Originally Posted by Pontiac Jack
I'm not sure why you consider them "advanced". Those huge(!) chambers need correspondingly huge domes on pistons to achieve any compression ratio. The resulting combustion space configuration is the exact opposite of modern chamber design.
Thanks for posting the pictures- I hadn't seen a nailhead chamber in many years.
P.S.- You can edit posts for a while- I think an hour- after you post.
Jack-here's why I consider them advanced-reread my post "advanced for the 1950's"- i.e. for their time- pentroof chambers with centered plugs are still in production, and used today in many GM cars, and other makes as well.
Buick had a V-8 with shaft rockers and pentroof chambers in 1953, when Pontiac still had a straight 6.. Furthermore, Pontiac never DID get a shaft rocker setup on their V8, ever- and shafts are superior in stability, to ball stud rockers.
The plug location in center is better- the 3.4 liter DOHC in my 1995 Pontiac, uses the same pentroof chambers and centered spark plug- albeit with 4 valves per cylinder and shallower chamber. Ditto for old my Saturn 1.9 liter DOHC engines. Many other engines, used pentroof chambers and centered plug recently. It is the easiest way go get 4 valves per cylinder.
So I stand by my statement- Buick was way ahead of their time. Today, the pentroof/center plug deal is common, in any commuter 4-cylinder engine.
You are correct in stating a huge chamber volume and domed piston are passe' for production passenger cars- that is mainly due to EMISSIONS- these engines polluted a lot, like all other engines of that era.
But not so for racing, where emissions doesn't matter. Every Top Fueler and Pro-Stocker or NASCAR engine runs some sort of domed piston today (look at them). T/F and F/C engines run pistons with huge domes in them.
this is all relative- a bread/butter Pontiac 400 is more modern and has more potential, than any Nailhead- which is why they quit makin' nails ! big airflow they ain't ever had, even ported they only hit around 225/155 cfm i/e- basically stock Pontiac D-port territory, the biggest valves that will fit are SBC 1.94"/1.50"-yet these nailhead fans shell $1000-$1500 to port to this level- the quickest nailhead I've heard of yet street legal is an 11.0 car at 122 mph
Intake Flow at Lift (000=No value listed)
053-110-157-180-190-195 1.87” Nailhead Head (no porting)
059-119-164-179-183-184 1.94” Nailhead Head Conversion by Carmen Faso
062-127-171-197-212-219 1.87” Nailhead Head Ported by Greg Gessler
061-121-172-201-215-223 1.94” Nailhead Head Ported by Steve Magnotti
Exhaust Flow at Lift (000=No value listed)
045-077-099-114-119-120 1.50” Nailhead Head (no porting)
048-082-112-120-124-125 1.50” Nailhead Head w/valve job by Carmen Faso
048-083-108-130-138-141 1.50” Nailhead Head Ported by Greg Gessler
052-093-126-141-150-153 1.50” Nailhead Head Ported by Steve Magnotti