Re-establishing Centerline on Cam

[JimNolan]

Jay,
   I've got a cam that is 282/296 adv dur (214/224 @.050) and 114 LS and 109 CL. Would you go as far as 106 CL to try and bring the power band down. I'm trying to get more gas mileage at a lower rpm. It's a 63 Galaxie XL with 390 ci/ 10.4 SCR / 7.9 DCR and .043 Quench running a C6 Street/Strip from Broader and a 2.75 Trac-Loc. Thanks, Jim

[jayb]

Your theory is sound, but I'm not sure how big of a difference another three degrees would make in the powerband.  My guess is that you wouldn't see any significant change in mileage.  You don't happen to have a wideband oxygen sensor on the car, do you?  Any idea what your A/F is at cruise?  If you knew that , you might be able to have more of an effect by changing the carb jetting.  A lot of engines run rich in the midrange...

[Barry_R]

Agreed.
Lean it out on the primary jetting until you feel it start to surge at cruise and then go up a jet or two from there.  Use the power valve channel restrictions to bring in WOT fuel for WOT A/F ratio.  Tune the transition point with power valve vacuum selection.

[My427stang]

I have a little bit different experience.

First, Barry and Jay answered your question correctly on shifting the curve down, but I don't think it was necessarily the right question for cruise mileage.  If you dyno'd a 109 ICL cam then dialed it in to 109, my guess is the entire curve would be very similar with a little nod to the 109 for the peaks.  So the WOT curve under power wont move much

However, would you notice part throttle response going from 109 to 106? 

I think it would be very noticeable, for example, I took my 427 from 108 to 105 and it was dramatically better part throttle and gained 3 in of vacuum at idle and it was far happier in 4th gear (back when it was a single plane 427/4 speed/3.70 with a 300 adv/250@.050 108 LSA cam)

In addition, in 2001 I had a 2000 Dodge Ram EFI 360 that felt flat to me, after realizing they retarded the cam for emissions, I took it from stock 110 ICL to 106 and it picked up noticeable response down low and idled much cleaner.

In both cases, I based it off intake closing point, but even in the late 80's I used to advance stock SBC cams in trucks because they were so much happier at 4 degrees advanced.  I didn't know why back then, but they did real well and after initial experimentation I kept doing it.  Old school experimentation basically after hearing the old guys used to retard them for RPM.

However will you get get better gas mileage?  My guess is that having the cam advanced and some careful tuning, the engine would be more efficient part throttle and therefore it would get better mileage.  How much?  Probably not a huge gain, but my guess, and almost a promise, is that you'd like the way it ran.

[JimNolan]

First, Barry and Jay answered your question correctly on shifting the curve down, but I don't think it was necessarily the right question for cruise mileage.  If you dyno'd a 109 ICL cam then dialed it in to 109, my guess is the entire curve would be very similar with a little nod to the 109 for the peaks.  So the WOT curve under power wont move much
However, would you notice part throttle response going from 109 to 106?
I think it would be very noticeable, for example, I took my 427 from 108 to 105 and it was dramatically better part throttle and gained 3 in of vacuum at idle and it was far happier in 4th gear (back when it was a single plane 427/4 speed/3.70 with a 300 adv/250@.050 108 LSA cam)
In addition, in 2001 I had a 2000 Dodge Ram EFI 360 that felt flat to me, after realizing they retarded the cam for emissions, I took it from stock 110 ICL to 106 and it picked up noticeable response down low and idled much cleaner.
However will you get get better gas mileage?  My guess is that having the cam advanced and some careful tuning, the engine would be more efficient part throttle and therefore it would get better mileage.  How much?  Probably not a huge gain, but my guess, and almost a promise, is that you'd like the way it ran.

Guys,
   Thanks alot. On FordMuscle.com I get to hash things over with My427stang and another guy PSIG that seem to give a lot of good advice on FE engines. Now that I've found this forum my ability to find answers is greatly enhanced. My427stang, glad you're on here.
     The cam was made special for me when I decided I wasn't going to drag race the car. I call Lunati and told them I wanted to run 87 octane gas. They made the cam for 110 CL. I moved it down to 109 because I thought a 7.9 DCR would still allow me to use 87 octane. I am just above 87 octane at 109 CL ( 1/2 tank 87 and 1/2 tank 89 still lets it ping a little, 89 octane keeps it from pinging altogether) I think a 106 CL will keep me in the 89 octane bracket.
Jay, got your book. Awesome. I like the way you explain things. Please don't think that this information your giving me is trivial. I put over 10,000 miles a year on my cars. By the way, the Galaxie got 13.78 mpg overall with the 1400 mile trip. The highest was 15 -16mpg on interstate doing 65-70 and the lowest was 11.5 - 12.5 around Tupelo and secondary roads with towns in between.
   I'll work with the jets right now. I'm running a 6.5 power valve with 15"  manifold pressure at idle now .  I think I'll go ahead and lower the CL of the cam to 106. Might not help that much but unless told otherwise I don't think I'll hurt it. I'm turning 2234 rpm @ 65 mph now. I just wish my power band were further down the RPM scale. Thanks guys, Jim

[machoneman]

Do you run a vacuum advance ditzy and if so, have you an adjustable dashpot (or can vary the vac advance curve) to maximize total (cruise) advance?.  If you have no vacuum advance, I'd still fool with leaner jetting and a 1 step up at a time PV (6.5 to 7.5, then up 1/2 step thereafter) but adding a vacuum advance dizty can give pretty good mileage gains.

