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400 sbc cam swap.... help on choosing a cam ?

Discussion in 'The Hokey Ass Message Board' started by awsomeears, Jun 5, 2013.

  1. awsomeears
    Joined: Feb 5, 2011
    Posts: 159

    awsomeears
    Member

    Current cam is ' Unknow ' but the motor makes 20" of vacuum so its probably stock and idle is well :rolleyes: zzz

    400 SBC rebuilt
    Pistons are .40over about 3/16 dish, basically a fresh stock short block.
    Heads are aluminum Edelbrock RPM 6071 head, 2.02 intake and 1.60 exhaust with a camber of 70cc
    Crane Roller Rockers 1.6
    Weiand Tunnel Ram and two holley 450's
    4-speed
    2800lbs
    4:11 Gears

    As it sits now the car runs great, runs cool and burns ZERO oil [​IMG]

    MY Goal would be to live up the idle and add some power, I have a full 3" stainless exhaust that sounds great past 1500 RPM but other then that its a cricket !

    I do realize the motor is probably in the 9.1/9.2 range for compression so I won't be blowing any women's skirts off at idle :)

    With my searches I find guys are sticking around the .460 .490 area

    I will not spin this motor past 6,000 RPM, hell maybe 5,800

    I do appreciate your help and ideas

    Just did a full compression check and all 8 cyls are 175-180psi.

    Thanks guys !
     
    Last edited: Jun 6, 2013
  2. verno30
    Joined: Aug 25, 2008
    Posts: 1,028

    verno30
    ALLIANCE MEMBER

    I have ran many Summit brand cams in the past with great success. I use the K1104 kit which is a 224* duration and .465 lift with stock rockers. 1.6's will put you in the .500 range.

    With the current compression ratio, I woudl not go much more cam than this as all the cylinder pressure would be bled off and comprimise the performance.

    Just my $.02
     
  3. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    Thumpr 279TH7

    [​IMG]

    Advanced cam good for low compression.
     
  4. awsomeears
    Joined: Feb 5, 2011
    Posts: 159

    awsomeears
    Member

    Hoop98

    The thumper cam you referred to was actually recommended during a conversation I just had, or the comp extreme energy cam.
     
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  5. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    GMTA :) Heck given your specs those will do the job, IMO anyway
     
  6. mustang6147
    Joined: Feb 26, 2010
    Posts: 1,847

    mustang6147
    Member
    from Kent, Ohio

    Go with the Thumper Hoop posted...

    It seems your gonna be compensating for the converter, with the gears...

    That thumper will be right though.... Make sure your valve spring seat pressure is between 85 and 110.... more towards 110...

    More after that would be drop the gears to 3.73 and match the converter to the cam.... Depending on the converter you have presently...
     
  7. spinout
    Joined: Jan 15, 2008
    Posts: 333

    spinout
    Member
    from Dallas, TX

    Sounds like you have very low compression. The old Isky 280H grind works well with low or high compression. Good lopy idle, killer power up to 6500 or so. Check it out.
     
  8. davidh73750
    Joined: Apr 21, 2009
    Posts: 1,536

    davidh73750
    Member

    Im getting ready to do the same thing on my 400 in my 55. ditch my smog heads for vortecs and go with a mild howards cam. 400's are not a high spinning motor so thinking lower rpm range
    http://www.summitracing.com/parts/hrs-112571-12
     
  9. slammed
    Joined: Jun 10, 2004
    Posts: 8,161

    slammed
    Member

    Build torque with your displacement. Push you back in the seat hard. Make usable street driven power. Or go with a sound over substance grind. Every cam maker/seller has a chart to give you an idea of what each selection has for expectation.
     
  10. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    Thumpr vs 280H

    [​IMG]
     
  11. awsomeears
    Joined: Feb 5, 2011
    Posts: 159

    awsomeears
    Member

    Just did a full compression check and all 8 cyls are 175-180psi. All were very very close to each other.

    With those numbers I'm guessing 9.1 to 9.3 just from comparing other searches on good old google !
     
