zredbaron

I'll chip in further to offer another perspective and to hear myself talk. Six one-way, half-dozen the other... in the end you get the same result. (In theory, ironically. Too soon? ) Personally, I tend to stay away from numerical estimates and was always more interested in the relationships between the parts. I tend to pester the experts asking why this new part or adjustment will or will not bring me closer to my power (and sound, let's be honest) aspirations. (Not all elders appreciate this line of questioning, some see it as challenging their answer, but I digress...) From my technically educated and indirectly experienced (the hard way, as a consumer) perspective, the NA L6 starts to make 'real' power (let's call it the 225-250 whp benchmark) when the parts are all specifically selected to run together. In other words, when the parts are in tune with one another, as opposed to a bunch of haphazard performance add-ons slapped together (stereotypically by buying all the upgrades in the MSA catalog). I know the OP isn't shooting for 225whp, but perhaps another perspective (less numbers, more practicality) may shed some light. The OP has made it clear he values his numbers above all, but there are always silent readers, after all. In my case, I had Sunbelt build the very next head after JohnC paid for all that R&D (still owe you beers for that!). HybridZ is abuzz with "the power is made in the head." I also add that the head alone doesn't produce much power in and of itself; the other parts have to be there, and it has to be tuned. Common sense, perhaps, but still. I then "slapped" a full race-prepped head onto a Nissan Competition (yeah, it's old!) 3.1L bottom end. The cam I selected was NOT the cam that JohnC's R&D had resulted in -- the stroker wasn't compatible with the cam unless the pistons were significantly valve-relieved. The engine breathed through MSA headers and triple DCOEs with 36mm venturis. This resulted in ~200 whp. I also will add that tuning on the dyno, timing only since I didn't bring the jets, produced a 9% increase in hp and a 6% increase in torque. This wasn't even a tune that included A/F adjustment. This is in stark contrast to the OP's claims that tuning accounts for 1-2% of power. Also, peak hp was at about 6300 rpm. This was also a sizeable camshaft jump from about .465" lift with 270 or so duration to .525" lift with 290/274.8 duration. The next upgrade wasn't as big of a jump parts-wise (debatable, the cam is pretty nice). The bottom end was beefed up (forged slugs), but it was the same specs aside from the valve reliefs in the pistons. Unbalanced. The main changes were switching to a Sunbelt cam that the head was built for (not identical to John's, but close), adding about 1.0 to the CR (to a target of 12:1), and going to full race fuel (VP 109) from 100 octane. From what I understand, the cam was responsible for most of the new-found power: 265whp @ 6000 (lower rpm, despite the aggressive increase in duration). My engine is also in contrast from the OP's claims regarding the need for rpm - I experienced a 33% gain in power and a reduction in peak hp rpm, presumably for primarily VE reasons. The cam was still a Sunbelt cam, it had the same lobe separation, etc. Lift went from .525" to .565", and duration went from 290/274.8 to 326/315 duration. This was with the same ignition, same street headers and same carburetors I was using all along. The cam simply realized more flow potential of the street-performance intake/exhaust that the full race head had been patiently waiting for all along. Still is, too. For me, the lightbulb turned on when I had the head off for this year's round of upgrades (undynoed). I had the head flow-tested and was very surprised to learn that my peak flow numbers *exactly* coincided with the lift numbers on my 2nd Sunbelt cam! It was almost as if the cam was profiled for the flow characteristics of Sunbelt's head work, weird! And yes, I realize this is a race head and not what the OP was looking for. Concepts remain. The point of all this, is that from my perspective there wasn't some numerical relationship for me to out-engineer the engineers, but rather good-old-fashioned trial and error (paid for by those before me). If I wanted to sound technical, I would probably say something to the effect that the volumetric efficiency was maximized through careful measurement of flow characteristics and then the cam was profiled to match. You can (and should!) pay for this "VE matching" / "part tuning" to also include the bottom end, intake, and exhaust... "how fast do you want to spend" comes to mind here. Bottom line, for me it's the relationships that matter. Conceptualizing the significance (and assigning proportional value) is worth much more to me in engine-building decision-making than any set of mathematical guidelines. Sure, I recognize that when I consult an engine builder, numbers will ultimately play a part in my engine design. The difference is, I consult the experts for their numbers to meet my conceptual goals, I don't dictate to them what the numbers should be... But hey, that's me. Technique only.

