What is a normal good rpm idle?

[Moparal]

Well, since I dont work right now, I am tinkering with my car on and off. After I did the gauges, I decided to pull the breather off the carbs.

I have been letting the car idle at around 850 since I assembled the engine. Today I was checking the mixture screws and lowering the idle screw which I have done before. It doesnt really matter how low you idle it. It idles ok at 500 rpm's but I really can't hear the engine when setting in the car. The throttle response is the same with no hesitation at 500 or 850 rpm's.  The outboard carbs kick in around 1500 or so either way. Nothing loads up.

So on an average hp cam , is lower ok?  It's chryco's favorite brand   comp   xe275hl   I'd like to try something else, but this cam just seems to work good with my set up.   4 speed car, so is around 650 good?  The original sticker on the fender said 650. But it was a 318 4 speed back then.

[Bullitt-]

Guys used to tell me that if you idle too low that oil pressure can drop causing damage, 750-800 is on everything I've read.

[Moparal]

Yeah, I noticed oil pressure isn't a problem on my car. The original fender decal says 650 in neutral

[moper]

I like the slower idle speeds. But.... the camshaft is oiled by splash only. I do know several guys I respect who run very aggressive lobes on thier cams and they spec a high idle speed to help keep the cam lobes oild... like 1200+. I prefer have it 850 or lower.

[the_engineers]

I think it really depends on the cam you have.  My Voodoo shaft would never sustain an idle at 500, 650 or possibly 850.  I've got it set right now at about 950 and if I don't stay on top of my idle mix adjustments, it'll die like a Harley.

[Chryco Psycho]

I usually hit around 750 - 800 , with larger cams more is sometime nessisary but usually can be tuned to run in the 800 range

[Aussie Challenger]

  Sounds like your guage might be out, idling below 700rpm usually causes a lope and that can cause carbies to run rich/lean at idle and often stall. Reading the other thread you posted I gather your motor is still fairly tight, high oil pressure. The 440 6pks I've worked on ran around 800 - 850rpm with non stock cams ( slightly better than std. ), and they idled sweetly, slower became a problem.   

[Moparal]

I used an autometer tach when I was trying it out yesterday. I wanted to compare it to my dash tach. The dash tach is slow to register at low rpms, but but in general was very close to the autometer. I only had 1 tach hooked up at a time.

It had slipped my mind about cam lube at idle. But the cam and engine are broken in now I am sure. I ended up adjusting the idle at 800 rpms and hooked the dash tach back up.  I run stock 70 model exhaust all the way to the tips.  I don't leave the car idleing for long periods of time anyways.  I was just curious as to how low it would actually idle.  But the fender decal with the air fuel and timing settings did say 650 in neutral, so that got me wondering.

My race engine idles at 1500.  But I launch at 5500 and shift at 6800 in first and second and come through the traps at 7200. Different ball game there.

My street car is not used for drag racing. Just this little bigger cam, bigger valves and mild port job is all. It's just a cruiser.

[cudagirl4406pk]

Mine is set to 900 in park and sits about 800 in drive.

[422STROKER]

Al, my Chiltons manual spec is 900 in neutral(stick) for a 1970 440 six pack with 10.5-1 comp.

Tom

[Moparal]

thanks alot

[422STROKER]

No sweat Al,

I have this old book that has so much info in it.lol  It covers all makes(american) from 1964-1971 and is a great resource.

Tom

[Moparal]

look uo 70 318 4 speed in barracuda. See if it says 650 in neutral. The original decal I have says that

[422STROKER]

It shows 650 in 69 and 750 in 70.  So looks like the book may not be perfect.  But all the 440 six pack stuff shows that idle(900).

Tom

[rabarrett]

Something to consider here are emissions standards. Around the end of the '60's emission standards were tightened up, causing cams to change, timing settings to change,etc. The reason for the higher idle speeds were due to the leaner mixtures and reduced HC's. Idle speeds are typically established by the cam used. I would not set the idle much below 500 rpm, but if the engine likes those low settings, with no stalling or lope, set them as low as will support smooth performance. Typically below 500 rpm, the air flow through the carb reduces fuel flow, but that depends on the carb as well. If the engine responds smoothly at low settings, fine. The specs were typically for emissions only. Those having top pass emissions testing will typically require higher idle speeds.