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Technical /SBC cam profile with Rocker Ratio

Discussion in 'Traditional Hot Rods' started by 70executive-Catalina, Sep 2, 2019.

?

1.60 Ratio Rockers too much?

Poll closed Sep 10, 2019.
  1. Yes I lost power overall

    0 vote(s)
    0.0%
  2. I lost low end power only

    0 vote(s)
    0.0%
  3. No I gained power but suffered valve float at high rpm

    0 vote(s)
    0.0%
  4. No I had significant gains. Recommend 1.60 rockers

    33.3%
  5. It worked on a different cam profile

    33.3%
  6. Power gains not worth money due to clearance issues, rocker prices, etc.

    33.3%
Multiple votes are allowed.
  1. A CARB number is a California thing. It makes your parts legal and considered to be stock replacement parts in the state of California. It stands for California Air Research Board. My heads are one off.

    To get the proper pushrod length you use a push rod checker, you can buy a set up complete with instructions from Summit racing. I don't actually use one I use a very old tool setup that I have had for over 45 years. Dial indicator, light spring and a brain basically.
     
    raven likes this.
  2. DDDenny
    Joined: Feb 6, 2015
    Posts: 13,770

    DDDenny
    Member
    from oregon

    Not all parts play nice together.
    When the time comes and there is a good chance it will remember.......Smith Bros. Pushrods, Redmond Oregon

    https://www.pushrods.net
     
    Last edited: Sep 2, 2019
  3. Motors have a tendency to do one of two things, you either become a mechanic or you quit. Taking the time to figure it out, is the better of the two.
     
    pbr40 likes this.
  4. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 66

    70executive-Catalina
    Member
    from Canada

    Yes and probably the better of the two options (run the heads and slap any ol ods in vs get 1.5-1.55 roller rockers with matched rods ) is to wait to swap the heads and cam until I can run my ideal set up. The 441s run well for now
     
  5. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 66

    70executive-Catalina
    Member
    from Canada

    Joe H can you reply again please? It’s not showing up here on the blog
     
  6. Dyce
    Joined: Sep 12, 2006
    Posts: 1,889

    Dyce
    Member

    The 441 and 461 heads flow just about the same. The only gain you with 461 heads is more compression, which is good when going with a larger cam. The original heads on my 350 in my 40 chevy were stock 1.94 441s. The exhaust seats went away so I built a new set of 441 casting heads with 2.02 and 1.6 valves, angle milled to 68 cc, and screw in studs and guide plates. The 350 had a stock cam and I didn't want to mess with it, so I used 1.6 rockers.
    It made a huge difference in how it ran. More power through a very broad range.
    Of coarse I wanted more, so last winter I put a comp 260h cam in it and left the 1.6 rockers. Now, of coarse it is a little dead off idle to around 2000 rpm. It has 308 gears and a stock converter, so it has a lag now. I'm tempted to put 1.5 rockers on just to see what it's like. My ultimate goal is to put 4.11 or 3.73 gears with a 700r4. With cam changed it is always a trade off. Increase power by increasing flow trough bigger heads, not so much. That's why a big block can get such a broad torque curve. The heads flow good.

    Just giving you my latest experience hoping it might give understanding.
     
    70executive-Catalina likes this.
  7. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 66

    70executive-Catalina
    Member
    from Canada

    This is a perfect answer thank you so much for sharing that experience! I’ve heard a lot of guys go with 3.73s and since you have the over drive why not go with 3.90s or 4.11s and a 3000 stall? That eliminates the 0-2000 issue that may just be a an issue with the cam moving your power curve up.
    Thank you again Dyce and good luck!
     
    Dyce likes this.
  8. alwaystiredlong
    Joined: Jan 1, 2010
    Posts: 115

    alwaystiredlong
    Member

    70executive-Catalina likes this.
  9. 70executive-Catalina
    Joined: Dec 20, 2018
    Posts: 66

    70executive-Catalina
    Member
    from Canada

  10. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,632

    gimpyshotrods
    ALLIANCE MEMBER

    [​IMG]
     
    triumph 1 likes this.
  11. Mimilan
    Joined: Jun 13, 2019
    Posts: 639

    Mimilan
    Member

    What about one of those SUHC SBC's [Single Under Head Cam :D ]

    That's an old engine! it has a 2 barrel manifold and old 265 style exhaust manifolds.
    It looks like they bolted "Cam boxes" onto stock heads
     
  12. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,632

    gimpyshotrods
    ALLIANCE MEMBER

    It appears to be exactly that.
     
  13. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,972

    sunbeam
    Member

    I don't understand how the gross cam lift changed by changing rockers?
     
  14. oj
    Joined: Jul 27, 2008
    Posts: 6,247

    oj
    Member

    You put 1.6's on what is pictured and you'll bend/break things up with those rotator cups. Even with 1.6 ratio you're still around a .500 lift so the 'Z-28 Drop In Spring' (I have no idea idea why its called that) will work really nice and replace the keepers & retainors with 10deg steel. You may not have to elongate the pushrod holes since the extra lift is on the other side of the rocker and if the pushrod didn't contact the head with a 1.5 then it won't with 1.6, length won't change either.
    Dunno your questions about carb & intake or your idea of 'performance'. But if you want to make power, the 461 head is a decent one, you'd go with single plane intake and 750ish carb.
     
