Stock hardware

[BigBlueIron]

At what point are the stock head bolts and main bolts a concern? And beyond that when do you move to studs, with an iron block that is.

[JimNolan]

For mild street/strip I've never used new head bolts. I always used the originals except for my aluminum head 410 and I used the bolts Edelbrock had for those heads. As for rod bolts I always replaced them with new bigger bolts and nuts, I was always afraid to use the old bolts. You're usually getting the rod resized anyway so might as well put in better than you take out.

[Rory428]

On most of my FEs, including the very low 10 second 428s that I used in my Fairmont drag car, I reused the original Ford head bolts and main bolts many times, with zero issues. I have used ARP main studs on #1 thru #4 at times, and my current 428 has ARP head bolts with the TFS aluminum heads, mainly so I can get a socket on the head bolts with the headers on, as the stock head bolts have larger hex heads, which prevented putting a socket on them. The ARP head bolts have a smaller hex head, so even a thick impact socket will clear the header flanges.

[blykins]

At what point are the stock head bolts and main bolts a concern? And beyond that when do you move to studs, with an iron block that is.

From an engine builder standpoint, when a customer buys a $20-30k engine from me, I don't think they'd like to open it up and see 60 year old bolts in it.  Now with that being said, I think there are specific situations where a factory bolt would be fine.

On aluminum heads, you need a washer to keep the bolt head from galling the aluminum, so an ARP kit is pretty much necessary there. 

As for main studs, I don't always drink the Kool-Aid that you see on the internet about always switching to studs at a specific point.  It all comes down to clamping force versus the load and I see an awfully lot of aftermarket SBF blocks come through here with main bolts, albeit they are usually 4-bolt mains.  But if an FE block is gonna split, IMO a main stud is not gonna stop it. 

The heads can be a different scenario, aluminum blocks have to have studs, and Fords are always down on clamping force there because they only have 10 fasteners per side.  With any kind of forced induction, it would be a wise choice.

[My427stang]

Brent nailed it, a couple other points

- Aftermarket heads generally need an aftermarket bolt because of no room for a socket AND the washer he mentioned
- I am not a stud fan on the mains in a 2-bolt FE, I have never seen cap walk with a bolt, but have seen studs on #2 and #4 walk on a 428 block
- My gut tells me the stock bolts on an FE, assuming they torque well, are almost indestructible, BUT, like Brent, the added 100 dollar note for high quality, washered bolts that torque without as much friction is very hard to beat

I'd like to give a simple answer, unless some sort of resto that needs stock style head bolts, up to about 6200-6500 rpm with a common rotating assembly, new ARP head and main bolts, and associated deck plate hone and main alignment is where it's at.

I wanted to give a higher RPM, but at that point, I think you need crossbolts or maybe a pinned main, so it doesn't push you to studs as much as it pushes you to a solution

[CaptCobrajet]

I think stock head bolts are fine on iron heads with 10-ish static compression ratio. Washers and better bolts for aluminum heads or high compression.  Head studs need long threads and deeply rooted in aluminum blocks.

On mains, the stock bolts will work fine on stock and mild apps.  Past that, the ARP studs are a victim of a mistake on their part.  A few years ago, they started using SHORTER thread length on the block end which makes zero sense.  Bolts are better than that.  If you want studs, you should use the 351W studs, and bottom tap the existing holes in the block.  It will root deeper and spread the load further into the main bulkhead.  On #5, the Buick Nailhead stud works good.  Longer root and spot face the cap, and you can get the stud just below the pan rail.  I like main studs in higher horsepower stock blocks if done correctly.  We sometimes only do #2 and #4.  They take the most abuse in a V-8 engine.  There is less stress on the block with a long rooted stud in tension than a bolt that is twisted and in tension. Cap walk in stock blocks with good clamping is either due to detonation or lack of good snug register to hold the cap in the saddle.  Dowels are wonderful but not a lot of room in OE blocks, and hard to locate without upsetting the stock register.  You don’t want the dowel and register working against each other.

[FrozenMerc]

I know this is a bit of an apples and parakeets comparison, but Caterpillar recommends replacing rod, main, and head bolts after 3 engine lives (2 rebuilds) on their C15 / C18 product line.  I am sure Ford never thought about it's FE engines being rebuilt multiple times and still in service nearly 70 years later, often at much higher then designed power ratings, but there is probably some validity to Cat's recommendation.