10 MPG to 13.5MPG from timing alone

[70C10Toejam]

re-timed my truck recently.
short back story...when I got it, it ran great with good power. It didn't ping, but it would kick against the starter when starting it hot. found the timing was set to 18 BTDC. set timing to 4, according to mfg. Power dropped off, would bog out when stepping hard on gas from standstill. Mileage dropped too.

as stated, reset the timing to 12 BTDC, since posters said they liked 8-12. The milage jumped from 10 to 13.5 to 14 MPG. Doesn't fight the starter, and just spins the tires from a standsitll, truck doesn't even move unless I let off.

This is a Goodwrench 350 with 8.5:1, factory intake etc

[ChevLoRay]

Good to read....my original block in my '69 is going to get replace with a Goodwrench 350. Did you change the cam? I'd like a little bit of a lope, but still want it to be streetable. Am I dreamin'?

['68 longbed]

get the cam with the specs of the '57 fuely cam. beautiful lope. it has a little different duration on the lobes. sounds like a lot larger cam but very streetable

[70C10Toejam]

I didn't change the cam...but I did replace the points with HEI (while it was set at 4*)(and widened the plug gap). Would like to put in a mild cam, and Vortec heads.

Streetable lope??? don't have a clue if it is possible, how much lope and still drives well, just cant help on that one.

[Bob 68327]

The 300 horse 327 cam makes good power with a little lope very streetable. 291 dur 447 lift should be available from Speed Pro

[Morgsie]

Originally Posted by Bob 68327

The 300 horse 327 cam makes good power with a little lope very streetable. 291 dur 447 lift should be available from Speed Pro

I put that in my 305. Works good enough for a DD. 10x better than the original of which half the lobes were worn round.

[mnunn454]

Congrats on the 30% improvement in fuel economy. Detroit's got nothing on you.

Were it me, I'd continue to advance the timing as far as I could without experiencing any pinging/detonation. If that causes the starter to buck, then I'd dial in a little more centrifugal advance and leave the base timing at around 10 or 12 BTDC. SBC's generally like about 35-37 degrees total and no more than about 12 degrees initial. That means you need at least 25 degrees of centrifugal advance.

[Scott68-93-97]

Originally Posted by mnunn454

Congrats on the 30% improvement in fuel economy. Detroit's got nothing on you.

Were it me, I'd continue to advance the timing as far as I could without experiencing any pinging/detonation. If that causes the starter to buck, then I'd dial in a little more centrifugal advance and leave the base timing at around 10 or 12 BTDC. SBC's generally like about 35-37 degrees total and no more than about 12 degrees initial. That means you need at least 25 degrees of centrifugal advance.

Make sure your overall is between 35-37, that will help your top end power, as for the cam buy a compcams 268xeh it has almost .500 lift is very steetable ran it on my old 350, no need for converter change since power band is 1600-6000 beutiful lope and an even better sound when your on it. the duration is also still low enough to give you an idle that wont knock your teeth out I beileive it is 218 at .050 lift and I still had 17 inches of steady vacuum with the distibutor at 10 degrees initial. One last thing on the cam dont advance it this cam is already ground at a 4 degree advance

Another trick if you set your initial at 20+ you can run stop bushings in the centrifical advance so your overall doest go up to high then you have the best of both worlds off the line and top end but again good luck stating it when its hot

[70C10Toejam]

Here is what my Summit HEI is spec'ed at: (supprised I could still find it)
Mech. ad. : 14*at 2200 RPM
Vac. ad. :10* at 11 inches (vac. I presume)
Total advance: 24* at 2200RPM

So...If you add the 12* initial, it should be 36* total at about 2200?????

I do have a set of lighter (earlier) and heavier (later) advance springs that came with the dist. (dizzy shouds tooooo much like something Snoop Frog would say)

Any suggestions with this setup?????????????????????

Have not checked the total advance at this time.

[mnunn454]

Only suggestion I would make is to set the total advance at higher revs than 2200. Strong springs make the total come in later, weaker ones earlier, but you still need to know where it "tops out", so you don't exceed about 36 or 37 total.

Once you have the total set where you want it, if you experience any pinging at mid-throttle or under acceleration, then you can change the springs, adjust vacuum and mechanical total amounts to make the pinging subside w/o changing the total amount. In other words, anchor the total advance where you want it and work backwards from there with all the other adjustments until your timing stays a little shy of pinging under most circumstances.

Just my thoughts.