425 Camshaft questions.

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

  1. telriv

    telriv Well-Known Member

    Bob was doing 12.80's in late '79, early 80's. Our best to date is a tire spinning 11.08ET@122MPH. The 60 fts. went up accounting for the 11.08. If the 60 ft. would have remained the same that 11.08 would have been a 10.8!!!!! The low compression, fairly heavy '51 Henry J, street driving, has run a best of 11.18ET@119MPH. Same ole story, we're all looking to go faster.
  2. 6671

    6671 Well-Known Member

    Comp cams chooses the ICL's and that is what creates the LSA. If the duration someone wants is high and they open it early, say 10* BTDC, it will close too early and create too much comporession. A small cam can act like a larger cam with higher cranking compression. Just close the intake sooner. Opening the exhaust lobe sooner also helps top end.
    As far as a rocker making the nailhead rev to 7100rpm and still not drop off less than 30HP is truly amazing. How did somebody determine that the stock rocker was flexing so much to limit the lift ratio to a 1.4:1?
    Well, the O-lap is 13.4*, just at the limit for stock pistons? If anyone gets aftermarket pistons and plans on a larger cam be sure to get notches. Wasn't this cam tested before? I would think it would make it's power at a higher rpm range due to the high durations but it is also a regrind of an old nailhead 109* cam, right? That makes the ramp different due to the smaller base circle. It was also designed for a 455" motor, right, so it will actually act like a larger cam in a 425/428" if bored oversized.
    How is the "Lobe area of 24.52*rpm determined as I have not seen this vefore and that is what GSGTX was speaking of when he told about the advaces in cam tech. The 218* lobe actually has a duration of 131* at .200" lift according to the Comp lobe data. A highnenergy cam has 124* at the same .200" lift. This is the lift where flow really counts. The .050" is a standard so we can actually know the difference between cams and manufactures. ADVERTISED durations could be rated at .001. .002, .006 or even .000" of lift. I have an advertisement for the stage 2 cam from buick and it says the exhaust lobe has 360* duration, IT NEVER CLOSES!
    I would be ineresting to see the cam installed at 2* advanced, 4* advanced and straight up. I bet the early advance would be the quickest, IMHO anyways. Have an adjustable cam gear? Tony
  3. 425 2X4 Nailhd

    425 2X4 Nailhd Well-Known Member

    It is possible to have over 360 dgrees of timing on the valve open period as it is taken at the crank which has 720 degrees total. Remember the cam turns at half speed.
  4. gsgtx

    gsgtx Silver Level contributor

    thanks for posting this,it should help everybody pick out a camshaft.
  5. funkyriv

    funkyriv Well-Known Member

    what are the other specifications on your cam from CompCams?
  6. gsgtx

    gsgtx Silver Level contributor

    218*-230* at.050. 262*-280*at.006. 504-490 lift with 1.6 rockers. 110*LSA 108*center line. it has super fast ramp.close to a roller cam.its on a XFI lope on intake which is really a roller cam specs.no way you can run stock valve springs with this cam.
  7. wkillgs

    wkillgs Gold Level Contributor

    Andy, I do most of my comparative Dyno 2003 sims using the stock flow data from Mike Kamm.
    VP-clearance.....Based on what I've measured, Any overlap at 0.050" may result in v-p clearance under 0.100"! I would like to hear if you guys have different results.
    Isky has a method called VOTC to determine if their cams will fit an engine.
    I wish all manufactures would adopt those specs. Sure would make it easier to pick a cam.

    Tony, I measured mine and got a ratio a little over 1.6 with the stock rockers at max lobe lift. Tom's Rollers gave me 1.9 ratio, and some adjustables (Buick or Gotha, not sure) gave me 1.5 something.
    I have no idea what actual lift is at 6000 rpm tho!

    Damn, you're making some serious power with a cam with rather mild specs!
    Your results show that true cam performance is more than just advertised specs.....it's the lobe design that does it.
    I've been getting the impression that Comp Cams is probably the most progressive designer out there. Wish they would add some Nailhead cams to their catalog. All they list now is the Thumper series.
  8. funkyriv

    funkyriv Well-Known Member

    Thx! i wouldn't know a super fast ramp XFI roller lobe from any other camshaft lobe profile if you hit me over the head with it LOL. how do you spec a roller or any other profile? Not sure why Walt thinks 1/2" of valve lift is mild on NH. isn't that 50-70thou more than others?
  9. gsgtx

    gsgtx Silver Level contributor

    its not only the cam but a little of everthing,i had head work done,light weight pistons,even the lighter wheels,the fresh air scoop, roller rockers,headers with x pipe. in another post i said i had the 2 smaller air cleaners on the 2x4s.when i was on the dyno took them off it pick up 14hp and 22 pounds of torque.never would of guess that.
  10. wkillgs

    wkillgs Gold Level Contributor

    Erik, I'm looking at his duration specs of 218/230, which I'd call moderate....about the same as my Poston NH400.
    Hey, did your Comp Cam data card say what lobe design was used?
    I just found the 'cam Lobe Master catalog' on the Comp Cams website.....look under "information', then 'online catalogs'. It list specs for all their lobe designs.
    The Isky site has similar info on their site.