  12. icsamerica
    Joined: May 23, 2012
    Posts: 62

    icsamerica
    Member

    I have a 406 with trick flow dual spring super23 heads and 6 inch Scat rotoaing assembly and holly tunnel ram intake. Comps extreme energy makes great midrange power but the ramps are so aggressive they slam the valve shut and I hated the noise. I also wasnt impressed with the top end power... it had none above 5500 with a XFI260. I called comp and they sold me a custom grind extreme energy 224/230@.50 and it still made no top end power and the lift was higher. The valve train noise make my engine sound like a diesel. I tried new lifters, new steel roller rockers, 2 diffrent rocker adjustment techniques still noisy.... I think the valves were slamming shut and floating. I just installed a Lunati 6011 cam...its 219/227@.050 and I just set the timing before dinner today. The valve train is much much quieter and the exhaust note is much smoother and more pleasing to me More growl...less rap rap rap. I'm going to tune it with a wide band O2 this evening and drive it. Stay tuned. I'm hoping the less aggressive closing ramps will stop the crash/float so I can get some more RPM out if it. Make sure you order your cam with a small base circle for the 400 you may need since you dont know for sure what rod is in it.
     
    Last edited: Jun 6, 2013
  13. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    OP said 5800 max
     
  14. BadgeZ28
    Joined: Oct 28, 2009
    Posts: 1,032

    BadgeZ28
    Member
    from Oregon

    I use a comp cams extreme energy 284/296 camshaft. I think the lift is about .512? All comp valve train. Pro Magnum roller rockers, high tech pushrods.
     
  15. awsomeears
    Joined: Feb 5, 2011
    Posts: 159

    awsomeears
    Member

    Good Info...

    McGurk I'm not sure about the rods, When I did swap heads I really should have measured stroke for the hell of it.
     
  16. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    Oh darn all those 383s and 406s turning over 6000 must not have heard of your rule :)
     
  17. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    It has performer rpm aluminum heads
     
  18. awsomeears
    Joined: Feb 5, 2011
    Posts: 159

    awsomeears
    Member

    The engine came to me running but had small port 305 heads on it, I bought the eddelbrock 6071 heads with 1.6 crane rockers had steam holes drilled and I installed them. Piston are 40over and are slightly dished, the current cam is unknown but I'm thinking of getting #1 cyl to TDC removing the rocker and backing off, then set my magnetic dial indicator and see what the lift is to see how Stock the cam is ?
     
  19. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    I m sure given a choice it would be a longer rod, but opinions are not facts. We are all giving our opinions, it is not a fact that a 1.48 engine can't go 5800 RPM.

    Here is a dyno chart of a stock 400, a Thumpr one step up in duration, with vortec heads and 8.5.1 compression.

    [​IMG]

    Of course, if they were starting from scratch they would have done it different;

    "The low peak-rpm numbers are also indicative of the low static compression. The deck height's being more normal would have created roughly 9.5:1 compression, which would have kicked the power curve up in the rpm range, and all the power numbers (both torque and horsepower) would have been drastically greater. Because the pistons were sunk so far down in the hole, there was no way to machine the block to repair that problem. The correct way would be to add a 5.7-inch stroker rod and custom piston with a D-shaped reverse-deflector-style dish that would create somewhere around a 10.0 to 10.5:1 static compression ratio with a tight quench to the head using the zero deck approach. That would drastically improve the compression, the quench, and the power."

    He has asked for advice and we are both offering our informed opinions. I took in to consideration his desires and gave my best advice. Your opinion varies. It is not in dispute a 6 inch rod would work better but he is looking for a cam to make good power under 6,000 with a good sound. I don't think he has to run a RV cam, he already has something like that.

    If he is going into the short block follow the advice above to get a nice quench and around a 9.8- 10-1 static with a 5.7 rod.

    details
     
  20. mustang6147
    Joined: Feb 26, 2010
    Posts: 1,847

    mustang6147
    Member
    from Kent, Ohio

    The question was for what looked to me a stock GM crate motor.... Hoop is right in his original post of the thumper. The rest are variables.

    He wants a nice reliable engine, with an aggressive sound and if he desires, he can smoke the tires. Or bitch slap a rice burner stop light to stop light.
     
  21. studebaker eric
    Joined: May 9, 2008
    Posts: 1,509

    studebaker eric
    Member
    from Diablo Ca.

