87 305 TPI changed over to 90-92 Speed Density. My oil pan rusted through and had to be replaced. Instead of fighting with it, I pulled the engine from the engine bay and replaced the oil pan with a new one. When drained the coolant, I noticed there was some oil in the coolant. Checked everything I could think of and found nothing out of the ordinary. While researching, I read an article about putting sealant on the head bolts since some go through into the cooling passages. I suspect that when we had the heads off the engine prior to it going in, we torqued the bolts in sequence but I don't remember using anything on the bolts. Hence, the leakage. My question is should I replace the head gaskets or can I just pull the bolts a few at a time, seal them and then re-torque them? Hate to have to tear everything apart to replace the gaskets if I don't need to, but will if I have to.

 

Yes you MUST use sealer on the head bolt threads. They are all drilled all the way through the block deck into the water jacket. All 17 on each side including the 7 short ones along the exhaust side.

Pull and reinstall the bolts ONE at a time. Not "a few". Use the Permatex/Loctite "Hi-temp automotive thread sealer with PTFE". NOT silicone of ANY type; since head bolts move so much all the time, it will inevitably tear up, get rolled into little *****, and leeeeeeek. Put a bit under the shoulder of the bolt head as well. Torque them to NO MORE THAN 65 ft-lbs. No need to change the gasket, at least not for this reason.

Not impossible that the reason the pan rusted through, was the coolant leeeeeek.

 

Oil is not going to get into the coolant through the head bolt threads.
Head bolts on a SBC do go into the coolant passage and they need to be sealed when installed. What happens is the coolant is pushed up the threads and you'll find coolant in the oil. It will also corrode the threads and the bolts over time. I've used Permatex non hardening sealers on head bolts and thread sealers, it all works. As mentioned don't use silicone and I put a little oil under the head of the bolt.

 

Either of these will get you there:

 

PTFE is actually a better lube than oil. Oiling PTFE actually increases the friction of something rubbing against it.

https://www.engineeringtoolbox.com/f...nts-d_778.html Compare the coefficient of friction of steel/PTFE to steel/steel w/grease or "light mineral oil" whatever that might be exactly.

Use the thread sealer w PTFE under the shoulder of the head bolts. NOT ONLY is it a better lube, BUTT ALSO it seals, whereas oil does not.

 

Cool! Thanks for the advice! I'll pick up some non silicone sealant and pull the bolts 1 at a time.