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What Is Your FE's Idle RPM's
I just had my 427SO which is stroked to 468 using Holly 830 CFM and Edelbrock Alum. Heads. Comp. is 10.5-1. Idle is around 1000 RPM. Crower cam #16333. I will be using this mostly for the street im my ERA. What does your FE Idle at?
Regards Mrud |
Since my new engine is not ready yet I can only tell you about my old one. Ran a 571 lift / 236 dur cam and would idle between 800-900 RPM. New engine will be a 605 lift / 242 dur cam and I expect it should idle around 900-1000 RPM.
Clois |
When cold my FE428 idles at about 650~ and then when the engine and oil warm up the idle is at 750 to 800. At these low idle speeds the engine is turning slow and the exhaust note is very pleasant and rumbly. The down side of this low idle is when cold at 650 RPM or so, the idle is rough and I do get some shake but this leaves when the idle rises to the 700+ range as the engine warms.
My engine's carburetor (Holley 850 Double Pumper 4150) has no choke and as such when the engine is cold I have to attend the engine with pusling the gas pedal. If I just started it up and took my foot off the gas it would NOT idle but die. I have to use my gas pedal as a choke as it were. This sounds crude (it is) but works out well in practice. I have 3.31 rear end so to drive the car slow (in a parking lot for instance), I do need the low RPMs. When I had the RPMs higher in the 1000 range, I had to feather the clutch to do slow driving and since my clutch is a racing type (it is either IN or OUT) feathering the clutch is nearly impossible. Hope this helps? |
Thanks for the input
Thanks guys that does help. I could drop the idle another 100 and put it in the 875-950 rpm range. Can't wait to drive this beast!
Thanks again mrud |
Watch you oil pressure at low RPM idle speed. When my car is cold the oil pressure is 65~ at idle but when warmed up the oil holds at 30ish and instantly rised to 60+ with a blip of the go pedal.
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It really depends on the duration of your cam. Standard FE cams operate well from idle to 5500 rpm and nose over. HP hydraulic cams work well from 2500-6500 rpm. These need more idle to sustain vacuum to keep your fuel flowing, typically 850-1000 rpm. Solid cams are effective into the 9,000 rpm range, but similarly as duration (the amount of time a valve is opening, is open and closing) increases, the amount of idle that is required to sustain it also increases as manifold vacuum decreases
Really big cams need a lot of idle. It isn't uncommon for really big cams to need 1000-1300 rpm to generate enough vacuum to operate. Less than this the vacuum signal at the venturi's is reduced causing irregular idle and lugging. That is an extreme case. Manifold vacuum at idle in those situation may be as low as 3-5 inches. You didn't mention what your camshaft duration is. Crower doesn't list it on their website general info. If it is a typical performance grind 750-900 rpm is fine. |
I'VE GOT A 427 S/O IN MY E.R.A.
I'M NOT SURE OF THE CAM SPECS BUT IT'S HOT AND THE COMPRESSION RATIO IS 12.5:1. IT IDLES VERY NICELY (IF THAT'S THE RIGHT WORD) AT 850-900 RPM. Y'ALL HAVE A REALLY GREAT DAY. BLACKJACK |
MRUD,
I have a similar set-up to yours with a mild cam. 800-900 works well for me. |
MRUD,
When the engine is hot, it will idle at 800 rpm. |
right around 900
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Stock single four barrel 427 SOHC - idles at 1300 rpm.
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Comp Cams .600" 242°-252° 11.5 cr 2x4s warm 650 rpm
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Guys... just wondering... if my memory serves from my garage days as a kid, if your car has hydraulic lifters then the idle can be lower as the oil is pumped up thru the valve push rods. If you have solid lifters then there is no oil delivery thru the valve rods and so you have to have a higher or sufficient RPM at idle to lubricate the upper end.
Is my understanding of this correct and still valid or is this memory a 1960's wives tale? As you get on in years... some things get cloudy. ;-) |
427 side oiler
Isky cam with 250 duration, .525 lift. Idles at about 950, but I'm still futzin' with the setting the timing advance and am going to re-jet the carb on a dyno so who knows where I'll end up. I did notice that with more base advance I could get a lower idle rpm. As I backed the advance down to around 18 it didn't like to idle below 1000 rpm.
I guess my question is - what's the right answer, or probably more appropriately how do you best determine the right answer for any given setup? Thanks! Scott:JEKYLHYDE |
mrud Sorry I have not gotten back to you been very busy this last week. With FI my 452 idles at what ever I want, With the small cam in it 501-533 675rpm is nice. There is no lope or rock on the motor. With the ERA stock system side pipes, it's very quiet. Chaplin has hear my car and asked if it was running. Next motor with 583-607 484 with the same FI will be a little louded. Both motors have hydro lifter cams. The crane 533-566 is a nice hydro cam with a little lope. Just remember those side pipes cost you 20-40hp when racing. There are some other tricks you can do, alum flywheel, racing side pipes, matching the intake, cam heads, and exhaust for the best performance. 1note, I like tork motors first, hp comes second. I didnot have time to run your motor on the dynosim yet but guessing 475hp and 520tork with the numbers you gave. 6200 rpm limiter, you will have a good strong motor for years to come. Add a peroiler to the system for startups and if you roadrace, autocross, or do drifting%/ :D This will help save the motor under hard abuse. Rick Lake Ps you have my number
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thank you
Rick and the guys who responded,
Just a note to say thank you to my post. I am very excited to hear your response. On the SOHC with and idle of 1300, that has to be one hard to control engine! Rick, 475 HP sounds just fine for my ERA and cannot wait to drive this spring. Car is done at ERA, just waiting for engine. Thanks again. Mrud |
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