425 Camshaft questions.

Discussion in ''Da Nailhead' started by John Codman, Aug 5, 2010.

  1. wkillgs

    wkillgs Gold Level Contributor

    QUOTE=gsgtx
    Guys, a tight LSA makes more PEAK torque/power & often more AVERAGE also!

    >>>> OK, I agree...it just plain makes more power

    QUOTE=gsgtx
    It will make the PEAK power at a LOWER RPM than a wide LSA.

    >>>>I don't see that. Tight LSA makes more power at higher rpm's so the peak is higher, and the rpm is too.

    QUOTE=gsgtx
    A narrow LSA will also have more overlap and allow running higher static compression ratio's due to the "bleed off" of the extra overlap.

    >>>>No, it's the opposite.
    The point the intake valve closes determines the DCR. A cam with MORE overlap (but same duration) would close the intake sooner....INCREASING DCR.
    Overlap is at the end of the exhaust stroke/beginning of the intake stroke, so that doesn't affect actual compression.

    QUOTE=gsgtx
    Race motors running very high compression ratio's also run very large cams partly for this purpose.

    >>>> That has more to do with duration, not overlap..... more duration bleeds off compression (DCR), so with bigger cams, a higher Static CR is used to make up for that .

    QUOTE=gsgtx
    Static compression means very little FYI, it is the effective ratio or dynamic ratio that counts.

    >>>> I believe that is true at lower rpm's, but it changes at higher rpm's since air/fuel velocities and even efficiency increase at higher rpms.


    I think the best solution is for one of us to win the lottery, buy a dyno, and test every cam out there!
     
  2. gsgtx

    gsgtx Silver Level contributor

    Sorry, I didn't mention the duration remaining the same-GSGTX
     
    Custom65GS likes this.
  3. telriv

    telriv Founders Club Member

    A "NAILHEAD" is NOT a SBC!!!!! Nor a SBF!!!! Or any other example out there for that matter!!!!! Just like ALL engines they all have their idiosyncrasies. I am sorry, but how many thousands of $$$$$$ has been spent engine dyno testing just a "Nail" by ones good self????? Or swapping various cams??? You've got some of your figures backwards. Do some more research!!!!! Then come back & tell us WHO HAVE DONE IT what you find out.
     
  4. wkillgs

    wkillgs Gold Level Contributor

    LOL!, I just KNEW Tom would jump in and tell us we're all wrong!:grin: :bla:

    FWIW, My blue car has a big Isky cam with 108 lobe centers and 245 duration. It's sluggish on the low end, but rips over 4000 rpm!

    I went to the other extreme on my red car....Milder Poston NH400 with 114 lobe centers and 218/228 duration. LOTS of low end. Top-end power is 'still to be determined', following a few more beak-in miles and tuning.
     
  5. gsgtx

    gsgtx Silver Level contributor

    just for the record the last 2 posts my friend wrote, he is really in to cams. anyways the 108 cant make up for that much duration.every 10* of duration on the intake moves the power range up 500 rpms.245-218=27 thats moving the range up about 1200 rpms you said the 245 comes on at 4000-1200 rpms. so a 218 would come on about 2800 rpms,I bet it would make peak torque at about 3200 on a dyno.a stock cam comes in at 2800 RPMS with a 209 duration on a 114 LSA.218-209 is 11*so the 218 would move it to 3300 rpms from the stock 2800 rpms. the 108*might move it down to about 3100-3200 rpms. my 218 cam on the 110 LSA with 2x4s makes peak torque at 3400 rpms peak hp at 4750 rpms on the dyno, the 2x4s also moves the peak torque up.mine might peak at 3400 but it stills turns on at 2800 rpms and has more torque at 2800 than a stock engine.
     
    Last edited: Sep 12, 2010
  6. doc

    doc Well-Known Member

    Well, I dont know about LSA , CSA,USA, spca, cia, or any of that stuff,,,:laugh: :laugh: all I do know is that Years ago I stuffed a 091 super cat cam into a 401 engine , straight up on the timing marks,,, and it ran very good.... and lasted,,,, I did not have to do any special thing to it, and it handled big carbs just fine, in fact enhanced them , I think.... and that is all I base my opinion on,,, experience....:Brow: :laugh: I see a lot of guys buy and install a cam that is too much cam for the engine service that they are planning , because they like the way a cam sounds....when a engine is a torque engine and 6000 rpm is the top rpm,, why buy and install a cam that will rev to 8000?????:Do No: and then wonder why the engine dont run as good as we hoped.... Sure i like to hear a good hot cam,,,, in a drag race only engine....but that is what a lot of guys do, they buy , based on how they think a cam will sound.... I hear it a lot, ''man that thing is gonna hit a lick''.....we aint racing cam sounds, we are racing nailheads.....in a way ALL of us are right, no one is wrong on all points,,,, and no one is right on all points... if you put a big cam in a car that has 2.93 gears out back, aint gonna run near as good as it would if it had 4.11's or so gears....for that matter you can take a plain , ''grocery getter'' engine and put a stiff gear behind it and it will really move...for what it is.... look at the whole pkg....:Brow: :Brow:
     
