Vaccuam settings

MountainMoparRobin · Post by **MountainMoparRobin** » Fri Jun 16, 2006 4:29 am

OK
I for the first time in my life now have a vaccuam guge and would like to experiment with setting the carb and timing with it, now do ya set the carb first, or do you set the timeing first with the gauge???

JJ · Post by JJ » Fri Jun 16, 2006 8:55 am

Robin,if you have a varible timing light try this: for your set up run your motor to about 2000 rpm and set your timing to 34-36 degrees (unplug the vacuum advance first). Idle it back down and see where your timings at. If your curves where it needs to be it will be around 12-14 degrees with that cam. With your cam it should idle pretty good around 800-900 in drive. Hook up your gauge and turn your idle mixture screws till you get the highest vacuum reading. Recheck the timing one more time for grins. Some people like the vacuum gague, I seem to have just as good a luck with the idle drop method.

MountainMoparRobin · Post by **MountainMoparRobin** » Fri Jun 16, 2006 2:51 pm

JJ
I haven't had the vacuam advance hooked up since caming the motor, the distributor is curved, crank advanced, timing light no longer of any help, distibutor curve is high, I'm guessing that the timing needs to be check and moved first, then the carb, last set at the carb shop for emissions test, only using 1% of possible 2.5% raw power, I will tinker a little on it but mainly got it for the 83 D150 with the 318

JJ · Post by JJ » Fri Jun 16, 2006 8:11 pm

I know alot of guys disconnect the vacuum advance for a hot engine but it sure helps milage.

MountainMoparRobin · Post by **MountainMoparRobin** » Fri Jun 16, 2006 8:47 pm

Actually its a dog, with it hooked up, huge difference without it, I was surprised at the big feel able difference

MountainMoparRobin · Post by **MountainMoparRobin** » Wed Jun 21, 2006 6:16 am

OK
I tried setting the carb and timing by vacuam and it put the timimg too far advanced, so I did it my way, I can't see using vacuam settings, back to reliable ear

Jeffc · Post by **Jeffc** » Wed Jun 21, 2006 10:20 am

Just what kind of a vaccum signal were your getting
at differant rpm?
Are you running deg tape on the dampner?
What is the lift/degr's/rpm of the cam and was
it degreed to the crank?
Compression of engine?

MountainMoparRobin · Post by **MountainMoparRobin** » Sun Jun 25, 2006 5:53 am

Hey Jeff I knew you have done this, this was on the 440 I built, and keep in mind I'm at 6000 feet above sealevel, the instructions give the adjustment for the altitude, but any way idling, around 900 rpms, this is with the Mopar Purple cam 484/284, keep in mind idling is also a constant lumpy lope until 1200 rpm, the gage at the carb was 10 and it made only 1 hg change no matter how far out I turned the air fuel mixture screws, then with just less than half inch of advance it went to 17 hg and of coarse the more advance I went the more vacuam, but the advance was way too much for it will ping under heavy excelleration, thats with 9:5:1 compression and everything is set for Rpm ranges 1500-6500 rpm, and yes it will do the 6500 rpms I also run Hemi valve springs, and of coarse I have the MSD 6AL ignition system, the distributor is curved and 4 degree advance on the crank

etsweptster · Post by **etsweptster** » Sun Jun 25, 2006 9:57 am

Robin,

If you really have the cam advance 4 degrees, you shouldn't be able to run 6500 rpm! It sounds to me like it might be retarded instead of advanced. Have you ever done a compression test? Also, how did you advance the cam? What brand of timing chain did you use? I have seen some timing chains off by as much as 8 degrees from what they claim. That is why you should always have your cam degreed, or use Edelbrock timing chains.(At the machine shop I used to work at, the Edelbrock chains were the only ones that were within 1 degree of being accurate).

