Camshaft decision between two cams

Discussion in 'Engine Topic' started by kpb, Feb 27, 2020.

  1. Allen B

    Allen B New Member

    Messages:
    17
    Likes Received:
    10
    Joined:
    Jan 1, 2010
    Location:
    Powder Springs, GA
    I have built my 383 three times over the past 20 years, (all with the same bottom end which is 9.8 compression, same trans, rear and car) I would recommend aluminum heads over vortex due to their ability to dissipate heat better and in large part flow better. The heat dissipation will allow for more timing and lower octane gas without detonation. Your cam choices will not generate enough hp in higher rpm range for head flow to matter much. A good set of 2.02 or 1.94 valve GM heads from the 60’s or 70’s will provide adequate flow, vortec’s, and aftermarket will flow even better.

    The heads I have used for the past five or so with great luck are in the below link. They come fully assembled and set up for FT or roller hydraulic cams, make that choice before you buy the heads so you don’t have to buy valve springs.

    https://skipwhiteperformance.com/ca...minum-heads-64cc-straight-plug-nkb-274_92658/

    In 383 combo#1 I used the Holley system max II kit which had Holley heads that included a lunati cam very similar to your suggested cam. The lunati power was strong in the idle to 4,000 range and flattened out. The lunati cam lost a lobe at about 20,000 miles, but in fairness I was not using oil with proper zddp and pot ash content. This is how I learned that lesson and did 100’s of hours of research on oils. More on oil below...

    The second 383 set up used a comp cams XE 274 cam which is a bit bigger than you are suggesting. This cam will require non-stock valve springs that will be in the above suggested heads. It will also require a mild stall converter, mine is a 2,200 stall which was plenty for the cam.. Idle characteristics were medium lope but very streetable and still pulled about 12 lbs of vacuum. This configuration was my favorite in retrospect and would have left it alone but lost oil pressure at idle due to cam bearing failure. This cam pulled from idle all the way to 6,000 rpm’s, it sounded good at idled, lope was not obnoxious in traffic and pulled like freight train through the entire rpm range.

    The third and current 383 set up uses a Howard’s Hydraulic roller cam, comp roller lifters, and the above recommended heads set up for a roller cam. Much bigger lift & duration in this cam because a roller will allow such with reasonable idle characteristics. I am a little disappointed that the off idle is a little lazy compared to the EX 274, I strongly suspect due to the heavier roller valve train and additional duration. I don’t recall the exact cam specs but are roughly 235/240 duration at 50, and .600 lift. The retrofit roller valve train is also noisy, more like an LS engine. The engine flattens out a little above 5,000 rpm’s but generates noticeably more mid-range power.

    If you are concerned about the flat tappet cam failure pay the extra $100 to get it nitride treated (this may require ordering the cam from the manufacturer or through a live person at Summit or Jegs). Also a MUST use high content zddp and pot ash oils. The two that have the proper amount in independent lab testing are Valvoline VR1 and Royal Purple HPS. Not any Royal Purple, only Royal Purple High Performance Street both of which you will likely have to order from Summit or Jegs. Use a good mineral based break in oil, Driven, Comp Cams, Royal purple break-in and many others will due. I typically change the oil in the first 250 to 500 miles, this allows not only for cam/lifter to wear in but rings and bearings to seat as well. I am a fan of driving easy the first 1,000 miles, alternate rpms, no WOT, minimize highway runs to keeps rpms alternating. Old school I know but it works.

    my son has a 68 mustang with a 347 stroker and the XE 274 cam and it is awesome, but he has a manual and lighter car.

    I am a fan of the Comp XE series cams, they have excellent power bands, generate terrific power for their cam size and are reasonably priced. Especially compared to a roller even if you pay extra for nitride treatment on your flat tappet cam.

    I have another car 1980 Z28, totally stock 350 except a comp XE 256, and the power difference the cam only made when the engine was refreshed was unbelievable. Once the car warms up you can’t even hear it has a cam, very tame.

    In the final analysis I would recommend the nkb heads in the link above, and a nitride treated comp cams XE 256 or XE 268, dual plane intake and 650 or 750 cfm carb. 750 cfm would probably work better with vacuum secondaries in a heavy car with a tight stall converter. These will get you low to mid 300’s HP and generate good torque with mild to stock idle characteristics.

    The comp cams website has a desktop dyno called “cam quest” that will allow you to put in your engine specs, choose different cams and provide a power and torque curve. I have found it to be very reflective of reality.

    Best of luck!
     
    kpb likes this.
  2. Misfire

    Misfire Member

    Messages:
    51
    Likes Received:
    1
    Joined:
    Jan 27, 2007
    Location:
    Doraville
    Dude! Thats pretty big cam for smallblock with AC to deal with on the street. I've always been a BB person which you can over cam to the moon, But with a smallblock I wouldnt go over .500. Just did some work on 79 vette that had around .500 ish motherthumper in a 10:1 350 that i thought was perfect for it, really sounded good and ran great, just my 2 cent's. Forgot that your running a stock converter? I Dont think anyone of those will work.
     
  3. jeff swisher

    jeff swisher Veteran Member

    Messages:
    1,667
    Likes Received:
    536
    Joined:
    Apr 26, 2018
    Location:
    Yukon Oklahoma
    The lift is not a big issue especially today with the excellent valve springs we now have.
    High rocker ratios get you another benefit.
    235-240@ .050 can be pretty "tame" in a 383 and do realize not all cam lobes are created equal .