Don, Save your money and listen to the passel of world-class experts here on HybridZ. Many of the members replying to your thread are among the most experienced and educated minds out there in the L6 motor niche. I used to think I was smart enough to figure it out on my own, but four engine *RE*builds later, I now know that I was given the answer all along, I just didn't like the answer. (Not a good reason!) It wasn't that I didn't believe them, it was that I thought my solutions would also work. I may very well *be* smart enough, but intelligence requires experience to be of any value. When was the last time conjecture was worth your hard-earned dollars? In short, even if you had read books or taken classes on a subject... would you tell a lawyer how to present a case, an airline pilot how to get you there, or a surgeon how to repair your body? Then why be any different with engines? The wealth of *experience* on HybridZ is priceless. And it also happens to be free... if we're able to swallow our pride and hear it. Don't be like me and waste years and thousands of dollars to realize such a mistake... , Mark PS - Great thread, guys.

Thanks. I wasn't sure whether I'd be deforming the floor or the headers.

Bump. No opinions on the headers being physically pinned flush against the firewall/floorboard?

When I rebuilt my race motor in 2008, I tossed my Nissan Competition "Euro damper" and bought my race damper from Dave Rebello. He has customized some products from BHJ, and I can absolutely confirm that they're very stout products. I'd recommend giving Rebello a call to verify application.

Thanks guys! I have to admit how glad I am that I hauled the car around to half a dozen fabricators... I really scored big finding Carlos. He did some truly fine work, the kind you just don't normally see that often. The other shops concerned me that they would cut corners and not deliver what I was asking to pay for. It was an incredible amount of additional labor, but he was genuinely excited about the project and it shows! No plans on returning to VA in the foreseeable future, John. I'll miss the car clubs, but well, that's about it. Goodbye, Navy!

I'd like to point something out / pose a question regarding the video. I was surprised both at how much quieter the car was than expected and also how smoothly it idled (relative to before the rebuild, when it was actually tuned). After talking to a friend, the conclusion regarding it being quieter than expected is that this is due to both proper exhaust scavenging and the larger diameter primaries / merge collectors. Mostly because of diameter of piping. As for how smooth the engine ran.... the carbs were in no way synchronized, jetted or even tuned for idle mixture. I'm not sure if this is a testament of the tuned exhaust, crank balance or both. (Not to discount the importance of fuel + ignition, but both were present before this smooth condition.) This video was taken about 20 mins after the engine was first started and warmed up. I'm particularly inspired by the fact that the only time you can *see* the engine move was at startup when the cam's overlap just about kills the start. I wonder how much of it running so smoothly is the crank balance vs. the exhaust scavenging. Thoughts?

And final assembly drew near. I literally started at 9pm that night, and in these pics it was about 9am the next morning. I was leaving for the airport at 11am and had to wrap this up, get it running and slap the car in the trailer for the next 4-6 weeks. There weren't the bodies to push it up the trailer ramp, and no one wanted my car left out in the commonly opened building. Ready, go! Getting close. I don't think I had drained the old fuel yet. I'm pretty sure this is right around final assembly. Minus the valve cover breather hose. This was definitely complete because I can see coolant on the ground. Evidently I only finger-tightened one of the thermocouple housings. Oops. And finally, a short video with audio... And yes, that's as far as I've gotten. I won't be back in Arkansas for at least another month.

