Hey all! So i have just installed a new TA stage one intake with a 4bbl and its been amazing, however im having an issue with my in gear idle. I have adjusted the idle screw and have about 800-1000 idle in park however when i shift into gear it drops to about 500-600. Car sounds great and feels smooth however my oil dummy light starts to flash, if i give a little gas it goes off. (installing gauge tomorrow AM for more accurate reading) just curious how i can get my i gear idle about 100-200 rpm higher with out having to be at 1200rpm in park?
What weight oil do you use? Does it only happen when motor is hot? How many miles on motor? My 72 350 had 70k when I bought it and had zero oil pressure at hot idle with straight 30w oil. I finally tore it apart last year with 140k miles and found that the cam bearings were bad causing the low oil pressure problem. Hopefully you just have a bad sending unit or excessive oil pump gear clearance.
Set the idle mixture with a vacuum gauge to maximize idle efficiency. Sounds like you have some tuning issues on top of the low oil pressure.
Any other engine modifications? More initial timing can help an engine idle better in gear. If you still have the original distributor, part number 1112109, you can advance your initial timing to 12*. If not, another trick to get more timing at closed throttle is to connect your vacuum advance to full manifold vacuum.
I have a 112 cam installed as well, I’m thinking it might be timing too since all else runs great. I had timing adjusted for the 2bbl carb didn’t retime after intake manifold install. I will do that today or later this week.
I’m using 10w-30 I live in SoCal. When car is in park my idle is great and pressure is solid. Has a new cam, water pump and oil pump.
Here in sunny Central Florida I change oil viscosity between summer and winter even though our winter isn't really much of a winter. 10w30 during winter and 20w50 during summer. If I keep the 10w30 in the motor when it gets hot here, my oil pressure (on a new motor) drops to about 10 psi on a 90 degree day at idle in gear. I prefer it to be a bit higher so, I switch to 20w50 and oil pressure stays at about 20 psi at hot idle in gear. I don't use the idiot light but you might try 20w50 to see if you can keep the light off in traffic while idling in gear.
I had an engine with a flickering oil light when HOT at idle in gear. Gauge read like 2psi. When I heard Denny Manner say that these engines will idle at 2psi all day, I stopped worrying. As long as pressure goes up 10psi per 1000 rpm, let it rip.
The drop on rpm from in park vs in gear means your idle isn’t strong enough. Timing and or idle mixture would be my first thought. I would start with adjusting the idle mixture screws to get Max vacuum readings in gear. Have a friend hold the car in gear with the wheels blocked and brakes on while it’s adjusted. Lower the idle speed as you get the mixture dialed in.
It may just actually be low oil pressure. If the idle seems ok and the car isn't stalling. then your options are to switch to thicker oil, or get the car to idle slightly faster, or rebuild the engine. I like the idea of getting a gauge first and checking the actual #. Also I am with Adam in that if it's just a flicker at idle and the pressure looks ok when you are at speed, ignore it.
installed new gauge pressure at idle is just below 10, adjusted the timing and changed the oil. no more issues. thank you everyone for the input and advice! She's running as smooth as silk now.
On my original 350, the nylon came off of my timing gear and wound up clogging the oil pickup. Same symptoms. Wound up costing me the motor before I realized what had happened. -Bob C.
