Tony D

A leaking anti-backfire valve... hmmmmmm that seems more like an open path from the air cleaner to the AIR system in the exhaust. I know if the check valve on the AIR manifold is leaking you EGR to your air cleaner....heavily There is a reason I went digital... Remember my longstanding commentary: "Anybody who says 'carbuerttors are easy' has never tried working with them in a precision environment!" A couple of more months Ray, and you will start thinking of ways to convert those SU's into Megasquirt Powered TBI! I know I did...

with 013 warpage, you should check the TOP of the head as well. Likely it is warped as well, and getting to the point where tower bind is getting possible. One way or the other it looks like you will be shimming the towers after a matching cut top and bottom...you could possibly be looking at a cam drop relative to crank centerline of 1mm (010+013+013=036" or roughly 1mm worst-case if the head was not decked top-and-bottom the first time) I would get a head thickness reading and make the decision from there. I would keep a standard gasket (if the CR remains sociable) and shim the cam towers to get the right cam-to-crank centerline dimension restored. Or go with the Kameari Adjustable Chain Idler assembly ($500?+) Tomei makes top-notch-stuff. I'd have no reservations using any of their componentry, but what you have may not require anything special other than the cam tower shims. That way you have 'standard parts' for a consumable for your racer and not something you will have to wait to order in when it breaks again...

OMFG did he really just say that? Dude, you are feeling entitled to information, and calling people names or insinuating they are on some 'high horse' because of your own ignorance is insulting to those of us who were at (apparently) your level when we were in our early teens. Just because you're 21 doesn't entitle you to special dispensation from the rules of the forum, or of the common courtesty of searching and reading. DISCRIMINATION IS NOT A BAD THING! You have been told it is, but that's a fools errand. You look at an apple with a worm in it, and DISCRIMINATE when you say "I'm not going to eat that worm, it may make me sick!" You are ASSUMING it is discrimination BECAUSE you are new to the forum. It is simply people INFORMING you of your transgressions against the site rules and ettiquette. Like I said, maybe you need to read the 'Why is Hybrid Z so...' before you start lashing out at people and calling them names for pointing out YOUR misconduct! This issue is YOURS to deal with, not the boards. You want to ask questions here, follow the rules. I have overstepped my commentary bounds already, and will stop now. But I can't believe that whining swarf was actually posted to this board. That alone makes this entire thread (to paraphrase Elaine Benis off "Seinfeld"): "Shedworthy"

A better statement might be 'No US SPECIFICATION L28'... There are PLENTY of JDM engines floating out there as replacements which not only have flat tops, but in some cases SLIGHT DOMES. 'Never Say Never' I have been running a 1977 FLAT TOPPED PISTON N42 Head and N42 Block combination in my turbo car for years. Decades, in fact. Horsepower was similar to yetterben's levels but I didn't get greedy nor did I have a 'boost fetish' that compelled me to keep upping the boost beyond the capacity of the chassis to turn a corner and apply all the power it could produce... As for 'all the questions'----I think the OP needs to read the sticky "Why is HybridZ so..." and thank his lucky stars he got any help at all here asking questions which obviously were not researched very well at all. "Getting Help" doesn't mean spoonfeeding people information. You can tell all the most complex things in the world to a 13 year old, but if he doesn't do some pre-reading to figure out what you're telling him it's all a waste of time, space and effort. Why am I always the designated attack dog? I'm a harmless fuzzball. Really. I enjoy wiping noses and that kind of motherly crap.