Don't get me wrong, a 284 purple shaft can run to 6500 rpms, but it should be done making power around 5500 if it is advanced 4 degrees. Installed straight up it should be around 6000. I have run several 284 and 292 purple shafts, and they idle reasonabley smooth at under 1000 rpm. The 69 satellite I sold to my neighbor idles with a nice lope at 850 rpm, and it has the 292 purple shaft. It's all done pulling at 6200 rpm, and I have installed straight up. He can run it up to 7000 rpm, but it slows down 2 tenths at the dragstrip if he shifts it at 6400 instead of 6200!

There is a 73 Charger that a friend of mine built for his daughter to run in the high school class at Pueblo. It has a 284 installed straight up with 1.7 ratio rocker arms.(which makes the cam even bigger) It flat falls on it's face over 5800 rpm, but he doesn't have ported heads. I believe that it would pull at least another 500 rpm if he would let me port them. The good news is, we will find out next year because he is going to let met do just that this winter.

MountainMoparRobin · Post by **MountainMoparRobin** » Sun Jun 25, 2006 10:54 am

the cam isn't advanced,its straight up, the crank I advanced when I installed a new timing chain set here last year, the crank gear had 4degree advanced, normal and 4 degree retard, I did this to help in the low end torque since I'm running the 3:23's, and infact it worked, I didn't loose any rpms although I have never shifted at 6500rpms when racing on the street I have shifted at around 4800-5000rpms depending how far ahead I was, I haven't came across anything under the 13 second street driven. it has never actually reached peak, never had the need, haven't taken to the track either other than watching you run, I will however make it out there just not ready, It has a definate rolling lope under 1000 rpms but thats because it has the 484 lift, I just was doing some more fine tuning but vacuam gage doesn't seem the way to go, I actually have it running better off the ear and tune than other methods, by the way its also set up for emissions right now with the 101 jets, will be changing them soon steping up larger, had carb shop do some work on the carb last year and got it set for emissions, will take it back so they can use the machine and we are going after at least 2% of raw power instead of the current 1%, I'm also running 3lbs of fuel pressure so under full throttle it starves alittle but thats simple adjustment just turn up the fuel regulater

I'm absolutly sure of everything I'm the only person who will ever touch my motor or truck

I probably will be talking to ya about some porting around the Colorado Sweptline Super Cruise time though, I'm interested in the stock head flow for the same reasons you have

etsweptster · Post by **etsweptster** » Sun Jun 25, 2006 11:59 am

The advance on the timing chain is the advancing of the cam that I was talking about. When you use the 4 degree advance keyway on the crank, you are in fact advancing the cam 4 crankshaft degrees. This means that the intake valve(and exhaust valve) opens (and closes)4 degrees sooner in comparison to the crank than it would if it were installed at 0 degrees advanced (or straight up). I think you would find that if you ever tried running the engine up past 6000 rpm that it quit pulling and nose over hard. Retarding the cam back to 0 would move the power band up 500 rpm, which means you would lose 500 rpm of torque on the bottom end to gain 500 rpm of horsepower on the top end. At our elevation it is almost always beneficial to advance the cam like you did due to our lack of air to compress.

There are 5 factors that determine actual compression, or cylinder pressure. They are: Static compression ratio (the ratio of your pistons, how thick the head gasket is, and the cc of the heads), the cylinder head material(aluminum or iron), the elevation of operation, the final displacement of the engine(cubic inches), and the closing point of the intake lobe on the camshaft. As you can see, the latter is one of the keys to cylinder pressure. If you advance your cam to move the closing point of the intake lobe from say 45 degrees ABC to 41 degrees ABC you gain 4 degrees of the compression stroke to build more compression. You would now have 139 degrees of up stroke as opposed to 135 degrees. The secret to pump gas horsepower is to run as close to 170 pounds of cylinder pressure as possible. Any more than that, and you have to back the ignition timing off to keep it from pinging. Less timing means less power.

All cam manufacturers grind in some advance to their camshafts. This is the centerline. It is the degree at which number one intake lobe opens in relation the alignment dowel on the camshaft. If you install a cam with a 110 degree centerline at 106 degrees, you have advanced it an additional 4 degrees. Obviously if you get a Racer Brown, or any other company's cam that is ground on a 106 centerline, you would not want to advance it 4 more degrees. It is important to study the actual cam card specs to determine whether or not you want to advance your cam.