Next up, the pulley system, etc: I also had the water pulley powdercoated. Part of my Kameari order included this adjustable alternator bracket. Wasn't that expensive, so I included it with my order for the motor mounts. Also new in this pic is the 280Z alternator with internal voltage regulator + diode conversion from MSA. Much better than my crappy setup before, which included a broken wire that prevented charge reaching my battery. Essentially I raced last year off of the battery as an expendable electrical tank. Oops, no wonder I had to charge it all the time. Getting ready for the headers. I verified my spark plug wires were still consistent after 600 miles, they were. In the 2008 rebuild I went into the weeds with them. I called Electromotive and they evidently use this specific EMI suppressed wire that's 800 ohms/ft or whatever it was. They told me they send the most spark energy to the CC with about 1250 ohms of resistance. So I cut all my wires the same length to match that resistance. I checked them all this go around and all were in the 1250-1275 ohm range, so I'm good still. No amount of cursing will convey how long it took me to get the Stahl headers installed. The frustration was further compounded by my attempt to keep the ceramic texture as clean as possible (dirt magnets!). I first assembled the headers into their final 6-2-1 design, and bolted them together and fastened the spring retainers. After wrestling the headers and the manifold bolts for about 30 mins, I finally gave up and decided I couldn't get the flange to clear the bolts unless the header was disassembled. So I took it all apart. Even then, it was a ton of wrestling just getting them on. Then came our favorite game of getting the thick washers that retain the bottom of the intake manifold onto the bolts. The thick primaries interfered in a laughable fashion. I spent a lot of time on a bench grinder shaping one of my custom spacers. The spacers were essentially thick washers with two tiers of thicknesses. The Stahl flanges were much thinner than my Canon intake manifold, so I needed a step washer to properly fasten both sides. Surprisingly enough, I don't have a picture of the stepped washers anywhere. You can see them installed, so I'll try and show that later when I'm with the car again. After messing with the bench grinder and the step washers for at least an hour, I finally got the headers bolted up. I get under the car and start assembling the primary collectors and merge collector. Fail. The merge collector wasn't even close to having the real estate to slide over the exposed pipe. Back to the drawing board. I loosened the headers, removed them, and assembled the primary collectors without the merge collector. I put this assembly back on the head and loosened the nuts as far as I could. This play allowed me to tilt the bottom of the headers just enough to get the merge collector over the exposed pipe. Whew! Took me another 30 mins to get it all the way on. Then I went back and tightened the header on and checked for clearance. Sure enough, the merge collector is pinned against the firewall's corner. Sigh. But wait, I forgot about the stepped washers! FML, now I have to loosen everything again, and wrestle the intake manifold to get the damn washers onto the bolts. Probably another hour later, I *finally* had the headers bolted up. Took me at least another 15 mins to get the retaining springs on. For one of them I simply could not get my hand to it: The obstructed portion of the merge collector is exactly where the pipe is touching the firewall's turn. It's not barely touching, it's solidly flush. I don't know what that means for the pipe or the car, but I'm not removing those headers. Someone please break it down for me? I'm thinking I'll use a turnbuckle if I have to cinch it away from the firewall. I could do it with the headers hot so they are slightly more malleable and may cool into a new position slightly. Anyone see any red flags? I did eventually get the carbs installed. God, I hate our manifolds. So of course I would love for anyone's opinion on the issue with the headers being up against the firewall corner....

This is everything unloaded once I reached my Dad's ranch in Arkansas. He has a large metal building that's fairly new (5-10 yrs?) and therefore is a wonderful place to work on a car. Too bad it was so damn hot! I literally had to work at night. Even then I sweat my ass off. Humidity is the devil.

And final assembly drew near. I literally started at 9pm that night, and in these pics it was about 9am the next morning. I was leaving for the airport at 11am and had to wrap this up, get it running and slap the car in the trailer for the next 4-6 weeks. There weren't the bodies to push it up the trailer ramp, and no one wanted my car left out in the commonly opened building. Ready, go! Getting close. I don't think I had drained the old fuel yet. I'm pretty sure this is right around final assembly. Minus the valve cover breather hose. This was definitely complete because I can see coolant on the ground. Evidently I only finger-tightened one of the thermocouple housings. Oops. And finally, a short video with audio... And yes, that's as far as I've gotten. I won't be back in Arkansas for at least another month.

