jeffp

Having the cam one tooth off changes the timing about 9 degrees if what I was told was correct. The thing is that one tooth is WAY to much either way and the engine will iether not run at high rpm's or it will not run at lower rpm's if the cam is off one tooth. Your cam, I don't know all of the specifications, and if the ones you listed was lobe lift or valve lift. The duration is not to much, provided you are flowing well through the head and have no back pressure on the exhaust. The vacuum should have told you all you needed to know. With a cam like that you should have 11-15 inches at idle. Lower is either a leak, or incorrect cam timing. Cam timing is critical on this cam configuration. One degree of timing will make a significant change in the low end performance. So what is the opening and closing points of the intake and exhaust lobes? Also what is the lift of the lobe (the actual lift of the lobe from the cam card) Valve lash, again this is critical, a change of .001 will change the opening and closing points of the valve by about 5 degrees of crank rotation. So you can see that a few thousands will have significant affects of how the engine runs. I recommend a cam adjuster sprocket. You can get a nice unit and then go at it again. There is the write up on degreeing your cam, all of the information is there to explain what each adjustment will do to the cam card.

You do know Frank, that BHJ Dynamics now makes a damper/super charger assembly. I know it is not as cheap as what you have made, but I think you may like the part.

I don't know how is aware of the fact that I have a set of roller rockers for the L engine. There was ONE cam designed and ONE roller head ever built. I got on to this stuff because I am still planning on building this head. So you could say I have researched this whole topic at length and had a few ideas I was going to go with. The first thig I looked into is the spring. I was looking very closly to the spring comp cams makes for their bee-hive springs. This will reduce this harmonic, or remove it all together, I have heard mention about a number of times. The spring retainers will be reduced in size by about 20-30% and lighter. Also I looked into titanium retainers for this application. (NOTE: if you want to reduce the weight of the retainer then go with the titanium set that now can be bought.) The valves are then next. A 7mm stim is in order for this head, stainless steel and go for it. So there is now a vendor on the titanium retainers, use those.

You are not alone on the schematic, I just happen to have one. I had the box backwards engineered when I started into all of my changes and modifications. I paid to have the schematic made and sent to me. After examining the unit, my recommendation is to dump it! the box does little for the engine performance, and since I am at about 600hp andthe box is falling down I now have to change it out again. I was able to make mods to the circuits to increase the dwell duty cycle of the output. I went a little to far with the pulse width as it starts to misfire at 6800 rpms. A simple cap change to a .1 from a .047 did the trick. The thing is this: The output is being triggered by a .1 micro farad cap to give the box the quick response. This is good, but the problem is the spark duration gets chopped to about 508 micro seconds, or about a 1/2 milli second. This is not a problem with a N/A engine, but you start running into trouble with a high boosted engiine in the 600hp range there just is not enough spark duration from all of my testing. I have been working on this one for some time along with the Z31 ECU modifications. If you want the schematic let me know I can make a PDF of it and send it to you. REGARDS: Jeff

"Then you need to worry about whether the driveline can handle it (both the trans and the diff, not to mention the axles, suspension, brakes, body and pretty much everything else on the car)." LOL, I feel your pain man!

I know of the coil packs being used on an RB application. The thing is, the scattered spark type coil pack in my opinion is not a good part for a performance engine. They work well on engines that are running in the 300hp ranges, but I would never consider them for any real hp goals. There are just to many systems out there that will do what you want without all of the problems of retrofitting the coils on an existing system. But send Bernard a post or email and he can give you the skinny on how to install them.

Hi there, I have had two heads done for my car. Robello racing did the first head and Gerolomy did the second head. Both heads were completed and machined very well. I spent more money on the Gerolomy head, and I went with Ferra stainless steel valves, so there were some differances in the two parts. I will say though, for the money give Robello a call and get a quote from them. Dave has made some Excellent design changes in the head that gets the flow numbers the same, and in some cases higher then a head with the bigger exhaust valve believe it or not. I have gotten nothing but excellent quality from both head builders, but Robello is cheaper.

