Those of you with a 408, what did you do to break it in? How many miles did you put on it before you let 'er have it?
408 break in?
lowlife12
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Here's a couple pics from cruise night last night. Every wednesday night the car club meets at Napa for a little meet, then we drive somewhere for dinner. There were about 15 cars last night and every seemed to think the Dakota was pretty cool. I've owned the truck since '05 and this was the first cruise night i've been able to drive it on. It was cool...
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Who said 500 miles is the magic number? It doesnt take that long for the rings to seat. Maybe 15 mins of operation, if that.
Wives tales are hiliarious sometimes.
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And what was the problem? Improper bearing clearances?
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Glad to hear ya made the cruise! Dak looks good!
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4,711 Posts
Yes a 408 is a 6.7. Its a 4" stroker crank with a .030 bore. You can buy it as a crate motor, build it yourself or have someone else build it (JM, shady dell etc). Power will depend on how you set it up. There are alot of variables including heads, intake setup, compression, cams, boost, nitrious etc.
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so how did you manage a 418?? Wouldn't that be like .090 over??
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4.1" crank
nethumb: That's what I'm running in my setup, but with the .060 overbore it makes a 425, on the normal .030 overbore it's a 418.
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4.1" crank
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beating on an engine when it's new will not make it break. something being incorrect, like AF ratio, bearing clearances, ring gaps, piston to cylinder clearance, etc. is what will make it break.
if you have a flat tappet camshaft, you need to hold RPMs at 2200 or so, varying the RPMs for 20 minutes. shut down, let it cool.
change the oil and drive
roller cam--fire it up and drive.
then take it out and build up cylinder pressure--think WOT at 15 mph in 5th gear. this is what seats the rings.
change the oil a lot when it's still new. when you drain the oil, and it no longer looks like metallic brown paint, then you're ready to go.
do not be afraid of your engine. improper break in can be just as bad if not worse than improper piston to valve clearance.
if you have a flat tappet camshaft, you need to hold RPMs at 2200 or so, varying the RPMs for 20 minutes. shut down, let it cool.
change the oil and drive
roller cam--fire it up and drive.
then take it out and build up cylinder pressure--think WOT at 15 mph in 5th gear. this is what seats the rings.
change the oil a lot when it's still new. when you drain the oil, and it no longer looks like metallic brown paint, then you're ready to go.
do not be afraid of your engine. improper break in can be just as bad if not worse than improper piston to valve clearance.
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Nascar and motorcycles and I would suspect other motor sports will run their engines at 1/2 throttle for X minutes then 2/3 throttle for Y minutes then 3/4 throttle for Z minutes then full throttle for a minute to break them in before throwing the motors out on the track.
Does anyone know why this process wouldn't work just as well for a street engine? Since were talking about beating on engines to break them in.
Does anyone know why this process wouldn't work just as well for a street engine? Since were talking about beating on engines to break them in.
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