Next up, the pulley system, etc: I also had the water pulley powdercoated. Part of my Kameari order included this adjustable alternator bracket. Wasn't that expensive, so I included it with my order for the motor mounts. Also new in this pic is the 280Z alternator with internal voltage regulator + diode conversion from MSA. Much better than my crappy setup before, which included a broken wire that prevented charge reaching my battery. Essentially I raced last year off of the battery as an expendable electrical tank. Oops, no wonder I had to charge it all the time. Getting ready for the headers. I verified my spark plug wires were still consistent after 600 miles, they were. In the 2008 rebuild I went into the weeds with them. I called Electromotive and they evidently use this specific EMI suppressed wire that's 800 ohms/ft or whatever it was. They told me they send the most spark energy to the CC with about 1250 ohms of resistance. So I cut all my wires the same length to match that resistance. I checked them all this go around and all were in the 1250-1275 ohm range, so I'm good still. No amount of cursing will convey how long it took me to get the Stahl headers installed. The frustration was further compounded by my attempt to keep the ceramic texture as clean as possible (dirt magnets!). I first assembled the headers into their final 6-2-1 design, and bolted them together and fastened the spring retainers. After wrestling the headers and the manifold bolts for about 30 mins, I finally gave up and decided I couldn't get the flange to clear the bolts unless the header was disassembled. So I took it all apart. Even then, it was a ton of wrestling just getting them on. Then came our favorite game of getting the thick washers that retain the bottom of the intake manifold onto the bolts. The thick primaries interfered in a laughable fashion. I spent a lot of time on a bench grinder shaping one of my custom spacers. The spacers were essentially thick washers with two tiers of thicknesses. The Stahl flanges were much thinner than my Canon intake manifold, so I needed a step washer to properly fasten both sides. Surprisingly enough, I don't have a picture of the stepped washers anywhere. You can see them installed, so I'll try and show that later when I'm with the car again. After messing with the bench grinder and the step washers for at least an hour, I finally got the headers bolted up. I get under the car and start assembling the primary collectors and merge collector. Fail. The merge collector wasn't even close to having the real estate to slide over the exposed pipe. Back to the drawing board. I loosened the headers, removed them, and assembled the primary collectors without the merge collector. I put this assembly back on the head and loosened the nuts as far as I could. This play allowed me to tilt the bottom of the headers just enough to get the merge collector over the exposed pipe. Whew! Took me another 30 mins to get it all the way on. Then I went back and tightened the header on and checked for clearance. Sure enough, the merge collector is pinned against the firewall's corner. Sigh. But wait, I forgot about the stepped washers! FML, now I have to loosen everything again, and wrestle the intake manifold to get the damn washers onto the bolts. Probably another hour later, I *finally* had the headers bolted up. Took me at least another 15 mins to get the retaining springs on. For one of them I simply could not get my hand to it: The obstructed portion of the merge collector is exactly where the pipe is touching the firewall's turn. It's not barely touching, it's solidly flush. I don't know what that means for the pipe or the car, but I'm not removing those headers. Someone please break it down for me? I'm thinking I'll use a turnbuckle if I have to cinch it away from the firewall. I could do it with the headers hot so they are slightly more malleable and may cool into a new position slightly. Anyone see any red flags? I did eventually get the carbs installed. God, I hate our manifolds.

Thanks Jon! New LCAs are definitely on the list. As are CV joints one day... uh oh, what's this I see in your signature about them? This is everything unloaded once I reached my Dad's ranch in Arkansas. He has a large metal building that's fairly new (5-10 yrs?) and therefore is a wonderful place to work on a car. Too bad it was so damn hot! I literally had to work at night. Even then I sweat my ass off. Humidity is the devil. When the head shop repainted my block, they neglected to paint the thin transmission cover plate, so I started with some sanding, priming, and painting: Which I of course had to apply to the other side. Overall, I was fairly pleased that I didn't screw it up. I also did the same to the brake master cylinders:

This pic was taken right before the car came back with the fresh paint. Here is my garage staged with parts and even a rebuilt motor under the cherry picker... Lots of goodies await! The boxes on the left contain new HyperCo springs, a new muffler + tip, Stahl headers, adjustable sway bars (w/ heim joints), etc. My fenders are wrapped up in the blankets under the cowling. The b!tch supervised. Zeppelin's her name. (Evidently when using that word properly, it still gets censored... sigh.) I wanted to seal up the motor as best I could prior to travelling across country.

