RB240z Posted February 6, 2009 Share Posted February 6, 2009 A slight bump to this thread... BRAPP, when will we see this "very custom" head you speak of? The intake manifold itself is the biggest red flag I see, especially when looking at your torque curve. Your torque curve is indicative of typical OE L-6 EFI intakes. Keep in mind that the OE EFI intakes, ALL of them, have a runner cross sectional area that is only 53% the cross sectional area of a 280-Z intake valve! You can see the bottle neck here. Now there are couple/few members that have been able to produce torque curves biased more towards the upper end of the RPM band with the OE EFI intake, but most if not all of those have some form of modification for enhanced flow, and those examples are the exception, not the rule. Once you swap out to different intake, whether it be an SU intake modified for EFI, a custom scratch built intake, or even the 4bbl intake set up for EFI, with everything else you have, just retune the MS for optimum power, your torque curve will be much more robust above 3600 RPM which means your HP figure will be much higher, if not being a larger number than your torque figure! Regarding cams. For Turbo L-6 engines, cams are still in the magical black art realm. With what little documented development regarding Turbonic L series cams, it seems everyone has an opinion on what lobe specs work, many have had a custom cam ground, and as far as I can tell, pretty much all of these have worked successfully for that particular application! Even David Vizard talks about a wild beyond belief cam profile with NO overlap that produced over 1000 HP on street driven SBC! We have members here that have made great power and run phenomenal ¼ mile times with the Z-gad grind. Garrett has ran low 11’s in his Turbo L-6 powered street 280-Z car with the stock Turbo cam and Thagard intake manifold! Another credible source prefers a particular stock N/A grind on performance Turbo L-6’s! If it were an N/A, Supercharged, or Nitrous charged L-6, or even an SBC, I feel comfortable with coming up with cam specs for those application as the variables involved are pretty consistent and fairly well known. Make it a Turbo and with the continually changing intake to exhaust pressure ratios involved, the optimum intake and exhaust valve event timing now is going to be totally different, and depending on the always changing int-exh pressure ratios within the RPM range, throw in differing intake and exhaust Turbo housing designs, different turbine and intake impellor designs, just slightly changing the cam specs, lobe separation angle, etc, will alter the intake to exhaust pressure ratios again therefore requiring a different cam lobe profile for optimum performance. You can see how this becomes a viscous cycle, akin to a dog chasing his tail…. I will offer this tidbit of advice, first time mentioned publicly anywhere regarding Turbo L-6 camshafts. I keep in touch with Rebello Racing on a semi regular basis. In those talks with the owner, the discussion of L-series heads is always the core topic. Being as he has probably more L-6 dyno time than anyone in the country, I personally put a lot of faith in his opinion regarding what does and does not work on the L-6. Regardless of the absolute numbers his dyno declares, it is within those numbers of what combo produces more and most consistently that I’m interested in. In his playing and tinkering with the Turbo L-6’s on the Dyno, he has developed an affinity for one of the stock N/A L-6 cams. Which one? Well, I am not at liberty to divulge, lets just say, he prefers it over the stock Turbo grind and even the other aftermarket Turbo grinds he has tested. (we are currently building a very custom P-90 head for a Turbo application, with 1mm oversize Ferrea exhaust valves and one of these cams with Rebello springs, which will be up for sale, very soon…) I short, I recommend you leave the cam alone and spend your money/time on an intake manifold. Then, if you are not satisfied, look at a different cam, possibly a stock N/A Cam... Hope that helps, Paul Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted February 6, 2009 Administrators Share Posted February 6, 2009 A slight bump to this thread... BRAPP, when will we see this "very custom" head you speak of? Pictures were posted in the parts for sale section some time back. Head is sold and now is in California, hopefully to be up and running this summer. For what its worth, another HBZ member, very credible source of technical L series info, contacted me with a similar report using the N/A cam on his boosted L-6. Quote Link to comment Share on other sites More sharing options...
