RPM limits
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Fleet Mechanic
Joined: Aug 2010
Posts: 1,574
Likes: 6
From: Cranbrook, Ont., Canada
RPM limits
HI Gang !!!! I need some educated guesses as to the RPM limits of my mildly built 400. Some specs are .030 over... cr 9.3.... comp roller cam, lifters and 1.73 roller rockers on studs with guide plates cam specs... 224/230 dur@ .050 and 513/513 lift @ .050, long tube headers, performer intake, 650 holley, 3 angle valve job, ported exhaust and gasket matched intake ports. I am getting ready to break this engine in a bit before I let her unwind. I KNOW this is not an engine that will rev 8000 rpm just need to set some parameters for myself (I tend to over do things a bit) AND the little girl so I don't blow her up. It took a LONG time to get tjis far.
Postmaster
Joined: Nov 2011
Posts: 2,553
Likes: 10
There can be several limits... valvetrain stability depends on cam profile and springs for example. ASSUMING springs and cam are matched up per cam manufacturers recommendations and machining and assembly are right on target here are some guesses:
Shrapnel Alert: 6000 RPM
Usable Power: 5100 RPM
Sustained Operation (eg. pulling hill with load): 3500 RPM
With a flat tappet cam, best to run no load at 2000 RPM or a bit more for 20 minutes to break in the cam. Timing and mixture need to be set close and having a buddy around to top up the radiator after start up and check/adjust timing is a big plus. High zinc oil needed as well.
After that I would go pretty easy for a couple hundred miles. Occasional full throttle but keep it under 4000 RPM. After that, see what she can do with close eye on oil pressure and temp.
Shrapnel Alert: 6000 RPM
Usable Power: 5100 RPM
Sustained Operation (eg. pulling hill with load): 3500 RPM
With a flat tappet cam, best to run no load at 2000 RPM or a bit more for 20 minutes to break in the cam. Timing and mixture need to be set close and having a buddy around to top up the radiator after start up and check/adjust timing is a big plus. High zinc oil needed as well.
After that I would go pretty easy for a couple hundred miles. Occasional full throttle but keep it under 4000 RPM. After that, see what she can do with close eye on oil pressure and temp.
Thread Starter
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Fleet Mechanic
Joined: Aug 2010
Posts: 1,574
Likes: 6
From: Cranbrook, Ont., Canada
My bad ... yes the springs are a double with a damper, retainers are titainium with single groove locks. heads have ARP studs as do the main caps and ARP rod bolts. Rods have ben polished resized and the entire assembly balanced. OH and the block has also been alined honed. The finish honing of the bores was done with a torque plate and TMI cam bearings were used.
Elder User
Joined: Jul 2015
Posts: 687
Likes: 4
From: CT
I second the 6000RPM redline. The 400 has a long stroke. That was a good job on getting the rods resized with the ARP rod bolts. But they're still stock rods which were not made to go much past 6000RPM in my opinion not fact at all.
Sounds like a healthy engine. I would get it on a dyno and see where your power falls off limiting it to 6000RPM unless theres members here with a similar built engine/ or engine builder suggests any otherwise.
Besides the stock rods, I do not know what you did as far as oil modifications, chamfering the oil holes on the block and crank areas. Wire-brushing each hole and crevis in the block on tear down etc etc. Past 6k oil shear becomes an issue which can airate the oil and lead to pump cavitation if the oil can't drain out of the heads fast enough which will grenade your engine. That and your main caps may walk past that/ rods will start to flex at the crank.
Sounds like a healthy engine. I would get it on a dyno and see where your power falls off limiting it to 6000RPM unless theres members here with a similar built engine/ or engine builder suggests any otherwise.
Besides the stock rods, I do not know what you did as far as oil modifications, chamfering the oil holes on the block and crank areas. Wire-brushing each hole and crevis in the block on tear down etc etc. Past 6k oil shear becomes an issue which can airate the oil and lead to pump cavitation if the oil can't drain out of the heads fast enough which will grenade your engine. That and your main caps may walk past that/ rods will start to flex at the crank.
Tuned
Joined: Sep 2003
Posts: 348
Likes: 2
From: Northern Michigan
There can be several limits... valvetrain stability depends on cam profile and springs for example. ASSUMING springs and cam are matched up per cam manufacturers recommendations and machining and assembly are right on target here are some guesses:
Shrapnel Alert: 6000 RPM
Usable Power: 5100 RPM
Sustained Operation (eg. pulling hill with load): 3500 RPM
With a flat tappet cam, best to run no load at 2000 RPM or a bit more for 20 minutes to break in the cam. Timing and mixture need to be set close and having a buddy around to top up the radiator after start up and check/adjust timing is a big plus. High zinc oil needed as well.
After that I would go pretty easy for a couple hundred miles. Occasional full throttle but keep it under 4000 RPM. After that, see what she can do with close eye on oil pressure and temp.
Shrapnel Alert: 6000 RPM
Usable Power: 5100 RPM
Sustained Operation (eg. pulling hill with load): 3500 RPM
With a flat tappet cam, best to run no load at 2000 RPM or a bit more for 20 minutes to break in the cam. Timing and mixture need to be set close and having a buddy around to top up the radiator after start up and check/adjust timing is a big plus. High zinc oil needed as well.
After that I would go pretty easy for a couple hundred miles. Occasional full throttle but keep it under 4000 RPM. After that, see what she can do with close eye on oil pressure and temp.
Piston speed in fpm = stroke in inches x RPM ÷ 6
Shrapnel alert @ 4,000 ft/min on stock rods and crank I believe is an appropriate term.
Thread Starter
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Fleet Mechanic
Joined: Aug 2010
Posts: 1,574
Likes: 6
From: Cranbrook, Ont., Canada
Thanks Guys Your points are well taken. I do agree on the 6 grand theory and yes, the power is pretty much all in at 5500, so no sense pushing it any farther. So with that being said, she should be a great street cruiser with a C6 with a shift kit, a 2200 stall converter and 3.70 gears with a power trax locker. This old boy is gonna have some fun soon. When I figure out the picture thing I will post some for you guys. Again thanks for the input.
Tuned
Joined: Sep 2003
Posts: 348
Likes: 2
From: Northern Michigan
Thanks Guys Your points are well taken. I do agree on the 6 grand theory and yes, the power is pretty much all in at 5500, so no sense pushing it any farther. So with that being said, she should be a great street cruiser with a C6 with a shift kit, a 2200 stall converter and 3.70 gears with a power trax locker. This old boy is gonna have some fun soon. When I figure out the picture thing I will post some for you guys. Again thanks for the input.
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Elder User
Joined: Jul 2015
Posts: 687
Likes: 4
From: CT
Tire diameter will make a difference on acceleration and cruise speed.
Around town and back roads I bet it's going to be a blast. Highway small tires and 3.70s not going to be going 70 but still should be a nice truck.
Around town and back roads I bet it's going to be a blast. Highway small tires and 3.70s not going to be going 70 but still should be a nice truck.
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Thread Starter
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Fleet Mechanic
Joined: Aug 2010
Posts: 1,574
Likes: 6
From: Cranbrook, Ont., Canada
I believe they are a26" diameter tire. Radial T/As 15" diameter rims. Up here in Canada speed limit on most Hwys and roads is 80 KPH so 70 MPH will be a rare thing.. unless I can't keep my foot out of it. lol
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