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@braap: Have you had the chance to drive your LSx/M3 yet? It looks like an amazing setup.

I hope everyone had a nice holiday. Please see my inline comments. I'm still working through the L-Series cooling thread... lots of information there. I'm just surprised that an aluminum cylinder head has so many issues with cooling, and hot-spots. The Heywood book looks excellent although I have a feeling some of the math is over me head. Maybe I'll grab it along with Frank Honsowetz's How to Modify Your Nissan/Datsun OHC Engine. Agreed. I guess I am sort of thinking about it the other way around. If any one part did determine an engine's general behavior and characteristics it would probably be the cam. And like you said, pick the characteristics (RPM, desired torque/power, etc.) you want, pick the cam that gets you close to that and then go from there. All very good advice. I got to ask though, with duration of 280+ degrees, aren't you just pushing the intake fuel/air charge right out the exhaust port? Your last configuration for example uses a cam of 310 degrees duration and .550" of lift. I think the biggest cam (in terms of duration) I have run in a SBC has been around 230 degrees duration and .5" of lift (and that was 2.02"/~51mm intake valves, and 1.89"/~48mm exhaust values). How does the engine idle? Can you drive it on the street without constantly having the engine stall out? That thing must sound like a beast. I'm going to assume you went with such a long duration cam for high RPM power... is there any chance you have a dyno chart for any of your engine configurations? I would be really interested in seeing what the torque curve looks like, and where in the RPM you start building power, and what the average horsepower over an RPM range looks like compared to the peak horsepower. Of course, it would be totally understandable if you don't want to share that kind of information or are unable too. Your current info regarding your various engine configurations, and the approximate "back-of-the-napkin" prices have been more helpful than I have words for (other than thanks!). So you are basically saying that unless, I'm really interested in going with an all out "race-engine" (of course, I don't exactly know what that means for an L-Series but I can guess) configuration, it's not worth focusing on squeezing as much compression as possible out of a given combustion chamber/cylinder head/piston combination especially since the L-Series heads are so prone to detonation. All that approach would get me is a greatly increased risk of engine damage should I screw something up (too lean on the carbs, not enough advance, low octane gas... *cough* E85 *cough*, etc.) with a pretty marginal benefit in terms of performance. So the high static compression ratio and big duration cam is essentially just asking for trouble? On your E31 with dished pistons setup, what exactly do you mean by "heavier pp"? (I'm not not familiar with that term.). And is there any chance you have some rough numbers behind what a "a LOT more power" means? I know at the end of the day, "the-seat-of-the-pants" dyno is really the one that counts but I'm still trying to re-orient myself from SBC-land with it's plentiful and affordable after market (e.g., Hot Rod's 500/500 383). Thanks once again for everyone's input.

Sorry for the extended absence... I had to do some "real life" stuff ("real life" sucks). There is much excellent information so far! @Dan Baldwin: Thank you very much for sharing the details of your buildup. That was exactly the kind of information I was looking for. I'm just trying to get an idea of what it takes to make a N/A aspirated L6 perform decently without spending $10K (although, since you haven't attached estimated prices... maybe you did spend $10K? ). @Gollum, didier, johnc: The other half of preventing detention is dealing with cooling and fuel issues as you so rightly pointed out. Using good quality gasoline seems like a good place to start but I imagine fuel charge homogeneity, fuel atomization, and appropriate fuel:air ratio are all very important in maximizing the performance potential of a given cylinder head/combustion chamber/piston combination (that's probably a topic for the Induction sub-forum). However, a quick question... why does the cooling system suck so badly on the L6 series cylinder heads? Is it just a design limitation? Is just 70s tech? http://www.davidandjemma.com/mazda/FAQ/quench.htm While I am definitely not a mechanical engineer, I have been reading up a bit on combustion chamber design and quench. Now, I cannot say one way or another, whether that guy in the linked article has any clue what he is talking about, but most of it seems to ring true... although there seems to be a lot of weaseling. For example, why does adding quench (say a flat top piston combined with an N42 cylinder head) aid in creating fuel charge homogeneity via "better mixing"? Other than to prevent detention, why would you prefer a lower static compression ratio setup like the N42 over the potential higher static compression ratio you could generate with a P90 or P79? Where I come from what you are looking for is as a high of a static compression ratio as you can get away with, a small volume combustion chamber (that is, the low surface area to volume ratio) and a cam with the duration to match. Maybe I have no idea what I'm talking about? (I should probably go re-read all my Vizard books).

