390 idle prob

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Dec 5, 2004 | 02:05 AM

joegeoghegan317

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From: eugene

390 idle prob

I have finished rebuilding my engine, and now it was time for tuning. I tuned her all up and everything sounds great when I have her idleing, My problem is when i put it in drive or reverse or 2nd or 1st. I have an automatic and its a 390. When i put it into gear its like the rpms go down and its like it wants to die. On flat ground its okay and just idles crappy. It will drive and go and all is fine, But on my driveway up hill... If you want to call it a hill even, when in drive the truck still rolls backwards. usually, or at least my past 360, she would either still roll up the hill when off the gas completely, or would stay put. So i'm really confused on this. Its really idling sweet when in neutral and park. I have her at 9 before top dead center. Here are the specs on my cam.
# 274/286 advertised duration
# 230/236 duration @.050"
# .562/.565 lift
# 110 degree lobe separation
# RPM power range 1800-6000
# Hydraulic cam

I would really like any help. Ive started with my mixture screws, and it ran a little better but thats it.

Dec 5, 2004 | 05:04 AM

jowilker

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From: Creedmoor, North Carolina

What is your ideling rpms? This could be too low, because when you put it in gear it will slow the engine down. I would start at the carb.

John

Dec 5, 2004 | 06:42 AM

SRD4X4

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From: Annapolis,MD.

Agree with jowilker,manual says idle-550 as a base,which is too low for an auto.

Dec 5, 2004 | 07:33 AM

jwrboss302

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Joined: Apr 2003

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From: ipswich USA

vacuum gauge

Have you put a vacuum gauge on at idle? This will tell you a great deal about carb adjustments and also how much vacuum you are pulling at idle. The cam sounds a little agressive for what you are looking for.
JWR
72 F250 CS 390 NP-435

Dec 5, 2004 | 09:59 AM

flyboy2610

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From: Lincoln USA

Also make sure nothing is clogging the idle outlets for the fuel. They are tiny holes located below the throttle plates. It doesn't take much to clog them.
And check your fuel filters.

Dec 5, 2004 | 12:58 PM

joegeoghegan317

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From: eugene

thanks guys. A couple notes: Its an edelbrock performer 1406 series electric choke. I dont have a tach to check my rpms or a vacuum gauge. Is there a way to get some of those for pretty cheap? Also a side not, I just remembered that I dont think that i did my timing with the vac advanced off and the the hole plugged, What are the effects of not doing that? thanks... Also another side note.... I sandlasted stuff while my engine was at the machine shop getting bored over, and i think a little bit of that stuff may have got inside the carb. Its a newer carb, but if i had to put some new parts on it to see if that was the problemswhat part or part numbers would i need?

Dec 5, 2004 | 01:11 PM

joegeoghegan317

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From: eugene

Ok im an idiot. Im not sure if this is what it is or not, i cant check either cuz im in a different town, but i remembered my brakes were makeing a leaking noise inside the cab (the sucking noise) then i started thinking that it might be the booster diafram making it run lean, and we all know how are engines run when they are lean.. haha.. anyway im just going to plug the vaccuum line on the intake manifold where my brake booster goes. then see if it still does it. I also realized that i did pull the vac advance, but i never plugged it. I remember telling myself the vac leak shouldnt effect my timing too much. Anyway i am still interested on my questions on my last post also