Interesting head modification

Discussion in ''Da Nailhead' started by wkillgs, Sep 6, 2008.

  1. Rotted Honda

    Rotted Honda Member

    I knew they would flow much better numbers- all I did was cut off the flange and straighten the port- I've been taking heads to the flow bench for 15 years now, and if there's one thing you learn really quick- the straighter the port, the more the flow- also the bigger the port, the more the flow, but you have to have big cubes and rpm to use a really big cylinder head.

    the heads on my 455 Pontiac are 290 cc intake ports that flow 317 cfm, with 470 CID under them. Engines are air pumps, and IMHO, airflow is everything. You can have too much at a certain point, but these passenger car engines like the nail, are so under-ported to begin with, you can't overport them. They were designed so your mom and grandma could drive quietly to the store, but yet get up and go when dad or jr. kicked it to the boards.

    for the record, I didn't leave the nailhead group, they banned me for some bs reason

    those heads were rusty, yes, you'd be too if you sat outside for a couple years ! make an intake for those heads, and port them, and you'll make some bodacious HP

    here's a pic of my Pontiac 470 CID w/tunnel port heads

    good thread, worth reviving, can't believe my nailhead experiment heads ended up in a thread somewhere, but this makes it all worthwhile- I took a lot of s#$t from people on the nailhead group for these unorthodox ideas- for some reason they had tunnel vision blinders on, and didn't want to entertain any new airflow ideas. Those guys were all hung up on zoomie heads, with no collectors, which have been proven time and again to actually lose a bunch of power

    ps- I called myself rottedhonda, because I hate those damned noisy imports with the 4-cyl and fartcan exhaust !
    Last edited: Oct 18, 2009
  2. Rotted Honda

    Rotted Honda Member

    guys, this isn't rocket science, you don't need Max's patterns, etc. Just cut off that flange, straighten the port, and it WILL flow more- it can be a chainsaw, lawnmower, motorcycle, or nail head V8- it's as simple as that, airflow likes a straight path, just like water

    but let me elaborate, I would NOT straighten the port inside where it meets the valve guide, if you look in there, you'll see it has a twist to it, that creates swirl- it would be advantageous to leave the bowl area alone.
  3. Rotted Honda

    Rotted Honda Member

    the cutoff heads still flow more, and the mod is very quick/easy to do, it took all of 10 minutes to cut that flange off on a bandsaw- compared to about 30 hours of grinding to port the heads

    the work will be, making an intake to fit it
  4. Rotted Honda

    Rotted Honda Member

    nailhead was a good street engine, but a pretty limited racing engine, especially compared to what was pounding around in the 1960's- Hemis, Ford 390-427-428, Pontiac-Olds 455's, Mopar 440's- any of them could spank a 401/425 pretty badly.

    in all out form you can get a nail into the 10's like Tom T. and his buddies did, but the other "brand x" engines bust into the 8's naturally aspirated, and they do it with airflow and high rpm HP

    the nail was designed with torque and fuel economy in mind foremost, it wasn't a true racing engine. But you can mod it in that direction. There's no reason to stay restrained to the factory porting design. Improving it will yield a higher HP/CID ratio than the stock config had.
  5. Rotted Honda

    Rotted Honda Member

    Pontiac, Buick, and Cadillac went to 3.25" mains, so they could go from expensive forged steel cranks, to cheaper cast cranks, and add to the bottom line- save $50 per crank times the 100's of thousands of cars they make, it adds up to millions of dollars

    so there's 2 ways to make something stronger, either use better material (forging), or make it bigger physically in size (bigger casting)

    nailhead forged cranks were way better than the cast 3.25" main jobbies. The cast cranks eventually crack in the rod journal fillet area in high HP applications
  6. Rotted Honda

    Rotted Honda Member

    I'd have to disagree with your opinion there- because rest assured what I was trying to do, was make a 425 nailhead into something like a tunnel port 427 FE Ford or 427 Chevy- those made 600 HP and were able to beat the Mopar Hemi in NASCAR in the Daytona 500 1967, even though it only had a wedge chamber
    Last edited: Oct 18, 2009
  7. Rotted Honda

    Rotted Honda Member

    hope you guys don't mind the post attack, but I have to play catch up on this thread- the nailhead had an expensive shaft rocker system, and the rocker arms were relatively much more expensive than the stamped steel Chevy type. The forged rods crank cost a LOT more to make, just price a forged vs. cast crank for any engine. A cast crank may be $100-$200, while a forging may be $500-$1000. Same deal with rods.

    just about all the American V8's of the 1950's had forged crank/rods during the 1950's, that included Pontiac, Olds, Cadillac, Chrysler. That's just how good they made stuff back then. The worst thing that happened was, the Japanese, then Euro car invasion, made the USA Big Three cheapen their stuff to compete and stay profitable- and the reckless union labor contracts they signed. That money had to come from somewhere.

