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Cam selection

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Andreas, Sep 22, 2000.

  1. Andreas

    Andreas 1/2 ton status

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    Ok, boys (and girls). Want your thoughts on cam selection for my sb 406, which currently is being rebuilt. The 406 will do it´s duty in my Blazer when I´m done with it, so torque is pretty necessary, although it isn´t ABSOLUTLEY VITAL it puts out 350 ft.lbs at 1500 rpm, or so. It´ll see much more street than dirt....and I´d like to give my buddys 66´Fairlaine a run for its money someday[​IMG].
    So, specs are as follows: 406 cui, about 10:1 comp ratio, Performer RPM intake and ported & polished Chevy "powerpack" heads with 2.02 & 1.6 valves, headers of course. Haven´t decided on carb yet. Either a Holley 600 or my trusty old Q-jet (4MV). Basically, I wanna get the largest cam I can and still go with the stock torque converter[​IMG]. Ok, I could switch to a higher stall one, but I rather not (I´m on a budget here [​IMG]). I will go with roller rocker arms later on, so take that into consideration. I could go with a smaller cam and 1.6 ratio, or a larger cam with stock ratio. Keep the lift under .500 though, I think I have stock springs on the powerpacks. Had my eyes on the comp cams magnum 270 and a set of Rhoads lifters, but the cam selection these days is HUGE so I really don´t have a clue what to get, or what combination to get. And, yeah, it´ll have a gear ratio of 4.56 in the axles and 35 or 38.5" tires someday. Let me hear from you, engine gurus [​IMG]

    Andreas

    406cui of pure sh*t[​IMG]
     
  2. JimmyDie6.2

    JimmyDie6.2 1/2 ton status

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    Trucks are for trucken and cars are for racing..so race your friends Fairlane in a car, unless you have deep pockets. As for the cam.......high lift, short duration. check summit/jegs for their cam suggestions.
    PS-Ford sucks
     
  3. Donovan

    Donovan 1/2 ton status

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    Here is a couple place I would go before you just pick a cam and go. I have screwed up to many times on getting cams that I thought was good.http://www.elgincams.com and http://www.ultradyne.com. Take a look. I would go with maybe around 268-272 advertise duration on a 112 lobe separation.

    Donovan
     
  4. bablazer73

    bablazer73 1/2 ton status

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    IN MY OPINION. the heads are too big. Bigger valves are nice for higher rpm air flow but suffer at low rpm. the air moves slower and lets the fuel turn back into liquid form. I would have chosen a set of heads with smaller valves and smaller intake runners than those heads. smaller intake runners and valves increase intake velocity. results- better low end torque.I would also stay away from "magnum" cams. They use equal lift and duration on intake and exaust. If you are running a full exaust, you could be better off with a cam that has more ex duration and lift. this will allow more time for the exaust to escape. crane cams offer some cams that are designed for 4x4 trucks and not some yahoo kid with a camaro that wants to sound fast. chosing the right cam is one of the most important things you can do to an engine. it alone decides when and where the power band is. research it. call crane cams. I would also considering the smaller valve heads. IN MY OPINION!!!!!

    your right. I don't understand the jeep thing!
     
  5. Andreas

    Andreas 1/2 ton status

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    The heads are newly resurfaced and has new valvestem seals, so I´ll stick with those. I do have a set of 882´s, but they need so much work on them I won´t bother changing. About racing my friends Fairlaine....well I´m not looking to beat him, just give him a match[​IMG]. It´s difficult selecting cams for the smallblock as a cam too large for something like a 262 would be no problems at all for a 406. The reason I´m asking this is I´ve heard of ppl following recommendations, only to discover the cam was way to mild. My Blazer is a fun-only car and MPG is not something I care for. So, what would be a good choice for a 406 with about 10:1 comp ratio ? How about the comp cams Xtreme 4x4 270 ? It has a "in" lift of .480 and a "ex" lift of .498? The spec on it says it likes a 2200 stall torque converter, but I think I can get by with a stock one when I have 56 cui more than the test engine. Of course I´m not sure about what displacement they tested the cam on but I suspect a 350.

    Andreas

    406cui of pure sh*t[​IMG]
     
  6. Roostr84

    Roostr84 1/2 ton status

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    I was thinking of dropping in one of the comp extreme 4x4's in my 383. Right now they look like the best thing going. As far as size, for the same cam the larger the engine the milder it will seem but it is my experience that if you are trying to decide between two different sizes to go with the milder one. Plus you can always add bigger rockers if you want to later, to bring it up a little. Just think about what you are really gonna use this truck for. If you are towing or offroading then you will want the low end torque. If you want a highway warrior then go to a little larger cam. HTH
     
  7. Andreas

    Andreas 1/2 ton status

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    I want something in between[​IMG]. That´s what makes it so hard. One thing though, I wont be doin´ any towing at all.
    Another thing, I´ve heard several bids on what the stock springs can take. Some ppl say keep it under .500, some say keep it under .460 and I know a guy who has a cam with .520 lift on his stock springs, but that is an absolute maximum (according to him) and it´ll probably wear his valvetrain down pretty fast.

