I don't know about DII's, but D1 exhaust manifold bolts are SAE. If yours are SAE I wouldn't use metric.

 

Thread cleaning kit. Best $50 I've ever spent (thought it seems that the price has gone up a scosche).

Craftsman 48 pc. SAE & Metric Thread Restorer Kit - Tools - Mechanics & Auto Tools - Automotive Specialty Tools

 

That's the Kastar Hand Tools KAS971 set. You might find it somewhere a bit cheaper.

 

you're correct on the bolts, 3/8 x 16 matched up perfectly. I had read another post a while back but couldn't find it again, it was saying the same thing, that they were essentially Buick parts that land rover had used and tweaked a bit.

I ran the chase and then replaced the two messed up bolts with SAE and worked like a charm, no miss threading or stripped aluminum. Hopefully just another couple hours of reassembly and an oil change (pretty sure coolant spilled in taking it all apart) and should be up and running.

 

Good.
Remember, never crank them in hard and fast.
Crank forward, reisstance - stop.

Crank back.
Then forward again.

But if you are going thru this - could be cross threaded.

I bought some new old stock exhaust bolts from a guy in Buffalo NY on eBay.

The exhaust bolts are supposed to be tossed out and not reused on a headjob.

New bolts.

Well I reused mine - save for the one I snapped getting it off.

 

I've never heard of the exhaust manifold bolts being single use. I can't imagine why unless they are severely rusted, which wold be true for any bolt.

 

Land rover pretty much says in the RAVE to replace every fastners no matter what, probably the one of reason there bills as so high every bill have $50-100 added to it for new hardware. I think they call for new valve cover bolts everytime they are open too.

 

I couldn't find anything about the manifold bolts in the RAVE but hindsight I probably should have just replaced them with grade 5 or 8 SAE bolts and reused the spacers. I sure it would have made things a bit easier and cost about $8.

I ended up replacing my valve cover bolts,they were pretty much at the end of their useful life, it looked to me like they hadn't been replaced last time the engine was pulled apart.

Little bit of loctite too, hopefully it'll keep them torqued a little longer.

 

I've no idea what manual you're using, but none of the Land Rover manuals I have, Factory (paper or RAVE) or Haynes, D1, DII, Defender or RRC, says to replace exhaust manifold or rocker cover bolts.

 

From RAVE 12-2-19
"6. Noting fitted position of 2 long screws or multihex
bolts, remove and discard screws/bolts
securing rocker cover; remove rocker cover."

And from RAVE 12-2-48
"1. Remove 8 bolts securing exhaust manifold and
collect spacers. Discard the bolts."