First I would just like to express my appreciation for everyone who has taken the time to reply to my questions! Why would one prefer dished pistons matched with a N47 or N42 cylinder head over flat pistons matched with a P97 or P90 head? Is this the whole quench vs. non-quench debate? At this point I haven't purchased anything beyond a rather clean '71 240z that's had some mild engine and suspension work done on it. I'm really just in the bench racing stage of figuring out exactly which kind of car I want to build and how I want to go about it. The underlying question for me really is something along these lines: if I did everything except the head porting myself could I build a 275-300hp 3.1L naturally aspirated L28 for around 5K? But posting such a general question seems contrary to forums rules or at least their intention; so at this point I'm just trying to fill in some gaps in my understanding (i.e., climbing the learning curve). @Lazeum: Ahh, no worries, I was just curious. It sounds like you got a pretty sweet setup. What kind of lift? Lobe separation angle? Overlap? It's not that I really have a need to know all about your cam? It would just be nice to put some numbers on it, that's all. As for my comment about valve overlap and the compression ratio... you are absolutely right. I was thinking along the lines of compensating for a large overlap by raising the compression ratio so the remaining fuel/air that isn't inadvertently pushed out of the combustion chamber on the compression stroke is "compressed" further and more energy is thus extracted from it. (This may be a completely wrong understanding of engine dynamics.) I'm also under the impression that a lot these high horsepower NA L28 engines make most of their power past 4500 RPM, which is why I sort of mentally connect them with a high compression ratio and cam running a relatively large valve overlap. (This is probably completely wrong also). So getting some mild "street" porting done, along with the machining and cam tower shims for $1500 is not realistic? I'm not trying to disagree with you, I honestly just don't know. In the SBC-world $1500 dollars gets you pretty close to nice set of aftermarket heads. Why would you prefer a N42 with flat tops over a P79/P90 with flat top pistons? The advantages I see in the N42 are better CFMs with big "race" cams and the square exhaust ports... is that correct? I guess you get the desired compression ratio without having to machine the bottom of the head but you lose the combustion chamber shape of the P90/P97, which to my untrained eyes looks like it has better burn characteristics. Thanks again for everyone's help.

Thanks for everyone's replies. Is there any chance you could post some more information about your Rebello cam (lift, duration, etc.)? So would $1500 be a reasonable amount to expect to spend for getting a head like a P79 ported? Does your figure include the price of the cam? This is great info! Thanks! I know, at least in a general way, that duration and valve overlap play a significant role along with the compression ratio in determining an engine's characteristics, including how close you get to detention. Again, I have just read that these heads are *really* prone to detention... Is there any chance you have some more specific information from your cam running in your 9.75:1 with a 270 setup? Yeah and they seem to be substantially cheaper, hence my interest in them. If I can get a good P79 for $100 less than a P90 and for my planned application there's no significant difference, that's $100 dollars that could go somewhere else. Braap had this to say in some older threads about the liners: Source

First thanks for the reply. Second, which sticky are you referring to? The L6 heads; pics and descriptions thread or the big and nasty headwork thread? I read that the P90 has square exhaust ports instead of the oval shaped ones on the P79. Is that another reason to avoid the P79? If so, why? This is also the first I have heard of exhaust liner breaking... that does not sound good.

Everything I've read here on the forum points to the cylinder head as being the place to make power with the L6 series. If I understand correctly there are a couple of important points: 1) The L6 series is very detention prone making anything above about 9.1:1 on pump gas (92 octane) dangerous, especially when running an engine without electronic fuel and ignition management. 2) The L6 cylinder head, regardless of their castings, in their stock form just don't seem to flow very well. And since getting fuel/air mixture in and getting exhaust out again is the name of game, this is a serious problem unless you are using forced induction to overcome these limitations. So if you are a fool like me and you are considering ignoring everyone's advice to "just do a turbo or V8 swap" and instead go NA (I'll probably do the V8 swap anyway!), the cylinder head seems to be the place to put your money. Am I on the right track so far? All the stuff I've read for NA engines seems to point at using a P90 or N47 for a naturally aspirated L28 application... why not the P79? They look like they have a pretty good combustion chamber shape, and with some porting (at least according to BRAAP) they can flow well enough. If you shave .080" or so off the cylinder head and use flat pistons you should be able to get a decent compression ratio, run a nice lumpy cam, get good burn characteristics and decent CFMs once ported. So why does it seem that there are not many of these around? Is it one of things where it costs a little bit more for the P90 so you might as well get it? Is it just an availability issue? Did I just ask a really stupid question?

Here's some recommended reading for anyone in my shoes who is following along: NA 3.1L Way more than you ever wanted to know about L6 Cylinder Heads L6 Cylinder Head Descriptions Japanese NA 3.1L - 400hp

Thanks for your reply. I'm definitely planning on doing the work myself (that's part of the fun!) and it's not the first engine I've built so I have some experience with the process (although with a different engine). I'm also not adverse to taking my time buying affordable parts. I just wanted to know if my goals were at all realistic or if my enthusiasm was getting the best of me. The EFI vs. carburetors is hard choice for me. On one hand, I love the mechanical look, feel and sound of carburetors (not to mention their affordability compared to EFI). On the other hand, it seems pretty hard to argue with the technical merits of a well-tuned EFI system; it is just so expensive... (new tank, pump, lines, filter, pressure regulator, manifold, injectors, ECU, etc.). Anyways, it is kind of a smaller version of my LS1 vs. L6 debate. Choices, choices. I suppose I need to do some more research...

