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Sanity Check My Tuning

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Red20 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Topic: Sanity Check My Tuning
    Posted: Jul/15/2017 at 9:55pm
Anyone using the vacuum advance canister that came with their MSD billet distributor? I've been running without one, and though it runs great, gas mileage isn't exactly good. This is my daily driver and I'm getting a painful 8 mpg. I do drive it like I stole it and cruise down the I-5 at 3000 rpm. I put the canister back on today. According to my cheap dial back timing light, this thing is adding 18* at idle! Off of the car with a vacuum pump, it started moving at 5 in.Hg and was at full travel at 15 in.Hg. I haven't actually checked it installed and in the car.

I pulled the Quick Fuel SS 680 vacuum secondary carb (basically a Holley with billet metering blocks and base and secondary spring rate adjustable externally via a screw) also and checked the idle transfer slot exposure which was way too much. I cranked it back down to about .040 or a "square" portion of the slot showing. Then I adjusted the secondary throttle stop to slightly expose the secondary transfer slot. I also backed off the fast idle screw to ensure it wasn't holding the throttle open any. Once back on the car, with vacuum advance disconnected and at 14* initial, I adjusted idle to 800 RPM and since I dont have a large overlap cam, adjusted all 4 idle mixture screws to best vacuum which was a pretty steady 17 in.Hg. After, hooking up the vacuum advance, I lowered the idle with the secondary throttle blade stop screw. From there, I rechecked the idle mixture screws and made a very minor final idle adjustment with the idle speed screw to about 750-800 RPM. Finally, I kicked in the fast idle cam and adjusted the fast idle (which is always a few hundred higher with a fully warmed engine) to 1500 RPM.

So with the aggressive MSD vac advance can, I'm idling at 32* BTC. Now all of that is according to my cheap timing light and old balancer. I haven't used or made a TDC checker on this engine. I also didn't hook up my multimeter on the Tachometer setting (which is cool) to see what total I was getting and what RPM. I just revved it up and turned the dial on the light to keep up until the mark stopped advancing which is hard to do all at once and saw it go a little past 50*. Vacuum at idle with vac advance hooked up is an extra inch or two.

Distributor setup is as follows:   MSD billet dizzy with 21* bushing and one heavy silver and one blue spring. Even without vacuum advance, I was getting too much advance too soon and pinging at part throttle up hills, so I slowed the curve. Mechanical only, I'm at 14* initial 35* total, all in around 2800, if I remember correctly.

After getting it all dialed back in, I took a drive through town through 25 to 45 mph zones and on the interstate from 65 to 115 mph. I purposely slowed down to lug a little up a hill in 3rd gear and didn't hear any detonation (TH350 w/2500 stall converter). The exhaust note is slightly different at some lower RPMs, I notice. It pulls at lower RPMs with noticeably less throttle angle required. I've read varying numbers for fuel efficiency gains when installing a vacuum advance canister with most guy's reporting 20% increases. I hope to see something similar.

SO...anyone see anything concerning or something I could do better?
1969 Javelin SST "Screamin' Banana" - 16k original miles, warm 360, TH-350, Model 20 TracLok, DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 9:58pm
Well crap that was long. If you read the entire thing, I probably owe you a beer.
1969 Javelin SST "Screamin' Banana" - 16k original miles, warm 360, TH-350, Model 20 TracLok, DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 10:19pm
So, where do I collect my beer? It all looks pretty darn good, the basic advance numbers are all reasonable, the idle being set with the secondaries is nice to see and overall looks pretty good to my eye.

The butt dyno rules and if it feels good and is not pinging, then mission accomplished. I don't know about 20% more mileage, but maybe since it was so poor before you will get there. 20% of 6 mpg is only about .8 of a mile, so perhaps more reasonable than I think!

Seriously, your post reads like a tutorial of how to set up the timing. Please keep us single digit mileage guys posted on what final results you get!

Thanks!

Chris

PS: Only thing that springs to mind is to do a plug read as a final check. If it is running a bit advanced you could consider restricting the vac advance a few degrees. If the engine likes what you have, great, but perhaps a few degrees less might be ok too.

