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Author
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Topic: idle speed?
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Milkman385
Journeyman Posts: 9
From:
Registered: Feb 2005
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posted 04-04-2005 10:35 PM
 
What speed in RPM's should my car be set to idle at?
I have a 1966 Ford Mustang
a 1971 302 Engine (without the smog equipment)
with a C4 automatic transmission. If I go by the book i have and use the settings listed for 1971 302 it says my combination of engine and transmission should be set to idle at 575 RPM's. Is that correct?
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whiteknight289
Gearhead Posts: 1391
From: Wheaton, IL, USA
Registered: Mar 2004
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posted 04-04-2005 10:50 PM
That's about right, but you should really be your own best judge. I like to set the final rpm when the engine is warmed up, foot on brake, trans in Drive, then lift my foot off the brake to see if it 'jumps' or just slowly and calmly starts to move forward. I don't like the feeling some cars give you like they are going to stall at a stoplight, neither do I like when they want to race thru the intersection.
Scott
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68mustang351w
Gearhead Posts: 558
From: San Jose, Ca
Registered: Sep 2004
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posted 04-05-2005 05:28 AM
i got 550 revs but whiteknights answer makes perfect sense. Im sure you will end pretty darn close to 550 though. Good luck... David F.
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Milkman385
Journeyman Posts: 9
From:
Registered: Feb 2005
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posted 04-05-2005 02:26 PM
Okay, so I reset it from the 1500 RPM's it was set at. Only now it barely runs, and has a ticking sound. I had to reset the timing too. What's the maximum RPM's my 302 should be running?Weird thing, with it set at 1500 RPMs it seems to have run the best. It wouldn't lurch at lights, it would just coast. With it set to 575, it pretty much doesn't move unless i gas it. [This message has been edited by Milkman385 (edited 04-05-2005).]
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68 Coop
Gearhead Posts: 5847
From: Mesquite, NV. 89027
Registered: Oct 2004
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posted 04-05-2005 02:56 PM
Wecome to mustangsandmore Milkman. Here's a very simple way to adjust the idle in gear. Pull the car up to a parking block, scotch the wheels, ect... With the car in D, adjust the screw until the engine starts to die, then set it to where you like it. It took me a while to get mine right too, but I did it this way, and it idles right around the target of 550/600 in gear. If you are around 1500, from my experience, your timing is too far advanced. You also have to re-adjust the air/fuel mixture screws. The parking lot at work runs uphill/inclines a little, so I scotched the back wheel in case it died. Just made it a quest to get it right, and it took a little work, but the end result is worth it. Make sure the car is warmed up before you start this, maybe take it for a 20 mile cruise before hand. Hope it helps, it did for me.------------------
William
68 Coupe
"Restomod in Progress"
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Milkman385
Journeyman Posts: 9
From:
Registered: Feb 2005
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posted 04-07-2005 01:04 AM
So even with the Idle set to 600 and everything adjusted up my engine labors at idle to keep from dying, there's a knock or two(probably one of my lifter's). I have a 600 Edelbrock 4bbl on my 302, is that sufficient? My car has never really even run right and the best it's ever run was with the idle uped really high, even then it tended to miss occaisionally. What do your cars sound and drive like compared to modern vehicles?
PS All of my carbs have run very lean even when set rich, the most recent of the four is the 4bbl edelbrock which I bought a calibration kit for and currently it is set to it's limit almost. I have 289 HP heads on my 302, someone have mercy upon me and tell me what I'm doing wrong.
[This message has been edited by Milkman385 (edited 04-07-2005).]
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Dave Gibson
Moderator Posts: 10769
From: Norfolk, Virginia, USA M&M#166 MCA#47921
Registered: Aug 99
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posted 04-07-2005 03:24 AM
Just did the tune up on the wife's 289 2V this past weekend. Put the dwell meter on the car to check rpms. The car was a little high. Reset the idle to 825 in park and then checked it in drive, 625 rpm. Car is much happier now that the timming is set right and the idle has been adjusted. Each car is different in it's own way. Adjust it until it's happy/your happy.Dave & Terri ------------------
'65 Mustang Fastback
'66 Mustang Coupe
'02 Explorer XLT
Common sense isn't common anymore.
