Small block cam with stock valve springs

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  1. Willmopar318

    Willmopar318 Member

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    there is soo many choices out there, what cam can I run with the stock valve springs in my 84 fifth, I'm going to put my edelbrock 4 barrel intake and 650cfm carb and electronic ignition in at the same time. I would like it to sound good and have the low end torque for around town light to light. I'm also going to put my 8 1/4 with 3.23s in too
     
  2. Demonracer

    Demonracer Member

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    Your best bet would be to get a complete cam package (cam, lifters, & springs) so all of the components will work together. Having the heads checked & getting a quality valve job done will give you peace of mind that everything will work together. Spending a little money now beats spending a lot of money later. Mixing & matching pieces can be a nightmare.
     
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  3. 89.Fifth

    89.Fifth Well-Known Member

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    I would go with something like this:
    Crane Hydraulic Flat Tappet Camshafts 693971

    The specs don't give the full cam card but you want something with an intake closing around 46 degrees and an overlap of about 32-38 degrees @.006

    That usually means around 248 degrees advertised. Lift you want around .420 on the intake and .450 on the exhaust
     
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  4. Duke5A

    Duke5A Well-Known Member

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    That cam is 192@.050" duration on the intake side with 1000-4000 RPM range. Is that any better than the factory cam? Sure doesn't sound like it.

    If you're not willing to change springs, then don't even think about changing the cam. If you weren't on the other side of the state I'd say you could borrow my spring compressor. Changing out springs with the heads on the motor isn't that bad. If you got a compressor and a compression gauge, you can take the hose off of the gauge and hook it up to your compressor. Fill the cylinder with air to keep the valves closed while you swap out springs.

    A Comp Cams XE-262H would be a good fit with a 3.23 gear. 218@.050" duration will give it a bit of a lope on the exhaust and has an advertised range of 1300-5600 RPM. With the torque curve starting that low I wouldn't even worry about the factory torque converter.

    Only thing I'm unsure of is the compression ratio. I thought closed chamber 302 heads weren't introduced until 1985. If your heads are open chamber the compression could be in the toilet. Someone else will have to chime in on this.
     
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  5. 89.Fifth

    89.Fifth Well-Known Member

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    I have this:
    COMP Cams Computer-Controlled Camshafts 20-612-9

    And it's down off the line compared to my factory cam. Plus it's pretty lopey for my taste. Everywhere else it's great but to me it's not a fantastic tradeoff. I calculate my DCR to be around 7.7:1 with that and that's considering I'm starting out at 9:1 at best. 302 heads, zero deck, 0.040 head gasket.


     
  6. AJ/FormS

    AJ/FormS Well-Known Member

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    coming from 2.45s, 3.23s are a 32% improvement, off the line.


    Any next bigger cam, installed with a later-closing intake valve angle, will give up cylinder pressure, and thus have LESS power from idle on up to close to the torque peak or even after. Each 3.5 degree later closing Ica (about 1 cam size represents about 5psi.
    Going from a 240 cam(stock) to 252(a 360 cam) is 12*, and half is on the intake side so 6* of pressure loss, so 9psi, about; depending on where they were installed at.
    If you are starting with a low compression 318, in Cedar Springs: elevation 856ft, your pressure may already be less than 130psi, so you cannot afford to lose ANY more pressure.
    If you decide to put a cam into it, it better be a solid-lifter type, which installs at or near the same ICA; else you will be disappointed.

    If after the 3.23s are in, you feel you still need more snap off the line, then install a hi-stall TC, something like a 2800, which my LA318 really liked, also with 3.23s.
    The next go to is a higher compression ratio.
    and the cam is thus last, cuz now you are set up for it.

    At sub 8/1 Scr this should not be on your list, and if you put it there with no other changes, prepare to be slow to 35 (or more) mph with those 2.45s. Or 25mph with 3.23s..

    I like this;
    and this;
    and this;

    There are ONLY two things wrong with using a 318 for a modest performance increase;
    1)the lousy cylinder pressure,
    2)the lousy cylinder pressure,

    Everything is reasonably fine until someone installs a cam with a later closing intake angle; instantly, with no other changes,making a bad situation worse.

    If you want more snap off the line, your #1 modification should be a higher stall TC.
    If you need to sustain that snap, your #2 modification is rear gears.
    If you need more power everywhere,in first gear then you need to increase the cylinder pressure.
    If you need more power in second gear,at higher rpms, THEN you need a bigger cam; but be advised, a bigger cam always always, with no other changes, trades away low-rpm power to get that higher rpm power; that's just the way it is. ......
    Idle lope is a by-product of bigger cam, and tells you how much the low-rpm operation has been compromised. If you put a cam into your lo-C 318, big enough to notice the lope, with no other changes; you will just have created a big lazy dog of an engine from stall to ~3200(or higher). With 3.23s, 3200 is about 30 mph, with a 25.5" tall tire.This is the opposite of what you want.
     
    Last edited: Jun 6, 2020
  7. BudW

    BudW Moderator Staff Member

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    First, valve springs wear out over time.

    Second, 318 valve springs are only good for a certain lift AND for a certain RPM. If you get a 318 to go over 4k RPM (I'm guessing on that number) then you have the potential for valves not closing at a higher RPM. There is more to the story of valve springs than lift, sometimes.

    Third (and by the way), valve springs to wear out over time - so its always good to get new ones and go with ones recommended by the camshaft company.
    BudW
     
  8. AJ/FormS

    AJ/FormS Well-Known Member

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    I've been getting ~4500 out of my smogger-teens with stock parts. The 360 2bbl springs,shimmed up "some", that I have been using, have been going 5000/5100 for me, on stock heads,with 273 gear,and stock HFT lifters lightly preloaded.
    Believe it or not, in first gear, the 318 cam is still sorta pulling at 5000; with the 1973 cam, a 4bbl, small-port intake, TTI's, and dual exhaust.
    But the pay-off is that when it outshifts first at 5000, it then drops into Second gear (A904) at 2960, right in the fat part of the torque curve, and with 3.55s, this is 44mph, so away we go! 60 will be ~4200, right on,or very close to, the power peak.....
    IMO, with a 2800TC, for a streeter, this is a great combo . With factory parts and machining, it's probably as good as it gets.