    I run the comp magnum 280H for my personal daily driver that does pull heavy loads often in my 350".

    Decent MPG and great power, 350" and it will break the rear tires loose with light power brake at 1500 rpm. Yea a pretty tight converter in it. Works well for heavy pulling.
    When race time comes I slap in my 4500 Stall coan.. but I ran that with my 268H cam also for better ET.
     
  4. Silverback

    Silverback New Member

    Messages:
    2
    Likes Received:
    1
    Joined:
    Feb 7, 2013
    Location:
    DC Metro
    Well, I'm going to go against the trend, mainly because you're ending up with a badly matched combination with either cam, and you're building a lot of cubes, fairly high compression for the combination and I'm assuming standard pump gas, carb/old school ignition, and then adding even more load down low with the stock converter and gears (FWIW, even a stock engine, stock cam will usually be happier with a slightly taller than stock stall converter) and all this is going in a big/heavy car. The problem with all this is that you'll be fighting detonation all the time with the smaller cam, the much bigger advertised duration of the CC cam and tighter LSA will bleed off some of that pressure and make it run better on pump gas. I suspect that with the lunati you'll get stuck running premium and/or severely retarding the timing to prevent it from pinging on a hot summer cruise...
     
  5. RxRmechanic

    RxRmechanic Member

    Messages:
    42
    Likes Received:
    13
    Joined:
    Jan 17, 2020
    While I suspect some of you may have strong opinions about what I'm about to suggest... Please understand beforehand that I don't mean to start a firestorm. Just bringing a ponder to the think tank. Don't shoot! Just like so many of you, I'm a truth seeker. After doing significant research, I've come to the conclusion that for camshaft's cryogenic treatment MAY be an option worth exploring if you're really dead set on staying flat tappet with you're cam choice. This treatment changes the structure of the material creating unsurpassed protection against wear. I was informed that camshafts take well to it, lifters not so much.. You can likely find a vendor nearby if you search local. I found one local (Vietnam Veteran) who did this for the Navy during his career and started business post retirement. Unfortunately, he's passed away. So, they're out there! Please, do your own research if you're as skeptical as I am. Myself, personally.. I want to stay flat tappet on the street for logical reasons of my own. I know I'm not alone. Some people swear by 'em and some swear at 'em but rhoads lifters ( I don't believe) are not junk thrown from a Maersk container from God only knows where into a branded package by a couple of temp-agency meth heads. Ditto with what COPO said: The "laser hole" lifters IIRC, sold by Crower. Hey! Great!! Those are special pieces that someone's breathing on and are intentionally purpose built with some sort of quality control and attention to detail! Worth the extra loot on a gamble if you ask me. After countless hours of research and reading countless blogs over the years, I've come to this ugly conclusion.. There's a couple of brands that have such a wide swath market, they just don't care anymore if you're ft cam gets wiped and trashes your investment. (consider how UD Harold was treated) As far as they're concerned they'll always have another excited stupid hillbilly in line to sell their magazine hyped products to. As long as they have an army of die hard loyal customers to defend their failures on ZDDP they'll continue to skimp on quality control and attention to detail to turn around and say "Oh sorry to hear about your bad luck, we'll sell you another ft cam or hey, how bout a roller set up for another cool $1200.00 buddy".. So, it strikes me as.. They don't seem to care about you or your investment when it comes to running a flat tappet for whatever your personal reason. Bottom line. Not a rant. Just another man's opinion.
     
  6. G72Zed

    G72Zed Veteran Member

    Messages:
    1,937
    Likes Received:
    779
    Joined:
    Sep 8, 2015
    Location:
    Canada
    Good points RxRmechanic, and if the concern with Nitriding a cam treats the outer shell, but perhaps softens the core, you can always look into some "Tool Steel' lifters instead.

    They are expensive, but can be used on multiple cams for R&D, and being rebuildable (refaced), it may be the right option in some cases. The ones from Trend & Howards come with the offset EDM in the solid version that I like.
     
    RxRmechanic likes this.
  7. Plant Engineer

    Plant Engineer Veteran Member

    Messages:
    404
    Likes Received:
    108
    Joined:
    May 17, 2017
    Location:
    Fort Mill SC
    I'm an ME and I have colleagues who are metallurgists and we have had good discussions on cryo treatments. I read a lot of the white papers on the subject etc. Cryo treatment has its place with tool steel although its really part of the initial stress relief process after heat treatment. It is completely and absolutely worthless as in a total waste of money on cast cam lobes. It does nothing. Nitriding, which is a surface deposition process is useful and widely practiced already.
     
    RxRmechanic likes this.
  8. RxRmechanic

    RxRmechanic Member

    Messages:
    42
    Likes Received:
    13
    Joined:
    Jan 17, 2020
    THAT is good information to hear coming from a metallurgic specialist. So some people swearing by it is like a placebo affect. Be it rotors, timing gears, chains, transmission parts etc. A lucky coin if you will.. Well I'll be doggone. Standard run of the mill hydraulic FT lifters are machined cast steel are they not? The tool steel solid ft is definitely worth the money for a serious stick on the street! G72Zed, right on!
     
  9. Plant Engineer

    Plant Engineer Veteran Member

    Messages:
    404
    Likes Received:
    108
    Joined:
    May 17, 2017
    Location:
    Fort Mill SC
    Its like CBD oil. If it works for you thats great but there isnt much science behind it. Yeah most cryo treatment is snake oil. Its part of a stress relief process after heat treatment. For that it works but its not going to do anything to a cast iron cam.
     

Share This Page