OK, this subject pops up once in a while with those who say you need the hardened exhaust seats and those who say you do not. I am of the camp that says you do not need them if using stainless steel valves and good valve margins.
I have been following along and reading the series of articles (6 issues) found in the magazine Poncho Perfection ( Poncho Perfection ? Don Keefe Reinvents the Pontiac Magazine
) on rebuilding a raffle ticket give-away Pontiac engine built by Nightmare Performance in North Haven, Connecticut (for you guys in the New England area). The engine is 462 cubic inches and features a flat-tappet cam, and approximately 475 HP and 525 lbs-ft.
Last month and this month was the head work - checking, measuring, porting, & assembly. What I did not notice in the photos or the text was any mention of hardened exhaust seats. So I emailed the owner, Darrin Magro, and asked him why he did not add hardened seats or mention this in the text.
Here is his reply
: "I never install hardened seats in production cast iron Pontiac heads because they are not designed for them. You MUST however use a lead substitute to make the exhaust seat live. The proper seat width and a good quality stainless steel valve alone will not do it. Drivens Defender/booster is the best additive and it does 3 things; saves the carb during storage, gives very small octane increase and makes the exhaust seats live. ½ bottle per tank full for normal driving and a full bottle per tank full when racing. We use it on every car in the shop."
Never heard, nor used this product so I cannot say if it works or does not, but coming from a man who specializes in Pontiac engines and has been around for a while, it must work. Not too badly priced and I see several places do carry it, so it may be something you can get locally. https://www.drivenracingoilsales.com...r-10oz-bottle/
MY opinion is still that you don't need to add hardened seats (on a non-boosted engine) if you use the stainless steel valves and have good seat margins. If you plan on doing any towing or anything that runs the engine hot on a regular basis - turbo/nitrous, then the hardened seats that other shops will install may be a consideration OR the fuel additive
. I plan on a small shot of nitrous on my engine, so I do believe I will be using this additive.