Got to go with Spork on this one, a Forged stock-specification L28 piston will be roughly the same cost as a 'custom' one where you specify different ring land configuration, different oil wiper, maybe different pin height or diameter. Forged is Forged. Now, you order Small Block Chevy Pistons and you get 8 for what half a set of Datsun pistons cost. Volume and turnover is your friend. Chances are just about every reputable forged piston manufacturer will have BLANKS 'on the shelf' suitable to be turned into an L28 Piston, so knowing that, the costs are minimal to do any real custom changes in basic setup. Like Spokr said, if you specify a 3/4" thick uncut dome, or some special combustion chamber matching dome the price will likely be higher. Maybe not, some places charge $50 a set wholesale to do a 'special'. But 'stock forged pistons' to me would mean forged, and not cast. And in that frame of reference, they will all be about the same cost. Forged is Forged. That being said, looking around for things like Vega pistons, or old Corvair TRW Forged Slugs can net you a forged piece at 'cast' prices (once upon a time...) The engine doesn't care 'where' the piston was supposed to go into, and if you're boring match the block to whatcha got! Big thing is pin diameter, Pin Height, Ring Configuration, and Overall Diameter. Searching catalogs can net interesting discounts if you don't mind having a coupla few pistons left over as spares...

"My point with the cam gear was that you could probably swap the gear alone and get similar results to going to the early cam with a lot less labor, not that changing cam timing doesn't make a big difference." If that's what you meant to say, you should have said it in the beginning. The response is the same: the opening and closing times on the valves are different early to late and "a couple of degrees makes a big difference"... The later cams are not the same as an early cam with overall advance / retard. And even with a stock cam, gains are to be had by degreeing it to the engine it's installed into....stock or not. The original question was 'should I shave the head 0.080" while it's off'.... "NO" Coming from someone who did it above I believe the answer 'in retrospect' was it was a waste of time and money as well. This is all from leaking / weeping coolant. "ALUMA-SEAL" Argue about an aftermarket cam all you want, you have obviously missed the absurdity in the original posts, missed it when I pointed it out, and now have steered the conversation so far off track that YES we are 'going round and round'.... For the THIRD time my original statement was "LEAVE IT ALONE IT'S NOT WORTH THE TIME AND EFFORT" Is this clear to you yet, JM? Flexicoker seems to have gotten something out of it. IMO I don't see the advantage of turning an otherwise strong-running bone-stock engine which runs on regular gas into a (for all intents and purposes) IDENTICALLY PERFORMING engine which REQUIRES permium fuel to run around. You can get at least 147 RWHP on a stock low compression, stock EFI'd, F54/P79 on REGULAR GAS. If that engine isn't there yet, I'd suggest he spend time optimizing what he has FIRST before making the universal mistake of cutting, modifying, and altering a subpar/subperforming engine! You can put a Holley Dominator on that 318, but it doesn't mean it's actually a 'performance upgrade'. How many people spend a couple grand on their engine, and then are disapointed that the ratty looking stocker that rolls onto the dyno after their car rolls off spins it up to an equivalent number, or even higher (been there, in the ratty car...) All this 'incremental' stuff is just that: Incremental. It still is a system and some stuff just doesn't make sense to do first. Like milling the head for compression when you have sparkplug wires that are leaking to ground and misfiring at the top end. Not saying that is the case here.... but like I said in the beginning: What quantifiable result is he expecting to obtain from this modification? He's worried about the cost? If you are worrying about the cost of a marginal or incremental modification: SKIP IT! Like you said: CONTEXT. Read what the OP wrote, and consider he's worried about the $$$ expended. It's not YOUR car JM, it's his $$$ and his car. My advice would be 'pass on this one at this time and keep the car reliably running on regular fuel until you CAN afford it without reservation...'

It was 1999. I would have to look at the dyno sheet from our testing, we both advanced and retarded the cam up to 4 degrees in each direction and took the position that gave us the best torque. I remember for our application that 2 degrees was the ticket. This DOES NOT mean that 2 degrees is some magic number and this is where you set every cam. We spent $200 in dyno time testing the cam in various positions and took the one that gave us the best torque/HP split. Subsequent testing with different induction systems on the car gave similar results. The only way to know is buy a sprocket and try it on your particular build. Someone said: 'Big difference? By whose determination?' so this was illustrative of such an instance. Best $200 we spent in 'performance modifications' to that point. $200 for Dyno Time. Until you do that, you're just guessing. The torque and HP we picked up from that change allowed us to pick up our first record at ElMirage.

