Re: straight 8 head resurface

Posted by 1929ClubSedan On 2023/7/3 18:22:33

My experience is to take as little as possible, these heads can bow but only slightly often less than .020. I would recommend taking it to a automotive head specialist with the latest machinery. If you know anybody who races drag cars and regularly gets heads worked over the workshops those people use have state of the art machinery. You are not looking to increase compression by a lot if at all. The compression on the early eights is only 4.8 to 1 and cranking pressure is only 72 psi at sea level, the higher the altitude that will drop. The last head I had done took off .017 on a robotic machine. You are not looking at increased performance just to tidy things up if or as required. These engines are not designed to give high performance mainly due to the surface area of the compression chamber. I would be a little conservative. If you are replacing a gasket I would stick it down with a sealant like Permatex Aviation Gasket Sealer which you paint on, or a product called Hymolar which comes in a spray can. Also give both the block and head a good clean up plus clean up around the valves. Give the head a good clean by getting the machine shop to flush it out. Any scale inside the head can hit the gasket and damage it. Once the head is on you will need to torque it down. No more than 50 foot pounds, go to 40 foot pounds and run the engine to temperature and let it cool then go to 45 foot pounds and run it again to temperature and let it cool overnight. Come back and go to 50 foot pounds and leave it there. After a long run you may get a couple of pounds as the gasket bedded in and sealed. Leave the torque wrench at 50 foot pound and the nut may go down quarter turn at maximum. I would use a good quality calibrated torque wrench ideally deflective beam they tend to be the most accurate.