    Comp lists 'tappet lift at TDC' which should help determine a cams valve-piston clearance! (geeze....I'm such a geek)
  11. 6671

    6671 Well-Known Member

    Find the lobe numbers for that XFI lobe that GSGTX spoke about. Teah it has 218* at .050" lift BUT at .200" lift it has 131* duration. More than any other hydraulic lifter cam that Comp or any cam mgrinder has. That 218* is more like a Dual Energy Hydraulic intake lobe rated between 223* & 227* at .050" as the former has 128* duration at .200" lift & 134* duration at .200" lift. The XFI has a QUICK ramp!
    For PTV clearance it is duration that causes the piston to hit the valve and not lift. Usually between 5* and 10* ATDC is the closest point so when degreeing the cam measure the PTV also as most do NOT do this.

    The Thumper even surprised Comp as the article when the cam firsat came out stated that the Comp engineers thought they had reached the zenith of hydraulic cams went. The Thumper has that 107* LSA & a 102* centerline, that opens the intake lobe EARLY! The exhaust lobe of course has a centerline of 112*, a late opening for an exhaust but the high duration is what helps that make power up top. As GSGTX stated it is the combo that makes the power. If one had the cash and got a roller that would open the valves even quicker and rollers actually don't need as much spring prsssure as many might believe. It is the cost that prohibits the use of them but back in the day(Tom?) that they were more common in race applications anyways.
    Maybe we could get Jim Bell to add to this forum? How old would he be now? He's a sharp Businessman at least. Making a SC for the Mustang with the tens of thousands of them on the road was a very smart idea. Too bad he left the Buicks though now that the cars are becoming as popular as they were back in the 70's but there does need to be more testing by nail owners and not just one guy. I guess Tom was pointing at me b ut he seems to be the guy who has spent the thousands testing but I would ask, "WHEN"? Remember times change. The W30-10 cam may work out OK but not make much more if at all over the 218/230 specs that GSGTX uses. 232* is too much for a nailhead. GSGTX knew that the nail was a torque motor and worked within those parameters and this results speak for themselves. Tom stated a guy was running high 12's back in the late 70's but with 3.23's and a 2-speed? Maybe with 4.10's and a 3-speed or 4-speed. How about stret cars. Even Lennie "Pop" Kennedy ran low 12's with a nail with 4.30's and open headers, imagine what he would have said to 3.23's and a stock 2-speed? I read about the availability of an adapter for the 700R4 tranny for just $295. if that is a complete kit it will open a lot for nails as I had stated that a 3.55 gear could be used and in first gear have a 10.xx:1 ratio plus the converter's multiplication, can you say big slicks!, and in OD be running in effect a 2.41 gear. Heck go 3.73's or whatver gets the motor to hit the traps at the max rev point and still have a 2.54 gear when in OD! Cruise at 65mph at 2300rpm or so.
    Make a name for the nailhead. Get some magazine time and the other guys wuill come out of the woodwork and maybe the manufacturers will finally make what the nailheads need, more MODERN parts like those cams that GSGTX runs. How about your car GSGTX, send some pics and numbers to every mag that does articles on old muscle and you never know! The, UGH!, AMC guys have gotten a lot of play in the mags and they can get about everything a Chevy can for their motors. How about a modern header, stepped to a 1 3/4" tubing? Imagine an Edelbrock RPM intake? Pistons with the pin relocated up so the weight could be dropped a significant amount. 4 valve heads, possible? No engineer here but even 2 small valves would beat the single small valve of the nail. Still be a nailhead too as it would have to fit the stock intake and exhaust manifolds, just change the rocker assembly. Don't some heads even have a pushrod running through the port on some motor?
    Some forums have monthly 50/50 rsaffles for parts and the extra goes into a fund for doing some of the things I have listed, even if the manufacturers say no it may get some/even one thinking but it will take numbers. Remember when Doc or Wilkill spoke of a single 4-bbl. intakle, suddenly TA was working on one! No vendor wants to be left behind as they are racing also, for our cash! Just some food for thought. Tony
  12. gsgtx

    gsgtx Silver Level contributor

    the NH400 has a 272 duration at .060 comp cam has 262 at .060. the comp shows a faster ramp. 262 to 272. both at 218 at .050. the NH400 is on a 114 LSA comp 110 LSA. these two cams will act, perform,and sound different. lobe# 5085 intake 5216 exhaust
  13. 6671

    6671 Well-Known Member

    The hydraulic roller would be an awesome choice except it is cost prohibited. Lobes 3014 for intake, 218* at .050" but a whopping 143" at .200", the exhaust lobe #282 has 230* at .050" but 152* at .200"!

