FORGED?

[eZ65]

Im bored so i thought id share with you all what im thinking. I keep holding off on ordering my 347 because i want to be sure I dont regret what i get...

Its a 347 w/ afr 185's, air gap, blah blah blah, anyways approx 450hp 430tq, Im considering wether or not I should get forged internals or not. I should be ok without them but if i ever want to put some juice to it I would need the forged. But wouldnt I also need a 4 bolt block in that case? Seems a stock block would go before the pistons.

 

[Starfury]

At those specs, forged pistons are a must. Forged rods wouldn't hurt either, but a forged crank may be overkill. I'd be worried about the block as well without any kind of main girdle.

 

[eZ65]

There are arguments as to wether or not a main girdle really does work. It pretty much just keeps the block together if you split it down the middle. I doubt it will save a stock block from anything. Forged rods and pistongs = $600

 

[Starfury]

It prevents small amounts of crank walk, which can be disastrous. While sbf's aren't really known for having this problem, at 450hp on a stock block, I'd start to worry. But I do agree, it's not going to keep the block from splitting down the middle. Ideally you'd be running a sportsman block, but that gets pricey real quick.

 

[monkeystash]

Saying "forged" really doesn't cut it when talking cranks and rods. Almost all aftermarket cranks and rods are forged, but what really matters is 5140 or 4340. 4340 is much stronger than 5140 and usually twice as expensive. There are several companies that make budget 4340 rods like Ohio Crankshaft and Scat. Scat actually just came out with a budget 4340 capscrew rod too which is stronger than their bolt through.

As far as forged pistons, well you mentioned the bottle down the road, so they are cheap insurance. However, if you don't go that direction, hypereutectic pistons are cheaper, have a higher silicon content, fit tighter, and are generally lighter than forged pistons. Personally, I'd go the forged route to allow for options down the road. Keep in mind, hypereutectic pistons can handle bottle or boost, but are less tolerant of detonation because they are a weaker alloy.

Now about the main girdle, would I spend the extra money, probably not for your application. If I were pushing the limits of a stock block at 600+ HP, maybe then. What I would do, and what I see not done time after time in performance engine builds is quality fasteners. ARP or equivalent fasteners are a must in my opinion. I would use main studs and head studs, not bolts in any performance application. I would also use the best rod bolt that is offered for my rods. Many companies offer ARP2000 or L-19 rod bolt upgrades. Most budget rods are just offered with ARP 8740 which is a minimum in my book. Make sure your engine builder checks rod bolt stretch too, as that is what keeps them tight.

A 4 bolt main block is a huge waste of money for your build, your money is better spent elsewhere. If I were you, I'd use a 5140 crank, Scat budget 4340 capscrew rods and the lightest forged pistons you can afford. Don't forget the ARP fasteners.

Also, if budget allows, buy a billet flywheel and quality balancer (not a $60 Performance Products balancer,) and have them balanced with the engine internals. Don't forget the ARP fasteners here too.

Good luck and let us know how it goes!!!

 

[Starfury]

There's nothing wrong with the $60 Performance Products balancer While I agree, I'd probably be thinking about something a little nicer for a 450hp engine, I have one balanced to my 331 rotating assembly and it works just fine. It's much better than a factory style balancer, and it has dual bolt patterns for different pulley options (important for pre-68 owners).

There are plenty of aftermarket high nodular iron cranks available. I have one (Scat) in my 331. Also, Scat has had 4340 cap screw rods for at least 5 years, because I have those as well.

 

[monkeystash]

Ok Tad, well my Dad can beat up your Dad!

Yes, there are plenty of cast steel or nodular cranks available too, and they would also be a fine choice for a 450HP motor.

Scat has been in business over 40 years, so a rod that came out in the past few years is still relatively new. BTW, I should have noted I was speaking of the I-beam, not just assumed by stating budget.

As far as the balancer goes, I just don't understand building a 3 to 5 thousand dollar motor and using a $60 balancer. While it might be "fine;" at 6500 rpms I'm going to want the longevity insurance of a quality balancer.
;D

 

[Starfury]

Haha

Well, I partially agree. Like I said, for a 450hp build, something better would probably be a good idea. They do make an SFI approved balancer that would help you sleep better at night

But still, for my 331 street motor (that I happily spin up to 6200) and for most other people running their cars on the street, the $60 unit is probably going to be just fine.

Oh, and those cap screw I-beams rock They did force me to have the machine shop notch the piston skirts, but no big deal, and those rods are NOT coming apart

 

[eZ65]

$600
To upgreade my motor to an all forged rotating assembly with
4340 Crank, H-Beam Rods, and Forged Pistons

SFI flexplate = $69

ARP headbolts are already included
And using 7/16 ARP rocker studs

 

[monkeystash]

That sounds about right. Can you mix and match? Say go with a nodular crank, H-beams, and forged pistons? The only down side to the H-beams is the weight. While they are strong, they also weigh a ton. See if they have a 4340 I-beam like in the picture I posted above. Also, what pistons do they offer? SRP, Probe, KB, TRW??? They are not all created equal. Some are really heavy, and there are 2 types of alloy used, 4032 and 2618, just to make things more confusing! Are you sorry you ever asked now?

 

[eZ65]

no actually i understand metals through designing golf clubs so im into it. Ill give them a call today and check on the I beam and pistons.