Most of what I read is failure under boost, or a certain power level which it becomes the weak link, but ive even heard rumors of flex. In a n/a scenario, if the rotating assembly is balanced to a higher degree, it should last in theory, correct?

 

Most people I don’t think are gonna spin it high enough to hurt it, especially with streetable cams. I wouldn’t trust it with mine, but 6500 is way different than 8000+. You might break a cast crank with a large blower that stresses the snout, but I’d bet detonation has killed more than anything else.

 

Agreed, I’m just not clear on what the actual limit is based as a stock engine, if the cams and intake are maxed to 6000rpm, there is no benefit to spinning to 7k.

If your head can flow, valvetrain can handle it, and cams and intake are good to 7k, I can’t find any reason to not have it balanced accordingly and run stock crank.

I’ve yet to find factual evidence showing they don’t last. I’ve read articles where there were future plans of boost where it was cheap insurance to upgrade, and other articles that leave a lot to the imagination on quality of the build causing a failure. This leads me to believe that with the right combination and a well thought out build and proper tune, 7k redline should be doable, and dependable.

 

For what its worth this is exactly my build but I'm not even close to finished. I'm still trying to find out if the normal gen 2 or 3 5.0 has better or the same rods than the roadrunner 5.0.

 

A well known drag racer friend of mine got his start in the modular game by making the swith to a mark8 short block with aviator heads. Backyard shadetree mechanics built, that engine ran a season of passes well over 8000rpm. Be reminded its and aluminum block and cast crank.

 

If you are buying a new crank, the difference in quality between a 300 dollar cast crank and a 600 dollar steel internal crank is like man and woman.

 

I think he is talking about using the factory cast crank versus buying a forged crank.

 

Definitely paying attention to this post as I am now in a similar boat, where it looks like I need to rebuild the block and was hoping to be able to use the Cast Crank for a predominately NA build but will occasionally spray a little 50 - 100. It may be worth noting that on Modular Head Shop's site they sell a short block with forged pistons and rods, but the stock crank and note that "This short block is a great choice for anyone looking to use up to a 250 HP Shot of Nitrous or Up to 18 lbs of boost."

 

OMG wtf am I doing here lol. I didnt notice it was in the mod motor section. I dont even know what those motors look like, sorry guys. Carry on

 

Hang out and learn a little!

 

So, now that we can all somewhat agree, it’s suitable enough for the application, I will definitely be working close with the machine shop to get it as close to perfect balance as possible.

Not being fluent in cam specs, with flat tops w/reliefs and pi heads, valve lift will be a limiting factor. No real reason I’m spinning higher rpms if it can’t flow or make more power. Heads have been ported, and plan on using the edelbrock intake. Again, cam specs are going to be the limiting factor on how high we are going to rev.

 

Will this engine serve a purpose, like drag racing?

 

The cam timing plays a bigger factor in piston to valve clearance than valve lift. On a factory heads, even with good valves, around 225-230 degrees @ .050 and PTV clearance will start getting tight. 230@.050 size cams should be good to 65-6800 for peak power.

 

I have ran my car all year at a 7krpm limiter. Stock Crank, forged pistons and rods that I didnt even balance. Stock PI heads with cms .600 springs. Leaving the line @ 5500rpm with boost. So far so good. Probably 30+ passes down the track this year.....
CMS 2.5 blower cams - .536/.540 lift, 228/235 .050 duration, 114 LSA

 

2vboss drag racing only. Very little road use.

 

You are 100% correct, internet myth. These are the same dip####s who come in and say the cast crank "limit" is 500hp. Plenty of ppl making big power on cast cranks. NA guys prefer them, they are lighter than the forged jobbers.

Cast crank, boss rods and then your choice of forged pistons is kinda the go-to combo these days. Cheap, strong as hell, WORKS. For a little more money a lot of ppl go with the Molnar power adder rods which is a good upgrade from Boss but not really needed IMO.

Also I shift my cast crank at 7200. Been doing it for awhile now.

 

I'm in the process now switching from my v3 blower to a precision 76/75 turbo. Should be another 100hp and ftlbs next year with e-85. I'll report back when the cast crank let's go..... Or the boss rods.

Sent from my SM-G920R4 using Tapatalk

 

Should my 331 in my '93 expire, I will likely seriously look into an Explorer 2V with BOSS rods and forged pistons topped with a Kenne Bell at a conservative 9-10 psi. And yes run the cast crank.

 

Just drop a 4V into it. Just freshen whatever heads you get, boss rods, $550 pistons and boost to the moon. Or Coyote.

 

you sure like them 4v’s!

 

Yeah!....and cut the key off the exhaust cams so that you can advance them like 10°