Timing & Gas Milage

[Rich72C10]

Today I decided to dive back into my distributor after getting settled with I had done back earlier in the year. While I had hoped to be running with my rebuilt carb, that was a bust. Though my general MPG is 13~14 MPG on long trips with the one my brother rebuilt last year and my timing setup.

I am still at 12° Initial timing and not long ago when I punted my truck to the shop to try and get that rebuilt carb going, she came back to me set at around 4~6° Initial timing. Not sure why they did that but she drove like the crap. 12° seems to be my happy place.

That gets me to what I been thinking about changing, the distributor springs. I have been running Silver/Copper since day one of my new distributor. What I noticed is when I reach 1.5k my engine wakes up, like a 1/3 of the HP came online - it's like a surge of power. So I decided to change out the silver spring out to have Copper/Copper springs. This brings in more timing and then maxes out at 20k.

Well, that 1.5k surge is completely gone, I can no longer feel anything remotely like a transition of engine power kicking in. I have more pep and my power is smooth as silk throughout my RPMs. After a test drive around the neighborhood and getting on the interstate, where I punched it while getting on the HWY, it's just all around fabulous. I couldn't find anywhere I lost anything, only gained better performance and a better feeling ride.

I might try Silver / Silver at some point but I couldn't image I'd be happier with that setup.

[ChevyGuyNC]

Ah, so you have a Pertronix dizzy... I'm stock, but I'm sure there are springs avail for that... Dang... more $ to spend, lol .

[Rich72C10]

Heard from Cliff after he got my carburetor, both a email and a actual voice call just a bit ago.

First thing, Cliff told me that Quadrajet Power (Mark) learned from him and used to get premade carburetor kits from him. Then Mark became a full on competitor and parts source. Cliff says Mark is a okay guy but really doesn't know these carburetors in / out. For example, my current 78 (and onward) carburetor are the best, where as the 72s are pretty crappy and need specialized work.

1. It has a very lean idle calibration and HUGE upper idle air bleeds, stock for that model.
2. Jets have been increased from 71 to 72 and using the stock 36B primary rods.
3. The hanger was pretty low but I was able to remove the APT screw and install an external one for full control there.
4. It doesn’t have much idle bypass air. The accl pump seal is junk, N/S small with windows so it would drain down more after shutdown.
5. Primary power piston hanger arms are bent, one is down slightly, the other is up so it would not be providing even fuel to both sides at light engine load.
   
6. It has lead plugs in two different places, both have been drilled out but tiny holes in the plugs that were in the main casting so very little bypass air.

Basically, my 72 carburetor has no chance to run right, it is extremely lean and there is not enough fuel being sent to the engine (until I am WOT). This is also the reason why I have problems in morning getting started. He said I would have to more or less need the choke plate nearly closed off to get started.

Also my problems are compounded with my 350 rebuild that has dish pistons and a mild RV Cam. He also expects that my head gasket is to thick (compared to the factory stock thin gasket) thus messing up even more something call the "quench". Though he says these issues are completely normal on 350 rebuilds. Basically the carburetor needs to be rich, not leaned out.

I was also happy to learn he tests the carburetors on his test engine to figure things out / tweaking / final testing, though he isn't pre-testing this one as there isn't a point until he rebuilds it.

[LT7A]

Interesting. So initially you had sent your carb to Quadrajet Power but have decided to have Cliff Ruggles rebuild it? Hopefully he can set it up very nicely for you, as it sounds like the later one is doing a heck of a job at the moment.

[Rich72C10]

That is correct, if anything I learn a lot from Cliff via his emails and his voice call. Just that alone is a heck a lot more than I got from Quadrajet. Cliff not only listens but pushes for all the details he can get what you "think" you need.

[custom10nut]

Originally Posted by Rich72C10

Update Pertronix 02/09/21: Canceled my Pertronix Ignitor III D7100700. Seems the Ignitor III does not work well with older OEM Tachometers - something about multiple spark. Though it appears using the Ignitor II D100700 is okay with OEM in-dash Tach. I am now looking directly at Pertronix site and have submitted a tech question.



Changed Ported to Manifold Vacuum 02/09/21: Idle went up by ~150 RPMs, so lowered it back down to ~650 RPMs. Truck is puncher off idle/full stop and preforms just as well, if not better when WOT. Matter of fact, I was able to spin the wheels at 3/4 peddle from the stop sign. No ticking / knocking that I can hear. But this was only getting her up to 50 and testing WOT between 35~40 MPH. There is only so much I'd speed around town LOL

Changed Ported to Manifold Vacuum 02/09/21 Part II: I put about 60 miles on last night. 80% 55~70 MPH and the rest town driving. I got 12 MPG

Installed PerTronix Ignitor II D100700 & Flame-Thrower II Coil 45011 02/13/21: Now getting a full 38° Max Mechanical Advance @30k, with a 12° Initial timing @650 RPMs. Also no apparent issues with my OEM Tach that I see so far. Vacuum canister on PerTronix actually works (even the TSP replacement canister I got in the mail will not hold vacuum).

