flows 22% richer in stock setup. By "Performance" carb it appears Edelbrock just means "richer" setup for the 1405.

So, I decided to try going leaner with the SD setup. My first step was to go one step leaner on the primary rods by replacing the stock 60/52 rods with 62/54 rods (10% reduced fuel flow area). This go me slightly better mileage (maybe 15.5 vs 14).

Next, I replaced the stock 78 jets with 76 jets. The leaner rod/jet combination should flow 22% less fuel. And, my mileage made the big jump to 18 avg with up to 21-22 mpg on the interstate. Oddly, the plugs looked slightly grayer with this leaner setup than from the stock setup.

Enthused, I decided to try another step leaner on the rods going to 64/56 which provided 32% less fuel flow. On an interstate drive of 170 miles I averaged 22.7 mpg but experienced slight surging at steady state speeds. So, I went back to the 62/54 rods. That is what I am now running.

I have not changed the secondary jets although I have a set of 10% leaner jets I will put in if I ever take the carb off the engine again.

I did not experience pinging with any of the leaner setups using 87 octane gas. My compression is about 8:1, HEI distributor with 16 initial, 20 mechanical all in by 3000 rpm, and 15 vacuum advance on manifold vacuum. With the 204/214 cam the engine pulls 18 in. hg vacuum at 750 idle rpm. I also have the 2004R transmission with overdrive, 3.42 rear gears and 18 inch tall rear tires. At 60 mph the engine turns around 1725 rpm.

On a recent 160 mile color cruise with 8 other street rods on the back highways of Tennessee I averaged 19 mpg.

This car is not a daily driver. I have put 2700 miles on the car with this Street Demon carb in the last 1.5 years and am happy with it. It does take extra cranking and a few pumps of the gas to get started after sitting for more than a week.

I think I paid about $10 for a set of rods and less for a set of jets.

Hope this is useful to someone,

John