I use the Tomei from Japan, they have a nice etched degree wheel and are accurate. A couple of degrees makes a big difference. Our torque band went from 6000-7500 flat and level when the cam was 'straight up' compared to a 2 degree change resulting in that SAME LEVEL OF TORQUE being available from 4500-7500. It just opened up the bottom end and didn't seem to change anything up top. Having your torque plateau widened by 1500 rpms would be classified as a 'Big Difference' in my book. If you want to dispute that is not a 'big difference' we will have to agree to disagree. It was the difference between not being able to 'pull the spread' at speed and breaking records. Before the change when doing drag strip testing we would shift to third and you could literally count 1...2...3 before the wheels broke free and the car started accelerating again, passing through the traps at 13.08 at over 100mph and spinning the wheels all through the end of the 1/4 mile (3.36 gearset, and stock diameter street radials.)

It takes all of maybe 5 minutes to install it. I can't imagine any easier installation. It plugs into the factory harness in three places (light place for each bucket and the body harness going to the right headlight), and provides a plug for the no-longer used factory body harness to the left bucket. Attach the power lug to either the alternator B+ stud, use a sheetmetal screw to ground the relays and mount them in one fell swoop. Come to think of it, it was more like 3 minutes... It goes on my list of 'must do when buying a new 240Z to drive' right up there with 'replace lights to 55/100 H4 Beams and new water pump'...

But that costs $240, now doesn't it? And some dyno time to get it 'just right'. It's not just a retardation, the opening and closing events are slightly different as well. A couple cam degrees makes a big difference even though it doesn't seem like much. There is someone making nice replacement spraybars now out of billet aluminum, with 'cooling grooves' on it.

Wow, I was out of the loop. Was that on WCR forums?

Some grinders balk at regrinding drilled cams, the solid one will likely be a better bet. While the head is off, don't forget to open up the oiling restrictions in the top of the block to the recommended size (in the Blue Book) for good top end lubrication. With the crap oil these days, this helps. With the holes opened, you will have plenty of oil up top as long as your oil pump is in good condition. If you haven't installed a turbo/auto pump, now would be a good time to do so for additional flow capability.

"BTW, I have a P90 that I shaved and I'll suggest something in the middle that picks up on some of what both Tony and Jon say. The cost to shave and shim the head was in hind sight, not worth it. But it's rather cheap and easy to put a reground cam in while you have the head off. I used a Delta Cams regrind of a stock L28 cam (don't remember which one) that makes great power from 3500 to 6500 and still idles great. Plus, with the lower compression you can be sure to run full advance without detonation, something that's iffy with a CR in the 10:1 range, especially on hot days." This is more along the lines of what I was getting at: the CR increase will give you nothing but problems running regular gas, in addition to rendering a head useless for any other use. You didn't say the head was ALREADY OFF and NEEDED PLANING. In that case: shave AS LITTLE as possible. If you didn't port the head ($$$$$) it's coming off AGAIN anyway to have that done, so if you shave it now and anything happens between now and then, you're in the market for a new head... The "A" cam is better than the later cams. Notwithstanding JM's comment on them all being 'dinky' or whatever, they do have timing which promotes higher rpms than a pedestrian L28. Drive an original L24 and an original L28 powered anything and realize the 'zing' above 4000 just isn't there in the late models. The key is in the cam. And speaking of 'incrementals'---you will change to a solid cam and spraybar ANYWAY so why not do THAT instead... and like suggested have that early cam reground to something that will be slightly better than an early cam. That will pay LOADS more dividends than ruining the head by shaving it 080. Which, I think I said in the beginning...

Google "GM SERVICE MANUALS" and Fifth Suggestion was Helm, Inc Couple of clicks got me here: Slothless Clicky for Manuals Enter what the JY told you the year and model was and you have the order blank online for the appropriate service manual. Like this one, only $150 for the SET! I revert to my original statement regarding easy access of manuals for domestic vehicles in today's market. Though I was amazed to realize that Helm did ALL the domestics. Imagine that...

