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Recommended Idle RPM 427w?
Seems the consensus of motor builders is to not let your hi-performance motor sit at idle too long, give it a rev now and then if you're stuck in bumper to bumper or at a long light. In CA we have some that last 4 minutes by-the way. I've also read that an 800 RPM idle is pretty common. The question is - why not set your idle up to 1000 or even 1200 so you're not vulnerable to those "lost in thought" moments and forget to rev it when not moving? Granted, you're going to burn more gas - don't care about that.
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My Roush specs call for 900 RPM and I don't see any reason why it would not be good to let it idle at 900 RPM for an extended time. I think the need to rev the engine at a light is more about telling everyone you want to race. I like the lopy idle sound of the engine while I'm waiting for the light.
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I've always had my engine idle rpm run where the engine sounded "happy". That being 950-1000. Of course, this all depends on how much cam your motor has. Mine was a 418W with .565 lift, 242 duration and 110 lobe separation. No real need to goose the gas after a few minutes idling. Heavy traffic, as a habit, is not good for any hi-po motor.
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Solid rollers need a little higher idle than the other cams, especially the ones without pressure fed lifters.
As for all others, Zoom said it best, just set it to where the engine is happy. |
A block that doesn't pressure the lifter gallery, such as some FE built for solid lifters, I can see concern for extended idle.
A guess the question should be directed to the engine builder, who is saying limit idle time. Ask exactly why should the engine not be allowed to idle for extended time. What is the concern? |
Extended idling
My understanding is that at least for Windsor-based motors, there isn't enough oil feeding the valve gear at revs lower than about 1200. Extended idling leads to relatively short valve gear life.
grybrd123 |
... just set it to where the engine is happy - just curious, what's the criteria for a happy idle? these motors get "happy" at rpm's making real power :)
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You'll know when they're not happy...:LOL: You can tell by listening if they're laboring to stay running or not.
Generally most of these hydraulic roller engines will idle at around 800-900 rpm without issue. My solid roller engines get about a 1200 rpm idle. |
got it, my experience on bikes has been - that point where you tune out the low rpm vibration, motor slips into a good rhythm. depending on your cam, I guess that sweet spot is a little different for everybody.
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The recommended idle for my Roush 427IR (fuel injected) is 1000RPM. Sometimes it dips down to 900 or so when warmed up but when cold it starts off at about 1200 and goes lower when warmed up.
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Also if your car has power brakes you may need a higher RPM to keep them happy.
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I was thinking you might be thinking of them GM engines that can't take the idle as the oil pressure drops so low. A Ford has more oil pressure at idle. If you have 20 PSIG oil pressure that would be fine for an engine at idle. Sure, I wouldn't idle an engine for an hour, but a few miunutes at a light or even 15 minutes can't hurt anything as long as you have good oil pressure. But really, what do I know....
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If you have a solid-lifter-only block (like an early 427) there is no oil gallery to the lifters. At idle the splash oiling to the cam and lifters is inadequate over a long period. With hydraulic lifters or the oil-fed solid rollers it shouldn't be an issue.
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950 idle, and without even thinking I always give it a little rev during a long light or stopped traffic. Its a natural thing to do. I also never get on my engine without the oil thinned out with some heat, and. when stone cold--- hold an rpm around 1800rpm for a minute Just my routine learned from years of racing with an older crowd.
Now I'm the old one! Lou |
Common sense on this
AL427SBF AL alot depends on the size of the carb, camshaft profile, oiling system, type of lifters, and pressure at idle when hot.
Here's my 2 cents Solid roller motor with or without pressure rollers and under .700" lift, 1000 rpms. This is also with a hvhp oil pump making about 30-40 psi at idle If pressure numbers are lower than another 100-200 rpms. I don't like revving a motor, just increase until you have good psi numbers. This also depends on if the motor is center oiler through the lifter bores or a solid block or a side oil block with the crank and rods getting oil first. The other big thing is valve lash setup. Don't matter how much oil is spraying on the camshaft and rollers for the lifters, TOO much lash is going to hammer or pound out the camshaft or the rollers in the lifters. Will not matter if they are caged bearing, or solid bar. I feel a solid bar lifter will last longer either way. I do believe that idling is the worst thing for any solid lifter motor even with oiling modes to help oil drip on to the camshaft from the lifter bores. The real ticket would be to install sprayers to shoot on the camshaft and lifter location. This is like the diesels. Good luck. Rick L. |
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