Cross over pipe to manifold bolt threads are 8mm 1.25 pitch.
Rear manifold to exhaust downpipe threads 10mm 1.50 pitch (EDIT to 10mm)

Got those broken bolts out...

Pats self on back..and anyone that'* ever dealt with broken bolts in something like that understands.

Always good to have more information. Napa had previously tried to sell me 5/16 bolts or some nonsense while I kept telling him.. it'* METRIC

I had to replace one crossover bolt last time. So I did both of them and the DP bolts. Worth the time while you're at it. These bolts get seriously heat-stressed.

And since I'll be pulling it off again soon...a little anti seize is going on there..

DONE!!!

Just drove it around the block.

Nice!! Glad you got it fixed.

Absolutely! Good Job! How did you manage to get them out?

Wasn't a fix..lol. I took it off to swap and realized the new one I had wasn't right. Travis at GT Powderworks/Hulkspeed is getting the right on out to me quick...but I wanted the car back together to drive.

On getting the broken studs/bolts out. I was lucky. Anyone that has gotten broken things out knows it'* a matter of luck, skill and perserverance. In this case the old manifold had three pieces still in it. Both crossover pipe to rear manifold bolts broke. These are long and stick out the backside, therefore I PB blastered them more and pulled on out the back with vice grips. The other was stubborn and I used my little homeowner map gas torch to heat it. Luck was with me and it came loose..but wouldn't come all the way out. I drilled it nearly out and w/pressure relieved I got the rest of it out. An exhaust manifold to downpipe stud remained and came out easily with the vice grips.

Usually you need a good torch like a mechanic or exhaust shop would have. Oxy/Acetalyne I think.

Then...having too many tools pays off. I have a couple tap sets (Thanks again for the 70+ piece set Dad) I tapped out the threads to clean them up, and picked up fresh bolts for the reassemby.

Good job!! I dont know what I would have done if I broke a bolt nevermind two Actually this reminds me of the time I broke a rocker arm bolt while trying to tighten it. A mechanic told me to tighten it while the engine was running. It looked dangerous since there were moving parts in there and well, I didnt listen and broke the rocker arm bolt. My fix? I put the valve cover back on and drove it that way until I couldnt anymore

If I remember correctly, it was an 81 Chevy Citation LOL

With that anti-sieze on there and swapping it out again shortly, it should be a breeze next time (relatively speaking of course). Did you do anything special to get at that rear mani?

Interesting you ask this. Yes..I did do something special. I learned from experience. Last summer I did the rear valve cover and it was a PITA because I was unfamiliar with how to get at the bolts that held on the engine hoist bracket. Then a little while back, VPTruman came over and we did his valve cover gaskets....and I learned something new.

To remove the bolts for the bracket that holds the connector for the O2 sensor and fuel line clip, stand on the driver side and lean in...it'll be a snap. Then the engine hoist bracket while looking far away..is also easy from that same angle....simply lean a little further.

Take the plugs out for safety, flop the wires etc out of the way. Then I've found my universal sockets come in handy with the EGR to manifold pipe. there isn't a good straight shot with the manifold and the trans dipstick is in the way as well. Actual sockets that have the universal as part of them. Gets that L27 throttle body bolt and EGR to manifold bolt easliy. (Right tool for the right job).

The downpipe to manifold bolts were the only ones that worried me. It'* a tough access area except from above. I tried and was going to round the bolts with ratchets and regular wrenches. Picked up a set of craftsman wrenches with 6 point box end. (aka the end looks exactly like the head of the bolt, no extra points). Fought a little.and won.

I've got too many sets of wrenches now....but each set has a specific purpose and quality when you need it.