The point is that it's better to leave the damn thing alone than start going after 'incrementals'---if you really think an 080" cut is worth the effort, then so is swapping to the "C" cam, and blah blah blah... You want an incremental increase from a P79, throw it in the dumpster and stick a properly dressed N42 on it. Why cut a turd? To get one that doesn't smell quite as bad. Sometimes absurdity does not come across well on the internet. But I am also at work and couldn't really put a lot of effort into making it really over the top. Given the choices given originally, I think I said it more than once that 'leaving it alone' would be the best thing to do. And that Aluma-Seal was a better remedy for an 'all stock' engine as opposed to pulling the head for a gasket change. If you are going to do it, do it right (not all at once, but for gods sake why waste time on a P79???????)

Sad day indeed. Best wishes to Floyd and the rest of the Family.

Good Point, the L24 cam is solid and not particularly applicable to the later cam tower setup without a spray bar being added. I always run internally oiled cams with a spray bar anyway... I guess in that instance, my recomendation would be just "leave the head alone and Aluma-Seal it!" The P/N is all over the internet. They are NLA from Nissan I believe, but they are in engines all over the place. The early cams in an L28 get rid of the 'slow to rev' complaint people blame on the longer stroke.

Nobody said do it all at once. What do you realistically think you will gain by bumping the compression? You will still have an L28 cam, which peaks at what...5300rpms? Finding an earlier stock cam from an L24 will change the way the engine reacts, allowing more useable rpms, and I posit a more effective horsepower increase. Do you really intend to port and polish a P79 head? And if you do, what will your long term plans be, do they include rpms over 7000? If so pistons are on the horizon and then you are stuck with a shaved custom head with a strange combustion chamber requiring custom cut compression increasing pistons. I'd suggest you skip the planing of the head. I think there is some thought down the road this will be something other than a waste of money. But the head will come off for porting, so why do the head shaving now? Why not wait? The cost of the shaving will not net much IMO. Other than a higher than stock compression ratio meaning now you can run premium gas all the time instead of regular. Whereas a stock early cam that lets that L28 pull to higher RPMS will keep you on pump gas, increase your power, not require shims, valves, nothing (I mean the rocker arms are supposed tobe resurfaced, but if you get that cam from another older head...might find those matched rockers as well... If this is a question of "should I do this now?" I'd say skip it until your plans solidify more. You are polishing a turd. When's the last time you heard of anybody buying a 'performance P79'? OH, BTW....if money is a concern....I'd try half a tube of Aluma-Seal on the head gasket to stop the weep first. Ford would put that much in every car off the line at the factory (Volvo as well) so that is something to seriously consider if the engine is running well and has no other ills other than weeping a little coolant. I've done this one on several engines myself!

A solenoid or 'bump switch' to open a small orifice venting air around the throttle bodies is a scab fix. They were used on some cars (a late model Corvair, for instance) when emissions at idle needed enleanment but transition needed a lot of fuel... Small spring-loaded arm set to be tweaked and crack a rubber stopper over a hole in the base of the carbuettor straight to the manifold. Soon as you cracked the throttle, the spring put the stopper over the hole and vacuum sealed it tightly.

Argh, you completely missed the point! OK. ASSUME the SAME linkage on both TB's. 60mm and 50mm. Now, calculate throtle plate opening area. NOW, from a 0% rotation to 10 Degrees rotation, calculate the RELATIVE THROTTLE OPENING CHANGE between the 50mm and 60mm T/B. Because the 60mm flows an appreciable figure more (and knowing what that number is will allow you to 'pair that' with an equivalent 50mm T/B opening) you need LESS throttle angle on the 60mm body for the same 'modulation'... By using that formula, you will know EXACTLY how much to alter the linkage to give similar tip-in characteristics between the two. When you look at the valve flow coefficient the non-linear response to a linear rotation characterized in degrees may be plotted, and valves of different flow characteristics may be made to feel as though they are identical. This is what happens with fly-by-wire. For all intents and purposes the TB opening is 'linear' as you use the 50mm as your baseline to compare with a 60. You manage the DIFFERENTIAL CHANGE to make modulation similar. And to do this you need FAR MORE non-linearity on the 60mm TB than you do on the 50 to get the same 'feathered throttle' feeling. If you want to split semantic hairs fine, but you're throwing out the baby with the bathwater arguing a moot semantic point. Throttle opening is in degrees, and THAT IS LINEAR and comparable between the bodies. The flow given per angle of throttle rotation is not linear, and far mor dramatic at low throttle angles on the 60 relative to the 50. Don't loose sight of what is being discussed. You will miss the forest in all the trees. You've already been discounted in the discussion as not being able to 'feel' the flow difference with identical linkages (a physical law at work there, BTW) kind of means stating the obvious (not linear throough 90 degrees of motion---who said it was?) is not contributing anything to the thread.

