YellowFever Posted February 1, 2008 Share Posted February 1, 2008 Below is a comparison of my #1 intake lobe wipe pattern using .170" and .160" lash pads. Valve lash was set to .008". And here is the same comparison on the exhaust valve. Valve lash was set to .010". I'm leaning toward using the .160" lash pads to keep the wipe pattern a little closer to the pivot end of the rocker arm. Do any wipe pattern experts wanna chime in and give me their recommendation for a mild street engine? Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 1, 2008 Share Posted February 1, 2008 If this was my personal engine, I would set it up with .150" instead of the .160" I keep my patterns CLOSE to the pivot point. Will be a little noiser though. Put .180" on that scenrio if you want real quiet. Quote Link to comment Share on other sites More sharing options...
YellowFever Posted February 1, 2008 Author Share Posted February 1, 2008 If this was my personal engine, I would set it up with .150" instead of the .160" I keep my patterns CLOSE to the pivot point. Will be a little noiser though. Put .180" on that scenrio if you want real quiet. Thanks, I'll shim it to .150 and see what it looks like. I'm not real concerned with a little valve noise. Does the pattern closer to the pivot result in more lift at the valve? Well, here's what that intake valve looks like with .150" lash pad height. Is this too close to the pivot? Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 2, 2008 Share Posted February 2, 2008 That to me is perfect. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 2, 2008 Share Posted February 2, 2008 I'd probably go with the .160's. If you want more lift get a bigger cam. That's my take anyway. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 2, 2008 Share Posted February 2, 2008 I have ran them with that same amont or less than that before. You will have no problems. BUT you MUST check every rocker. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted February 2, 2008 Share Posted February 2, 2008 I have ran them with that same amont or less than that before. You will have no problems. BUT you MUST check every rocker. I agree that you can run the .150 safely but I also understand exactly what Jon is talking about. If you do not have a reason (such as rule limitations) why not use a bigger cam and a more ideal wipe pattern? Dragonfly Quote Link to comment Share on other sites More sharing options...
TimZ Posted February 2, 2008 Share Posted February 2, 2008 I agree that you can run the .150 safely but I also understand exactly what Jon is talking about. If you do not have a reason (such as rule limitations) why not use a bigger cam and a more ideal wipe pattern? Dragonfly Maybe I'm missing something - assuming he checks ALL of the rocker wipe patterns and they come out the same, what's non-ideal about the .150" pattern shown? Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 2, 2008 Share Posted February 2, 2008 Maybe I'm missing something - assuming he checks ALL of the rocker wipe patterns and they come out the same, what's non-ideal about the .150" pattern shown? Your not missing something, you and I are on the same page. With ALOT of cam grinders, you are fixed on certain duration VS Lift. I like to get more lift than alot of cam grinders want to give for certain durations, so I cheat the rocker. I have machined my own lash pads to get all of them exactly where I want them. Sometimes ten thousands incriments is too much as well. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted February 2, 2008 Share Posted February 2, 2008 Maybe I'm missing something - assuming he checks ALL of the rocker wipe patterns and they come out the same, what's non-ideal about the .150" pattern shown? My untested idea is that when the valves are going at 7000 rpm plus the wipe pattern might not be as exactly placed as it is when the engine is spun by hand and doing 3 rpm. I'd put it in closer to the center just for a "margin of error". Is that necessary, maybe not... but it would make me more comfortable. Plus, as I said, it is not necessary to run so close to the edge to maximize the lift if you can just buy a bigger camshaft. 1 fast z says the valvetrain runs louder when the rockers are offset like that. I'm guessing that they don't run louder because it's better for the longevity of the engine. I understand trying to maximize what you've got, but if you want more lift it seems to me that there is no reason why you can't maintain the rocker geometry as it was intended and just run the larger cam. If it were an ITS motor I'd understand. Quote Link to comment Share on other sites More sharing options...
YellowFever Posted February 2, 2008 Author Share Posted February 2, 2008 Thanks for all the input. I have ordered a set of .160" lash pads (Courtesy Nissan had them in stock, MSA was backordered until May). Since this is a mild street engine I didn't really want to push the wipe pattern to the limit. I like Jon's idea of a "margin of error", although I will still check the rest of the wipe patterns with the new lash pads installed just to be certain that none of them run off the edge. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted February 3, 2008 Share Posted February 3, 2008 Your not missing something, you and I are on the same page. With ALOT of cam grinders, you are fixed on certain duration VS Lift. I like to get more lift than alot of cam grinders want to give for certain durations, so I cheat the rocker. I have machined my own lash pads to get all of them exactly where I want them. Sometimes ten thousands incriments is too much as well. I have a lot of respect for your knowledge but I also understand that not everyone who is going to read this is going to be as knowledgable and accurate as you are. Although I have not personaly experienced it what I have read is that you are completely safe as long as the lobe never goes off the rubbing pad of the rocker but when you live on the eadge you are that much closer to accidentaly going over the edge. My engine being slightly more than a mild street engine has the wipe pattern right in the center as a peace of mind type of thing. Dragonfly Quote Link to comment Share on other sites More sharing options...
