[Frank T]

Does anyone have experience with not being able to put hardened seats in older factory Pontiac heads?

https://www.youtube.com/watch?v=XJK0rvY0lPE

I have alot of respect for this guy, his videos are very good, so Im hoping someone on this board knows a machine shop (preferably in the north east) that can put hardened seats in factory heads successfully. I have a couple sets from 1969/70 (#11 #16sm) that need them.


Thanks
Frank T

[Half-Inch Stud]

I've been a stubborn proponent of leaving the PMD iron seats alone for the ride. Let em wear....because they don't.

[25stevem]

If intake seats in the heads you have are very sunk and or beat up then your better off going with a oversized valve to get back on fresh iron and then just put seats on the exh side.

[b-man]

So if hardened exhaust seats aren’t necessary or have limited benefits then why did the factory install those on what most would consider to be the ultimate evolution of the iron Pontiac head, the ‘73 - ‘74 455 Super Duty ?

Probably because they were intended to see some hard use with the SD clearly being a high performance engine. Not all would be hammered on constantly like a race engine but most of them definitely would see plenty of full throttle fun by those who spent the money for that option.

So why wouldn’t Pontiac enthusiasts want to do the same to their own iron high performance heads while they’re at the shop for porting and/or a valve job ?

I had hardened exhaust seats installed in my 1964 9770716 421 HO heads since why not ? I was spending the money to completely rebuild them and to me that’s just another important item that should get done during the process.

I also replaced several intake seats because they were too rust pitted to clean up. To me it’s mandatory on the exhaust seats. On the very early 20 degree heads with factory 1.92/1.66 valves there’s zero room for an oversized intake valve to fix this issue, the valves are simply too close together.

I did experience heavy exhaust seat recession on a pair of 1971 #66 455 heads, anywhere between 1/8”’ to 1/4”. So it does happen, they had 30k miles of daily driver use with a 068 blueprint cam and factory RAIV stamped rockers.

[Schurkey]

Originally Posted by Frank T

Does anyone have experience with not being able to put hardened seats in older factory Pontiac heads?

https://www.youtube.com/watch?v=XJK0rvY0lPE

I see this on Buick forums, and on Oldsmobile forums. It comes up on Chevy forums. I don't spend much time on Cadillac, Mopar, or Ford forums, but it's probably discussed there, too. Everyone's scared of hardened inserts, and they even go so far as to claim that the "high nickel" iron in [insert favorite manufacturer name] heads don't need inserts because "the heads aren't made of mush like Chevy".

The machinist I use says that "some heads are tricky". But the benefits outweigh the issues.

Get the RIGHT hardened inserts, and IF (big IF) you hit water, there's various ways of sealing the head--waterglass, Loctite anaerobic compound, welding/brazing the casting hole, etc.

True enough, with intake seats it's beneficial to just cram in larger-diameter valves to get back to virgin metal. It's the exhaust valves that really benefit from the hard seats.

[geeteeohguy]

Originally Posted by Half-Inch Stud

I've been a stubborn proponent of leaving the PMD iron seats alone for the ride. Let em wear....because they don't.

I agree. Have run the stock seats in all of my Pontiacs for 45 years with no issue.
If I were towing a boat or a trailer running high load most of the time, or running extended periods of high rpm, I would upgrade. But I drive mine as they were designed to be driven and have yet to have a problem. Have seen many MORE problems with replacement hardened seats falling out, or heads being damaged during their install.

[Half-Inch Stud]

Originally Posted by b-man

?..........I did experience heavy exhaust seat recession on a pair of 1971 #66 455 heads, anywhere between 1/8”’ to 1/4”. So it does happen, they had 30k miles of daily driver use with a 068 blueprint cam and factory RAIV stamped rockers.

Never seen such meself; I would have to imagine 0.010" wear, as ever seen on any PMD iron head i've opened up.

Must be something in the regional gasoline huh.

[b-man]

Originally Posted by Half-Inch Stud

Never seen such meself; I would have to imagine 0.010" wear, as ever seen on any PMD iron head i've opened up.

Must be something in the regional gasoline huh.

My thinking it was lousy Edelbrock 5857 valve springs letting the valves bounce off the seats more likely.

It was really only a 5000 rpm engine at times.

I was pretty blown away seeing how bad the valves receded. The engine wasn’t running poorly that I could tell.

[Gary H]

I've had three different Pontiac engines in my shop that had bad recessed exhaust valves. Two engines had 6X heads on them, and other was a mid 60's head. One head had two exhaust valves sunk so bad it couldn't be saved. Too much damage to even put a 1.77 valve in. So, my experience is that although rare, it happens on Pontiac's too.

