Justice -

Not really, the bottom ends of these engines are pretty stout and the Diamante SOHC block appears to be the best of the SOHC blocks strengthwise.

I'm waiting to hear from the machine shop on whether the bores will clean up enough to reuse the same pistons. If not, it'll probably be cheaper for me to prep another Diamante block than buy another set of $650 forged pistons.

BUT -

I'd like to find out if there's an ARP main stud that will fit the SOHC main girdle.... there's nothing listed for the engine, but perhaps I can find someone at ARP that knows more than the last ignoramus who told me they had nothing to fit the SOHC heads..... even when I gave him the size and thread pitch. Funny how it was the same size as the DOHC..... I guess nobody ever told them.

If you don't want to use (or if I can't find) main studs, you can do what I did in this engine - use the bolts from the Diamante DOHC block.... they have more bearing surface under the head than the SOHC bolts..... just make sure the girdle area where the bolts will seat isn't burred from the SOHC bolt.

When you rebuild yours, the best thing for the bottom end is to get a later DOHC crankshaft and rods so you'll have the forged (and supposedly nitrided) crankshaft. From what I've read, the rods are also stronger. I don't know if only a turbo block had those, or if all of the later DOHC engines used the better parts (I think so). I used the crankshaft and rods from a later DOHC Diamante engine and there is a definite difference in particularly the crankshaft..... it's a brighter color than the SOHC crankshaft and has a real nice long ring to it when you strike it with a hammer..... so it at least appears to be forged steel.

I'd also recommend spending ~$200 for balancing the rotating assembly. I had my crankshaft static balanced, then dynamic balanced. The rods were balanced via beam weight. Pistons were custom and no balance was needed.... you might want to check yours if you use cast pistons. The flex plate and harmonic balancer were also checked. It made quite a difference in smoothness. At idle the engine doesn't even wiggle and as it revs, there's no noticeable torquing..... and it revs quickly. There's nothing wrong with an OE oil pump, but I tried a stock Beck-Arnley from NAPA and it works fine (I need to clean it), seals were all OE from a rebuild gasket set.

I did install seal surface repair sleeves on both ends of the crankshaft - they're available from NAPA as are the (expensive) installation tools. The seal surface sleeves require extreme care when installing the seals because the extra thickness tends to cause the seal lip spring to jump out of its retainer groove, so be very careful if you use those. You can install the seals at new depths to avoid the old grooves, but I wanted to try these.... I do like them, but would be remiss if I didn't warn you about the possible consequences.

Oh, I had the machine shop install ARP rod bolts, which requires resizing the big end bore - a tricky operation for a shop that's not well-equipped. It's easy to get back rods that aren't the same length from big-to-little end. If you install those, you'll want it done by a good machine shop before you have the rods balanced.

I'm assuming you'll deck the block - so you'll want to move rods and pistons around to get the same deck clearance on all cylinders. If you want to avoid some hair pulling, I'd suggest using pistons that can be installed with full floating wrist pins so you can swap rods from side-to-side to allow for differences in crankshaft throw dimensions by using a shorter or longer rod. Ideally, you would have a perfect crankshaft and identical rods, but it ain't gonna happen without spending a lot of money, so the next best thing is to identify the differences and have the ability to adjust for fit. If you use full-floating pins, you'll have to rebush the rod small ends, so that decision also needs to be made before the rods are balanced.

I really like the ARP head studs. They completely eliminate the issues with 3.0L head bolts. You still need to clean the block threads with care, but there's no longer a depth issue. There's plenty of threaded length on the studs for worry-free installation and they'll take a lot of torque.

The FelPro pan gasket seemed to work very well - they make two styles. I used the more expensive of the two.... it has ribs that run the length of the entire pan flange. It may not be necessary, but it is probably slightly more reliable than an RTV seal if there's any flange warpage.

Some of the blocks were milled poorly around the water pump flange area. Check the water pump fit before you install anything into the block so if necessary you can improve the fit for the pump flange surface. I've seen it necessary to use a grinder to lightly knock down high spots under the pump outlet flange area on the passenger side of the block face.

Back to rods again - Last year, Eagle had some ESP "H"-beam rods for the 6G72 for a reasonable price of around $300/set - maybe they were closeout prices because they're no longer available at any price anywhere that I've looked. I thought about them then but considered them overkill for a 6000rpm engine. They might have been a bit stronger than the OE forged DOHC rods, but I figured if the late DOHC rods were the same as what's in the 3000GT TT engines, they should be plenty strong. I am looking longingly at a set of "H"-beams from 3sx, but they're real pricey for what they are and really an unnecessary expense - particularly for a N/A engine. They do eliminate the cost of conversion to floating pins, balancing and ARP rod bolts and if I had to do it all over again, I'd probably buy these:

3sx Rods

I guess that pretty much covers the bottom end. It's not a difficult engine to rebuild - just has a few quirks that are uncovered over time.

Frank