stano Posted January 21, 2019 Share Posted January 21, 2019 I believe harden seats did not come in the heads until 1973 for Chevrolet engines.. So I would guess that none of the first gen Monte Carlo has factory harden seats in the heads. Could we have comments on what people are doing with their heads as far as harden seats in heads? Leave the heads alone. -- put in harden seats (ALL) -- put in harden seats on (exhaust only) -- change to a later head that has harden seats. If changed head that has factory harden seats, what casting did you use?? Don't have harden seats and use additive in gas? what ever you did, have you had any problems with valves? any mileage on, not harden seats heads, and any mileage on any fix you may have done. to heads for harden seats? We welcome any comment but we are asking for a regular highway driving car. thank you stano Quote Link to comment Share on other sites More sharing options...
MC1of80 Posted January 21, 2019 Share Posted January 21, 2019 I personally have not put hardened valve seats in any of my engines that did not have them from the factory. The 496 in my 70 SS has the original seats for 990 heads, the 71 402 in my 4 speed that is rebuilt, same thing. No hardened seats. You will hear all sorts of opinions on the subject. It's really up to you and your engine builder. Again, I have not put hardened seats in heads. Never had an issue. Even in the engines I have had just for racing. Pontiac 455s and even the 468 in my cavalier. Been freshened up many times and always good. Have daily driven many vehicles without hardened seats many miles. Never a valve problem. Usually a cam love rounding out or a bearing problem have happened. Used pump gas, no additives, and some race fuel when racing. Mostly for the smell. Lol Just my .02 Quote Link to comment Share on other sites More sharing options...
Canuck Posted January 22, 2019 Share Posted January 22, 2019 I've owned my 70 Monte for 22 years and have put on over 70,000 miles in that time. The car has a total of 120,000 miles on it. No issues. I run Chevron 94 octane in this car and runs great. The engine has never been apart. Quote Link to comment Share on other sites More sharing options...
Steve G Posted March 16, 2019 Share Posted March 16, 2019 i have had a bunch of engines without hardened seats and never had one issue... i was pushed by a machine shop to have hardened exhaust seats installed in a set of heads once and one seat came loose.... disaster.. never again Quote Link to comment Share on other sites More sharing options...
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