[tom s]

My shop wont do a set of iron pontiac heads without doing hardened seat.He knows they will come back to him with the gas we have now.FWIW,Tom

[25stevem]

One has to understand the time line of the SD455.
This motor was well in the works by Pontiac engineers even though the 455HO came out first in 71 and 72.

During this time induction Hardening of the valve seats was just starting to be tried out in the regular production heads and I think the engineers by then new it would be prone to cracking, but it was the only cost effective way to live with no lead fuel., especially when they new Cats would soon be required and this would increase the heat the heads would have to live with.
This is also why the 1.66" valve became standard fair in later years.


Now lets add to this that in terms of the Intake valve, the 45 degree seat valves as used in the SD heads beat up a valve seat in the head way more then a 30 degree does , especially as ware takes place and the valves then start to rock around and slide over the seat area in the head on there way to being fully closed.

We also know that two versions of 45 degree multi angle valve jobs where used in the Exh side on the SD heads, one version used a 3 angle job, the other only 2.

Long story short I don't think the engineers wanted to have what they new would be rare heads have a greater chance of cracking by using the induction hardening procedure, so they opted for seat incerts.

The fact is that even today with non lead fuel and 10% Alky a 30 degree seat Intake that is .060" wide when run with no more then 135 psi of seat pressure will last a good long time.

[Half-Inch Stud]

I'm reminder of my stepson's Auto Technician Training manuel; it had many images of valve head and seat failures. As i read the caption for each failure mode ( and brand engine) I assessed the conclusion "well that never happens to a PONTIAC HEAD.

I sure got to wondering how PMD was so fortunate, and figured on the rewards from good R&D.

As we all know, the PMD heads #1 stock wearout/failure mode is worn valveguides, leading to oil consumption.

[Formulajones]

I've had stock seats in mine for the last 25 years back when I built the engine. I tore it down about 5 years ago with over 70,000 miles and everything was perfect. I do run a pinch of 2 cycle oil in the gas for a little lubricity. Been doing that for going on 30 years now in various cars. Don't know if that contributes to longevity but it certainly doesn't hurt, but it does absolutely help to keep things clean. I'm not a fan of todays fuels but it's what we have.
Worth mentioning I've always had flat tappet cams in this engine and nothing more than 130 lbs. on the seat. Of course results will vary depending on several variables. Everything else here aside from the bug has hardened seats in it.

[mgarblik]

Complicated subject IMO. Really depends on condition, use, rarity of castings, and customer preference. Just helped a student with a set of 1968 original 400 heads. Stock rebuild, cars and coffee type weekend driver. Probably 2000 miles a year. Guy is 60 years old. If he drives it until he is 85, that's 50K miles. It had 160K on the heads and mild recession that we easily machined. No seats for this guy. Not necessary IMO. When I do replace them on big Pontiac heads, I do all 16. That way I can put in shallow inserts, .200-.225" deep. Intake first, then cut the exhaust to interlock the two seats with a full diameter exhaust seat. It's allot of work and expensive. Your talking around $800.00 by the time you buy 16 seats at $15.00 each, That's $250.00 and about 6 hours labor including the valve job.

[P@blo]

My machine shop does not recommend the hardened exhaust inserts on a Pontiac head. This is for street use involving no towing or extended higher RPM use however. Something along the lines it is not needed but it is my money if I want them.

Strange how some guys have bad valve recession while others do not. Might be a stupid question but could it be the quality of the cast iron or possibly valve guide machining accuracy?

[Formulajones]

Originally Posted by P@blo

My machine shop does not recommend the hardened exhaust inserts on a Pontiac head. This is for street use involving no towing or extended higher RPM use however. Something along the lines it is not needed but it is my money if I want them.

Strange how some guys have bad valve recession while others do not. Might be a stupid question but could it be the quality of the cast iron or possibly valve guide machining accuracy?

I don't see it as strange. There are a ton of variables that would affect it. Just a few that pop into my head are spring pressure, camshaft lobe profile, valve job angle, worn guides or work valve stems causing movement.

Truth is, while some say it's fine and others say they've had wear, we have no idea what all the variables might be or how the engine was taken care of in the first place.

[tom s]

Kind of funny,a lot of people dont have the money to do things right but somehow find the money to do it over!Tom

[tom s]

He has done many heads for me and never paid attention that he had put seats in them.Dport and tunnel port heads.Need to look at my bills more closely!Tom

[SRR]

I have to believe if a set of heads has had numerous valve jobs there isn't going to be a lot of meat left to work with, plus if the machinist is heavy handed, well some guys could break an anvil. I think lean mixtures, sustained RPM and running hot have a lot to do with burnt valve seats.

[Bermuda Blue]

I would think the chances of hitting water are dependent on the casting number of the head. Would be nice to get list of casting numbers which should not have hardened seats installed. Maybe someone who is friendly with Butler or SD could consult them and post their responses here.