im currently running a 3856206 head with stock valve configuration except for a higher performance spring to match the mild lift cam, stainless valves, and hardened seats to run pump gas. question is I am looking to change to 3931063 for a more period correct head for my car, the heads i am looking to purchase have been jobbed to 2.19- 1.88 valves with.590-.600 lift springs can I use this head configuration without damaging my current setup, or do I need to change current piston/ cam setup? if so what kind of performance changes can I expect? horsepower vs fuel consumption. I have no idea what type pistons I have, as I have not yet removed the old heads. thanks in advance

Per Mortec, it looks like you may be gaining about 4 cc's of combustion chamber volume which will drop your CR. some.

Probably somewhere in the neighborhood of a 1/4 a point CR. lower??

You may be able to get some/all of it back by running the .022" thick steel shim headgaskets??

pdq67

U should have no problem with valve clearance running a mild cam. What size motor are U running???? From your post Im assuming your running a 69 396 (period correct 69 #063 heads). If your running a 396, the small bore size along with a "mild" cam I dont think U would realize much if anything by going to the 2.19/1.88 valves not to mention the added cost to the heads of upgrading to larger valves. Running smaller 2.07/1.72 stainless valves with some port/cleanup work would due U just fine. Spend the extra money somewhere else.

thanks for the replies guys, supersport I would buy the heads with the valve job already done. that is they already have new HD 219s and 188s. This was my concern about valve clearance, and spring pressure. how much effect on performance would this compression loss have? they are the right price. only downer is not hardened seats or stainless valves. you are correct in assuming the 396 cid block