Two things I would do, since you are in the design phase of the build. I would point the injector towards the the incoming air flow. I wouls also place the injector as close to the inlet port as well in this configuration. The second thing I would do is make the tubes (with the injector bungs) removable, so that you can turn them around to point the injector to spray with the air flow into the port. Oring the tubes and you should be in there. You will have some ideal advantages with this design. The first thing is that you can test the intake both ways to see if there is an increase in fuel atomization pointing the injector one way or the other. The second thing that is really cool, is that you can then tune the intake for your driving needs, meaning you can shorten, or lengthen the tubes to get the intake for a running rpm range to work the best. This to me is an excellent test bed to do some testing of the various components that are regarded as a performance change like velocity stacks, length and the like, for each runner. Anyway.

I was considering this part for a short time. The big thing is this. You will have to be flowing a fair amount of air to make the 80mm TB worth anything. So you can get the numbers, @ 600hp you will be consuming bout 1050 CFM into the engine. So if you look at that figure the 80mm part is good for flow restriction considerations. The thing that makes this part a little difficult is the amount of air it will flow with the throttle plate cracked open during cruise. You will find it somewhat a pain getting the gas pedal right to run at light loads. That is what I have seen with a 62mm TB and compared that to a 60mm TB I like the 60mm part better, as it is easier to drive the car. I guess it could be a little more efficient, but I don't run my car at WOT all of the time, so a little restriction is ok for me, just get a bigger turbo that is capable of getting into the 3.2 pressure ratio levels and you should be just fine.

Hi Tim, I was running the innovate dynamic had on their dyno, and I was running my techedge at the same time. I th8ink the techedge is a more accurate sensor(The NTK sensor you give your first born for) The plug gap did not have any affect on the car that I could see, that is when I got the idea that the boost was not blowing out the spark and there was another problem. I started at .028, then to .025 and finally.020 on the plug gap. I did note that when I was looking at the plug fire on the scope with the gap to .020 I could see that the voltage was being crowbared @ the plug. I was beginning to see not the spark of the plug, but rather a squarewave output at the plug that was intermittrantly showing its ugly head, so fo me .020 is just not enough gap. I am corrently testing my new driver @ .030 that is about 80 volts per .001 gap to bring the total voltage differential required to about 2400.00 Volts to spark the plug. Then there is the rotor gap to contend with, say .025 that will require higher Voltage potential to jump the rotor and then the plug, another 2K volts so that is a total of about 5K volts or so to spark the plug. Then add in the added cylinder pressure when the car is runnig, and we are looking at somewhere of about 20-25K Volts under boost minimum. BIG PITA. I have some components on order for the driver. I was running the FET driver chip at about 80% dutycycle and it was getting hot. I had to go this route as the chip was an inverting output, so when connected to the FET driver transistor, if I did not watch it closly it would burn out the coil and the driver. I have done all of the above thank you LOL, two coils toast, one driver transistor, and one transistor driver chip. I guess I am a little slow at figuring out just what the heck is going on LOL oh well. The waste gate spring, well I am still not decided on that one yet. I am running only one line to the waste gate currently. I have been told that the dual hose configuration is better for control of the gate. I have tried this setup one time but I was having problems with the recirculation valve. The car would not boost over 12psi so that is when I started reverting back to a known working setup. I need to try this again with thedual lines. I was able to verify one thing with the soft spring, the TIAL 64mm gate will not vent all of my exhaust to 7K rpms. I was sure it would not, 1 1/4" tube to vent all the exhaust of the engine, that is about 300hp @ stock boost levels. Tim, you just may want to consider removing the bumper from the car when you are on the dyno. I did this the last sesson, and it really helped significantly. The car still got hot, but nowhere close to where it was running. The heat soak the first dyno run was incredible, and a little scary, I think I did do some damage in the way of longevity of the turbo it got so hot, and that was the big thing with the AFR's, when I got them to 12:1 or so the exhaust turbine was not glowing so much LOL, and the car seemed to run better overall. Anyway, my parts will be in thursday for the coil driver and I will start at it again and see how it goes.