As for gray exhaust pipes, I also remember those days as well where a gray pipe was a rough gauge of the a/f mix at cruise. Today, though, you won't see that clue anymore due to unleaded, oxegenated and often 10% ethanol-laced motor fuel. Any modern spark plug reading guide points this out and pics often show quite odd coloration due to the above. You can likely add  that single pipe wide band oxy sensor for as low at $125, given that you or a pal can weld-in the sensor bung. JMO.



 

[JimNolan]

Machoneman,
    I guess you can pretty well figure out my age by the tailpipe observation. My plugs are a pretty brown though. I do run a vacuum advance. I have it turned out about 5 turns. I haven't had a chance to play with it further. I have my mechanical gap set for 34 degrees total. I did have Mr. Gasket light springs on it where everything came in at 2200 rpm. But, I figured the vacuum advance cannister would be useless by crusing at 2250 so I went back to stock springs that has 30 degrees @ 3000 rpm / with 34 being tops. ( somewhere after 3000 rpm ). I've got my initial set at 14 degrees right now. I did have it set at 17 degrees but that only gave me 1" more manifold pressure so I settled for 14 initial and 15" manifold pressure at idle. Runs smooth at 650 rpm with the A/C on. Jim PS  I don't think I'm too far away from the best I can make it better I'll put in the time to get a couple more mpg out of it.

[machoneman]

I think I'd go back to the light springs for a faster mech. curve as one goes through the gears and see then if the vacuum advance provide an advantage. Even though your cruise rpm almost matches the point of maximum mech. advance, any off-throttle deceleration or light-pedal cruising should allow the vacuum advance curve to kick-in to the maximum. Heck, it would be pretty easy to do further vacuum advance testing with more turns and see what happens, as long as one listens for light knocking when hitting the pedal to accelerate up from cruise, then crank her back in 1/2 increments.

Brown is bad and it may pay to make your carb/timing changes and slap in a fresh set of plugs to ensure a good 'next time' reading.  Reading street engine plugs with modern pump gas is damn near impossible, hence the a/f meter recommendation.     

[My427stang]

Jim, on your advance curve, you said you are at 14 initial, and then 30 at 3000?  Are you saying 14 + 16 gets you 30?  or are you saying 14 + 30 = 44 at 3000?

If so, you could use more advance, I would recommend your 14 initial and then 34-36 fully in by no later than 3000.  Then the vacuum would be on TOP of that

[JimNolan]

My427stang,
    I welded up my mechanical llimit to make it a 10L opening on the limit. That's 20 degrees mechanical limit. Then I set my initial on 14. The reason I'm not getting 34 degrees by 3000 is because the stock mechanical springs won't let it completely advance to 34 degrees by 3000 rpm.
    When the light springs were in it ( 34 degrees total at 2200rpm ) it ran great going through gears BUT it would ping when I put a load on it from lower rpm's. I had my vacuum cannister screw turned out all the way just to keep it from pinging. I figured first hot weather and I'd not be able to keep it from pinging. That's the reason I went back to the heavy mechanical springs. Jim  PS  I can fine tune it to give my self the 34 degrees total by @ 2800 rpm. But, I didn't figure I'd have to worry about it since I was looking for best cruise timing, not WOT timing.
    That car runs like stink from about 40mph on. It's lucky to turn the tires over from a stop. It builds horsepower from around 3000 rpm up. If I didn't have to have such a high duration and LSA cam to burn pump gas I wouldn't be fussing with the dizzy. I just built too much engine for what I'm trying to do with it.
   

[My427stang]

Got it

Just keep in mind that a quicker mechanical advance curve has more advance at every RPM.

If all in at 2200 pinged but 3000 doesn't, I'd split the difference with one light and one stock spring and see, the motor should like the additional advance, and that alone may help cruise mpg a little

I basically built a simple linear chart with 14 initial, then all in by 2500 versus what you have now.  As you can see, it does add quite a bit of timing at your cruise rpm, might be worth exploring the mechanical curve a bit more (although of course I still think I'd consider advancing the cam for drivability)

[JimNolan]

My427stang,
    Remember on FordMuscle. com I told you I wasn't fooling with the cam CL until I saw how the stock radiator was holding up to the heat. Guess what, I found out today idling through the car show in 90 degree heat that the temp was climbing fast. I can't let that happen to me sitting in stalled traffic going around Cinncinatti or some place like that.  I came home and ordered a Griffin like my 57 has. So when I change the radiator I'll reset the CL. I'll just be carefull taking the chain cover off and try and save the gasket between the windage tray and chain cover.
    I'll go ahead and change the springs. I think the small stock spring is heavier than the Mr. Gasket springs so I'll use a Mr. Gasket for the leading spring and the heavier stock spring on the lagging side and see what I get. Jim  PS  I've played with changing springs so much I think I can get it done in less than 20 minutes now.

[My427stang]

What will you do when you get it all dialed in?  You are going to be bored 

I did the same things with my 489 when it was carbed, except it was transition fuel and accel pump.  I worked that poor 1000 Holley until I had to put helicoils in for the float bowl screws.  Eventually I got it where I wanted it, and soon after started the EFI conversion!

On second thought, maybe I should advise you NOT to fix it, it might save you money in the long run!

Ross

[JimNolan]

You're right. Retirement sucks when you're used to getting up at 5:30 everymorning and going someplace five and six days a week. I spend more money now trying to entertain myself than I ever did before. Jim