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  #16 (permalink)  
Old 07-18-2010, 07:10 AM
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Quote:
Originally Posted by red65mustang
kyle,
what the 11" in park and only 6" in drive (5Hg drop!!!) tells you is the motor is making so little actual TQ at idle (illustration say 75 ft/lbs?) that just the slight added drag/load from the slipping torque converter (illustration say just 30ft/lbs? drag) is to much for the motor to handle!!!
suggestion:
till you sort this all out you would be wise to kick it into neutral at red lights and raise the idle rpms to 1000...
Had that problem in 71-73 with my Javelin. 360 cu. in. with crower 3/4 cam 280/460 installed straight up, and stock converter (wasn't a lot of options with the Borg Warner cast iron tranny). Had to go with 16 initial and limit the centrifugal adv. on the mallory dual point dist. to keep from pinging. Red light involved slipping into N as the whole car would shake and just about die. Raising the idle so it wouldn't die in gear involved trying to hold it back with the brakes. It stll ran 14:20's in the quarter at sea level in first and second gear at 99 mph and got 16 mpg on the hwy with 3:54:1 rear gears.

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Old 07-18-2010, 12:05 PM
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My engine idles great though. With 15 initial, I can drive it away cold no problem. It idles at 850 in park, and 650 in gear the way I have it now. It doesn't ever try to shut off on me and doesn't jerk really when I put it in gear. The only problem I'm having with it is some intermittent run-on when I cut the ignition. It doesn't do it every time, just sometimes, but enough to make me want to figure out what's going on and fix it.

With the same engine combo, same cam advanced 3*, I had absolutely no run-on problems and I could run 89 octane no problem as long as I didn't get into it. I could even run 87 octane but had to drive very carefully. Still didn't have any run-on, so I know it's not the cam being advanced causing this.
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Old 07-18-2010, 01:04 PM
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Perhaps it's not the cam. If you get enough carbon build-up on the valves, it can get red hot and keep on trying to ignite. No spark required to do that even with the ignition turned off and as long as the engine keeps trying to turn over, it will still suck gas into the cylinder's from the idle circuit in the carb feeding the frenzy! Another word for run-on is pre-ignition. That's caused by red hot carbon built up from too low of an octane rating.

Like I stated in an earlier post, do a carbon knock of procedure and stay away from gas less that 93 octane and see what happens. There's a host of things that can cause your problem but I would start with the cheapest thing first. Save a couple of Oz's out of your next bottle of water, poor a little down each venturi alternately. Each time the engine will drop rpm, so let the rpm recover to a smooth rpm before you pour some in each venturi. Start and hold the rpm at about 3,000 rpm, cold engine. It works. I had the same problem with a 70, 10:1 engine that came in a 71 demonstrator car I bought.
Un-known to me untill I burned 3 valves. the owners manual recomended reg gas because the 71 engine had been dropped to 8:5:1 comp. in 71 while Detroit tried to de-tune the engines for emission reasons. After removing the heads to replace the valves, we found 2.02 intakes and 1.68 exhaust.
My uncle said if I had known this before the valves burned it would have been simple to knock the carbon off with the water and switch to premium gas. Since then, I've done it on several used engins with this problem with good results.
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Old 07-18-2010, 08:59 PM
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Thanks sqzbox!! I will definately try it just incase there is some in there.

UPDATE: I bumped initial timing to 22 degrees and it hasn't dieseled since. Except when I cut the ignition while cruising to check the plugs again, it ran on for a little bit but I think it might have been because I cut the ignition with the gas petal still depressed.

Here's my plan of attack. I'm going to weld up the distributor slots again to give me 22 degrees initial. Then I'm going to drill holes in the advance weights so that my centrifugal curve doesn't come in so quick (I'm using the heaviest springs). Hopefully be all in by 3000-3500 with no detonation.
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Old 07-18-2010, 09:56 PM
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ANOTHER UPDATE: I bumped the main jets from 74 to 76 and put the timing at 17/34 and with the vac advance plugged have no detination at WOT or going uphill in high gear.

The run-on never happened when I had the initial at 22. Now that it's back at 17, it didn't do it when I shut it off so it looks like it's an intermittent problem. I'll just have to drive it some and see where to go from there I guess.
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Old 07-19-2010, 08:55 AM
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"WOT up a hill"=only 1.5-3.0Hg signal at the carb base so the vac adv is fully off...
your operating on just base and just a little cent due to the strong/slow cent curve springs (which the cam doesn't like for WOT)....

get a long enough piece of small hose to reach the cowl or into the car and connect your vac gage so you can see what the Hg/vac adv is doing while actually driving....

it didn't diesel with 22 base because the gas stayed in a "mist" A/F suspension due to higher idle Hg...

