# Hardened Seats



## PontiacJim (Dec 29, 2012)

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/defender-booster-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. :thumbsup:


----------



## 1968gto421 (Mar 28, 2014)

Did Mr Mahro say what year heads he was referring to? My understanding is that the heads made in the mid-late 1970's have factory hardened seats because that was when unleaded gas became the rule of the land. Pontiac did this hardening to reduce warranty problems. My feeling is that Mr Mahro was referring to Pontiac heads made 1973 or earlier. Have you heard any more on this? Thanks, Jim.


----------



## bigD (Jul 21, 2016)

Here's what I've read. Can't verify any of it.

Pontiac did began hardening the seats for the '73 model year engines. 

There were some problems with the early years. That is why there have been MANY reports of 4X heads being cracked, between the seats. One guy said that almost every 4X head he's come across was cracked. 

Apparently, by the time the 6X heads came along, Pontiac had improved their seat hardening process. I haven't read of many cracked 6X heads, tho I'm sure there have been some, for various reasons. 

FWIW


----------



## PontiacJim (Dec 29, 2012)

1968gto421 said:


> Did Mr Mahro say what year heads he was referring to? My understanding is that the heads made in the mid-late 1970's have factory hardened seats because that was when unleaded gas became the rule of the land. Pontiac did this hardening to reduce warranty problems. My feeling is that Mr Mahro was referring to Pontiac heads made 1973 or earlier. Have you heard any more on this? Thanks, Jim.


The heads in the article are 6X's, but I think you missed the point. 

Nightmare Performance: "I never install hardened seats in production cast iron Pontiac heads because they are not designed for them."

He did not single out any specific head as to which ones needed the hardened seats or which ones could get by without them. Now I don't know if the 4X and up heads have hardened seats from the factory - which they may as *bigD* pointed out. *Pinion head *made mention that most of the 4X heads he has come across had cracks as I bought a 400CI with 4X heads and have yet to take them to my machinist to get checked out. I know Chrysler did a flame hardening on their seats to make them compatible with the unleaded gas. From what I have read, the hardening process does not go very deep into the seat and a good valve job will cut into and remove the hardened process. I would think that this may hold true for a hardened seat on a Pontiac head.

I have read that if you install hardened seats in a Pontiac head that boring the head for the seats can be tricky as they come very close to the water jacket and it has to be done with precision. I suspect that any core shift or heavy rusting could cause the machinist to break into the water jacket. So this might mirror Mr. Magro's reasoning for not installing hardened seats in any Pontiac heads. In the article, he does show using a sonic tester to check wall thicknesses on the head prior to his port/bowl work to make sure there is enough metal to do the work. If it is too thin in any of these areas, porting can risk hitting a water jacket or leave the metal thin enough that it could later crack.

Now keep this in mind, this is how he builds an engine. Obviously other builders do install hardened seats in Pontiac heads.

SD Performance: "High Flowing 4 Angle exhaust seats when converting to 1.77” valves or 3 angle on factory 1.77” valve heads or 4 when hardened seats are installed." 

Neither KRE or Butler mention hardened seats or offer hardened seats as an upgrade/option on their iron heads. Does not mean that they do not do it. Might be interesting to email them and see what their response is.

:thumbsup:


----------



## geeteeohguy (Feb 2, 2008)

Glad I don't have to worry about hardened seats in my Pontiacs, which run 1965 and 1970 heads on the engines. The '65 for the past 37 years, and the '67 with the 1979 heads the past 10. I don't tow a trailer, haul cement in the trunk, or run down the road at 3500 RPM, so no worries here.


----------



## tjs72goat (Jul 20, 2017)

My 72 has the stock 4x heads. I read an article where Pontiac induction hardened the seats for the upcoming fuels. As a machinist working in a shop where we actually build head and seat rebuilding equipment, I had an engineer (co-worker) who races and builds engines, cut and install hardened seats in my heads. My heads were good from the start also.


----------

