401 rebuild

Discussion in ''Da Nailhead' started by woodchuck2, Nov 23, 2018.

  1. woodchuck2

    woodchuck2 Well-Known Member

    Well, the 401 in my car has good power and runs great but i feel is getting tired. I have another 401 that i was told came from a 65GS so i will be posting up the marks i find to know for sure. The engine is clean and complete. My plan for now is to do a compression check on it sitting on the stand so at least i will know there are no major issues before tear down. I have pulled the valve covers just to get an idea of its maintenance history and it it spotless, no sludge or carbon build up. If it looks good i plan to keep the lower end stock, just freshen it up. I plan to change the cam to a thumper with roller rockers, port match the heads to the intake and do the intake mod. One of my questions is does anyone make roller lifters? Who is a good contact for OEM steel head gaskets? What can i expect for HP/torque? Once the engine is done and in the car i want to drop the gears in the rear down to at least 4.10's and if finances allow i will put the gear vendors overdrive in it. I want to keep up with these GM 383 strokers and big blocks if possible but still keep it a Buick at heart. Anyone have any other idea's or opinions that might better my goal?
    Donuts & Peelouts likes this.
  2. TrunkMonkey

    TrunkMonkey Well-Known Member

    Strap on a couple of snails...
    Donuts & Peelouts likes this.
  3. woodchuck2

    woodchuck2 Well-Known Member

    Thought of that, but if i were to go that far into it i would go with an LS/4L60E. I just gave away a running 5.3 with harness/pcm
  4. dual-quadism

    dual-quadism Black on Black

    Thumpr is wrong, they make power, but not great on driveabilty. Port match is a waste, power is in the bowl/valve job. PM me, will go over what you really need. FYI, if it has orig pistons, plan on a full rebuild.
  5. TrunkMonkey

    TrunkMonkey Well-Known Member

    I really wish I had the cam specs on mine. (I bought the engine rebuilt and the shop did not keep the records).

    It makes a ton of torque, pulls hard and runs very well. (it's "lumpy" at 550-1000. low warm, high cold/choke)

    I have a 401/2x4, wide ratio T-10 and 3.54 gears (Strange) and thanks to Dave (dual-quadism) the correct 12* distributor/Pertronix and coil.

    The engine is .060 over and compression test is 165-170.

    All that said, and I hate to "spend" someone else's money, I must say that nearly 50 years of doing things mechanical, the money and time spent to do a thing properly, far outweigh the cost and time of doing it over.

    There are a majority of people that are nearly equally split on spending your money on things that are worthless in the long term, or "short-stroking" you and selling a "cheap and easy" path that results in broken parts and money pissed away.

    Set the realistic goal (money and what you have to work with) and then formulate the plan and path to get there, then figure the time, money and expertise required, and if it all adds up, go for it. If not, recalculate until you find the correct answer.

    And do not dismiss the many combined years and experiences of people that can help you.
  6. Stevem

    Stevem Well-Known Member

    Port matching is a waste of time!

    The restriction is deeper in the port in regards to the size and shape of the valve bowl , the width of the short turn and in regards to the Intake port the dip in the port roof.

    As long as the Intake port flange is within 1/16" of matching the flange exit onthe Manifold your good, and in regards to the Exh port you want the entry in the exhaust manifold or header to be bigger then the exit from the head.

    In regards to the Exh Manifolds if your able to raise the roof by 1/8" then raise the roof of the Exh ports by 1/16" and go in1/2" deep into the port.

    The proper valve job on the Exh side for increased low lift flow can almost make up for what the port does not in terms of high lift flow above .450" lift.

    Here's a friendly warning about these nail heads and doing porting work in the valve bowls, that being you need a flow bench , a way to track velocity, and / or some who has worked on these Heads by means of a flow bench to guide you more so then other heads!

    The reason for this is the shallow depth of the valve bowls, especially the Exh bowl!
    The shallower the valve bowl is the faster removing metal will change flow numbers and unless you know what your doing and have a means to track port velocity then it's all too easy to decrease flow , not pick up air flow!

    One of the best things you can do to these Heads even if you are running Exh Manifolds is that when you rebuild them to step up to a 1.60" Exh valve .
    Last edited: Nov 24, 2018
  7. gs66

    gs66 Silver Level contributor

    Will be following along, I have a 401 rebuild in my future.
  8. gsgtx

    gsgtx Silver Level contributor

    I agree with everything above, expect for the last line. always go with the bigger intake valve, there's a 3 to 1 gain with a bigger intake vs exhaust valves.
  9. woodchuck2

    woodchuck2 Well-Known Member

    I suspected i would be referred to head work to get it breathing better. Question is who would be the shop recommended to do proper head work and be able to flow test them without destroying them. I live in upstate NY and would have no issue driving a ways to deliver them for proper head work. I recall reading somewhere the stock pistons tend to crack or break. I also read somewhere the 430 pistons can be used in the 401 and the 455 pistons can be used in the 425. Is this true? I would like to keep this as a cheap budget build or maybe i should say cheaper. I know its not a small block chevy that can be built for $500 but i would like to keep the budget under $3k if i can. I am hoping by Christmas i can get the compression test done and tear the engine down to see what i have. Going to take pics as i go.
  10. woodchuck2

    woodchuck2 Well-Known Member

    I stopped by my friends garage where the engine sits. Had to pick up one of my battery testers so i cleaned off a couple spots to get numbers off it. Here is what i found, anyone know the info off these casting numbers?