I haven't been trying to start a fight on this stuff. I just want my car to run correctly on the Nissan box. I did finally get some good pulls, but hell the car was misfiring from 6K-7K on the dyno and I think it has really cost me some power. Tony is correct, there are better systems out there, but I like the Nissan box for some reason, hell I don't know, but if I can get that box to work then I will be happy. Bernard the Nissan guru was also working on the box and tuning with me. He was scratching his head as well. I will say one thing though, we did get a good pull @ 15psi on the treet. I was on the rev limiter before I even realized it. We had a methanol injectoin system running on the car and I can tell you, the engine NEVER ran so smoothly period. I have a driver circuit I have been working on, but it is not completed yet. So I will have my answer later this week as to if the system is going to work or not. Tony is right, the ECU is modified to work, but if these modifications are all that are required then no problem. I will say my power transistor(igniter) is so much better then the stock Nissan part. I really think more Z31 guys have this problem then realize. So I have run into problems that others have not. For one thing, my engine is still making excellent power to 7K and guess what @ 5K is where all of my problems start, but if you look at the stock z31 power curve, I began to realize I am pushing the box higher then it has ever been pushed. The electronics, drivers specifically, for the injectors are not ideal, and the distributor/coil triggering is not ideal either. That is the problem LOL, all I got to do LOL. So with all of the dyno time I have done I have found out a few things. My engine runs the best @ 12:1 AFR's 11:1 is to rich. The 430.00 dollar Innovate wide band is not that good, it reads off somewhat, but it can be used to tune provided you figure out with the dyno graph, where the engine makes the most power. My car runs very hot on the dyno, no question about it. I got the water temp to 110.0 degrees C one time, very hot. I got the turbo very hot with 11:1 AFR's. I put the pic on my web page under the turbo link. So I basically ran the piss out of my car, and it does show some. I even turned the stroker to 7500 rpm a few times. so the engine has had a tough way to go again. The power is there no question. I have work to do on the waste gate as well. I tried a 5psi spring in the actuator and that has affected the total boost the turbo can get to. So I have to change that back. But the big thing is the spark, if I can get that right, no problem. If I cant get it right, then to the EFI system from Lance and that will be the end of it. I can tell you one thing though, if I HAD gone with a stand alone system from the start like the EFI system from Lance this would have been a done deal long ago. But I have learned some specific things that are very beneficial for me. Trouble spots and the like. But I have also made some significant progress with the Hp the total car can do and stay together. I just may have to freshen the bottom end again, we will see. #4 is about 6 % down in compression from where it was. I don't like that to much, but I knew it was happening to the car I think, the tell tell signs of strong oil smell when it was hot for one. So who knows, but I know one thing for sure, I will have the management sorted before any further engine work is completed. Anyway, nice pull, lean out the car and you will get your numbers. REGARDS: jeffP

Hi Phil, I can ask TonyD about this to be sure how megasquirt works. But, here is the situation on the Nissan box. The car idles at X speed with a duty cycle of say 1.5 milliseconds. The car is running fine. So as I increase the rpm of the engine, what then happens is the the dwell time of the pulse decreases to about half the the idle pulse width (positive pulse portion of the complete cycle) so in effect the coil spark time, or width of the spark pluse, the length of the spark, is cut in half. Now we know that it is going to take at least 1.0 millisecond to properly saturate the primary of the coil, so that when power is removed from the primary, the secondary pulse is about 1.0 millisecond. That is a properly charged and discharged coil. My coil is being charged for .5 milliseconds, half of what it needs, the secondary fire or spark time is to short to properly ignite all of the fuel in the chamber, a misfire condition. You are on the other end of the sprectrum. You are charging the coil excessivly at idle. What this will do is heat up the coil, heat up the trigger transistor in the megasquirt, at idle. So if you are running excessive dwell time that is what you will find. The car needs only 1.2-1.4 milliseconds to properly ignite the fuel. The thing to keep in mind is this. If you took your coil and connected it directly to the battery. The coil resistance of the primary is going to determine the current draw off of the battery. 12 Volts say 1 Ohm resistance of the primary will draw 12 Amps. That creates alot of heat, and if the coil is not a beef moster, you will open, or partially open the primary windings. And if you don't have a driver that is rated for at least 4 times that much current, you will over heat the driver and risk damaging that part as well. When you think that it takes only 1.1 milliseconds to charge, or saturate the primary of the coil, you then become aware of the fact that charge time does affect how much current the coil will draw. Now it becomes an issue of how long does it take to build the magnetic flux lines in the primary of the coil. Once the flux lines are being built in the coil primary, you are drawing only a minimal amount of current to get to that point because the power of the circuit can do work building the flux lines. Once the flux lines are built, or saturated, then the only current flow there can be is determined again by the resistance of the primary of the coil, in this case 12 Amps. Not good at all, and a waste of time. So if the pulse becomes to long, what will happen, is that it is now providing a sufficient pulse width to properly fire the plug, but what happens is the the individual pulses for each cylinder become to close together. What the coil sees is basically a 12 volt battery across the coil primary. Quess what, if the primary power is not switched off, you get no spark on the secondary of the coil. You lengthened your duty cycle, in effect increasing the pulse width of the spark at 7k rpm's to make the car run well, but sacraficed efficiency on the low rpm range. And if to excessive will eat coils and damage the megasquirt driver. A single coil car, will be good only for about 8 thousand rpm's that is if everything in the system is in perfect adjustment and the electronics are good enough to have the spark accuracy.

