single pattern versus dual pattern cams - is one "better" for street apps?

Discussion in 'High Performance Modifications' started by 76_TypeLT, Oct 1, 2010.

  1. 76_TypeLT

    76_TypeLT Veteran Member Lifetime Gold Member

    5,941
    41
    Jul 26, 2008
    Houston, TX
    So please excuse the noobie question, I am still learning more about cams (and other things). In the Vizard book I am reading, he is a proponent of single pattern cams (particularly for street type applications). As I am browsing cam companies' catalogs I see that pretty much all off-the-shelf cams are dual pattern (at least for hyd roller "street" cams I am looking at). Is there some reason that I don't see any single pattern cams? I am sure this is not a question that can be answered easily, but maybe the more relevant question is why would someone choose single over dual (or vice versa)?

    From my catalog browsing, it seems like the cams that would be most appropriate for my build have 6-8* more exhaust duration @ 0.050.

    I know I can get any cam grind that I'd want, so mostly curious why all I see in the catalogs are dual pattern.

    Thanks for helping me better understand all this!
     
  2. 489cid

    489cid Member

    82
    0
    Sep 29, 2006
    Aurora CO
    The main reason for dual patter cams as explained to me was the longer duration on the the exhaust side was to cover up the shortcomings of the head design. The exhaust side needs help to keep up with the intake. which sounded good to me, but could just be a pile of bs.
     
  3. hhott71

    hhott71 Veteran Member Lifetime Gold Member

    14,371
    0
    Mar 30, 2001
    Joplin Mo. 64801
    Both have been successful in the SBC.
    Find one that has the proper intake duration you need and the exhaust will be fine with the wisdom of the cam designer.
     
  4. 76_TypeLT

    76_TypeLT Veteran Member Lifetime Gold Member

    5,941
    41
    Jul 26, 2008
    Houston, TX
    I see, interesting.

    So not necessarily a huge advantage to running one versus the other in your opinion?
     
  5. high impact

    high impact Veteran Member

    135
    0
    Sep 14, 2010
    NW Indiana
    IMO if this is a street car then it doesn't matter much. Choose what works best for your total combination and the engine's intended use. Torque is what is most important in a street car along with everything matching the power band. I think most new cam profiles from reputable companies will be dual pattern as they attempt to squeeze every bit of power out of them.
     
  6. CNC BLOCKS

    CNC BLOCKS Veteran Member

    1,603
    1
    Oct 11, 2004
    NORTHEAST
    We use a lot of single pattern cams for most of ou builds more so when we are running a tight lobe seperation like 108 or 110

    Wider lobe seps do require more exhaust lobe from what I have seen.

    I see alot of guys who have good flowing heads like AFR's who will put a 10 split in them which kills the lower end and mid range.

    We build a lot of circle track engines and some of those engines require a single pattern cam do to the good exhaust they run.

    Here is a quote I did on another site on a HYD roller for a guy and we have seen very good results using this cam.

     
  7. 76_TypeLT

    76_TypeLT Veteran Member Lifetime Gold Member

    5,941
    41
    Jul 26, 2008
    Houston, TX
    Good feedback, thanks. So for a street machine, it's not much of an issue (if any).
     
  8. CNC BLOCKS

    CNC BLOCKS Veteran Member

    1,603
    1
    Oct 11, 2004
    NORTHEAST
    We run tighter lobe seps with single pattern cams ans so far on the dyno we proved it works!!!

    Good luck
     
  9. Todd80Z28

    Todd80Z28 Moderator Staff Member Lifetime Gold Member

    10,795
    1
    Jun 11, 2002
    Northern VA
    I thought it was basically about the cylinder head. I've seen it written that heads with high exhaust/intake flow ratios benefit from single patterns, whereas heads with weaker ratios require the split that favors the exhaust.

    I've done both with my engine- a single pattern first, and a wide split later. I have Trick Flow G1 heads, that flow 230-240 on the intake, and close to 200 on the exhaust. That's a high ratio, 80%. I ran the Comp 268HE for the first several years (218*, .454" lift), and then moved to the ZZ4 hydraulic roller (207/222*, .479"/.514") that's still in there. Overall, I think I had better throttle response with the single pattern. One thing I do know- I *CANNOT* make the engine happy unless it is idling fairly rich- it stumbles all over itself otherwise. Pipes are sooty on the inside, and I have tinkered for years trying to fix. I think it's over-scavenging because of the strong exhaust port. I'd like to go to a single pattern roller (something like Comp's 270HR 215*, .500") to see how it feels in comparison.

    That's just one experience, though, not a pro builder's.
     
  10. wookie

    wookie Veteran Member Lifetime Gold Member

    3,049
    0
    Jul 12, 2006
    Daytona Florida
    Nitrous likes extra duration and lift so we use split pattern cams on spray engines.
     

Share This Page