1 fast z Posted February 3, 2008 Share Posted February 3, 2008 Yea I guess you can say I live on the edge, and that can be seen with my two z cars I play with. My NA car is setup like I describe for about 40 thousand miles on it, with no problems. Had the valve cover off at about thirty thousand miles, with no problems showing. It runs GOOD as well. Like with all my post, take it as you wish, and it is all just for educating others with my hands on experience. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 3, 2008 Share Posted February 3, 2008 Actually, I would run the 150's and not give a second thought about it. Even if that was wiping off the end of the pad, it's going to be nosed-over almost instantly thereafter. Also, now that I went back and checked, the "How To Modify" book mentions running off the end of the pad towards the pivot is safer than running close to the valve end. The way the dynamics work on that, the pivot end is the safe end to 'cheat' on! BTW, verify your cam timing! Also, this 150 -vs- 160 is one of the little things that makes for more HP on the 'exact same engine'. Sometimes a little means a lot (ITS engines mentioned above...) Having a clear blue mark on the pivot end is clear indication you are 'safe'. Even with some theoretical movement, it's not moving as much as you have 'blue margin'---if it is, you have OTHER problems to worry about! Putting it dead center makes for nice geometry, but saying it's for 'safety' is a bit of a red herring. They don't move that much! Quote Link to comment Share on other sites More sharing options...
Dane Posted February 3, 2008 Share Posted February 3, 2008 Also, this 150 -vs- 160 is one of the little things that makes for more HP on the 'exact same engine'. Sometimes a little means a lot (ITS engines mentioned above...) Well...since the increased "average" rocker ratio doesn't just increase the peak valve lift...but raises the entire lift curve...you get more valve lift throughout the entire rotation of the cam. It makes me wonder what kind of increase in engine breathing ability this correlates to? This is purely speculation on my part, but I imagine it would almost be like running a stage higher cam profile altogether. Quote Link to comment Share on other sites More sharing options...
steveosupremeo Posted February 3, 2008 Share Posted February 3, 2008 SHAZAM!! I wish I would have known this when I was setting up my comp cams camshaft in my 77!!! %#$#$$% instead of waiting a couple of days with motorsport's overnight shipping!! It was supposed to be able to run stock lash pads with the cam and it came out wiping like the #150s in the pics...maybe a tad closer to the pivot but still with some sharpy on the pivot side of the pad. So I shimmed it and checked it and then spent $60 on #150 lash pads to acheive a look somewhere between the #150 and #160 pics. Runs a little better with the thicker lash pads, but I think I was getting more lift than my stock 8.3 compression could use. At any rate, I vote sticky to save others the headache! Quote Link to comment Share on other sites More sharing options...
katman Posted February 3, 2008 Share Posted February 3, 2008 Since TonyD mentioned ITS engines, here's another take. Don Potter, who is not only the most anal retentive engine builder on the planet but has also forgotten more about Datsun cams than most of us will ever know, always had us set up our ITS heads for exactly textbook centered on the rocker. By changing the wipe pattern to the pivot end in order to increase ratio you are also changing the shape of the valve event, which you cam grinder might not have intended and which might also affect spring harmonics. He thought in most applications you'd never see the difference anyway. That said, we set up our Sunbelt ITS engines halfway between your .150 and .160 pics. TonyD's proly right, go for it. Nice job on the photo's, BTW. Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 4, 2008 Share Posted February 4, 2008 Yes, I touched on this somewhere else in that VW's commonly use 1.25 rockers, and there are 1.5 and 1.7 ratio rockers available. When you use a cam designed for stock rockers, you can usually get away with running them on 1.25 rockers and get more lift and duration...but at the expense of an altered acceleration rate on the valves. You can run into problems when running the wrong ratio rockers. You can float your valves if you have the wrong set on there. They have different ramps and profiles when you are using 1/5 and 1/7 rockers. And they say so when you buy the cam. That all being said, we aren't changing the ratio all that much. For the same setup, you are merely optimizing lift and opening time available. What centering the lobe will do is keep the ratio as constant and near 1.5 as possible. If you draw out the wipe pattern on a moving piece of paper you can visualize the effect a bit better...at least I can. You 'slap' the rocker a bit more when you cheat the wipe pattern to the pivot due to the way the cam approaches the pad...but with adequate lubrication it's not a big deal. I'd put Don up against the late Racer Brown and Ron Iskendarian in the L-Engine Assymetric Cam Profile Knowledge Camp any day. If you've ever had the opportunity to read the Racer Brown articles on camshaft profile on the L-Engine, you are doing yourself a disservice. Find those articles and read them, they are a WEALTH of knowledge on the subject. And were written in the early 70's curiously... Oh, and from what I have seen (and you can verify it with your own degree wheel) changing the lash clearance you run will also change the cam timing for that individual cylinder. As little as 0.002" change in lash can move opening and closing events several degrees! It's all in the little details! Quote Link to comment Share on other sites More sharing options...
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