Good to hear John, and thanks for your hand in this project. The painter did a phenomenal job given the limitations I handed him. The corner with the brake booster and master cylinders wasn't accessible for him and the back firewall was like a thick layer of dirt and grease. It was disgusting to get it on your hands and stuck like gum. This was painted by the same guy that did my exterior in 2009. He has a large bay and paints 18-wheelers on occasion. He had some cement truck paint in stock that he said will become tough as nails over time. I went for the satin black. He also used some of my leftover red paint to hit the cowl and front trim in the hood supports area. I had him leave the crossmember alone. I'm going to remove it later and have it reinforced, the LCA pivot points relocated and then powdercoated a matching black. It even looks nice from underneath. Fabulous work. Carlos Cardounel of AutoDynamix Racing Cages in Richmond, VA: carlosc@peanddesign.com or (804) 380-8947. My local Z shop (Todd Wagner, Tidewater Z) redid my relay setup. I essentially had too many splices over the years and wanted it simplified. The non-oem wiring you see is to power the Electromotive ignition and also the fan relay system. To be cleaned up later. The Techno Toy Tuning camber plates look really sharp contrasted with the black.I hoped to use my Ground Control guts since I had custom collars fabricated for hood clearance, but they were incompatible. I'm having difference clearances issues this time. First the nut didn't allow the bearing to articulate, but an acorn style lug nut seems to have corrected that. Now I'm concerned that there might be play caused from a different spherical bearing diameter (induced by my custom collar). I haven't had time to investigate, I've more or less been in a rush to "slap it in the trailer and go." I'm in the middle of a move and by the time I got my car in this condition, I was already mostly packed up and out of my house in Norfolk, VA. (I just got out of the Navy and I'm not sure where I'll end up just yet.)

Split project thread: http://forums.hybridz.org/index.php/topic/101309-weld-in-camber-plates-custom-strut-braces-engine-bay-respray-project/ In the above thread I'm posting pics of the fabrication work and engine bay respray prior to installation of the rebuilt engine. As for ITBs -- Yes, eventually. I'm going to keep these carbs and see what I can get out of them and compare. That may be the only upgrade at the time, too, which would be interesting for dyno plot comparison. For the record I'm running 40mm Webers, which means a max venturi of 36mm, which were installed with air horns and a cold air intake plenum for years now. ITB's aren't for a year or two down the road, perhaps.

Here are my camber plates after they were welded in. I requested the shop to file down the welds and make it appear factory. They did a tremendous job, as you can see: This has the flanges tacked in and a reinforcement plate welded onto the outside of the tower. And you can see that this plate was also smoothed out, too. Preview of the final design: It's hard to tell, but reinforcement plates were welded to the firewall. They were then smoothed out like the shock towers were. The flanges, however, in all cases were never smoothed out. They are essentially showing off the quality of the welds, plus you can't really get in there to clean out the welds between the flanges. Looks good as is. This is the rear. I told him not to worry about smoothing out the plates because I would cover it with the vinyl interior skin eventually. We also miscommunicated about the rear. It was supposed to be an X with a horizontal top, but he made a triangular, bisected horizontal bar. Should have it done the way I asked eventually. It should be noted that JohnC recommended a larger washers/bolt (3/4", vice 5/8" as shown in the pics). I let the fabricator talk me out of it saying it was overkill. I probably should have stood my ground and listened to John. Overall, I'm quite proud of this shop's work!

Here are the "before" pictures: The engine has been removed, but the electrical system still needs to be cleaned up, camber plates welded in and the engine bay is to be resprayed, too. Also note how nasty the back firewall is and also how not clean / distinct the radiator firewall is. The brake lines area is just nasty. My recent repaint in 2009 wasn't a frame off restoration, so underneath the cowl and fenders I found some metal that hasn't seen daylight for about 40 years, presumably. What I hate most about this view is how small the tires look.

