how hot can you bake a block without damage to cure thermal coating?

[HemiJoel]

Hi, I'm looking at thermal coatings for the exhaust ports on a Ford flathead for a blown land speed racing application. To help keep the exhaust heat from the LONG exhaust ports thru the block out of the water. Some of the coatings require oven baking the block at 500 to 700 degrees for 60 to 90 minutes. Would this warp or twist the cast iron block, or cause any other problems?
THanks, Joel

[mag2555]

You had better practice out a long cool down session on any kind of junk iron head .
You want to find out how slow the cool down process needs to be so as to not have the valve seat area and guides move around too much that they can’t be made to seal up again with only a clean up valve job.

Call a shop that bakes blocks to clean then them and ask how much re-machining needs to done after a iron block goes thru that process.

I would plan on having a whole stack of thermal blankets on hand to slow the cool down process back to room temp into the 12 hour range after being up at 500 degrees or better.

[Walter R. Malik]

Hi, I'm looking at thermal coatings for the exhaust ports on a Ford flathead for a blown land speed racing application. To help keep the exhaust heat from the LONG exhaust ports thru the block out of the water. Some of the coatings require oven baking the block at 500 to 700 degrees for 60 to 90 minutes. Would this warp or twist the cast iron block, or cause any other problems?
THanks, Joel

Cast Iron engine blocks are often baked to over 800f degrees for thorough cleaning. That happens before any rebuild machining takes place.

[Paul Kane]

Hi, I'm looking at thermal coatings for the exhaust ports on a Ford flathead for a blown land speed racing application. To help keep the exhaust heat from the LONG exhaust ports thru the block out of the water. Some of the coatings require oven baking the block at 500 to 700 degrees for 60 to 90 minutes. Would this warp or twist the cast iron block, or cause any other problems?
THanks, Joel

We regularly have our cylinder blocks cleaned via Thermal-Cleaning which suspends/rotates the block over an open flame and heats it to ~500*F as Step 1 of this process. We have not observed any dimensional changes at those temps, ie, aline-bored mains stayed the same, etc.

Generally, cast iron does not begin to move, stretch, contract, or change properties (in any manner to the extent that you are concerned here in your inquiry) until it is heated to 900*F and above, and some of these characteristic changes occur depending on how rapidly/uniformly it is heated and cooled. So you ought not see any dimensional or property changes in your cylinder block if it is simply heated to just 600*F and then brought back down. It would be a good practice to execute the process with the block in a free-standing state—main caps removed/not torqued, etc—so as to allow for free-expansion & free-contraction of the cylinder block.

[BillK]

Our Bake and Blast system runs cast iron at about 600 degrees. Have never had an issue but I am always doing it before any type of machining. Not sure if I would want to do it after machining.

[PackardV8]

Does no one else remember the Indy stock block guys searching for SBC cores from dump trucks and school buses because they'd been thoroughly stressed and heat cycled?

[Walter R. Malik]

Does no one else remember the Indy stock block guys searching for SBC cores from dump trucks and school buses because they'd been thoroughly stressed and heat cycled?

Still do with 429 and 351W Fords. FF 361 and 391 blocks, too.

[rcull]

I am a bit of a backyard shop, but I bake at 750 degrees. I also use the oven for cast iron welding, and go somewhat higher than that. For long cool downs just make it the last job of the day and leave it in the oven. My old oven is still warm 14/16 hours later.

I have read articles where bake ovens can be used for stress relieving new blocks, I would expect your flathead to be very relaxed over time and not to have further distortion from the oven.

[HemiJoel]

Thanks for the replies. You are very helpful!

[rebelyell]

Does no one else remember the Indy stock block guys searching for SBC cores from dump trucks and school buses because they'd been thoroughly stressed and heat cycled?

Yes! A late friend owned and operated several car crushing locations in South Carolina. Seems they had some sort of relationship with State of SC/SC counties to buy their retiring school busses. He was also an avid racer/car owner. Thus, those busses w/ sbc had a home for each of their motors. Many of us got our cores from him. He was a great guy and a real joy to be around him; always! He passed 2004 and the business hasn't been the same. May our Lord always Bless and Keep Don Brewer.

all were 4-bolt main w/ steel crank.