  7. wkillgs

    wkillgs Gold Level Contributor

    gsgtx- was your engine run on a real dyno?
    I want to dyno test a couple of my cars. That's the only way to know exactly what the differences are....I like to see numbers and graphs!:grin:
    BTW, I found the full the article you quoted here:
    http://www.chevyhiperformance.com/t..._separation_angle_performance_test/index.html
    I have to read that later!

    Doc, experience is good, I'm still working on it!:TU:
    Our discussion on the '90' vs '91' cam does raise some questions:
    - Buick rated the early 425 with the hot '91 cam the same as the 66 425 with the milder '90 cam.
    BUT
    - in 1966 they advertised the optional Q-jet GS 401 'with a hotter cam' ,and rated it at 15 extra hp. I wonder if that has the '91 cam???
    ----> Something tells me Buicks' hp ratings weren't very accurate from year to year!

    Big cams..I agree, the big Isky cam in my blue car wasn't the best choice. I was 16 when I started building that motor, and didn't know any better! Still it's hard to argue it's a 'bad' cam when it produces a 13.40 time slip.
    Besides, it does sound awesome!:laugh:
     
  8. CameoInvicta

    CameoInvicta Well-Known Member

    Walt, you've been talkin' about how bad that cam sounds for years it seems. Time to post a video of it :TU: !
     
  9. gsgtx

    gsgtx Silver Level contributor

    yes a real chassy dyno with a straight line power curve from 2800 to 5200 rpms. 395hp at the engine 498 torque.after that i made a few tunning ajustments like jets and timing and a better exhaust system. i would put it at 401hp and 505 torque now.also went to the track ran a 12.80 at 108 mph with a 1.85 not so good 60 ft times. 323 gears 2 speed with a 218-230 cam on a 110 LSA.with a very streetable idle.that was my first nailhead i built. doing another one now with knowing a little more and not making a few mistakes that happen the first time with the engine builder.in a post about 2 years ago if you remember i was talking about the machine shop giving me the wrong pin height.
     
  10. doc

    doc Well-Known Member

    So, there.....:laugh: :laugh: :laugh: :laugh: :laugh:
     
  11. SpecialWagon65

    SpecialWagon65 Ted Nagel

    Awesome real results. Have you weighed your car?
    I like the power curve on my nail too, started measuring @ 3500 @ 450 torque, @ peak hp 4600 still 418 torque and 373 hp. very flat torque. Next week I may be testing again with a 425, W-30-12 cam. I hope to measure starting @ lower rpm,
    Ted
     
  12. John Codman

    John Codman Platinum Level Contributor

    I neglected to say this, But I would like bottom end torque that would rip the Pyramids off their foundations. I don't care what happens at 7,000 RPM because it ain't ever going to get there. It seems that the consensus is wide LSA's for low end torque. Is that right? :Do No:
     
  13. gsgtx

    gsgtx Silver Level contributor

    thank you. it weighs 3720 with me in it. mine came in at 3572 rpms for torque only a few less at 3400 rpms. hp came at 4663 rpms and at 4445 rpms it made only .4 horsepower less than at 4663 rpms. what cam did you use?
     
  14. gsgtx

    gsgtx Silver Level contributor

    i still say no that a wide LSA MAKES MORE ON TOP END THEN BOTTOM. go for a 111 LSA you cant go wrong right in the middle, lol
     
  15. SpecialWagon65

    SpecialWagon65 Ted Nagel

    W-30-10 cam, 232/232/110 .465 lift
     
  16. telriv

    telriv Founders Club Member

    Ted, going to test using the "Rockers" again???? The last Dyno testing we did our HP peaked at 5850RPM's & fell off like a mountain fall after-wards. With the "Rockers" on it held the HP till 7100RPM's & didn't lose 30HP. They CAN breath up top but you have to get the valves open!!!!!!
     