it diesels at 17 with much lower Hg because it's a "squirt" of gas size molecules (not a mist) from the carb at idle which likely/can be puddling back into a liquid in the bottem of the plenum (and coating the valves and chambers)...
............................
only 6Hg (worth of atomization force) in drive at 650 idle at a stop light = a SIGNIFICANT risk that liquid gas "is" getting into the chambers (liquid gas does not burn),,,washing the oil off the cylinder walls and getting into the oil in the pan to do damage to all the moving parts ....

that's just one reason why I wrote you need to raise the idle to 1000 and kick it into neutral at a light!!!!

to risky that 6Hg and 650 rpms is killing the motor,,,the gas is just "dripping" out of the carb due to slow A/F velocity from low rpms and no Hg due to the cam....

at 22+ base idle will likely be 13Hg plus at 900-1000 in park and because that is more HP/TQ power produced/available,,,, the Hg will/should then only drop by 1 or 2 when you put it in drive and add the convertor drag...

again,,,way way to many variables to give a specific "safe" minimum Hg in drive at idle,,,but for peace of mind get it to atleast 10Hg in drive so mix atomization will be better when the intake is cold at idle...
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Old 07-19-2010, 03:33 PM
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Did some tinkering today.

Running 23 initial @ 950-1000 in park gave me 13" of vacuum. In gear rpm droped to 650 with around 8". I don't think I'm going to be able to pull 10" with this cam without having it idled up above 1k or locked out timing which I'm not going to do.

I'll dissassemble the distributor tonight and weld up the slots and try to limit mechanical advance to 10-12 which would allow me to run between 22-26 degrees initial.
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Old 07-19-2010, 03:42 PM
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Your torque converter is a little too tight. A looser TC would allow a "freer" idle, w/o the idle dropping so much.
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Old 07-19-2010, 04:28 PM
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Quote:
Originally Posted by cobalt327
Your torque converter is a little too tight. A looser TC would allow a "freer" idle, w/o the idle dropping so much.
I know it sucks. That's the one thing I can't change right now. I can't afford the one I want, and I need the mpg this one gives me. It only flashes to 2300 and gives me soft launches.
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Old 07-19-2010, 04:51 PM
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Quote:
Originally Posted by kyle86
I know it sucks. That's the one thing I can't change right now. I can't afford the one I want, and I need the mpg this one gives me. It only flashes to 2300 and gives me soft launches.
I thought about what I posted after posting it- nothing like overstating the obvious!

I bet you've also thought about how cool an OD tranny would be, too! Kinda the best of all worlds, for a strong launch and economy potential.

But I sure can understand budget restraints when building and modifying our rides...
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Old 07-19-2010, 04:57 PM
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Quote:
Originally Posted by cobalt327
I thought about what I posted after posting it- nothing like overstating the obvious!

I bet you've also thought about how cool an OD tranny would be, too! Kinda the best of all worlds, for a strong launch and economy potential.

But I sure can understand budget restraints when building and modifying our rides...
Haha seriously!! and a lockup converter !! I'll eventually get there.
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Old 07-20-2010, 06:42 AM
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kyle,
what intake is on the motor?

and are you using a open "big hole" carb spacer?

Last edited by red65mustang; 07-20-2010 at 10:41 AM.
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Old 07-20-2010, 11:37 AM
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No just a little dual plane holley 300-36 street dominator.

The engine dieseled again today with the initial timing at 22 degrees. Then I figued there was no point in having it that high anyways so put it back at 17 and it did it there too. So I drove it home and when I shut it off, it didn't do it.

It seems that it only diesels when I shut it off about 10 or 20% of the time. I'm completely clueless as to what could be going on. It seems like outside temperature, engine temp, initial timing, idle rpm, none of them seem like a definate relationship to the detination. It's almost like it does it randomly when it wants to.

I tried spraying water from a squirt bottle into the carb yesterday but couldn't get it to steam out the exhaust. I'll try it again today and see how it goes.
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Old 07-20-2010, 11:51 AM
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oh I did notice a little oil on the outer ring of the new plugs I put in. I think this might be coming in from the pcv possibly since I noticed there was also some oil on the vacuum t-fitting. Could this be the exhaust valve seals? Even though they have unbrella seals on them, the intakes were leaking so I swapped them out for pc type. The guides are good and tight, I was thinking if it was comming from the valves it would only be overnight, but it doesn't smoke at all when I start it up.

This is frustrating!
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Old 07-20-2010, 12:13 PM
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Quote:
Originally Posted by sqzbox
Hey Tach-1, 40 yrs. ago I had a 3/4 cam in a 360 ADV. 3* with 10:1 and never had a problem. Would that be because the gas was 100-101 octane?

I often wonder how engines can run on today's 93 with ratio's like he has and get away with it.
Come on up here and run advertized 91 octane which in reality is more like 89. Thats a real joy
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