Mar 22nd, 04, 02:33 PM
Just recently acquired a restored 69 Z28 with a 302 motor. Car appears to have been restored professionally, possibly in Oregon somewhere. Unfortunately, I don't know if the valve seats were hardened. I was told these motors were high compression and would not tolerate low-octane, unleaded gas. This car could see as much as 150 miles a week, so just in case the valve seats were not hardened, would I be able to get by with just using a lead additive and an octane booster?
Do the majority of 302 restorers tend to harden the valve seats? It has to come up at some point and I am just wondering if there is a general consensus as to this practice to comply with today's fuels.
The motor does not appear to "ping" but we haven't driven it that much yet.
Mar 22nd, 04, 04:54 PM
I think that the hardened seats were introduced in the 70's If they didn't do the seat replacement during the last rebuild then I would run them til they recess. The heads won't be ruined but you are post-poning the enevitable.
Mar 22nd, 04, 06:33 PM
Another point of view. I did not change mine when it was rebuilt.
Mar 23rd, 04, 04:53 AM
I only paid $40 ($5 each) to have hardened seats installed in my 840 b/b heads when I was getting a valve job. I would definately do it then, but I would not pull the heads and get a new valve job at this point. I've heard you can go as much as 25,000 miles on unleaded before you have to fix it. If you are running octane boost with lead, you will never have a problem. The problem may be that the additive may be outlawed. (I've heard rumors of that)
Mar 23rd, 04, 08:11 AM
If you had a numbers matching head, I wouldn't run the risk of machining it just to put in hardened seats. If you hit a casting imperfection like a tiny bubble during machining it may render the head worthless. On a non-matching head then go for it when you feel that it is time for a full valve job. If the old owner was religious about running lead additive then you could continue, but if he wasn't then I wouldn't use it at all. Your main problem is octane if you have 11:1 compression. Also, if you run a high displacement water pump on a 302 in the 8,000 rpm range without a water pump to intake manifold bypass hose, you could be having leaking head gaskets down the road. Everyone that I know that has a 302 likes to rev it up once and a while just because they can.
Mar 24th, 04, 10:10 AM
Overblown issue, created by the marketers to convince you your engine will self-destruct if you don't use their product. Unless you're going to be towing a trailer at 100mph all day long, don't worry about valve seat recession. graemlins/thumbsup.gif
Mar 24th, 04, 12:27 PM
Imho, I would just add say half a bottle of good old Marvel Mystery Oil to a full tank of gas and the rest in the oil every so often and go right on down the road.
MMO is to me an old-time product that does great in this application.
It isn't a lead substitute but rather a valve-train top-oil lube.
Mar 24th, 04, 01:27 PM
A HUGE thank you to all of you! Your input has been great and has taken a huge load off my shoulders. We sold a '58 vette convertible to get this so you can see how dedicated I am!
Now, where can I get some decent camaro t-shirts because the only ones I have found so far are really cheesy! Thanks again! Your fellow bow-tie addict...muscle RULES!