    Andreas

    406cui of pure sh*t[​IMG]
     
  8. realsquash

    realsquash 1/2 ton status

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    I would recommend the comp-cams XE268H. A bud has this in his 400SBC and it honks, but works with a stock converter. I also have an xtreme energy in my 454, but that's a little different. Also, make sure you get matching valve springs. Stockers will not work very well with this cam.

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  9. Roostr84

    Roostr84 1/2 ton status

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    I agree that the 268 would be better. The specs on the other one just seem to big for a truck to me. I would say that stock valve springs are effective to about .480 lift i wouldn't trust them to do their job much more.
     
  10. Andreas

    Andreas 1/2 ton status

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    That sounds about right. Counting you guys, there are now 4 different ppl recommending the X4 268 grind. I guess it´ll be one of them then[​IMG]

    Andreas

    406cui of pure sh*t[​IMG]
     
  11. Blue85

    Blue85 Troll Premium Member

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    You can get a rebuilt converter for $100-$150, depending on what it is. Just get one that has a higher stall speed than the stock one, such as for a sports car that used the same transmission that your truck has. When I rebuilt my 700R-4, I used a Corvette converter instead of a Blazer converter. The price difference was about $10 between the two and I got a stall speed of 1996 vs. 1500-1600 for stock one.

    However, I definately don't recommend a very high stall speed for 4-wheeling unless it's all dune blasting.

    Just a suggestion in case you think that the only way to get a little more stall speed is to call Summit and pay $300.

    '85 JIMMY
    '90 paint/grill/trim 5"susp 33/12.5/16.5
    Fresh 350 B&M '87 TH700
     
  12. Andreas

    Andreas 1/2 ton status

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    Uhmm..I live in Sweden, so I wouldn´t call Summit either way[​IMG] Anyway, I hear what you´re saying. A stall similar to yours would be nice.

    Andreas

    406cui of pure sh*t[​IMG]
     
  13. realsquash

    realsquash 1/2 ton status

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    I re-read your posting, and I will change my recommendation a little bit. If this is your play vehicle, why not use a solid lifter cam? You'll get more HP and TQ for a given cam. You should only have to adjust it every 20,000 or so miles if everything is in good shape.

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  14. Andreas

    Andreas 1/2 ton status

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    Sure realsquash. Give me some recommendations on good solid cams. Are the grinds the same as on hydraulic ones?

    Andreas

    406cui of pure sh*t[​IMG]
     
  15. realsquash

    realsquash 1/2 ton status

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    The grinds *can* be the same, but usually they can use steeper ramps than a hydraulic cam. I'd go for a similar dual-pattern cam, only in a solid-lifter design. I don't have my cam books here with me, so i'll go look at the compcams.com site and post back. I would look for something in the 230 @0.050" lift range with a solid model. A little larger with solid lifters.

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  16. Donovan

    Donovan 1/2 ton status

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    I say you can put in what ever cam you want but what kind of vacuum are you wanting? Do you have power brakes? What kind of idle to you want? You want it to idle at 1000rpm's or more. What kind of convertor are you using? Is this a daily driver. Don't forget that you will have to adjust the valve maybe once a year are so. If I was building that engine I would go down to a machine shop that has a flow bench and spend about $50 and have a head flowed and call up Elgin Cams and tell them what you want to do with this engine and give him the flow figures and he will make the cam right.

    Donovan
     
  17. Blazer79

    Blazer79 1/2 ton status

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    A guy once recommended to get a desktop dyno (computer software for about $40). You just input all the specs you have and "try" all the different cams you like. It'll give you all the results without having to spend thousands on the realthing.

    <font color=blue>//////
    http://blazer79.coloradok5.com
    </font color=blue>[​IMG]
     
  18. realsquash

    realsquash 1/2 ton status

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    Yep, that's really the best way to do it. Talk to an engine builder about the cam first. Most of them know the BS from the facts. You have to match it to what you are doing. But there isn't any reason that a solid cam won't give better performance than a comprable hydraulic one for the same RPM range. A solid lifter cam can/used-to-be made to idle like a grocery getter. It just so happens that it is a requirement for 8500 rpm use and that's where they got most of their reputation as being race-only.

    Squash
    http://www.trailrunners4x4.org/users/realsquash
     
  19. realsquash

    realsquash 1/2 ton status

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  20. Andreas

    Andreas 1/2 ton status

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    Donovan. Nearly all of your question is answered in my first two posts [​IMG]. Yes, I have powerbrakes and stock converter. No, it isn´t a daily driver and I´d like a good idle with a little bit of stutter[​IMG].

    That dyno program sounds cool. Maybe a bit far off from the real world but as you said realsquash, it´s interesting for the ability to change a thing and see the result in notime.

    Andreas

    406cui of pure sh*t[​IMG]
     

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