Tony D Posted August 18, 2007 Share Posted August 18, 2007 A cam when ground is only as good as the guy grinding it, and is really NOT a 'bolt-on' part! You have to degree it, of course, but beyond that, you need to make a few dyno pulls a couple of degrees advanced and retarded to see which setting gives you the best compromise. Our Bonneville engine was PEAKY as hell and had trouble between the gears set 'straight up' we ended up making some dyno pulls advanced and retarded and found that at 2 degrees our torque band widened almost 2000 rpms! We didn't loose one bit of top end power (maybe 2HP as I recall) but we had a torque plateau that now went from 4000 rpms up, instead of starting about 5700 rpms and pulling to 8200! 2 degrees! Does that mean the cam grinder was off on his settings 2 degrees when he ground it? Does that mean the design of the valve opening and closing events was off two degrees when it was designed? Or, more likely, with the setup we had we got the best results at THAT specific point? I tend to think it was a combination of the grinder being inattentive, and us simply correcting an error that seems insignificant. FWIW, at four degrees we lost both torque and power, and going to the other extreme didn't net anything at all, and in fact was a net loss at every station. So what I brought away from it was 'it was close, but we had to make it right'---it was dialed in---what the cam card said was where the events occurred, but dialing it in to the engine regardless of what the cam card says is what netted us the ability to pull the next gear at 140+ mph and keep accelerating! Since this time, I have become acutely aware that sometimes the people they have grinding cams (regardless of source) may not be paying very close attention to what they are doing all the time! If you are concerned about torque, dial it in on a dyno. Tomei makes a nice adjustable gear you don't have to take the gear off to change it, just nudge the cam after loosening the clamping bolts! Good Luck Quote Link to comment Share on other sites More sharing options...
naviathan Posted August 18, 2007 Author Share Posted August 18, 2007 I have an adjustable gear for my 77. Very nice piece that doesn't require removing ti to dial it in, but for my DD, I'm not overly concerned with being perfect. I really just want some decent power to play with and some better gas mileage. That's why I switched to the MS-II and I'm working on getting another cam. I'd really prefer not to use my adjustable on the DD though. Quote Link to comment Share on other sites More sharing options...
naviathan Posted August 21, 2007 Author Share Posted August 21, 2007 "325 x 475 - He calls it the Hot Street." I call it 'lack of standard measurement'! LOL What are they measuring the duration at, when it bumps off the base circle till it returns? I would be very curious to see what their specifications stack up like when compared with others who use the '0.050" Lift' standard. It really cuts down the duration, and on an N/A engine .050' lift is where you start getting appreciable flows. Turbo is different, those valves crack at the right boost pressure and you are flowing from seat to seat. Tony, I got a response, all measurements are taken at .050". Sounds like this is the cam grind for me. hope that makes you feel a little better. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 21, 2007 Share Posted August 21, 2007 325 degrees at .050??? With only .475 lift? I am having time swallowing that one. Quote Link to comment Share on other sites More sharing options...
naviathan Posted August 21, 2007 Author Share Posted August 21, 2007 It sounded a bit odd to me as well, but I don't think Delta Cams is going throw numbers out there just to see what kind of bite they get. 325@ 475 should be pretty damned torquey, but with that kind of valve overlap the idle will have to be punched up to around 1k or more. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 21, 2007 Share Posted August 21, 2007 At this point I'll go out on a limb and say that something is not correct. I don't think I've ever seen cam duration over 300 degrees @ .050. It's like someone telling you that they run 100 degrees of timing advance or something. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted August 21, 2007 Administrators Share Posted August 21, 2007 At this point I'll go out on a limb and say that something is not correct. I don't think I've ever seen cam duration over 300 degrees @ .050. It's like someone telling you that they run 100 degrees of timing advance or something. Especially with under .500” lift, I am pretty sure it is physically impossible to get an opening and closing ramp that aggressive with the OE rockers, (or any available L-series rockers). It would take over .600" + lift to get that much duration at .050". I’m with Jon on this one. A 300 degree duration spec with less than .500” lift HAS to be advertised duration at say .002"-.005" valve lift, definitely not duration at .050” Quote Link to comment Share on other sites More sharing options...
naviathan Posted August 21, 2007 Author Share Posted August 21, 2007 I emailed the guy back. I thought that duration sounded way out there, but I'm no expert on that stuff. Still learning. Quote Link to comment Share on other sites More sharing options...
naviathan Posted August 21, 2007 Author Share Posted August 21, 2007 Got my reply.. thew 325' is @.006 250 @ .050 sorry for the confussion. Quote Link to comment Share on other sites More sharing options...
Guest datsunzman Posted August 29, 2007 Share Posted August 29, 2007 "325 x 475 - He calls it the Hot Street." I call it 'lack of standard measurement'! LOL What are they measuring the duration at, when it bumps off the base circle till it returns? I would be very curious to see what their specifications stack up like when compared with others who use the '0.050" Lift' standard. It really cuts down the duration, and on an N/A engine .050' lift is where you start getting appreciable flows. Turbo is different, those valves crack at the right boost pressure and you are flowing from seat to seat. I have to agree with Tony on this one. I've got an old buddy of mine that's an old fart who taught me that when you finally get it tuned right, it will actually quite down a bit, the exhaust that is. Dave Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 30, 2007 Share Posted August 30, 2007 250 at 050 sounds more like it. I have had four cylinders engines with 304 and 310 degree cams in them, and 325 is NOT a 'street cam' by any stretch of the imagination! I recall my bud with a Toyota who installed some TRD 310/304 duration cams in his 2TG, then went through his carburettors several times since 'it must have a vacuum leak or something, I can't get it to idle below 1700 rpm'...just by chance during the conversation he talked about no brake booster action, and having the 5Kg Flywheel on it and stalling at every stop sign and I said: "Did you put in the TRD Cams?" Uh, yeah, why? "Uh, er...Dude, you got 310/304 duration cams with 14mm lift, I'm suprised you got it to run at 1700!" Sometimes 'building it from parts' just doesn't end up being the fantasy we think it will be...top it off, the guy is 50+ and is complaining about in town drivability with the setup. :Rolls Eyes: And it has to use carburettors, Megasquirt will not be installed "just because"... :Rolls Eyes Again: Some people's kids...can't beat em...can't shoot em! LOL Quote Link to comment Share on other sites More sharing options...
naviathan Posted August 31, 2007 Author Share Posted August 31, 2007 So does that cam sound too small now or would it bee good for a street cam? I'm thinking the lift is a bit low. I asked him if he could find something around .500" lift with around a 250 duration. Quote Link to comment Share on other sites More sharing options...
Tony D Posted August 31, 2007 Share Posted August 31, 2007 Have you talked with Isky? They have stuff in that range. Ron tends to use a lot of lift comparatively with less duration. Gives a very nice all around engine. On your Nissan Core the out the door price is around $180. Not an El Inka $25 regrind for sure...but something that will work! Quote Link to comment Share on other sites More sharing options...
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