    That's 12* more intake duration and 12* on the exhaust, that is a quick opening cam!
  14. wkillgs

    wkillgs Gold Level Contributor

    A couple of cam comparisons:
    Edit: Lift and duration as measured on the camshaft lobe.
    Stock 66 401
    Duration at 0.050": 209 degrees
    Duration at 0.200": 111 degrees
    Lift: 0.267"
    Duration at 0.050": 208 degrees
    Duration at 0.200": 106 degrees
    Lift: 0.261"
    Lobe separation: 114.5 degrees

    Walts Poston NH400
    Duration at 0.050": 218 degrees
    Duration at 0.200": 125 degrees
    Lift: 0.302"
    Duration at 0.050": 228 degrees
    Duration at 0.200": 135 degrees
    Lift: 0.306"
    Lobe separation: 114 degrees

    GS-GTX CompCams 218/230-110
    Duration at 0.050": 218 degrees
    Duration at 0.200": 131 degrees
    Lift: 0.315"
    Duration at 0.050": 230 degrees
    Duration at 0.200": 137 degrees
    Lift: 0.306"
    Lobe separation: 110 degrees

    Eriks Compcams 224/231-112
    Duration at 0.050": 224 degrees
    Duration at 0.200": 133 degrees
    Lift: 0.313"
    Duration at 0.050": 231 degrees
    Duration at 0.200": 140 degrees
    Lift: 0.320"
    Lobe separation: 112 degrees

    Duration at 0.050": 218 degrees
    Duration at 0.200": ??? degrees
    Lift: 0.296"
    Duration at 0.050": 228 degrees
    Duration at 0.200": ??? degrees
    Lift: 0.309"
    Lobe separation: 112 (or 110?) degrees

    On the Dyno 2003 software, the 4 aftermarket cams perform VERY closely.
    It's not a perfect simulation, but it gives a general idea.
    The Poston NH400 falls off over 4000rpm.....but it does make the most low-end torque.
    Erik's Comp cam has the most duration, so it loses some low-end but has a great top-end.
    I'm impressed with how well GS-GTX's cam performs. It's right there with Erik's bigger cam at the top end, and has good low-end too.
    I have to point out....Real world results may vary!

    Back to John's original post....While the TA-25 would be a good mid-level choice, I'll bet CompCams could build a cam that optimizes your requirements.

    Attached Files:

    Last edited: Sep 22, 2010
  15. kitabel

    kitabel Well-Known Member

    rollers actually don't need as much spring prsssure as many might believe

    Not sure what you mean?
    The roller lobe can be designed to have comparable maximum acceleration and velocity rates as a flat tappet cam - but that removes a major advantage to using them.
    If the accel or vel is high, the spring rate must be high.
    The extra tappet weight (taller body + roller wheel + link bar) always requires more spring pressure.
    A roller tappet suffers severe damage from float off the lobe, and frequently high seat pressure is recommended to prevent this - a rev kit (which loads the rollers even when lashed) is very helpful.
  16. gsgtx

    gsgtx Silver Level contributor

    Walt,for the heck of it hows the stock cam do
  17. 6671

    6671 Well-Known Member

    Eriks Compcams 224/231-112
    Duration at 0.050": 224 degrees
    Duration at 0.200": 133 degrees
    Lift: 0.313"
    Duration at 0.050": 231 degrees
    Duration at 0.200": 140 degrees
    Lift: 0.320"
    Lobe separation: 112 degrees ** ERIK's cam card should say it has a 114*LSA with a centerline of 112* as it must ahve 2* advance ground into it. Check that out please. **

    Erik could you post the rest of your cam card data? Such as the installation centerline and intake close point and exhaust open degree? You should have 1.75* of overlap. The centerline is wghat I am interested in as Comp almost always grinds advance into their cams, 4* on later motors and 2* on older ones like yours. I would ecpect a 110* centerline. Comp knows an earlier intake valve opening makes more low end grunt as does the early exhaust opening but the exhaust is actually retarded when the cam is advanced. If straight up yours would have the exhaust centerline at 112* but I would say it is at 114*, that is 114* ABDC, 2* later than a 112* c-line. Gets confusing, huh? Does the stock cam really have .27x intake lobe height?

