I guess I DO! I went to pick up some stuff at my machine shop today. I gently brought up the topic about the necessity of needing hardened valve seats in my 77 Buick 350 cylinder heads. The shop reminded me that my exhaust valves were pretty "pounded in the head" and I REALLY needed them. They tell me you wouldn't believe what they see at the shop, valve recession wise, and NOT just on Buicks. I assume it's the "chemical fuel" what we all call gasoline that we put in our cars causes this. The pictures are from a random sample of one of my exhaust valves. Notice the pits on the valve seating surface that mate with the head. How far can a machinist grind or cut into head before you need to buck up for new valve seats anyway? Please, feel free to let me know what you think about this exhaust valve recession stuff on engines that get a pump gas only diet. ElectraJim
Wow, you ain't gonna spit lap that one back in place. Looks like worm wood Never seen it before, dunno about it, will be watching though.
As cheap as they are, why not? Just make sure they're installed by a *competent* machinist - sucks when one comes out (like in newer Ford Escorts, heh).
Keep in mind, this engine was never opened (untill I got to it), the engine has under 100K miles, designed in 77 with unleaded gas in mind , it's lowest compression, lowest output SBB 350 (I guess) from the factory. Would this make a difference?!?!? ElectraJim
If you ask 10 people about hardened valve seats you'll get 11 answers. Not saying any of them are wrong, but not saying any of them are more right than the other. Personally, if it's a casual summer weekend cruiser, I would not freak out about it. If it's a daily driver or race car than I guess that's a different story maybe....
Offhand, I'd think that's an unusual example there - maybe something bad from the factory? Buick blocks/heads were cast with higher nickel content, making them harder (ask a machinist) and more resistant to valve recession. I've seen several Buick heads with way more than 100K miles on unleaded gas with virtually no recession.
Yeah, you would think. Cylinder walls on this engine certainly don't show that happened fortunately. To elaborate more what the machine shop guys were telling me is in the days of leaded fuel, the lead would help "heat treat or harden" the cylinder head/valve contact point. After you grind that surface off for a valve job (w/o hardened seats), you loose that hardened head surface. ElectraJim
I think it's from rust. I've seen that before. If it sat a long time the valve faces and seats could have rusted. As for the lead hardening steel, in a word, no. How is lead ever going to harden anything? ever hear of Leadloy steel alloy? Very soft, very free machining. What it does do is lubricate the mating faces but the effects are not permanent. Once you stop using the leaded fuel it wears off fairly quickly. If you had valve recession there would be a clear wear band on the valve face and you don't have that. If the seats look no worse than the valves do then your machinist is just trying to make a buck off you. Jim
Rust eh? Hmm I didn't see any evidence anywhere else inside the engine besides coolant passages. I assume the intake valves would look similar then, right? Mabey not. Don't forget to vote everyone! :grin: ElectraJim
Na. I just think my tried and true machine shop is just trying to "take care of me". :TU: Hindsight tells me I wish I took macro pictures of the heads before taking them to the machine shop for further scrutiny. ElectraJim
I don't doubt you've seen high-mile heads with usable seats. But it's not because of the nickel. I hear this myth about added nickel content affecting valve life on every non-Chevy forum I participate on. Nickel content probably DOES affect cylinder bore life. More nickel = better/harder/longer life; less nickel = softer, shorter bore life. As far as VALVE SEAT LIFE, added nickel would make so little difference as to be not worth talking about. EVERY GM DIVISION (and, as far as I know--Ford and Chrysler and pretty much everyone else) went to hardened valve seats in the early '70's; in a few cases by installing hardened inserts--but more usually by providing a heat-treatment (via induction heating) to the valve seat area that produced a "case hardening" of the parent metal. Therefore even GM does not believe that added nickel--alone--is enough to prevent seat recession when used with unleaded gasoline. Your '77 heads came from the factory with hardened exhaust seats; almost certainly via the induction-hardening (heat treatment) process. As long as the case hardening is deep enough that the wear and seat re-grinding doesn't go through the hard metal into the soft metal underneath--you won't need inserts. If there's a lot of wear--you better add the inserts. The case hardening depth isn't all that deep. How do you know there's still some amount of the case-hardening left? Good question. I don't know. MAYBE an experienced machinist can tell by the way the "seat and guide" machine is cutting the seats--feed rate, noise, the way the chip curls out--whatever. I wouldn't count on that. IF (big IF) all the seats need is a quick touch-up--maybe you want to risk it. IF the seats need more extensive cutting--I'd have inserts added. Short story: Your heads came with hardened exhaust seats. Whatever you do, you will want to assure that the heads STILL have hardened exhaust seats when the valve job is done.
I hope I did. I spent the $ to have Gessler install them in my heads. I researched this awhile back... there's a bunch of info if you search on this site. I ended up using the info on Gessler's site as a final go-by.
Your valves show the typical pitting that comes with unleaded fuel used on cast iron seats. The higher nickel content is bunk, as stated earlier. The lead does not harden the seats. It leaves a film on the seats and valves that help seal the valves to the seats. It also fills in small voids that prevent the valve from seating completely. This is important ONLY for exhaust valve seats, intakes do not need them. Remember, these older cars needed valve jobs every 50k miles. I'd imagine that part of it was to clean the lead from the seats/valves as it would build up over time.
Spend your money somewhere else...77 heads should already have hardened seats! You got a spare 455 crank?:grin:
The lead does not harden the seats, it acts like a cushion between the valve and seat. However the action of the valve pounding up and down will, over time, work harden the seats.
I didn't take time to read all the post here, but some experience from years ago might shead some light. I worked for a dealership that serviced a fleet of Propane trucks. They equiped these to run off propane. They had been using Fords for several years and switched to Chevies. All the large (60Series) wore the exhaust seats out in no time. I mean they would get to where they would barely pull their self. You could take the valve retainer off with your fingers. Deal was that Chevies required a special head to run the stuff. The everready salemen had sold them trucks on the lot and we had converted them to propane. After we ordered and replaced the heads with ones with hard seats,no problem. What does all the above have to do with anything? Propane does not have any lube (lead) for the seats. That was always a lesson to me on lead and hard seats. Amazing that the Ford seats at the time were harder. Now the question, are Buick seats hard enough, by 75-76 sure, but no one wants to use those heads. Here's my take on hard seats, racecar- no, street car- yes. Jim N.