I don't know what system you are running, but I have had some significant problems with my ignition with the Z31 ECU. The biggest problem is this. When the car is @ 7 K RPM's the Nissan box will not provide enough dwell time to properly charge the primary of the coil to get a 1.2-1.4 millisecond spark dwell time @ the plug. I have verified this with my storage scope. The next problem is that you have to increase the basic dwell time to about 2.2 milliseconds to get the required spark dwell to ignite the burn correctly. That is not a problem @ 7 K RPM's, but at idle there is to much dwell time and the power transistor gets hot and the coil gets hot as well, makes for a short coil and system life. I have also verified that the MSD 6A box, @ 7K RPM's is also having difficulties maintaining its spark duration. So that is what your problem is, I dont know enough about megasquirt, but you need to set your basic dwell time, based on what the coil secondary is doing. Also set the plugs to a suitable gap, say .030-.040 (the gap will be determined by the level of high voltage potential the coil can make on the output.) then adjust the dwell time. So after that is made and the idle is good, then you need to start adjusting the Dwell DUTY of the trigger. What this compensates for is the closer pulse spacing of the trigger pulse to the primart of the coil. You cant increase the dwell time as that will affect your idle negatively. So make the duty cycle increase that provides the positive voltage to the coil, that will compensate for the increase in compression of the engine and maintain the 1.2-1.4 millisecond spark line. You are not the only person having this problem with the ignition. I know just about anyone running a standard single coil trigger from any ECU is going to have problems. This is just the nature of the beast when you are using one coil! There have been a number of fixes for this problem, but overall I don't think the system is good enough for a performance engine. You may get by running N/A but add boost pressures to the engine and you start to have problems. The thing about the mallory coil is that it is so big and makes such high spart, that in the points ignition the coil works very well. You can make the adjustments to the point dwell to get the happy sweet spot. The electronic ignition systems seem to have difficulty maintaining the required dwell duty of the spark duration @ 7K RPM's That has been my problem, and I can tell you it is costing you power. If you want to run your engine to 6K then you should not have problems. The thing that I have seen is guys swapping out coils with various resistance on the primary of the coil, and as you know that will change the current and the output of the secondary of the coil. Anyway, I am trying to work on a 555 timer circuit that will give me the shorter dwell duty at idle, but still maintain the dwell duty at 7K RPM's. big problem for me, and I am just about at the end of my rope with this problem.

What gear were you in? The one post mentioned you in 3rd gear, was this the case with the last run? Also what dyno are you running on? I have been tuning on a mustang dyno in forth gear. I have also had problems with EGT's on my car. I was able to decrease them when I pulled the bumper to get some air to the radiator a little better. I was first tunig for 11:1 AFR's, but found out the car ran stronger, and cooler with 12:1 I was talking to Ed about the car while it was on the dyno and he mentioned they were at times tuning for 13:1 on their high hp drift cars. I am still not finished, seems the car was in fact misfiring slightly and when it 6-7K rpms it was very apparent the car was misfiring. I dont want to post any numbers yet on the car, but lats say I am just about where I want to be in the Hp range. I made some changes in the wastegate spring and it appears to be affecting my max boost level. But the ignition is the key here. I think the Nissan ECU will just be able to squeak by @ 600hp at the crank. Nice run though, I am hoping to see those numbers.

