Make sure they are long enough. When I put my LS together, I had to go about 3 sets of bolts. I agree on the idea of ARP as that’s mostly what I used, but.., measure that exhaust flange thickness. Mine from Hardin were significantly thicker and so I couldn’t use standard exhaust manifold bolts…

btw what exhaust you running on that 6.2?

Cassell manifolds from Austraila. The log style are the only type that would fit in my boat. I have a brand new set of Hardin's that I now have to sell.

Have you tried dry fitting them in your bot using Hardin supplied bolts? I believe my Hardin bolts were longer than standard and I used those to order the proper length through my local ARP vendor. Tough to tell on pics of those Cassell manifolds how thick the flange is. Although Cassell says they ship with studs and nuts…. You may have your answer right there. Studs would be a whole lot easier than installing with bolts like I did. That absolutely sucked.

PS make sure you can install spark plugs before installing manifolds. My Hardins didn’t give enough clearance for the socket even on a universal. Cracked a plug had to take them off and redo it. I was….displeased.

Stage 8 locking header bolts. Never have to worry about re-torquing them, and header bolts have a way of loosing with heating/cooling cycles.

https://www.stage8.com/

I received the Cassell manifolds Wednesday afternoon the 13th Dec. On Thursday at 6:30 am ,I went in hospital to get my gallbladder and a 4.5cm stone removed. So I haven't had a chance to really play with them. I did hold them up against the head just to see if they where going to fit in my confined space. They will fit great. Funny thing, when I first started to think about the Cassell manifolds, they were priced in the $950 range. I emailed Cassell sale with some questions and then the next week the manifolds were priced at $1750 range. That brought one of those Aw-S---T. moments. Well the next week I went to their web page and the price was back down to $1200 range, so I jumped on them. But no bolts or studs were in the box with them. I did think about trying the Hardin bolts and looked for them in my shop by the boat. I had moved them to my basement to prepare some wood shipping crates for the sale of the Hardin manifolds. So the ARP studs should be here tomorrow. The Stage 8 fasteners really look nice. I bookmarked their website for my next need of fasteners. I need one more week of letting the four holes they put in my belly heal up, then I should be able to play with the manifolds and studs. All of you gents that have replied to my question are greatly appreciated! It's sure nice to have a great place like this forum to get great answers. Hope every one has a fantastic Christmas and one heck of a great New Year!! THANKS!!

Hope you heal up fast, and a Merry Christmas to you as well!

Is there any info on your project?
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​On my Nicson aluminum SBC log manifolds, I used studs and stainless acorn cap nuts. But the engine is exposed in a Glen-L Thunderbolt, so it.made sense to dress it up nicely.

Yes. My son just released the intro YouTube video for my boat project. Check out "Rosas Creative Works" I will be trying to dress this engine and area the best I can psych out. I googled Quicksilver seal and got a bunch of different products. Which one should I use? I'd like to see some photos of your boat engine and area? If any of you watch one of the you tube videos called Two old guys in a garage, Mine is six old guys building a boat. Our youngest gent is 66 and oldest is 83. 77 is the avg. age. Everybody has to have fun! No beer, just ice water and Snickers.

Ayuh,.... Quicksilver Perfect Seal,.....

It's pretty much Permtax Form-a-Gasket non- hardening liquid,....

Look into the brand Nord Lock. I use their products on my race car with great results.