  15. Fordors
    Joined: Sep 22, 2016
    Posts: 2,975

    Fordors
    Member

    46AC7CF6-7EC6-4F41-95FE-77EE84E5D144.jpeg
    The 3927142 spring is considered a “drop in” because it needs no spring seat machining to fit the head. A regular SBC spring has an installed height of 1.720 and on the seat it is about 80# and 200# at 1.220.
    The ‘142 spring, also known as the brown spring for the color GM painted them, is stouter with 135# on the seat and 290# at 1.220, or .500 valve lift.
    GM doesn’t catalog them any longer, those were from the Trans Am race era but Crane might have a similar spring.
     
  16. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,972

    sunbeam
    Member

    If you did not change the location of the valve or the rocker stud the only way to change the ratio is move the push rod end.
     
    X-cpe likes this.
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 17,632

    gimpyshotrods
    ALLIANCE MEMBER

    It doesn't. Net lift does.

    Valve lift gets changed. Cam specs are listed by how far the valve is opened, with a stock ratio rocker arm.
     
    Truckdoctor Andy and X-cpe like this.
  18. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,972

    sunbeam
    Member

    I agree I was just looking at his numbers
     
  19. oj
    Joined: Jul 27, 2008
    Posts: 6,247

    oj
    Member

    Yup, your right, I hadn't given it much thought but the valve side must be fixed and just the pushrod side can be changed.
    Good point.
     
  20. oj
    Joined: Jul 27, 2008
    Posts: 6,247

    oj
    Member

    Because cam specs are at the valve, in this case he said the Exhaust (?) was .460 with a 1.5 rocker ratio, so the cam lobe is (these number are not exact since the lift is @ .050 to get the slop out of the valve train, if you chuck the cam in a lathe and dial indicator for exact lift the number will different) anyway, divide the .460 by 1.5 (.30666, this is the theoretical lobe lift) and multiply time 1.6 = .49066, the new lift at the valve. make sense?
     
  21. David Chandler
    Joined: Jan 27, 2007
    Posts: 1,101

    David Chandler
    Member

    I ran stamped 1.6 rockers once. It was a 305 with ported small valve heads, and a VERY mild Wolverine cam. It ran quite well, all things considered. Had the cam been bigger, I'd have stuck with 1.5's though. Push rods were right up against the cast in guides, and should have been opened up. But I was young and poor, and threw it together. I pulled it apart for other reasons after about 40.000 miles, and they showed where they were rubbing, but no more than on a stock engine with more mileage. I have read that the friction from that can negate the power gained from the switch. But it was not run with both ratios to see what difference it might have made.
     
  22. pbr40
    Joined: Aug 10, 2008
    Posts: 790

    pbr40
    Member
    from NW Indiana


    I’m in a similar process. Not sure if you watch engine masters on you tube but they did a dyno session rockers non roller to full roller 1.5 to 1.6. I recommend pulling up. Lots of real world info dyno proven instead of bench racing.
     
  23. Tutashen
    Joined: Aug 8, 2015
    Posts: 12

    Tutashen

    1.6 rockers were used by roundy round guys running under cam lift rules that allowed using big block rockers if you want more lift buy a cam with more lift aside from the fact you have to check the geometry see if all your valve stems are the same height ,check that all your rockers are the same going to need a box of them to find 16 the same,then find 16 pushrods the same size,then check that the rocker hits the valve stem through 360 degrees rotation , i could make any sbc cam-carb-head-comp. run but how well is another question , for me building the motor an drivetrain to do what you want is the holy grail weather its go fast or drive anywhere you feel like going ,my G.M 1/2 ton look's like crap i only washed it once since i got it when i retired in 2012 and it looked like shit so never washed it again but having said that i would drive it around the country in a heartbeat with no worry's and um it's an cam lift rules 360 cube an under roundy round 283 stroked to 354 um also what are you smoking cause i want some :)
     
  24. Tutashen
    Joined: Aug 8, 2015
    Posts: 12

    Tutashen

    converter an driveline have nothing to do with motor lagging um are you saying it's slow or slower or that motors not running well ? a well tuned balanced sbc should run crisp no matter what it's sitting in front of imo
     
  25. southcross2631
    Joined: Jan 20, 2013
    Posts: 3,997

    southcross2631
    Member

    We ran 1.60 rockers on the exhaust side of our hobby dirt cars that had a stock stamped rocker rule and a not too sharp tech guy. We were issued a cam at the start of the season with an etched number on it and if you got protested they would pull the timing cover and chain and read the number and it had better match.
    He never did catch the rocker arm trick until after I moved to late models and told him about it.
    It helped the top end pull at the end of the straightaway. We never saw much gain on the intake side, but an unported head needs help on the exhaust side.
     
  26. This thread is like a Picasso painting....WOW
    Figure out what you are going to use the beast for...drag only street and strip.
    You call Crower, Isky or Summit to get the cam and other changes to make the
    car fly. I used 1.5, 1.55 and 1.6 rockers on my dirt modified for different tracks.
    I used a cam that would work on my hometown track. Different gearing for other tracks to keep the rpm's up at the end of the straightaways.

    cart-before-horse-slice-scaled500.jpg
     
    pbr40 likes this.
  27. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,727

    2OLD2FAST
    Member
    from illinois

    What was the jc Whitney story , this cam = 20 hp , these heads = 40 up , this carb =30 hp
    20 + 40 + 30 =90 hp ..
     
  28. 2OLD2FAST
    Joined: Feb 3, 2010
    Posts: 2,727

    2OLD2FAST
    Member
    from illinois

    Carb is California air resource board , whether or not a part can be used in California
     
  29. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,972

    sunbeam
    Member

    Stock 461 heads show very little flow increase over .450 valve lift. 190 cfm only 192 cfm when they went to .600 lift
     

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