Cam Specs: Lift. 450” intake. 460” exhaust Duration. 222 intake. 222 exhaust @ .050 tapped lift Centerline. 114” ATDC intake. 114” BTDC exhaust Just found this in my paperwork: “Normal engine manifold vacuum for this engine is 10-11” at idle (650-750 rpm). Hmmm, so I’m on the money after all at idle. So initially my vaccuum was well below the 10Hg threshold before the carb re-tune. I'll run it a while and see how it goes with the increased vaccuum.
this had a 283/powerglide, and got 13 around town and 18 highway. my late-model truck with 6.2 gets well over 18 around town. something to be said for technology!
I just put 760 miles on my 57, with some driving in the mountains with steep grades up and down. Averaged 15.5 mpg over the entire trip. 331, Muncie, 3.5:1 9". Ran the AC too. I thought that was good, can't compete with the daily, but driving it sure puts a smile on my face!
most here to help not Bash!! Thing just did not add up, Back to your set up , If TDC mark is correct , that set up will like 18, degrees of initial & probably more, then it might be hard to start unless you hook a remote button to get the motor spinning before turning the key on after high water temp probably over 160. The motor will like it the 18° or more then you have to worry about total that's when you have to crack open the distributor and limit it's Avance. & speed up your Idle to 1,000 rpms
WHY......are most folks hesitant to 'screw-in-some-timing!?? More initial until the starter drags (when engine is warm) then back off a couple degrees. Then see what 'cha get! EZ & cheap trick..... 6sally6
The Vac gauge still says it like more & its more happier @ that initial timing BTC @ Idle . My 39 Flatly liked 15 btc Spec said I believe was 4 -6 btc
You can "roll yer own" timing tape, or buy one tailor made if you want to get all fancy pants. About $5 probably. They are flourescent, so they are easy to read, which is kinda nice. You can give the distributor a big ole twist, and it will idle nice, but it will likely have too much total timing. The factory OEMs buggered everything up, and they probably came with advance springs as stiff as barbed wire. The first thing to do if you want better performance is get in there and straighten all that out. It is a pain in the ass without a distributor machine, but as somebody once said you will thank yourself every time you drive it. At the very least just make sure it's advancing the way it should, to factory specs, at 2000, 3000, 4000 etc.
I´m easily getting around 15-18 with my 331 ( 327 .040 L2166 , 60 cc camel humps, 234°& 244° @.050/Th350with 2400 stall/ 3.36 gears) in the 56 Chevy BelAir, the 355 in my old 34 Plymouth was very similar, but had 3.08 gears.Both can be driven at arpound 22mpg if you cruise at a steady 60-65 mph and going long distances. I usually can´t keep my foot out of it for that long so I ´m happy with 18. My wife´s 53 Suburban also has a 327 / Th400/ 2.73 gears and is all stock inluding the cam. It ran crappy with the worn out Quadrajet and I horribly screwed up rebuilding that ( I treid a few times, hahah) , so it has a 600 cfm Edelbrock now.It´s usually in the 17-18 mpg range. At 8 mpg we could not afford to drive our cars . I´d check all that has been said before plus see if you see excessive fuel drizzling into the venturis at idle. Edelbrocks are really delicate on fuel pressure.
MSD Balancer Timing Tape is only $5-63, We even used it on my stock 283 rebuilt. https://www.summitracing.com/parts/msd-8985 Have you considered a multiple keyway timing chain set where you can advance the cam another 2 deg [this will pull some more vacuum ,and wake up the engine down low] There is no reason why you cant get 20-22 mpg from that car and have it as a nice crisp "boulevard bandit"
PROGRESS !! I re-retuned the new carb with a vacuum gauge and drove the car 114 miles. Topped it off and the math says 12.67 MPG. I can live with that. Plugs are reading a nice burn. I’m also gonna swap plugs. Currently running Autolite 26 @ .035. Moving to AC Delco R45TS @ .045. We’ll see how that plan works out. All in all, I am as happy as a clam. Thanks to all that responded. I learned a few things once again.
Doesn't 26 =45TS ? 25= CR43ts. This plug to cold for around 9-9:5 I do not know for sure do those heads use 605 plug/ ac R44LTS6?
I'm just rolling with paperwork that came with the engine recommending the R45TS Yes, I thought the 26 was equivalent. This is the point where I sheepishly admit moving old plugs into a new engine.
Don't forget to really tune the carb, jetting, metering rods, etc. You said you were switching to 650, but don't know what model. That will help mileage and drivability.
Make sure your odometer is accurate. I keep a record of all the fillups, gallons and odometer reading, so I have a pretty good idea what mileage I get. Looks like you're on your way to the same. 13 mpg is a good start, and pretty much average mileage for an older car with decent performance, and gearing like yours has. As for all the comments about timing tape, etc. Get a timing light with a dial on it, and you can just look for the TDC mark on the damper, which is usually pretty easy to see. Most hopped up small blocks like 15-18 initial, and 32-36 total (plus vacuum advance on top of that, if you want to help fuel mileage a bit). I never have understood how adjusting the timing at idle with a vacuum gauge would tell me anything about what's happening when I'm driving down the road. Yup. The fun part is getting your car set up so it can do that under quite different conditions. Clicking off a 10.0 run in the quarter mile is one thing, cruising down the highway is another. Modern technology can almost get a car that quick, while still pulling around 20 mpg on the road. Using 60s technology, it's a bit more difficult...but hey, the lack of depreciation on a hot rod will buy a lot of gas
Buy a proper regulator that they have at the zone. Yes too much pressure can cause poor mileage. as well as poor tune and not running in your power band. Hell even the carb or the distributer can be a problem. Lots of things effect fuel mileage, its not one big thing usually, it is a whole lot of little things.
That sounds very much like the old Chevy L79 ,350 horse , 327 cam ,got to put timing to it ! They had a bunch of low-mid range power but fell off quick above 5k rpm
There is a lot of things you can do to carb set ups , some not Practical , think out side box, I have used controlled Vac leak with the old style Nos plate with a manual vale in side car , Like a Select a jet for Mechanical injection . I had a Blown combo years on carbs that would run lean close to top end pulls, So I used a plate set up for gas only to richen up with a RPM activate switch. Before there was a lot of electronics that I knew of or could not afford .
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