Motors Manuals were the choice of independent garages for years. They directly copied many of the sections of the Factory Manuals. I would put them right next to Factory Manuals---they were tools for professionals. Rarely, if ever, will you find a Haynes, Chiltons, etc in a real car shop unless it's a really obscure thing and they need a specification. I mean hell man, some of them can't get the FIRING ORDER CORRECT on a Datsun L-6!

Gasoline will expand about 10% by volume. If you fuel up and then drive, chances are good you will go the 19-20 miles required to give you space in the tank to then stop and eat and let the diurnal variation cause your fuel to expand. Venting of the tank is crucial to proper pump operation and getting a full tank when at the pump. It needs a high point to bleed the air out of the captive parts of the tank. JDM cars had a 1/4" overboard dump (my 73 for instance...) and that works just fine. See the other comments about using nylon adapters to convert the larger vapor recovery hoses to something smaller, more managable, and cheaper. a 1" band will not give you much capacity. Expect 22-27mpg if the car is running properly and you keep the speed below 80. That's about 3 hours at a stretch driving before you want to think about getting a tank of gas. It's a nice interval to stretch you legs. If you want capacity, cut out the spare tire well, and put in a 77 - 78 gas tank, they are 16 gallons. You CAN fit a 100L (32 Gallon) tank back there. No spare tire. Stock Datsun Part, NLA. Needed a special sender and dashboard gauge anyway. No, you can't use mine. I plan on using it in my Diesel Conversion. At 40mpg conservatively, I'll go 1200 miles between stops. Just about a days drive the way I do it. Forget about that kind of range with a petrol car, you will stop six times and waste 20 minutes a stop each time, so at the end of the day a petrol car will have to drive 2 hours longer per day to keep the same daily pace as I will be able to in my Diesel Z. Yeah, been across the country a couple of times... Yeah, I use a stopwatch and write stuff down...

Do the mass-flow calculations, and you will see preturbo is 'no free ride'---the mass of the air, while increased....also contains water. You can preinject before the turbo to the limit of 100% R/H on the outlet of the turbo. It must then go DIRECTLY into the engine as if any cooling of the charge air occurs condensation and liquid water will form. The density increase from latent heat offsets the loss of air due to water displacing it, so you get more power. If you had something that burned (methanol) then the latent heat issue is AIDED by the 'carried along' anti-detonant as it is burning as it goes. In either case, your cylinders stay really clean. Spearco Water Injection (2 Stage) on the car since 1979... You know they made them for N/A's back then as well?

Question is, what do you gain by the CR bump. Is it worth trashing a head that can then never be decked again without more shims, longer valve stems, etc etc etc... What realistic gains can be expected from this? I posit a cam change from an earlier engine might benefit him more than the bump in compression would.

ECU doesn't see injectors, they are an output device. The only thing it 'sees' is RPM, AFM, CLT, TPS, etc... You can put 370CC injectors on there and the ECU won't know the difference, it will just run pig rich as it has no method for pulsewidth alteration. It doesn't know 370 from 280 from 160 from 550 from 720CC injectors. It fires the same pulsewidth based on the input signals from the above input devices. There isn't even an O2 sensing loop to know that you're rich and to taper off the pulsewidth. It is a dumb ECU.