The changes are: New Pertronix Flame-Thrower II, New Flame-Thrower Coil & Wires. 12° initial timing, ~900 RPM idle (Park) and ~640 RPM idle (Drive).

I have a Mallory Electronic Conversion on mine, the Factory Tach works ,and it’s really pretty accurate

[Rich72C10]

Well, Cliff is all done - super fast service (took 6 month or more with the other guy). Oh, he says the the mixture screws where mismatched and malformed (bent)!

Parts list, on its way back to me tomorrow. So either this one will work or I am sticking to my 78 Carb LOL

Jets/68 Jets - 068
PRods - 42Primary Metering Rods/42
misc misc
Air BleedsAir Bleed/Screw In
APT Screw APT Screw
Power PistPower Piston Spring
Accl Pump Accl Pump seal
Gasket 158Gasket
Gasket 272Gasket Bowl cover
N&S 25-998Needle & Seat
Filter - MFilter - Marine
Idle ScrewIdle Screws Bronze

Also told me he redesigned the carb to be "pre-smog" like a '69 Quadrajet - plus other things - like remove lead plugs that had tiny air holes (that caused my whistling). Carb also installed on his test engine and ran for a hour.

[ChevyGuyNC]

Originally Posted by Rich72C10

Well, Cliff is all done - super fast service (took 6 month or more with the other guy). Oh, he says the the mixture screws where mismatched and malformed (bent)!

Parts list, on its way back to me tomorrow. So either this one will work or I am sticking to my 78 Carb LOL



Also told me he redesigned the carb to be "pre-smog" like a '69 Quadrajet - plus other things - like remove lead plugs that had tiny air holes (that caused my whistling). Carb also installed on his test engine and ran for a hour.

Good deal!! Wish I had just sent him mine instead of ordering the kit; it'd probably by done now, lol. I think I'll be able get to it this weekend...

I am sure yours will run great now. Let us know!

[Rich72C10]

Well, it isn't like I have not tried to get a good service, I certainly thrown a ton of $$$ at this carb :'(

So Quadrajet work was over $400 and took ~6 months with very little correspondence.

Cliff, cost a bit over $250 and less than 4 weeks turnaround. Plus TONS of information via email and 2~3 voice calls (where he called ME before, during and after repair)!

[Rich72C10]

Got the carb back from Cliff and install yesterday - every single issue is resolved. Last issue to test, cold starting. She started right up, went into fast idle and didn't die.

Cliff's rebuild is really out performing my '78 Carter Qjet.

[Rich72C10]

Had a bit of a problem with the carb after WOT/Hard Flooring it. When I let up on the pedal she started to run like total crap, which ended up that the carb was dumping fuel in from the secondaries (stuck slightly opened). The 1st time I thought perhaps it was a fluke, since it cleared up in when I got back to my driveway. Then it happened again and wouldn't clear up for anything.

After chatting with Cliff, I torqued the bolts down to much. I had it in my head the bolts needed to be 15 ft pounds but the manual actually says 14 (and I know a went a bit over 15 too).

Originally Posted by Cliff Ruggles

Don’t torque the bolts just snug them down, torquing them will warp the carb and can cause the secondaries to stick open slightly.

When bushings are installed the throttle shaft clearances are reduced to less than .001” so they can stick if over-tightened........

NO, do not torque those bolts or you will ruin the carburetor.......

So after getting my hand slapped, I reinstalled the carb using only my hand driver to get the bolts hand snug. So far so good!

In other news, I installed a new distributor from Progression Ignition. This thing is something else and so far I am loving it. The engine runs so much better, it is like night and day. I hope to tell the different but I didn't think I'd seen so much improvement over the PerTronix Flame-Thrower.

[Warrens69GMC]

Good info here!!

[ChevyGuyNC]

Originally Posted by Rich72C10

Had a bit of a problem with the carb after WOT/Hard Flooring it. When I let up on the pedal she started to run like total crap, which ended up that the carb was dumping fuel in from the secondaries (stuck slightly opened). The 1st time I thought perhaps it was a fluke, since it cleared up in when I got back to my driveway. Then it happened again and wouldn't clear up for anything.

After chatting with Cliff, I torqued the bolts down to much. I had it in my head the bolts needed to be 15 ft pounds but the manual actually says 14 (and I know a went a bit over 15 too).



So after getting my hand slapped, I reinstalled the carb using only my hand driver to get the bolts hand snug. So far so good!

VERY good to know for when I finally use the kit I bought from Cliff and rebuild mine.

[Rich72C10]

Glad my postings have helped someone!

So far still no problems, I drove around last night about 50 or so miles ... so now I am venturing out further away from the home garage LOL

[Rich72C10]

BTW @ChevyGuyNC - Cliff told me in a phone conversation that the 72 Qjet Carb is one of the worse, if not the worse Qjet. That was when all the pollution control was hitting GM/others. So not sure what Cliff's kit allows you to do but he did all kinds of stuff to my 72 Carb (said he made it into a 67~68 Qjet).

I mention that as you list your truck as a 72, so we seem to be nearly Twinkies!

