safe rpm range????
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Senior User
Joined: Aug 2007
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From: Ohio
safe rpm range????
i've got a 400, bored .030 over, have a comp high energy cam, edelbrock intake, carb, and headers. i got a 4 spd behind it. im pullin it more and more, but this weekend will b first pull with the 4spd (swapped from a C6 this year), and i was wondering, whats a safe rpm raange to push this thing to runnin down the track? has always ran well for me otherwise, just dont wanna push it too farr.
thanks
thanks
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Joined: Apr 2004
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What valve springs?
What rod and main bolts?
Stock valve springs probably won't work with your cam anyway, but if you have them, look for float around 4000 rpm.
Stock rods and stock bolts? 4500, maybe 5000 if you are lucky.
What rod and main bolts?
Stock valve springs probably won't work with your cam anyway, but if you have them, look for float around 4000 rpm.
Stock rods and stock bolts? 4500, maybe 5000 if you are lucky.
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Senior User
Joined: Aug 2007
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From: Ohio
ha well then. its got comp dual springs in it, came in the kit with the cam. i've hit 4-4500 on a run before, and have just went past 5 doin a quick rev up. but you can tell its a good low end motor. no full 300 ft pulls, but it has done very well and held its own when you consider that they put me in a class with guys knockin on the door of 4 digit horsepower. its burnt up 2 TCI automatics so far, so decided they were gettin exxpensive and swapped to this. hopefully it dont break at all, let alone anything expensive on friday.
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Joined: May 2006
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From: North Dakota
What's the rpm range of your cam?
On my 351M, bored 30 over, all stock bottom end, a lunati cam with a rpm range of 2500-5800 rpms , and valve float at 6800 rpms, I've ran it many many many times at 6000 rpms.
On my 351M, bored 30 over, all stock bottom end, a lunati cam with a rpm range of 2500-5800 rpms , and valve float at 6800 rpms, I've ran it many many many times at 6000 rpms.
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Joined: Nov 2008
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From: wyoming
sustained rpms!!
was speaking with my dezert racer friend. ran the 400's and 351m. liked the power of 400 but keep the rpms below 5000 sustained rpm. said the 400 rod caps are the weakness. upgrade to arp rod bolts to gain some durability. Said he popped 2 of the engines and both cases it was a rod cap issue. he did say he was all over 6000 rpm for awhile is several cases. 250 mile dezert race f-100 class 8 truck. said the 351m he beat the hell out of and no problems. the shorter stroke give a better rod ratio and by design it a better combination in stock rod situation. less piston side load with shorter stroke.
you can run it up in short burst but eventually your luck will run out. 6.580 divide 4"= 1.645 rod ratio. 351m has a 1.88 rod ratio. 1.88 way better for higher rpm. can use this little formula on all engine. 429 ford is around 1.73 nice ratio for abusing. in the 6000 rpm range.
like mention have to match up springs and valvetrain to cam for higher rpms. if a better rod is used like tim meyer uses in the 434 options really change for the better. not much for these long rods in aftermarket.
you can run it up in short burst but eventually your luck will run out. 6.580 divide 4"= 1.645 rod ratio. 351m has a 1.88 rod ratio. 1.88 way better for higher rpm. can use this little formula on all engine. 429 ford is around 1.73 nice ratio for abusing. in the 6000 rpm range. like mention have to match up springs and valvetrain to cam for higher rpms. if a better rod is used like tim meyer uses in the 434 options really change for the better. not much for these long rods in aftermarket.
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Senior User
Joined: Aug 2007
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From: Ohio
well i try to keep it below 5 so i should b ok. during the pull...i was very impressed. i did get it wound up right between 4500 and 5k goin down track. and what i like is taht these are good low end torque motors. sure helps ya out 
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with arp rod bolts, ive seen 6k rpms with no issues, but i wouldnt recommend it, 5500 max with the bolts...
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From: wyoming
fitted up btm/balanced really helps.
getting fitted up btm end and good clearances are a forgiveness factor built into engine. also straight crankline is a plus. polish rods to help keep oil weight off rods is nice and anything to help shed oil is good. windage tray in oil pan is nice. have a photo in my albums of built up oil pan kevko racing for a 400 ford. lots of cool photos of 400 stuff.
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