    Attached Files:

  11. TrunkMonkey

    TrunkMonkey Well-Known Member

    LR is a 1965 GS "400" (401) block.
  12. Bigpig455

    Bigpig455 Fastest of the slow....

    Call Carmen Faso in Tonawanda to see where he recommends for head work up that way...as far as pistons go, thats one place you cant skimp- you're in for 500-700 a set if you want this motor to make any power at all. Tom Telasco (Telriv) has a line on some good pistons, nicely priced.
  13. Stevem

    Stevem Well-Known Member

    Oversize intake valves in nail heads need to have the chamber unshrouded to really show what the can do, and to do such is a ton of work even without the CCing of the head and then the mill job to maintain the same compression.
  14. gsgtx

    gsgtx Silver Level contributor

    the non tulip valve makes up for the loss cc for unshrouded, most heads need milling anyways they seem to be a little warped anyways.
    dual-quadism likes this.
  15. wkillgs

    wkillgs Gold Level Contributor

    Carmen would be a one-stop supplier for everything you need for a stock or hi-po rebuild, even has his own cam designs. Anybody know what pistons he uses?
    Stock-type cast pistons+rings will be $450+. Tom offers the custom made forgings for around $850...That's money well spent if it's a performance build.
    The cast stock type are avail from Sealed power, Keith Black/Silv-o-lite, Engine Tech and Egge. Most, if not all, of those replacements will have a lower compression height that will drop your compression ratio into the lower 9's or more. And forget about the stock 10.25:1 rating from Buick, a production engine was closer to 9.8:1. You can only get 10.25 if you blueprint and mill the block and heads to the NHRA specs. Use the thicker composition head gasket and you'll drop compression even more. Tom's forgings are custom made to produce a specific compression ratio.

    Your cam choice will depend on your goals. Low rpm torque or higher rpm horsepower? Compression ratio needs to be matched to the cam. Pick your cam first, design the rest of the build to support it's power range. Comp has grinds other than the Thumper series, ranging from a stock type High Energy 260, to a higher performance Xtreme Energy series. They're not listed in their catalog, you have to call and ask. The Thumper is designed for a super lumpy idle which will not support power brakes. There are better choices out there. TA also offers a variety of grinds, as does Carmen. Joe (gsgtx) has tried several different cams and has built some of the best street Nailheads on the board. And of course, Tom T is likely the most knowledgeable Nailhead guy out there!
  16. Bigpig455

    Bigpig455 Fastest of the slow....

    Joe introduced me to Camcraft out of NC, I picked up a cam from them that will be going into my rebuild (whenever I get back on that project) - a pretty mild 218/222 spec'd out for a great 8.0 DCR at 110 straight up - I dont think anyone on here has run one yet, but on the desktop dyno and the DCR calculator it looks like a contender.....Better than a lot of other choices mentioned!
  17. woodchuck2

    woodchuck2 Well-Known Member

    Is this fella the owner/operator of J&C Parts in Tonawanda? I know there is not a local place here with a flow bench and i will certainly take the advice of have someone port these heads on a flowbench. So far from all the older posts i have read Tom T seems to have a good reputation with his pistons and roller rockers. I will be contacting him soon to pick his brain. I am impressed on how much torque the nailhead has in stock form but of course i want more so i want a fresh engine and plan to drop the gears down low so if i want to have a tire burner the great but if i want to launch it hard then i want it coming out of the hole hard and fast. So i guess way to describe it is i want the engine to have low to mid range power.
  18. Bigpig455

    Bigpig455 Fastest of the slow....

    Thats the guy. His number is 716-693-4090
  19. CameoInvicta

    CameoInvicta Well-Known Member

    Just to comment on the Thumpr, I went with it because I was spec'ing something similar, but stumbled on a very good deal for a cam and lifter package. I was planning on a little less duration, but with a similar spread, and a slightly higher LSA. Once the tune is dialed in (carb, timing, etc) it is very streetable, and with a vacuum canister supports power brakes with no problem. With stock heads and manifolds my car went 14.99 NA, and 12.99 on a 125 shot of nitrous.
  20. telriv

    telriv Well-Known Member

    Ain't gonna happen at 3K. You could spend that plus in head work doing it RIGHT. Pistons , rings, pin fitting,pins, 1K. Roller cam/ lifters & associated, 1.2K. Roller rockers another 1K+. 6.2K just in parts. Add in machine work & associated by the time your done an easy 10K.
    Keep dreamin' & saving $$$$$$.
    riv1964 and dual-quadism like this.

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