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68mustang351w
Gearhead Posts: 558
From: San Jose, Ca
Registered: Sep 2004
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posted 04-07-2005 05:00 AM
1500 revs at idle is way too high! Theres no reason it should be up that high unless thats at cold idle only. The 600cfm carb is more than enough for a 302. Adjust the lifters first then set the idle mixture & speed and timing as well. If its running rough/ missing, and everything else is fine i think that indicates a vacuum leak. Im no expert but i think the misadjusted valves is what can be throwing you off, someone correct me if i am wrong... David F.
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68 Coop
Gearhead Posts: 5847
From: Mesquite, NV. 89027
Registered: Oct 2004
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posted 04-07-2005 09:03 AM
Milkman, are you running stock points and condenser??? You might want to invest in some aftremarket unit, I run the Pertronix Ignitor with the Flamethrower coil, for more spark. A tune-up can NEVER hurt, unless you just did one. What are you gapping the plugs??? I gap mine at around 34, Autolite 45's, and they seem to work real well. Basically, you're just gonna have to keep playing with it till you are satisfied, but it can be done.------------------
William
68 Coupe
"Restomod in Progress"
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indyphil
Gearhead Posts: 3394
From: Senoia, G.A. USA
Registered: Jul 2002
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posted 04-07-2005 09:49 AM
The ignition system is crucial to a nice stable idle. Plugs, wires, cap etc... all must be in good working order. Timing must also be set. My points system would never run well so I switched to electronic. Points kept burning up and all the new coils, condensors and parts never helped. There are not many pros out there that know what to look for on a scope anymore so i went to electronic ignition and have not looked back.Of course all this assumes you dont have a bigger cam and a high stall convertor but you should be able to run at about 800 in park and 600 in drive without too much trouble. Mine runs good now - but you can tell its not a modern fuel injected car - it has a rumbly sound thats not real smooth but doesnt misfire - thats at about 600RPM ------------------
'68 coupe, '66 289 C code
engine, edel 600cfm carb, performer intake, dual exhaust http://www.geocities.com/ottouk_77/68mustang.htm
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Milkman385
Journeyman Posts: 9
From:
Registered: Feb 2005
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posted 04-07-2005 03:54 PM
I sure appreciate your humoring me, and giving me some of your time. In case you don't recall, I'm the person who posted on her about a month ago about vibrations, everything is new in that engine except my manifold and my 289 HP heads. I had the engine built, so I sadly do not know what's in it. I had Pertronix electronic conversion kit and flame thrower coil. I purchased a whole new distributor (with new points and condenser) just to be sure it was good. So my ignition kit isn't in that one. Honestly, it never run any better with the electronic ignition kit, for whatever reason. I wish I knew someone with a mustang that I could check out, see what one is supposed to be like, lol. I feel like such a looser all this time working on this car. The points are gapped to 0.017 the dwell is 28. I have Autolite 45 spark plugs gapped to 0.034 all as per specifications for a 1972 302. Oh and David, the lifters have been readjusted and checked so many times i cannot count them on my fingers. They are hydrolic lifters as well, so they shouldn't require constant adjustments. A mechanic I took it to didn't come up with anything and he checked the lifters with my settings, nothing different. I set them like it says in the book, putting the chalk markings on the balancer and then cranking it around and adjusting them as it is in the book (the firing order as I recall). You tighten them til the push rod is finger tight and then give it one 1/4 turn tighter. [This message has been edited by Milkman385 (edited 04-07-2005).] [This message has been edited by Milkman385 (edited 04-07-2005).]
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68mustang351w
Gearhead Posts: 558
From: San Jose, Ca
Registered: Sep 2004
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posted 04-08-2005 02:57 AM
Could be a small exhaust leak, they sound about the same. A lot of people set their idle mixture using a vacuum gauge, i think you have to adjust it to the highest possible vacuum reading but you have to keep resetting the idle as you move the mixture around a bit. Both sides should be out the same amount of turns. Regardless of everything else 1500rev idle is way too high. Sorry i cant help you more. Let us know what you try and what changes... GOod luck... David F.
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