[ChevyGuyNC]

Originally Posted by Rich72C10

BTW @ChevyGuyNC - Cliff told me in a phone conversation that the 72 Qjet Carb is one of the worse, if not the worse Qjet. That was when all the pollution control was hitting GM/others. So not sure what Cliff's kit allows you to do but he did all kinds of stuff to my 72 Carb (said he made it into a 67~68 Qjet).

I mention that as you list your truck as a 72, so we seem to be nearly Twinkies!

Yeah, he told me that too... we talked for a while. Wishing I'd just asked him to rebuild mine, but he had said he was semi retired and doing less so I didn't push it. He also said that since mine has most likely never been 'rebuilt' by someone before there shouldn't be any of the typical bad 'fixes' in there.

He also said my stock 350 is better than a rebuilt one, same as he told you for reasons of gasket thickness and 'quench' whatever that is. And don't get him started on double roller timing chains, lol!

Yep, a pair of two tone long beds! If I make it to Waxahatchie next year maybe I can tempt you into a road trip.

[Rich72C10]

Cliff did seem to be an older fellow (and that is saying something as I am pretty damn old myself) though he didn't seem imply he didn't want to spend time on my carb. Though perhaps he felt bad with all the sh*t I went through with QuadraJet Power? From time to ship to him and back to me, under 4 weeks.

It was like CRAZY fast service and we are still talking about things. Like did you know if your little vacuum spout comes out on the passenger side/choke you just put some Loctite on it to keep it in? I didn't, just learned that this morning from Cliff!

RE: Okay, if you make it to Waxahatchie from Florida, I will make the effort to come up from Austin! LOL

[ChevyGuyNC]

Originally Posted by Rich72C10

Cliff did seem to be an older fellow (and that is saying something as I am pretty damn old myself) though he didn't seem imply he didn't want to spend time on my carb. Though perhaps he felt bad with all the sh*t I went through with QuadraJet Power? From time to ship to him and back to me, under 4 weeks.

It was like CRAZY fast service and we are still talking about things. Like did you know if your little vacuum spout comes out on the passenger side/choke you just put some Loctite on it to keep it in? I didn't, just learned that this morning from Cliff!

I'd bet your story with QP probably tipped the scale, yes... and he sure does know a lot about QJets and engines in general.

RE: Okay, if you make it to Waxahatchie from Florida, I will make the effort to come up from Austin! LOL

Deal !!

[Rich72C10]

Just another reply from Cliff, which is nice background information on the Carb's bolts after asking should I re-snug them after a bit of time.

Originally Posted by Cliff Ruggles

With those 1/4” thick gaskets it will stay sealed up fine.

The 15 ft lbs thing came from the early years when they used a really thin gasket and metal heat shield under the carb.

For some reason most literature and service manuals still recommend that much torque, but sitting on a 1/4 thick gasket it will warp the carburetor and can cause running issues as well.

[Rich72C10]

So..... back to timing and mileage after going off topic on my 72 Rochester Quadrajet - though my newly rebuilt carb is tuned different that the 78 Carter Quadrajet!

Did a nice Sunday drive around the hill country here in Texas and got a very nice 18.5 MPG! With my new Progression Ignition and its app, I was able to watch my vacuum and keep it within 4 points of idle max (which is 16~17), unless I was taking off which then I tried not to go below 7~9 inches.

Also with the app, I can show you my timings too - see attached screen capture of my current settings.

[Rich72C10]

Figured I put this here too....

Getting a video was challenging, used my iPad Pro. Which I almost dropped when I took off. Looking at my video editor, 0-60 took 10.17 seconds. Not going to win any drag races that's for sure LOL


Video may not be embedded if you are using https for the Truck Forums (which you should be using https) - so just click the banner to get to YouTube.

72 Chevy C10 LWB SBC 350 - Nailing Pedal to Floor

[ChevyGuyNC]

Originally Posted by Rich72C10

Figured I put this here too....

Getting a video was challenging, used my iPad Pro. Which I almost dropped when I took off. Looking at my video editor, 0-60 took 10.17 seconds. Not going to win any drag races that's for sure LOL


Video may not be embedded if you are using https for the Truck Forums (which you should be using https) - so just click the banner to get to YouTube.

72 Chevy C10 LWB SBC 350 - Nailing Pedal to Floor

Hey Rich, that sounds awesome. Do you have an X- or H-pipe in your exhaust? Trying to decide if I want to add one...

[Rich72C10]

Hey ChevyGuyNC and thank you!

I don't have either of those... pipes come off the stock Ram Horn manifolds straight to no-named mufflers (my brother had them put on last year from a shop local to him on the cheep).

[ChevyGuyNC]

Originally Posted by Rich72C10

Hey ChevyGuyNC and thank you!

I don't have either of those... pipes come off the stock Ram Horn manifolds straight to no-named mufflers (my brother had them put on last year from a shop local to him on the cheep).

OK... mine are also straight off the Ram Horn manifolds into Magnaflow mufflers, a bit louder than yours. I have to have the donuts replaced though... probably going to do that in the next week or two.