15.0 mpg to 21.6 mpg!

[318willrun]

JMO

Don't tune to a number, tune for performance/mileage. That 12.2 number is only a suggested point and will vary greatly depending on engine, fuel, load and other factors.

For WOT, take it to a track and tune it for best MPH. That is where the engine is happiest at WOT. If it happens to be 12.2, OK. Likely won't be 12.2.

This should be a quote that's posted at the site signiture. I have always said, and always will say, numbers just get you in the arena. All the fine tuning, wether it be initial timing, full timing, jetting, and even carb cfm, should be determined by what the engine likes/wants.

 

[AJ/FormS]

It is actually a built 360. The car has no stripes,mags or scoops. Looks like a grandpa's car. 360, 4 speed and a 460 lift cam and 222 duration a .050. 3.23 with 26 inch tire and sure grip. still needs more tire. at about 70 mph at about 3200 rpm getting 16 mpg. around town less, only because my foot is in it all the time. And a/c blowing cold.

I think your convertor is slipping,lol.
The math says 70 should be 2923 with 26s... 3200 is 9.47% slip.
I suppose your tach could be in error. Or your tires smaller than 26pi=81.7 roll-out.Or your speed-O runs low,lol. Or "about 3200" means 3150 say. The errors are accumulative. For instance a 2% error in the tire roll-out and a 2% error in the tach, and a 4% error in the speedO makes 70.65=3136. Now that would be 7.3% slip from zero, and still in the wrong direction.
So IDK, something seems off. I think you got 3.55s.
The math with 3.55s says 70=3213
Jus saying.

I ran a cam like that with Eddies and 10.9 compression ratio. Also with a double O/D,and 3.55s;70 was about 1700, 895 was 2060. I'd like to tell you that I got 32mpgUS, from point to point on a 10 hr trip to the 2004 Carcraft Nationals in Minneapolis in 2004; but nobody believes that; so you didn't hear it from me. With a Holley 600 even. Of course I modded it; I mod everything; you should see my wife of 40 years, lol.
As to tires it, don't seem to matter much, in a streeter. My 245s went 12.9@106 for the one and only run I ever made with that 223/230/110cam.275s/295s were the same spin-forever deal. Even 325/50-15 DRs have to be babied out.And then they spin. The problem is that cam,lol: it makes too much low-rpm/low-speed torque. But it sure makes mpg! I loved that thing. When it died,I moved up one cam-size to a 230/237/110 and I lost a buncha mpgs. No other changes,at first.

 

[AJ/FormS]

agree with an O/D, but do not like the factory O/D gear split. thinking of the Passon hemi O/D.

I didn't like it either. However,the 222 cam will easily pull the splits. At least mine did. But it was a lousy street trans with 3.55s. Second gear hits 60@4400 with 27" tires. the starter gear is perfect at 10.97. But the quick way to 60 with that cam would be to hit it at about 5600, and that would require 4.42s. I tried 4.30s and that got me 60=5350, close enough. But the starter gear was now 13.29 which sucked. So I bought a GVOD, and wired it to be a splitter. And that worked pretty good. I now had seven useable ratios.
But when that 223 cam died, and I went to a 230*,And I got tired of now having to split all the time. So I called Passon and ordered up a 3.09 low/direct 4th gearset and now we're all set, with the 3.55s. Yeah, I lost the double O/D but I kept busting those anyway. So, now it cruises at 70=2408,with the GVOD, right where the 230* wants to be. And I can still split whenever I want to; and 7000=107 in second over and 113 in third. The ratios are listed in my avatar.

 

[Mattax]

Because when a driver lightly pushes the pedal, and holds it there, to gently accelerate, the engine consumes the limited amount of the shot.
Kindof.
The idle circuit can supply all the fuel needed if the throttle is opened lightly enough. The fuel through the idle circuit also is for off-idle. In the simplest terms idle circuit supplies more fuel to match the additional air because as the throttle opens, more transition slot is exposed to manifold vacuum. The transistion slot is a variable jet (and also variable air bleed).

Accelerator pump shot is needed to briefly cover the delay because the idle circuit can't respond quick enough to the throttle opening. A little more to it (Motorsports Village • View topic - squirter?) but thats the basic idea.

 

[spl440]

I think your convertor is slipping,lol.
No slippage, it is a stick. tire is actually a 235/60/15 which is approx 26.2" tall. RPM is approx because speedo not to accurate. Where i live is mostly 45-55 speed limit, which means I'm doing 50-60 mostly. the cam and gears work well for may application. Better cam and gears , yes,but this is a spirited daily driver. An O/D would change things up a bit. A little more cam ( thinking of going to roller) and gear, 3.91 or so. But to do that need more tire which means narrowing rear end and upgrade to rear disk while I am there,because the car is set up for road course. Also to keep the look of the car custom cop wheels for the wider tires. So the little change for me would be a big $$$ at this time. Any suggestions are always welcome.

 

[pishta]

I ran a Predator PXP on a 351C and got 5mpg. I slapped on a corroded AFB and got 12 with no tuning. All carbs could stand a wideband tune, but I dont think the PXP could get dialed in without the street idle PXI kit installed. That ship sailed years ago.

 

[7milesout]

Following up on the thread. Turns out the gears are 3.23. Which I kept. The TrueTrac is now in the car and I'm picking it up tomorrow. Looking forward to ... T R A C T I O N !

 

[dibbons]

Following up on the thread. Turns out the gears are 3.23. Which I kept. The TrueTrac is now in the car and I'm picking it up tomorrow. Looking forward to ... T R A C T I O N !

7miles out, Are you saying that during this entire thread that you thought/assumed/believed that you had a 3.55 ring and pinion installed but you were mistaken and you really have had a 3.23 all along? Just trying to understand all of this.

 

[7milesout]

No, not saying that. For a while I thought I had a 3.55's based on using online gear calculators, and my rpm at speed, tire size, etc. But finally at some point (when replacing the fuel sending unit), I spun the tire and counted the driveshaft revs, and it was CLEAR it was a 3.23.

It was at that time I was like, "no way I'm trying to find a 3.55, it turns too many rpm as it is." It was then I decided to stay with the 3.23's, and just replace the open diff with the TrueTrac. For a minute (when I thought I had 3.55s) I was thinking I would try to find 3.23 gears. I'm glad, as it turned out, that it had 3.23s all along.

I just didn't follow this thread up well enough to add all those details.