    Take a little time and use this link
    http://camquest.com/
    It is for a comp cams camshaft program. If you do the research and get the numbers right, it is a great tool. I learned that my engine would make better power with a smaller cam which surprised me considering what I had done inside it, and the "moderate" cam i thought i was running.
    I have never been a fan of the "thumpr" cams. while they may make power, from the outset they were designed to sound bigger than they are. Better to run a big cam with a set of Rhoads lifters. I would run the Isky 262 supercam, or the Comp Cams 270s In this engine, if it were mine, but I am a bit old fashioned too.
     
  22. Rokkern
    Joined: Apr 9, 2012
    Posts: 69

    Rokkern
    Member
    from Norway

    I would consider the voodoo 268 cam.
     
  23. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    The Thumpr's tight LSA and advanced EVO actually surprised them at how well it worked,

    I think the 270 would work just fine, but he did mention idle sound. Best thing to do is get some compression. For the best running engine I would say 10-1, XE268H, and ditch the tunnel ram but that's not the goal if I read the tea leaves correctly :)

    [​IMG]
     
    Last edited: Jun 8, 2013
  24. oj
    Joined: Jul 27, 2008
    Posts: 6,247

    oj
    Member

    Best get rid of those 1.6 rockers and put 1.5s' back on.
    the 280H or lumpitier 286H is the cam i'd go with if you brought the car to my shop - all the cam specs are for 1.5 rocker ratio. Like a .480 lift will become .512 with your 1.6 rocker ratio and the duration will go wonkers too.
    The 1.6 are for circletrack cars that have cam rules.
     
  25. 1971BB427
    Joined: Mar 6, 2010
    Posts: 5,569

    1971BB427
    Member
    from Oregon

    It's a 4 speed car.
     
  26. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    I just ran thru every cam in the Camquest range, winner is , tada XE274 H.

    :)
     
  27. awsomeears
    Joined: Feb 5, 2011
    Posts: 159

    awsomeears
    Member

    Do I need to worry about small cam base circle for rod clearance on my 400sbc with any of the cams listed, also my 1.6 rockers to be a issue ?

    As well my heads are equipped with springs that will except up to a .600 lifft, that is all I can pull out of the spec sheet I have. new comp springs are not that expensive but are they needed, finding real quick its not a A. job, its a A. B. C. and D. job. but hey I'm learning...
     
  28. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    The cam clearance should not be an issue. Get the nitirided lobes, follow the cam spring recs closely, used the zinc breakin and the 1.6's should only help.

    The XE274H will make the most power at 5500, the Thumpr will be a lil bit down (427 vs 445 for comparison) but sound more radical sound. Any more cam moves up the RPM, any cam that makes power at 5000 will be down on torgue and HP.

    jm2c
     
  29. awsomeears
    Joined: Feb 5, 2011
    Posts: 159

    awsomeears
    Member

    Hoop98 I ended up diving into my setup a bit more, installed my magnetic dial indicator on the top of the valve spring retainter and got

    .430 Intake
    .450 Exhaust

    Now there is probably a few thousands that bled down but I was able to do a nice rotation with my breaker bar..

    I'm not sure if this could be a way to find out roughly what a unknow cam could be ?

    Googling I found a stock 400sbc cam is .390/.410

    With my readings at least its consistent the intake is smaller lift then exhaust

    I know you can take your lift x rocker ratio but if I take my numbers its

    .430 x 1.6 = .688 and I doubt that

    Now that I'm typing this I have to think about geometry and how the rocker moves down, I think where I took a reading is completely wrong as its not on the True LINE of the cam lob, I'm thinking I could pop off the rocker and put my dial indicator on the push rod, but I'll still leave what I typed to be sure or debated :)
     
    Last edited: Jun 9, 2013
  30. falcongeorge
    Joined: Aug 26, 2010
    Posts: 18,341

    falcongeorge
    Member
    from BC

    so you ran the Isky 280H and the Voodoo someone mentioned??:rolleyes: This thread needs a link to the "ever raced a 318" thread...:rolleyes:

    Any cam you want, as long as its a comp...The Walmart of cam companies...
     

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