Essentially this is a 6+ month project primarily brought about by my engine having a coolant leak and needing to be pulled. The basic plan was this: 1) Remove engine 2) Rebuild engine 3) Weld-in camber plates (Techno Toy Tuning) 4) Have strut brace mounts and supports fabricated / incorporated into camber plate installation (based on pics from a similar implementation from JohnC) 5) Respray engine bay satin black 6) Install rebuilt engine This project thread will be in parallel with the engine performance portion of this iteration of upgrades: http://forums.hybrid...post__p__949205 The above link goes into detail regarding the NA engine upgrades and has a ton of pics of the new engine hardware, etc. In short, the engine is receiving full race headers, some valvetrain improvements and a high rpm cranskshaft balance. The engine rebuild will be updated in that thread, and the fabrication / chassis modification / respray will be in this thread. Some assembly and final pics in both.

Truth be told, I fired it up a few days ago for a few mins and immediately left it in Arkansas in my trailer. I'm out in CA right now visiting family and following up on some job leads. Still compiling all the pics together, but I'll get it up eventually. (So to speak.) Brutal not getting to run it on the road without a muffler before I left. Arkansas could give a ****, and I plan on making some noise and tuning it with my butt-dyno (no AFR, either).

Stahl headers are a work of art. I was giddy to say the least when they arrived: I was so impressed that these were hand made and that the merge collector, hand made from another shop, slid right into place. Phenomenal work. They really stood out next to the outgoing street performance headers. Each three way collector was 3-dimensionally coned into a diameter equal to that of the previous collector's final output. Checking for a fit on a similar head. Really make the stock intake ports look small! The ports were a point of contention with my local Z specialist. He talked down to the quality of the headers, stating that for the price I paid they should be ready to bolt up. I disagreed; at this level of performance they leave the extra material in place and EXPECT the customer to port match the headers to their head. How could Stahl know how much I've ported my head? So of course I had my head shop port match them: ...which obviously really opened them up and made a huge difference. Then I sent them off to SwainTech's White Lightning ceramic coating. Took about 4 weeks to get them back: They also coat as much of the inside of the pipes as they can (for NA engines only). Until I recover my iPhone pics, this is the best shot I have of the merge collector from SPD. JohnC also set me up with this beautiful piece of craftmanship. Truly remarkable once you look inside at how smooth it is and how perfect the tig welds are. You can really see the difference in terms of flow potential: You can begin to see how the scavenging effect is going to make a huge difference

Unfortunately there is a decent set of pictures that I'm missing (lost my iPhone). Should be recovered one day, but that doesn't help me right now. Since this thread is part performance and part personal project, here are some fugly "before " pictures: The engine has been removed, but the electrical system still needs to be cleaned up, camber plates welded in and the engine bay is to be resprayed, too. Also note how nasty the back firewall is and also how not clean / distinct the radiator firewall is. My recent repaint in 2009 wasn't a frame off restoration, so underneath the cowl and fenders I found some metal that hasn't seen daylight for about 40 years, presumably. Right around here I took some odds and ends to a fellow member of my Z club who does some soda blasting on the side: He's blasting my intake manifold here. (Kevin Surface, Tidewater Soda Blasting) All the odds and ends I had him spray. the hood springs are my custom duplicates of the OEM springs but of a lesser diameter for JohnC's carbon fiber hood. The kick plates and thermostat housings were tossed afterwards, as I was able to cheaply acquire Nissan parts from MSA. The motor mounts were toast: You can see daylight through the side of it and the cracks were quite noticeable since the engine was recently rebuilt in 2008. I guess that's fair when you have just about double the flywheel horsepower from stock. Right around this time JohnC helped me source some new motor mounts from Japan and mentioned that I could reinforce the mount brackets if I desired. I decided to take it to my local machine shop and I asked them to weld on new steel plates and then file the welds smooth afterwards. The theme here is for all my performance mods, especially the fabrication mods, to seem as if they came from the factory this way. This is how I got them back: Then I had them powder coated black, which match the Kameari mounts nicely: The new mounts are an extremely hard poly/ABS type of plastic. They were a serious pain in the ass to install, but that motor is now *in there!* Side note: I've upgraded the dimensions of my image uploads as a reflection of the times (ie data speeds and screen resolution). Are they too big for anyone?