John mentioned a filter and I guess that is a good unit. The thing about the Nissan oil filters is that not all of the filters have the flapper/sealer in the filter. That little flapper gasket seals the outlet of the filter when the oil pressure is not up. This maintaines the oil in the filter, so you don't have to prime the filter for each start up. What eill happen with the incorrect filter is that every time you start the car, you wil see a delay in the oil pressure coming up. So check the filter.

I would look at your bearings for the L engine. Seems Clevite stopped making the 77 bearings a few years ago. Then they came out with the clevite 777 bearings. As I understand, and found out from Dave Robello, the 777 bearing is about the quality of the stock Nissan bearings. So you have lost about 3 thousand pounds per square inch of abuse the bearing can take. The michigan bearing will handle 6 thousand pounds per SQ inch surface perssure, the Nissan bearing about 8 thousand pounds per SQ inch, and the old 77 bearing about 11,000 pounds per SQ inch of contact pressure. So what Dave did, and myself included, was to go with the new poly coating bearings. According to Dave these parts are just about bullet proof. He said he has used these bearings a second time in a build because they were so tough and showed no signs of wear. He NEVER used clevite 77's or any other bearing two times for a build. I figure if they were good nough for Robello, then I could use them myself. They have seemed to work out well for me. I would recomment this bearing as a replacement part for the 77 bearing. I have a sample rod bearing half. I will take a pic of the part and post it when I get time.

That was the first turbo I ran on my car. I liked the results I got with it. Spool will be right around 2500 rpm. That turbo will pull you all the way to 7k rpm's and give you right at 15psi of boost. You can calculate the Hp but it should be around 300hp so how much power do you want to make?

You are going to need a little more space on top of the carb in my opinion. You should shoot for at least 2" above the top of the opening of the carb. looks like that will be a fun ride, just watch your fueling and you will be fine.

What about UPS of FEDEX to name a few. Seems like to me that if you have to wait that long on the mail and still pay through the nose, then go with a better shipper. I don't think that would be to difficult to do. My company ships world wide, and even with the terrorist thing going on we still have a little control over how fast it goes.

I looked for my cam card but cant find it. I believe the duration @ .050 was 255 and 270 or so. I would not recommend the Isky cam unless you are race only, you will need good fuel for that cam, 87 octane will not cut it with boost. You guys need to realize the @ .050 readings are not that good for a turbo engine. You crack the valve .005 off the seat and you are pushing air into the cylinder under boost, so you really need to have a good handle on the opening and closing points of the intake valve. I would recommend the Elgin grind for just about any street car. Bernard has the old head and cam from my engine and according to him and his testing that cam pulls him to 7K no problem, and he also can feel the power coming on VERY HARD @ 5K to 6K and that seems to be the peek power point for that cam. I cant give you any info from my engine as the cam timing and valve lash was incorrect, the timing being changed due to the incorrect valve lash. So you will still get good fuel mileage with the cam, provided you keep your foot out of it. The thing you need to understand is that you are basically running tow engines, OFF BOOST, or the N/A operation of the engine, and that really is what you need to decide, how much do you want off boost for performance. Then you have the second part of the equation, BOOSTED. There is a VERY big difference between off boost and on boost of ANY engine. So get the power you want, within reason, off boost and go from there. I would not recommend trying to get 300hp N/A and then trying to boost the engine. A cam that will give you that much power, first of all, it will be making power in the 6-7K rpm range, be soggy on the low end, and innefficient at low rpm,s until you get the induction flowing well at higher rpm's. So go with a mild cam gerind. Get the lift high, the duration realitively short, and overlap no greater then 50 degrees. That will be your best setup for the L engine with mild porting. Myself, I went to the extreme, but in doing so, I am now setup to run just about any cam I want without spring bind. Smaller is not an issue for me so I can always roll back the cam specs and do more testing.

