Is it OK to add a mild performance cam to a 401 with 109K miles?

Discussion in ''Da Nailhead' started by 64 wildcat conv, Oct 10, 2017.


Is it OK to add a mild performance cam to a 401 with 109K miles?

  1. Yes, go for it!

  2. No, you risk damaging the bottom end (more blow-by).

  3. No, you'll get more performance gain by doing a stock rebuild.

  4. Depends on the cam.

  1. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    I've got a '64 Wildcat with 109,000 miles on the clock with a stock 401 (internally) that has never been apart as far as I know. The engine runs very well and burns/leaks little oil, maybe 1 quart per every 1000 miles. The compression pressures average 155 psi with a warm compression test. The max was 165 psi and the min was 145 psi. Using a bore scope it appears it still has the OE timing chain and sprockets.
    I need to replace the OE timing chain and sprockets for insurance and have been kicking around the idea of dropping in a TA-20 or TA-25 cam, lifters, and stage 1 valve springs. I do not plan to remove the heads. The engine runs too good to consider a full rebuild (and the $$$ isn't available at this time).
    I'd like to pick up a little performance now instead of withing a few years until the $$$ is available for a performance rebuild, but am concerned that the extra fuel and air may cause sealing issues with the rings. It responded very well to a recent ignition recurve so I hope a new cam will pep it up even more. I plan to run the engine with a rebuilt ST-400 with switch pitch.
  2. TrunkMonkey

    TrunkMonkey Well-Known Member

    That many miles on a 54 year old car is asking for trouble if you stuff a hotter cam in there.

    You will want to put the juice to it and be hard pressed not to.

    The new parts won't hurt it, but your right foot will.

    I would put the money into getting the parts together, as that will take a little time (and be fun learning) as you find all you need to a good and proper performance rebuild.
    As well as finding the machine shop (and assembler, if you don't do most of that yourself), and just take the 'cat out for leg stretching and enjoying that while you acquire.
    8ad-f85 likes this.
  3. telriv

    telriv Well-Known Member

    I agree with Michael. Do the timing chain & gears, drop the pan & clean it out. Maybe install a modern rear main seal as well as the modern timing cover seal (IN STOCK). AT 109K the possibility of a cracked piston is a REAL possibility. It can happen between 75K & 150K. Start saving now for the eventual rebuild. It's just a matter of when.
    Just my thoughts.

    Tom T.
    8ad-f85 likes this.
  4. telriv

    telriv Well-Known Member

    Forgot to add. If you DO drop the pan check the two bolts holding the oil pump pick-up screen to the pump. They are known for loosing up.
  5. Bigpig455

    Bigpig455 Fastest of the slow....

    So I put the spurs to a 75k motor, with Toms rockers, etc..and put 500-600 passes on it and got it into the mid 14's (14.52), and all that happened was it developed much more blow by. I was probably lucky, as OEM pistons are fragile, and so are the rings. I stopped and pulled the motor because it was numbers matching, but it could have gone on for quite a while if I didnt care about it. Thats the question - Are you willing to take a chance on blowing that motor? As Tom mentions, it could lose a piston at any point just idling around town. No guts, no glory!
    8ad-f85 likes this.
  6. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    Thanks for your recommendations. You're echoing what I have thought over the past 30 or so years in cars and bikes. No, I don't want to risk the engine. I'm not exactly easy on it as is, but there's no racing legal or otherwise. I guess I'll start Johnny Cashing the parts for a rebuild. I still plan to pull the engine when changing the trans and freshening up seals and replacing the timing set and water pump. Hopefully there's no unexpected surprises.
  7. John Codman

    John Codman Platinum Level Contributor

    Factory Nailhead pistons are good for about 100,000 miles. After that drive the engine very conservatively until you replace them. Tom's pistons are a great solution.
  8. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    Thanks for the advice, John. A full rebuild is TBD. Will definitely go with Tom's piston and rockers if the budget allows.
  9. doc

    doc Well-Known Member

    Follow common sense here,,,, You got it , because you asked the question to start with.... put your money and time into a engine rebuild... at that amount of miles , you got most of the goody out of the engine already.... Go with as good parts as the budget will allow and get to know a lot,, lot... about engine machine work.... for nailhead buicks.... do not,, do not fail to put in new cam bearings,,, they are a absolute for good oil pressure in the long run.... check out all my stickeys and cheap tricks.... they work and are low cost.... DO YOUR HOMEWORK,,,,, IT WILL SAVE YOU TIME/MONEY.... use name brands... Toms stuff is good too.... from the reports , I hear.... rebuild the starter when you rebuild the engine... IF IT AINT CLEAN ENOUGH TO EAT OUT OF,,,, AN ENGINE AINT CLEAN ENOUGH TO PUT BACK TOGETHER.... Doc....
  10. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    I used to do automotive machine work back in the 80s. I did everything but crank grinding. When the time comes I'll do disassembly and reassembly but farm out the head work for 2.02 inch intakes and mild porting.
    I have a few health issues that will keep me from any work next year anyway.
    8ad-f85 likes this.
  11. telriv

    telriv Well-Known Member

    NIX on the 2.02 valves
  12. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    That's what I was thinking, thought the 1.940" sbc size intake valve was the biggest intake valve that fits in the vertical chamber of the a Nailhead's head. Even if that size would fit in the head there would be a whole lot more shrouding to slow the flow than using a smaller valve.
  13. 64 wildcat conv

    64 wildcat conv Silver Level contributor

    There is a several year old 425 build thread that AMS did in Shreveport, La where they fitted Chevy 2.02 intakes. HP was over 400 and torque well over 500. Not saying I need that much to be honest. 350/450 at the crank would be my goal
  14. telriv

    telriv Well-Known Member

    You should be able to accomplish that with stock valves.
    300sbb_overkill likes this.

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