P.S. The lope of an engine is determined by the duration of the cam, not the lift. I run over .540 lift, but because my duration is less than the 284 purple shaft, my idle is 800 and very smooth. The stroke also has a big effect on the rpm range and idle charactaristics of an engine. When I had this cam in my 318 it loped like a race car at 900 rpm, and pulled hard to 6800 rpm. With the 4 inch stroke I have now, it sounds much tamer and pulls to 6200.

RussRoth · Post by **RussRoth** » Sun Jun 25, 2006 4:31 pm

MountainMoparRobin wrote: I actually have it running better off the ear and tune than other methods, by the way its also set up for emissions right now with the 101 jets, will be changing them soon steping up larger, had carb shop do some work on the carb last year and got it set for emissions, will take it back so they can use the machine and we are going after at least 2% of raw power instead of the current 1%, I'm also running 3lbs of fuel pressure so under full throttle it starves alittle but thats simple adjustment just turn up the fuel regulater

Robin,

Not sure those jets are lean at your elevation but they sound like they could be. If so they will contribute a great deal to your pinging problem. I leaned mine out a couple years ago experimenting. With no other changes it pinged so bad it was nearly undriveable.

Your timing needs to be worked out for your particaluar engine. Did you do that or did someone else decide what YOURS needed? Without a lot of experimenting or a chasiss dyno I don't think you can get it right, only in the ballpark. I run about 14-15 initial advance with a total of about 32-33 all in right @ 3,000 RPM. There is 9 degress (18 crank) in the distributor. I also run full vacuum advance. My cousin (engine builder. Used to build engines for Herschel Mcgriff) is the one that put me on to using full vacuum advance. He claims bigger cams sometimes like a ton of initital timing. Mine sure does. I'm not exactly sure how much it runs at idle with the vacuum hooked up but it drops off as I accelerate and doesn't come back in until you reach cruise and the manifold vacuum rises. On the street you are losing fuel mileage by disconnecting your vacuum advance. Under WOT it is out of the loop completely. This works very well on MINE, yours WILL be different but just some ideas for you to maybe try.

I thought mine ran pretty well until I went through the trouble to get the ignition like MY engine liked it. Took several months of playing and when I finally come up with a curve and had it done it really woke up.

MountainMoparRobin · Post by **MountainMoparRobin** » Sun Jun 25, 2006 4:35 pm

so then your saying the losss of bottom end is contributed to the elevation chamge from San Antonio where I built it to here in Lakewood with the elevation over 5200 feet? Your saying the same thing on the the advance only I'm looking at it from the crank where I made the adjustment, the ceterline on the cam is 110 degrees which I reduced now to 106 and when I go back to sealevel to race sounds like I'll need to change the crank timing again.
As I was saying before I have only shifted max of 5000 rpm, have not taken it out to see just how far the engine would rev before it has no pull but everything Intake and all is set up to go the full 6500 rpm.
I'll talk to ya in September about a port job on a different set of stock heads

Russ you got it I've been driving it and deciding if it could be better and trying different aproaches, and funny I'm considering doing a different curve, there is a curve kit in it but don't think I like it. I'm going to do some more messing with it before winter for early next spring I have something I'm going to add for more fast horsepower.

mopar400 · Post by **mopar400** » Sun Jun 25, 2006 4:55 pm

The 4 degrees at the crank is 8 degrees at the camshaft. If your cam is really at 110 straight up you are now at 102. When I was running the 400 in my challenger with the .484 purple shaft I did the same thing by putting it 4 crank deg. advanced by the chain sprocket. It sounded awesome at idle w/ a big lope but was a dog on the track. The only way to really know were you are at is to degree it in with a degree wheel. I think mopar performance recommends advancing the cam from 110 to 106. You need to check it and if it is out change the cam timing with adjustable bushings. Mopar400