The pistons were damaged from FOD, with the engine is running you would have seen a different type of marking, less defined then what you have there. The coating doesnot seem to last as well as some would believe looking at your pistons. I have always thought it was a waste of time for any engine that was not full race setup, and freshened frequently, but to eaches own I guess. I did notice the skirt and see that all to familiar scuffing, scratches and darkness of the skirt. That is due to the piston expansion in the bore, you need anywhere from .0005-.001 additional clearance to allow the piston to expand in the bore. How hot did you engine get at any one time? I had problems when the engine got hot one day almost full gauge reading, to hot, but what do you do when the engine gets that hot in the middle of nowhere, shut it down, I was afraid it would freeze up. So for this next build, give the pistons some additional clearance, forget the coating(waste of money long term) and try it again. You can call Robello racing, and they have a new bearing that is really good, and it is coated as well. Since you will need at least a polish of the crank journals, this would be a good time to get that type of bearing. I spoke to dave at length regarding the bearings, and he said they are tougher then nails, in fact he has reused these parts in builds, because they are so durable, much better then the Cleveite bearings everyone myself included, uses for extreme duty operation. Believe me I feel your pain, that is going to cost you for that fix.

Now that is going to take some doing. You want reliability, and power, well there are a number of good builders out there. Being a west coast guy, I used some of the builders out here. Robello racing did the bottom end of the engine. Nathan Gerolomy did, ultimetly, the head for the engine. Robello also does a very good head as well. You may even want to give Brian (OneFastZ) a call and see what he can do for you. 600hp is doable, infact 700hp is doable, but don't forget the fuel management for the car, most important to get a system that will perform well. Gentlemen OPEN your WALLETS! BEGIN! LOL

The first grind was .480 lift intake/exhaust 266 duration intake/exhaust Lobe center 112 degrees. I think that is about 48 overlap. intake open was 21 degrees@50 and exhaust I believe if memory serves me correctly 72 degrees. You can run the numbers and that cam came from Elgin cams in CA. You can easily get power from that cam, and if you have the correct combination of turbo and some mild porting, you will get spool @ 3K rpm,s Your topend will be right around 6K and you can run up to 7K The second cam is an Isky part, this cam is a little more radical, and I would not recommend going past this specification for any turbo L28. 55 degrees of overlap, .580 lift intake/ .540 lift exhaust lobe center 114, intake opens 31 BTDC exhaust opens 67 ATDC 290 duration intake 270 duration exhaust. Those two grinds will do just about whatever anyone with a turbo could want. The Elgin cam works very well, the Isky cam is really good, but it more of a topend cam.

I like the write up you did. I know that it took some time to get all of your information on this page, good work. I really like to see good data posted for everyone to use that is accurate. I really had a hard time of it for a few days doing the cam timing the first time. I spoke to Dave Robello, John Elgin, Ron Iskyderian, and Jim Wolf during this whole process. Lots of knowledge there, and it was very helpful to me in the process. Jim mentioned the fact that being a chain driven part the the chain and sprocket configuration will also change the cam timing due to the chain trying to ride up the theeth as it spun on the sprocket. So my solution was to get the chain to measureable tolerances with the tensioner I bought from Japan. I have a picture of it on my web page. So that took care of the chain slop issue. (I NEVER liked the tensioner Nissan used with these engines. I have had problems with the chain hitting the cover before when it was very cold outside. The oil just was not thin enough to provide the hydraulic pressure on the chain fast enough. So it was the idle rpm for a few minutes to get the part to work correctly. The second thing I did not like was the chain whip the engine would get from accelleration to decelleration, the chain has a tendancy to get a smooth bend in the trailing side of the sprocket, and again, you get the cam timing moving again. This was verified with the company that developed the tensioner. The were getting changes in hp because of the instability of the cam. so the cam in effect spends much of its time in a plus or minus cam timing situation. Plus the whine of the gears is cool LOL, loud, but cool.) So I got the stability of the cam timing with this part, and I think it is very helpful. The second thing that needed to be changed was the sprocket. This part needs to be adjustable as well. I bought the HKS part, no timing marks, but it adjusts like most of the belt driven adjustable sprockets/gears. Then I was able to acheive full adjustment of the cam, and control it better over the rpm range, accell and decell conditions. The lobes, now here is the meat of the whole shootin match! Nissans have a nasty harmonic in the standard valve train setup from Nissan. Now with the new technology out there, companies like Sunbelt, Jim Wolf, to name two for the Nissan stuff have developed cam/spring setups that work very well together and reduce the friction of the assembly by almost 50% so that is a very good improvement. So now we have computer programs that can analyze the operation of the cam and rocker in operation. The biggest concern is to NOT get negative curvature of radious in the polynominal representation of the lobe and rocker operation. This is what creates the harmonics, and will create a bouncing motion of the rocker on the cam lobe on the closing side of the lobe, hense the use ofthe asymetrical cam lobe. I got into this stuff hot and heavy when I was looking into doing a ROLLER cam for the engine, and I still want to complete that work. Maybe I will get it done here in a while, who knows. The cam guru that is working on the lobe configuration has not completed his work. So yes the knowledge is alot to learn, and I agree, you could spend a lifetime learning all of the need to know information when it comes to cam lobe design. Anyway good thread, I like talking technical information on a subject like the cam. The funny thing is that once I got sb ford, and chevy engine configurations out of my head, the problems I was experiencing with the timing became clear. I knew something was wrong, but it took a little thinking to figure out what it was. The thing timed very well after I had my head screwed on right. have a good one.

