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Old 03-30-2006, 02:09 PM
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400 small block what rev limit

I've just built a 400 small block engine 30tho over bore. stock compression pistons and rods, cast bowtie heads, stock crankshaft .eldbroke performer rpm cam. 750 dp holley. victor junior intake, engine has stock balancing. mallory electronic distributor with a msd 6al.

WHAT CAN I REV THE ENGINE to SAFELY

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Old 03-30-2006, 02:40 PM
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When I built my 400, everyone told me that the crank snout was prone to "popping' off. Some of this advice came from sprint car guys. Course, they abuse their stuff ALOT more than us street guys.

I put a 4340 crank in it anyway. only about $450 for a Scat on eBay.

I would say you would probably be safe to 5500, maybe even 6000, but I wouldn't push my luck beyond that. I forgot to look - did you use stock length rods? I think they are 5.545 or something. I know that increases your piston speed (over a 5.7 or 6.0 rod), which stresses everything more.
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Old 03-30-2006, 03:01 PM
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Only rev it to where the power drops off. You don't gain anything by "over" rev'ing the engine. With that cam and those heads I would say the engine will lay daown about 6000-6200RPM or so. Any decent small block can handle 6000RPM. Did you have it balanced? I am not sure what you mean by "stock balancing".

Royce
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Old 03-30-2006, 03:26 PM
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sorry i didn't have it balanced .budget rebuild just rings and shells. stock 400 rods.

thanks i'm running it in a 56 belair, if u didn't guess from my loggin name. ran 13.84 with a 350. same heads, cam, intake,ect. hoping to drop into low 13s. or even a 12.

cant believe how much quicker the car is off the line.
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Old 03-30-2006, 04:46 PM
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I say around 5000rpm even though your peak horsepower rpm will be higher. Stock 400 rods are the weak point in 400's. Since you used stock rod bolts, that will be your weak point.
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Old 03-30-2006, 10:25 PM
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With the stock cam, I'd say it will be all in by about 4,000-4,500. As stated above, no sense trying to get more out of it after that.
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Old 03-31-2006, 11:08 AM
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Ok with stock rod bolts, and it's not balanced. i would ptobably keep the RPMs down a bit. 5500 max but, I think it will lay down about then anyway.
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Old 03-31-2006, 01:24 PM
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thanks for the advise 5500 rpm it is then.

ok u got me worried my 350 would rev sweet to 6000rpm.

what the best way to get more revs out of the 400

shorter rods ? or aftermaket 400 ones.

the plan was to put a stroker kit in it next year.

any advise.
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Old 03-31-2006, 02:22 PM
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The easiest thing is to install better rod bolts. You really don't want shorter rods than a 400 came stock with. The rods themselves are not a problem, I ran factory 400 rods in a 383 I built. I rev'd it to 6300-6500 regularly. That engine is still alive and being abused in my buddies Nova (it's over 7 years old). It was balanced very well and I installed ARP rod bolts, polished the beams, etc..

A good set of aftermarket rods and a good balance job will go a long ways in helping the lower end live. Your cam and heads will determine how high the engine will want to rev. You just have to match your combination to your needs.

Royce
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Old 03-31-2006, 02:41 PM
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Camaroman is right about the cam and heads. You can run strong parts that will allow you to take this motor to the moon, but if your cam and heads only make power to 5500 RPM, then there is no reason to. If your 350 made power to 6000, then 5500 is probably a good estimate for max power in the 406. The additional cubic inches will bring the powerband down. It will start making power sooner and quit sooner.

Adam
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Old 03-31-2006, 04:45 PM
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I had ARP rod bolts on stock resized rods in my 1st 400 and it laid down right at 6000rpm. It lasted right at 3 months and then 2 rods let go one day. Here is a pic of the 2 rods that let go and as you can see, the let go at the big end where they are the weakest.
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Old 04-03-2006, 12:01 PM
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Thanks for the advise will run i at 5500 rpm then try increasing 100 rpm and see if my time slips improve.

last question how do u rate high volume oil pumps with deeper a sump.

my oil pressure has dipped on the 400, with stock pump. to 25psi on idle to 55 psi reving with hot oil.

it used to be 45 on idle 75-85 reving with a high volume pump in the 350 engine.

is this ok or should i swap with the high volume pump and sump.
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