Hmmm. So assuming stock horsepower is somewhere around 150hp on the L28, increasing the displacement alone might net 10-15 extra horsepower... but with a better cam and induction would numbers somewhere around 250hp be achievable for 5K? Maybe I should ask the question the other way around. If you had a 5K budget to build a naturally aspirated 3.0/1 Liter L6, how would you go about it? Sparing any heroics, would 250 or 275hp be attainable? From my flailing around the forum these kinds of results seem possible, but are certainly not the norm (as you pointed out there are better and more productive ways to spend 5K on L6). In my dreams, I would love to build a 300hp 3.0L that's naturally aspirated. I'm just wondering what kind of price tag would be attached to that kind of engine and whether my commitment to a 3.0L would be enough to overcome it. And I will repeat the mantra You can have slow, reliable and cheap. You can have fast, unreliable (err, broken) and cheap. Or you can have fast, reliable and expensive.

Double Post...

I hate to resurrect a thread but I figured that doing so was preferable to creating a whole new one. I'm sorry if I'm being an idiot but I could only find the 3.0L Stroker reciprocating assembly listed for sale on Rebello's website. Do they also sell a whole long block kit? How would such a kit compare to just using a LD crank, L24 rods, and KA24 pistons? The Rebello Stroker Kit is listed at $1,800 which doesn't sound too expensive considering everything is included, but I imagine shipping adds a lot to it (I can'tell from their website but it appears that you have to send in your crank as a core exchange?). Hypothetically speaking, if I had a 5K budget for an engine, would you recommend the Rebello kit over the DIY combo? What kind of rough, back of the napkin horsepower numbers do you think a moderate 3.0L could produce with a street-able cam and no head work? I've seen numbers all over the forum starting at 190hp and ending somewhere up at 290hp! (Of course, I know you can't just compare HP numbers straight across because of all the variables involved - I'm just looking for estimates).

How come they don't sell these in North America? Those are great looking headers! How difficult were they to build? How much welding experience do you have? Did you use a MIG or a TIG setup? (I'm just wondering how far away from my current level of expertise they are...)

I know this project is on permanent hold but I just wanted to stop in and leave some encouragement because 1) this is soooo badass and 2) see item 1. Perhaps one day we'll see one of these in a S30...

Yeah, seriously. I've never heard of machining costs over $500 dollars and I live in Alaska where it cost at least 30% more for ANYTHING. I think we've paid around $400 for having a block tanked, all the plugs punched out, bored, honed and the cam bearings pressed in. When you guys are quoting machining costs of around $2000 what are you including? Head porting, balancing, assembly? Any chance you could be more specific? Because $2000 for machining cost just sounds outrageously expensive for a street engine.

@cygnusx1: Very clever! Any ideas for what someone in my situation can do for a quick fix? The heat from the forks has melted enough of surrounding plastic on the fuse block to make proper placement of the forks impossible. I've thought about just putting a fusible link in its place so I can get the tail lights working again (currently, I've just used a test jumper to keep me rolling). I have an old fuse block but that I don't want to go all to work to replace the current one just to have the same problem happen again. Should I prep the old fuse block by making sure all the forks and backing plates are clean and then add a little solder to the gap where the meet? Will that eliminate the overheating issues due to corrosion? Or is the only real proper way to fix this issue to upgrade to one of the new MSA fuse boxes? While I was driving today I got a not insignificant amount of smoke coming out from either under the dash or from the steering column area. A quick look at the harness on the steering column didn't show anything amiss but then again, I can't see up underneath the dash completely. I'd say I got some electrical problems!

I'm having the same issue on my '71. The forks that hold the fuse for the tail/moving lights circuit have either got hot enough to melt the plastic of the fuse box due to resistance or the previous owner for some reason hogged out a pretty big hole where the forks and plate are supposed to fit. Regardless, it got hot enough to burn my finger when I stupidly touched the fuse end. I think I'm going to go ahead and check the connections (such as the light bulb sockets) on that circuit and see if I find the source of the extra resistance. It hasn't been enough to burn out the fuse but its certainly been enough to melt the fuse block to where I can't actually get a good connection anymore.

Awesome. Thanks everyone for all the great info and time put into this thread.

At the risk of sounding like a complete newbie (which I am)... the 240 has separate braking circuits and a bias value located on the firewall next to the brake master cylinder right? I would check but the car is being stored in another state.

This is pretty much my thinking as well. I figure if I can spare the 4-5K I'm planning for the engine build, then I can spare a few hundred to upgrade the braking system. I also like the idea of rear disc conversion simply because of the ease of maintenance compared to drums. However, if it's not an absolutely necessary upgrade for the kind of driving and power I'm planning on, I will probably just stick with the stock system. There's so much work I wanna do with the car, I'm having problems figuring out where to start! Suspension, brakes, engine, interior?

I have to agree. The stance is just perfect. @Shika805: Is the car lowered at all?

I was exaggerating for comedic value. So do you feel like the handling and brake feel was substantially improved? I mean for that amount of money, it's almost impossible not to want to a caliper swap.

So I got all fired up about doing the Toyota S12 caliper swap in the front and rear disk conversion but them I returned to the FAQs (see I do read them!) and thought about this:

If it hasn't been posted already, I thought this was a pretty cool article: http://www.hotrod.com/pitstop/hrdp_1011_cams_for_turbocharged_engines/index.html

@Bahraini240z: Very nice car! What size tires are you running?