    So they started putting cast parts in engines, and plastic parts in the dash and interior. Now they're using plastic intake manifolds that crack and melt from EGR heat.

    it became all about the bottom line- not quality- so the days of the classic auto are truly gone forever
  8. wkillgs

    wkillgs Gold Level Contributor

    Hey, good to have you back!:beers2:
    We need some fresh thinking for these old Nails! Nice to see someone take the initiative and try something out of the ordinary. I know Bob was picking up where you left off, but don't know if he's had the time to do so.
    Wish I had the time and equipment to give it a try.
    I'll bet many are hesitant to consider trying the mod since a new intake needs to be fabbed. That's not easily done.
    There was a glimmer of hope when Edelbrock was taking a 'who wants new Nailhead heads poll'. The word was a outside contractor was working on some prototypes. Somebody here knows who that was....would he care to give us an update???
  9. donut364

    donut364 donut364

    I would like to see some pix of these heads
  10. 66gsconv

    66gsconv nailhead apprentice

    I can help with a picture. It will take a few days.
  11. bob k. mando

    bob k. mando Well-Known Member

    hope you guys don't mind the post attack

    not a problem. someone doing serious theoretical work on any Buick engine is always welcome.

    actually, you need to "post attack" a few more times. then you'll be able to post pics. :beers2:
  12. The Old Guy

    The Old Guy Joe Taubitz

    There was an altered that ran in our area back in the 60s that was blown, and ran the blower through the exhaust and the exhaust dumped out of the intake side. has anyone tried this ??? :Do No: :Do No: :Do No:
  13. r0ckstarr

    r0ckstarr Well-Known Member

  14. bob k. mando

    bob k. mando Well-Known Member

    has anyone tried this ?

    are you asking for someone with personal experience or was this a more general question asking if it had ever been applied to a Buick before?
  15. Rotted Honda

    Rotted Honda Member

    they really were not anything special, one thing I found out after I cut them off, the port inside was wider than the port opening at the top of the flange- in other words that flange matches the intake manifold port size, and is choked down some- they bring the flow down in a smaller passage, then open it up to slow it down a little, then turn it to the side and down as it exits the valve opening

    there was a lot of tumble/swirl designed into the Buick nailhead- but you can only go so far with that. tumble/swirl does make more power, but it's no substitute for sheer airflow numbers. In other words, a head with 300 cfm and no swirl, is still going to make a lot more power than a nailhead with 180 cfm and lots of tumble/swirl going on in the ports

    if the flow is nearly equal between the 2 heads, then the tumble/swirl phenom can make a difference in power

    the problem with the nail was, it was just so darn underported to begin with- the original design was only made to feed 322 CID

    when it grew to 401 and 425, it was choking for air

    talking to Tom T. one day on the phone, we both agreed, going from 401 to 425 with the same head, only made a bad situation worse in terms of airflow, which is why the quickest nails are 401's- the smaller cubes are better matched to the airflow capabilities of the head

    with the stock flanges in place, you can't port the heads much at all, because the flange wall thickness limits how much you can grind, that will always be the choke area there- cutting the flange off, allows you to grind open the port more.

    I still have the 2 cutoff pieces of flange sitting in the bed of my pickup, I kept them just to show the difference in the port size, inside and outside

    pics to follow
  16. r0ckstarr

    r0ckstarr Well-Known Member

  17. Rotted Honda

    Rotted Honda Member

    if you look at a Buick nailhead cylinder head, it was obviously GM's knockoff version of a hemi at that time. It worked well for hauling around 4000 lb. cars smoothly at low-mid rpm, with decent gas mileage.

    but it needs way better cylinder head flow to be a true racing engine
  18. Silver Bullet

    Silver Bullet Well-Known Member

    Bob, what ever happened to these heads?
  19. 66gsconv

    66gsconv nailhead apprentice

    they are setting on my shelf. My spare time on the nailheads over the last 2 years has been trying to make a stock head and intake flow. I am still working on that when I can. I had to stop to finally spend time to get my car back together. Iwill say this, I got my own flow bench and started to play around with them. I never got the same .100 or 200 lift numbers,could be a couple of reasons for that. But I do remember that when I stoped I was at around 252 cfm at .600 lift and I know there is more. Also I dont think the head would be lazy, It was still a small runner and I still measured over 400fps velocity:TU: There is a lot to be said about velocity,I think the nails design can handle it. After reading this thread awhile back you have to wonder is the nailhead world ready for a cut off flange nailhead:laugh:

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