  17. gsgtx

    gsgtx Silver Level contributor

    wow amazing you make horsepower at 7100rpms yet your saying in a post that the heads cant breath and cant work with a 460ci stroker.. and 2* wider LSA can make 20 more peak horsepower difference, that to is amazing.when you agree a tighter LSA makes more peak hp. it like having your cake and eating too. yes i built my first nailhead with alot of help from you,doc,wkillgs and others on this forum but I also kept a open mind and did things different too.
     
  18. wkillgs

    wkillgs Gold Level Contributor

    WOW!:eek2: You da Nailhead king! ( I better get to work:grin: )

    Low-end torque is more a result of keeping the duration spec reasonable. More duration makes more power, but moves the powerband up....and you'll lose low-end torque.

    On Dyno 2003 software***, narrow LSA's make more power at a slightly higher rpm than a comparible wide LSA..... but the low-end power is about the same! ....no loss, all gain!
    I'm not seeing any downsides to the narrower LSA, except for idle quality and engine vacuum. (and fuel efficiency?).
    ***Now Tom tells me the wide LSA produces a flatter torque curve, and the narrow LSA is more 'peaky'......maybe the software doesn't reflect that characteristic on a Nailhead.

    But valve-piston clearance does get tight as duration increases, especially with a narrow LSA.
    The overlap spec is a good indication of trouble.
    Stock 401 cam is minus 19 degrees @ 0.050"
    My Poston cam is at minus 5 degrees, and v-p clearance was snug but near spec.
     
  19. CameoInvicta

    CameoInvicta Well-Known Member

    Walt, are you using actual flow numbers, or the generic crap that came with the program?

    Guys, you also have to remember it's not just a factor of LSA, both also of the intake centerline (ICL). There's a lot of science in camshaft timing - it's not cut and dry.

    Simply chaning the LSA, and keeping everything else constant, a wide LSA will usually provide more low end, and a tight LSA will usually provide more top end. But, if you change ICL at the same time as LSA, then that simple statement will most likely go out the window, because the timing points have all practically changed.

    Also Walt, from what I've researched, we can probably get away with running up to 13* of overlap, if you keep valve lift in check. Obviously if you want to run a lot of lift, you probably can't get away with as much overlap. I think something like the TA413 is probably as crazy as we can get without VP clearence issues.
     
  20. 6671

    6671 Well-Known Member

    From COMP cams:LOW LSA makes more torque <TABLE border=1 cellSpacing=0 borderColor=#333333 cellPadding=3 width=564 bgColor=#333333><TBODY><TR><TD width=554 align=middle>[FONT=Verdana, Arial, Helvetica, sans-serif]EFFECTS OF CHANGING LOBE SEPERATION ANGLE (LSA)[/FONT]
    </TD></TR><TR><TD bgColor=#ffffff><TABLE border=0 cellSpacing=0 cellPadding=5 width=585 align=center><TBODY><TR><TD bgColor=#efefef width=279 noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Tighten [SIZE=-1](smaller LSA number)[/SIZE][/FONT]</TD><TD bgColor=#efefef width=287 noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Widen [SIZE=-1](larger LSA number)[/SIZE][/FONT]</TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Moves Torque to Lower RPM[/FONT]</TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Raise Torque to Higher RPM[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Increases Maximum Torque[/FONT]</TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Reduces Maximum Torque[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Narrow Power band[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Broadens Power Band[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Builds Higher Cylinder Pressure[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Reduce Maximum Cylinder Pressure[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Increase Chance of Engine Knock[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Decrease Chance of Engine Knock[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Increase Cranking Compression[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Decrease Cranking Compression[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Increase Effective Compression[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Decrease Effective Compression[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Idle Vacuum is Reduced[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Idle Vacuum is Increased[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Idle Quality Suffers[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Idle Quality Improves[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Open Valve-Overlap Increases[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Open Valve-Overlap Decreases[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Closed Valve-Overlap Increases[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Closed Valve-Overlap Decreases[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Natural EGR Effect Increases[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Natural EGR Effect is Reduced[/FONT]
    </TD></TR><TR><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Decreases Piston-to-Valve Clearance[/FONT]
    </TD><TD noWrap>[FONT=Verdana, Arial, Helvetica, sans-serif]Increases Piston-to-Valve Clearance[/FONT]
    </TD></TR></TBODY></TABLE>
    LOW LSA makes MORE low end torque!
    </TD></TR></TBODY></TABLE>
     

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