Edited by ccowx - Jul/15/2017 at 10:23pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 10:31pm
Thanks Chris! I've gotten pretty confident in basic tuning over the years thanks in a large part to guys like you and many others here and at the IFSJA forum on top of what I learned from my Dad and Grandps as a teenager. It helps to have a few people sanity check you though.

I'd really like to see vacuum, advance, and o2 readings while driving. Better would be logging load, tps value, rpm, afr, egt, etc. I haven't even touched the base jetting of this carb yet. This is a 9.3:1 CR .030 over 360 with forged pistons, stock heads with just a touch of exhaust port smoothing and stud mounted roller rockers. Patriot shorty headers and 2" straight pipes (serious restriction) through Thrush welded mufflers. Performer grind cam and Air Gap manifold. 2.87 gears on 235/60R15 Cooper Cobras. It's a fun daily driver.
1969 Javelin SST "Screamin' Banana" - 16k original miles, warm 360, TH-350, Model 20 TracLok, DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 10:41pm
Oh, and the beer is in Oceanside. SoCal.

I'll do a WOT shutdown and read a plug when I get a chance. And I'll pull them all after a couple hundred miles. I looked at a few today before doing anything. Looked good.

And here's a tip for anyone looking for TDC on the compression stroke of #1: Get a brass fitting that fits a spark plug hole with a hose barb on the other side. Thread it in and run a hose down next to your face under the car while you turn it over by the crank nut. When it starts coming around on the compression stroke it'll blow right on your face and you'll feel and hear it very clearly. Then you can set your balancer at about 15* BTDC to be safe and drop in your distributor and point the rotor tip at the #1 terminal. You should be able to eyeball it +/- 5* of the 15* you were shooting for and get it to fire and idle.


1969 Javelin SST "Screamin' Banana" - 16k original miles, warm 360, TH-350, Model 20 TracLok, DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 11:29pm
WOT shut down is a great idea, but that will give you a plug read for WOT. I would suggest that in addition to WOT, you also do a shut down after a few minutes of steady highway cruising. With you having over 50 degrees of timing at cruise it would also be worth a check. Probably fine with your lower compression, but still worth a look see.

I also get single digit mileage and am cruising at around 3000 rpms on the highway, so I am curious to see what you get.

Thanks!

Chris
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2017 at 11:56am
I'll let you know what mileage looks like when I get through a full tank.

I need to make a stop plate to limit the vacuum advance total. I'm not getting any discernible detonation, but I can feel when it's going too advanced and lugging a little. There's definitely a point of diminishing returns with ignition advance. I think I'm going to shoot for 10* total vacuum advance and see how that feels. Without a dyno, it's all by feel, but I'm pretty in tune with AMC 360s these days.
1969 Javelin SST "Screamin' Banana" - 16k original miles, warm 360, TH-350, Model 20 TracLok, DAILY DRIVER
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Jul/17/2017 at 2:32pm
You might want to just take a chunk of rubber, say a kid's eraser, that fits over the pin on the vac advance can. You can make something fancier if you like later, but that is a cheap way to try it out. Make a couple with different levels of restriction and see what it likes.

Thanks!

Chris
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Post Options Post Options   Thanks (0) Thanks(0)   Quote needafasterAMX Quote  Post ReplyReply Direct Link To This Post Posted: Jul/18/2017 at 9:47pm
It all looks fairly good, the only thing I did not see is the quick un-scientific exhaust test.
Does your eyes and noise burn when you stick your face in the exhaust when it is running.
Or the scientific way with a O2 sensor. the only way to go to get the best fuel mileage.

The two quick fuel carbs that I had /have on my car where way Fat.
74 AMX, 401
Viper spec T56 6 speed trans
Hydroboost brakes with rear disks from a Avenger
3:73 TG rear,now Trutrac with 3:15
A Turbo is in my future.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/18/2017 at 10:05pm
Well, since the exhaust just dumps after the mufflers, I'm gonna have to shimmy under the back end to be unscientific. And to be scientific, I haven't dropped the money on an o2 sensor, sender, and gauge, but I sure wish I had. I have a bung in the exhaust still from when I was running EFI.
1969 Javelin SST "Screamin' Banana" - 16k original miles, warm 360, TH-350, Model 20 TracLok, DAILY DRIVER
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