Jeffc · Post by **Jeffc** » Sun Jun 25, 2006 5:28 pm

MountainMoparRobin wrote:Hey Jeff I knew you have done this, this was on the 440 I built, and keep in mind I'm at 6000 feet above sealevel, the instructions give the adjustment for the altitude, but any way idling, around 900 rpms, this is with the Mopar Purple cam 484/484, keep in mind idling is also a constant lumpy lope until 1200 rpm, the gage at the carb was 10 and it made only 1 hg change no matter how far out I turned the air fuel mixture screws, then with just less than half inch of advance it went to 17 hg and of coarse the more advance I went the more vacuam, but the advance was way too much for it will ping under heavy excelleration, thats with 9:5:1 compression and everything is set for Rpm ranges 1500-6500 rpm, and yes it will do the 6500 rpms I also run Hemi valve springs, and of coarse I have the MSD 6AL ignition system, the distributor is curved and 4 degree advance on the crank

Robin,
Have thought about installing a Ping control unit?
Air control screws will not really affect vac as you found out (but if too lean> ping). Timming will.
If all you were doing is drags, set up one way,
all road use anouther way> but since -with that cam- your multi function, you
may have to do adjustments to fit on the fly...
That type of unit will allow all kinds adjustment
to timimg at your finger tips, even differant fuels rateings.

Not sure (1/2" advance?) how many deg's, did you
mean .5 advance off 0 deg's?
What was your advance at 2000k> with/with out vac hooked.
If so at .5 deg you hit 17hvg? @ 900rpm?

RussRoth · Post by **RussRoth** » Sun Jun 25, 2006 8:08 pm

MountainMoparRobin wrote: Russ you got it I've been driving it and deciding if it could be better and trying different aproaches, and funny I'm considering doing a different curve, there is a curve kit in it but don't think I like it. I'm going to do some more messing with it before winter for early next spring I have something I'm going to add for more fast horsepower.

I'm thinking you might do better with a slightly different curve due to the elevation. I am at about 350' above sea level so not much elevation here. When I went through CO my rig was not running very well at all. I stopped in Leadville and pulled into a lot near the school. Then I saw the sign on the back of the bleachers that said "Proud to live in Leadville, CO, elevation 10,200'.

I realized why it didn't run right when I saw that, made a jet change and a bit of timing change and things got much better.

MountainMoparRobin · Post by **MountainMoparRobin** » Mon Jun 26, 2006 4:54 am

you hit it Jeffc, at 2000 rpms 17hg actually a little more, and the 1/2" was the turn on the distributor, which on this motor would be about 5-8 degrees, its very touchy, and the same 17hg, and Jeff I have the MSD 6AL ignition box, what is the ping control unit??? at the timing I have now there is no ping, I drove it Friday in stop light to stop light and 95 degree heat, did burn rubber at the lights with out trying and no pinging and the engine temperature was at 210 degrees, don't like it there but had no choice it was hot, got home and jumped in the Pool

and yes when at idle turning the distributor 1/2" gave me the same reading of 17hg. I also finally re-gaped the plugs to the .50 recomended by MSD and it made a difference also

more pep

Mopar400
you described just what the timing set said 8 degrees at the valves, funny you said when you did it to your car it was a dog? I had to do it to get more low end, it seems the elevation made it better than the TDC, when set at TDC it was a dog

Jeffc · Post by **Jeffc** » Mon Jun 26, 2006 3:49 pm

Made to work with the MSD-6 unit and is made by
MSD> Autotronics Controls Ping Conrtol-
Dash mounted knob that allows the driver to alter
spark timing at the turn of a knob.
Will enable you to retard timing under a load
or advance it to give better fuel/highway driving
under a low load.

Are you using any temp reducer in your cooling system
other than just anti-fez? (ice-cold?)
can't re-call names right now.... but there
are a number of products out there that will
help incress heat dissapation from the cooling
system. Of course the more advance you run the
more heat you have to get rid of......

MountainMoparRobin · Post by **MountainMoparRobin** » Mon Jun 26, 2006 10:10 pm

thanks Jeffc I will do some research

Sweptline.ORG