I am in the process of rebuilding my 289 heads. The question or questions that I have is about the use of harden exhaust. Is it necessary, pros or cons or any advise at all.
Doug,
Pros - you may have a little more latitude with unleaded fuel. With the oxygenated fuel we get in CA, this might be a plus to have it done.
Cons - cost. If you are super high revving you might suck a valve seat but I'd say its pretty unlikely.
If it were me, I'd put in new seats. If nothing else, you're buying peace of mind.
Cheers, -Kevin
I am in the process of rebuilding my 289 heads. The question or questions that I have is about the use of harden exhaust. Is it necessary, pros or cons or any advise at all.
For show & weekend cars, just toss in a little lead additive a couple times a year. It will never be an issue. Flat tappet motors like some zinc in the oil also. If it's gonna be a daily runner, then put in the seats or use Aviation fuels. amen
Isn't VSR ( valve seat recession) mostly an issue above 4000rpm? I remeber the MRI in the UK doing lots of research on this in 1999 before they phased put leaded fuel and tested all the various additives avaioable at the time.
Perios alloy headed engines were an issue.. But easy to switch to modern seats as per vehicles designed for ulp.
Any tiger with alloy heads would have ulp seats and most with original cast heads would be either mostly below 3000rpm most of the time .. Or if modified to spin up would likely have had seats replaced in the process.
The old motorcycle types and VW types would say that the leaded fuel that was run is still there impregnated into the seats, but I second Kevin's suggestion .
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