I have looked and read, and no where did I find the lash adjustment issue addressed. On The L series cam adjustment, the lash adjustment is critical to get the cam degreeded in correctly. I haven't spoken to Dave about this, so I am not sure if this has been addressed with him either. The L series cam configuration requires that you establish the TOTAL duration of the cam with the valve lash adjustment. Changes in the adjustment will affect the cam opening/closing points, and the lobe centers. The cam card says to go .010 hot for example. This was the case when I installed an ISKY cam in my car. So I made my adjustments and the duration was wrong, for both lobes. But more importantly, since the duration was affected, on BOTH lobes, guess what, the lobe centers were moved drastically from 114 to 120 degrees, not to good. So the first thing to do is to establish the total duration of the cam lobe by taking readings with ZERO lash. Verify the duration with the cam card. You should get two sets of information, the cam grind information, and the cam timing based on the adjusted lash setting. Once you have established that both lobes open/close as stated on the cam card, the overall duration should be dead nuts on the cam card. Good, now that you have checked the cam with the cam card, then you go to the second set of specifications taken @ .050 with the recommended lash setting. YOU NEED TO CHECK THE DURATION AGAIN to verify that the cam duration matches the cam card. IF IT DOES NOT! you will need to make to changes in the lash until BOTH the intake and exhaust durations match the cam card with the @ .050 setting on the cam card. A change of .001 in the lash will change the duration of the cam lobe by about 5 degrees of crankshaft rotation. You can see that a change of 5 degrees in the intake and the exhaust durations will change the opening/closing points of the cam, and when you run your nifty little cam calculator, you will see that the advertised lobe center will be off as well. Now we have a problem, if you run the car, you could QUITE EASILY make a peeky cam, meaning power will come up at X rpm, but it will be short lived and start to fall off again. NOT GOOD AT ALL. So find out what lash will bring the duration into the advertised specifications, check and verify both Intake and Exhaust lobes. Once the lash is set, then begin your degree testing of the cam timing using the @ .050 numbers. (AS A NOTE) I dont like to use the @ .050 numbers, because that will change the crankshaft realitive position as the ramp of the lobe is changed, so you still have room for error there. I use the ZERO lash adjustment, AFTER I HAVE ESTABLISHED THE LASH SETTING, and then degree according to the cam card. Once the cam matches the cam card on the intake, then go and verify the exhaust lobe just to make sure everything is still good. Always rotate the cam in a clockwise direction to keep the chain tight when making adjustments to the timing. This will ensure that you did not make an incorrect adjustment of the timing. The last thing to do is then go and make the lash adjustments to the intake and exhaust lobes based on your previous data. You can then check the timing one last time on the intake or the exhaust lobe to ensure the intake is open at the advertised opening point on the cam card for the @ .050 settings. You should be just about perfect if you have completed the adjustment correctly. VALVE LASH folks, this is KEY for ANY datsun cam period. When in doubt, check the cam timing with the degree wheel and verify your lash settings to bring the cam into the correct duration. This adjustment will make or break ANY engine build no question about it. So, I did not want to step on anyones toes here, but this is the CORRECT way to do L series cam timing. ANY other way is hit and miss in my opinion. One thing you need to realize about Dave Robello, is that he tests his engines on the dyno, and he does do the timing adjustments if required to find the SWEET SPOT of the cam in the engine. Granted doing a Nissan L series is not that easy due to the cam sprocket, and generally they are not to bad, but better knowing for a fact about something then to just guess that everything is good.