    That intake lobe has the exhaust lobe spec. it is rea1lly an extreme energy lobe that at 224* could have 2 choices, 134* or 137* at .050: but the latter has .505" lift on the intake. The 231* withg 140* @ .200" lift I could not find, have a lobe number?

    In the XFI family the 224* has 138* at .200 and a choice on 231* exhaust lobes, 143* or 154* with the latter having .547" lift and that intake at 224* has .520" lift, aftermarket pistons and notchers a MUST! On a 111* LSA that GSGTX suggested it would have 6* of O-lap.

    You can see why GSGTX said cam designs have come a long ways since the days of K-B camshafts and the old school cams are OLD! The E/I ratio is targeted at 75%, exhaust flow divided by the intake flow. It is quite possible to have an even wider split due to the anemic exhaust fdlow even after being ported. A stroker could use that larger exhaust lobe since it would have notched pistons and have lift numbers of .520 on the intake and .547 on the exhaust at a 1.6 rocker ratio.
    To paraphrase Tom the motor needs to breathe. The XFI cams sure do that!

    Thanks for posting all of that cam data! By the way that "091" cam is just about exact as the one used early 109* LSA instaed of a 114* so that is where that seat oif the pants feel came from as the only thuing we can "feel" is torque and that 109* made more peak and also came in earlier with torque. Roller rockers do is raise the lift which has a small effect on durations and it would also have the torque come in a tad earlier and coupled with the bottom end torque of these motors it sure would seem to have a lot more quicker and really down low. ( They are strong also and have less parasistic HP drag)
    Since the stock aluminum rockers are available adjustable now I wonder if they could take the spring pressures that the XFI lobes require? Anyone ever broken one, bent any? Saving the cost of roller rockers for the lightweight stock rockers would add another 15HP as that is what is claimed on those isn't it? Lightweight "beehive" springs if available for the nail and those rockers would make for a light rocker assembly for sure!~ Smaller diameter valve retainers, lighter weight. Problem is these are not drop in cams and a total rebuild is likely needed and not many Buick guys have that kind of cash to spend on a play type of ride. Where is Jim Bell?
    His nailhaed build up could be beaten easily with a car like GSGTX has and likely the 13.4x ride also, heck some tuning may be what that needs, advance that cam a couple of degrees and make use of it in a better way IMHO!
    Last edited: Sep 19, 2010
  18. 66gsconv

    66gsconv nailhead apprentice

    Hey Walt, could you post what you mesured on the stock cam and nh400 with Toms rocker.I was wondering how much they changed the duration ?
  19. telriv

    telriv Well-Known Member

    Bob, since the opening & closing points remain the same duration is not changed. If it is it will only be by 1* or 2*. Where the "Rockers" make the biggest difference is the ramp rise & the "Total" amount of valve lift. The quicker the valves are opened the faster the cylinder will start to fill when the pulling power of the piston on the intake stroke is pulling the hardest. The faster the cylinder starts to fill the more power will be produced. And, within reason, the higher the valve lifts the more fuel & air mixture will fill the cylinder. Why do you think that Buick used such a fast ramp rise. The "Rockers" only enhance that rise by make it even quicker. understand????

    Tom T.
  20. wkillgs

    wkillgs Gold Level Contributor

    Here's the Poston NH400 cam
    Actual valve lift/ then duration...with stock rockers/ vs Tom's rollers
    Stock rocker ratio approx 1.6:1 @ max lift
    TT Roller ratio approx 1.9:1 @ max lift

    Max lift with stock rockers= 0.493"
    Max lift with TT Rollers= 0.550"
    Lift/ Stock rocker duration/ Roller duration/ change
    0.100"/ 205 deg/ 211 deg/ +2.93%
    0.200"/ 167 deg/ 176 deg/ +5.39%
    0.300"/ 130 deg/ 145 deg/ +11.54%
    0.400"/ 86 deg/ 110 deg/ +27.91%
    0.500"/ --0---/ 60 deg/ :grin:

    Max lift with stock rockers= 0.488"
    Max lift with TT Rollers= 0.555"
    Lift/ Stock rocker duration/ Roller duration/ change
    0.100"/ 217 deg/ 223 deg/ +2.76%
    0.200"/ 175 deg/ 186 deg/ +5.91%
    0.300"/ 138 deg/ 154 deg/ +11.59%
    0.400"/ 93 deg/ 120 deg/ +29.0%
    0.500"/ --0---/ 69 deg/ :grin:

    While adding the higher ratio roller rockers doesn't add duration to the seat-to-seat duration, they do make a SIGNIFICANT improvement at the higher valve lifts!:TU:

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