I've been unsuccessfully trying to get my '66 Sport Fury with 383 started after a short hibernation of about 20 years. At first, it was cranking normally. After several cranking attempts, I started getting a spark and smoke from where the battery ground cable is bolted to the thermostat housing. The cable is bolted tightly(in fact, I haven't been able to budge it). Coincidentally, this started at the same time the oil light decided to start working when I turned the key on. I've never seen anything like that before. What would cause it? Also, I'd appreciate any ideas on removing the thermostat bolt.

Thanks,
Harold

Could be a bad ground or corrosion. Is there a ground wire from the engine to body? Clean all connections.

bolt the cable to STEEL/IRON! on the BLOCK or iron intake NOT to the aluminum housing/bolt or otherwise. It's smoking and sparking because it's a bad connection. It'll be hot if you touch it.

An impact can be good at breaking loose the corrosion of a stuck bolt.

The 66 housing will be steel if it's OEM

Does heating the bolt area with a heat gun help? I don't have a torch and am worried about flame in the engine compartment.

They are also fantastic at rounding off the heads and breaking bolts off.

The heat gun will do nothing, the open flame will get the job done. Flame will not hurt anything in there, unless you have a fuel leak with a puddle.

then use a 1/2 breaker bar with an extension (piece of pipe works good) & jerk it rather than a steady pull (same principle why impacts work). Holler how it turns out & yes clean/relocate those cables!

After 20 years the cables are probally junk.They might look OK but corrode on the inside.Like said bolt the ground to the block.That and heat the bolt as said.I used my 3/8 Impact a lot removing bolts thast were stuck.A good 6 point socket and some heat turn the power on it down and use some good penetrant.NAPA had/has good 1 gauge cables as factorys were light.If the bolt starts to move work it back and forth and keep heating and penetrant.ive also heated them and then melted bees wax into the threads.One reason I use antisieze on almost every bolt/nut.Rocky

You can also try striking the head of the bolt with a hammer. I founds this works for me most of the times when a bolt is froze and I agree use hand tools. Or if you don't need or want it to turn into a big project cause the bolt broke just cut that cable off close to the bolt and buy a new cable and ground it to the intake or the head....

X2 X2, I totally forgot about that. that'd be the FIRST thing I'd do (hammer and a brass drift)

Heating the bolt and then tossing ice water on it will work sometimes also.Never had any luck with smacking the bolt though.Too much rust in Ohio.Rocky

Rust, what is Rust I couldn't resist, please forgive me