This update has been in the works for about 6 or 7 months now. About six months ago when I first pulled the engine out I had the head flow tested. I wanted the numbers for future ITB calculations. The shop that he subsidized for measurement evidently was so impressed by the head that they hung onto it for a week and were very complimentary regarding its performance. As far as I know, flow numbers are about as comparable as dynos between shops, but here's something I put together for myself and I thought I'd share: I was particularly pleased that in terms of VE if I could pick anywhere on that graph to have my lift, it would be about .565", right where my cam actually is. I guess this is what happens when you have the camshaft developer also doing your head work. Thank you, Mr. Jim Thompson and JohnC for the referral. What was that about seven years ago I think? Man, this thread is ancient. Haha. For whatever reason, the flow shop ran both with and without the spark plug in the cyl. and provided both sets of numbers to me. Hmm. I decided to also have the crank balanced to 10,000 rpm. I can only run to 7.6k because of the outer-springs-only design, but I wanted to be able to hold the redline like it was my job and be smooth about it. Of course as a part of the balance was my new clutch and flywheel set: The new flywheel is 12 lbs, but what I like about it is that it's weight-relieved stainless steel, not aluminum with a modular friction surface. I'd rather have a solid one-piece rotor, just because it makes me feel better. Also while I'm at it, I picked up some lightly-used titanium valve spring retainers on eBay. They feel like about 1/4 of the weight as the ones they replaced. The outer-springs only design that the cam was profiled for are now installed, too -- 25% less seat pressure. And finally, he indexed all of my spark plugs with the head out in the open. The outer electrode is tucked against the side of the cyl. wall so the flame front propagates toward the center of the combustion chamber. Details. More to come but that's all the time I have for now.

I was thinking about starting a separate build thread for this year's engine upgrades, but I thought twice about it since this thread might be more appropriate. Now that this thread has been removed from the L6 stickies list and now a "FAQs-->Powertrain-->L6" thread relocated by the Admins, I thought I would pose the question to the Admins / readers since HybridZ is a forum after all: Should I continue to post my race engine upgrades and related dyno findings on this "FAQ" thread or start a separate build thread? My thoughts are that in this case it's nice to see in one thread how all aspects of the engine are tied in through the head, and how chasing around the new choke point relates to output of the motor on the dyno. Thoughts? If I get no replies I'll probably post the pics and data here...

I believe you are referring to post-collector piping, correct? This has of course been answered since your post and I won't repeat others' posts. If by exhaust "system" you include header primaries and collector, yes. Keep in mind he's talking about header primaries' diameter selection and NOT post-collector piping, but this is directly from Stahl headers: It's my understanding that too large (for primaries) is devastating because it decreases velocity and therefore scavenging effect, which is of course crucial for normally aspirated engines, especially ones with lots of overlap. I elected to not go with 1-3/4" but instead 1-5/8" primaries for a wider torque band, despite that my race motor was in this HP range with street headers. JonhC and Stahl both agreed that for an autocross motor this would suit my best interests. [...] Great point, Tony. I hadn't considered the irritating frequency range, and I would agree that when tone deepens (with larger pipes) it's less irritating and therefore seems less loud. [...] Also, the earlier discussions regarding post-collector piping have made me curious. I just might dyno the car with race headers+merge collector (no piping or muffler) and then once again after installing the full exhaust (3" mandrel). I don't think I'd be interested in cutting pipes to find the ideal length, but I am curious how much of a loss might be incurred due to post-collector head loss (friction). If I do this, I'll be sure and share the dyno results and pics of the exhaust setup(s). If nothing else, I'll have an excuse to hear the race headers + merge collector roar without a muffler...