Art Nadel Posted February 6, 2009 Share Posted February 6, 2009 Related issue. Valve Clatter. My L28ET with 2 1/2 " straight thru exhaust, manual boost control set at 14 PSI steady state at full power, stock injectors, adjustable FPR, Jim Wolf ECU, and PWR liquid to air IC, gained 20 RWHP on dyno by installing Schnider Cam and kit including the proper lash spacers properly fitted. HP 260 and Torque 310 Ft Lbs. with Schnider. Also was running more freely in upper RPM range, to 7,000. But was constanly having to reset the valve lash because of noise. A real pain. Tried all sorts of different clearance settings and could quiet it down, but before long the clatter would start again. The old high milage engine finally gave up, and so when I intalled a fresh long block, ( P90 head) stayed with the stock turbo cam. Set aside the head with the Schnider to deal with later. I do not make as much power now, and no point reving beyond 6500, but at least do not have to constantly remove the cam cover and spend lots of time restting lash. Any one care to comment on this? Art Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted February 7, 2009 Administrators Share Posted February 7, 2009 Related issue. Valve Clatter. My L28ET with 2 1/2 " straight thru exhaust, manual boost control set at 14 PSI steady state at full power, stock injectors, adjustable FPR, Jim Wolf ECU, and PWR liquid to air IC, gained 20 RWHP on dyno by installing Schnider Cam and kit including the proper lash spacers properly fitted. HP 260 and Torque 310 Ft Lbs. with Schnider. Also was running more freely in upper RPM range, to 7,000. But was constanly having to reset the valve lash because of noise. A real pain. Tried all sorts of different clearance settings and could quiet it down, but before long the clatter would start again. The old high milage engine finally gave up, and so when I intalled a fresh long block, ( P90 head) stayed with the stock turbo cam. Set aside the head with the Schnider to deal with later. I do not make as much power now, and no point reving beyond 6500, but at least do not have to constantly remove the cam cover and spend lots of time restting lash. Any one care to comment on this? Art Art, By cam and kit, you mean the recommended valve springs correct? You shouldn’t be readjusting the lash over and over. If you are, then something is wrong. Sounds like either something is wearing WAY too fast and way too much or possibly you are not tightening the lash adjuster jam nuts tight enough. Items to look at; 1) Worn Cam lobes. 2) Worn rocker wiping surface. 3) Worn lash-pad/rocker tip. 4) Valve seats moving in the head either falling out or valves are recessing into the seat. (not likely, but has been known to happen with the older heads and the soft intake seats). 5) Or your lash adjuster jam nuts are not being locked down tight enough and they adjusting as the engine is running. Quote Link to comment Share on other sites More sharing options...
Art Nadel Posted February 8, 2009 Share Posted February 8, 2009 Paul Thanks for the input. Good points. If and when I re install the Schnieder will be alert to those issues. But some locals have commented that they also found the Schnider set up noisey, so am wondering if there is too much ramp angle. Quote Link to comment Share on other sites More sharing options...
Pyro Posted February 9, 2009 Share Posted February 9, 2009 use thicker lash pads and adjust to 0.008"lash. I had to use 0.190" thick lash pad with my MSA stage 1 turbo cam also use a ZDDP oil additive with high performance cams. try using a NA cam for another 8 degrees of duration. Quote Link to comment Share on other sites More sharing options...
rejracer Posted February 10, 2009 Share Posted February 10, 2009 BRAPP, when will we see this "very custom" head you speak of? How bout now? Sitting proud... The deck Chambers Ports And special thanks for detailed documentation on the cam gear. I find accurate documentation invaluable . Install may be later this summer. I will document it in my turbo swap thread in "members projects" section when progress is made. Everything looks great on the head, I can't wait to get it installed. Well too bad I don't have all the supporting goodies for it just yet, and the final build will be in about another year and a half. It will end up on a stroker with either a t3/t4 hybrid or a garret ball bearing/liquid cooled turbo. The goal on this project is a quick spooling fast revving street build. Fun to drive is the number one priority on this, not drag times, or impressive dyno figures. -Robert Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted February 10, 2009 Administrators Share Posted February 10, 2009 How bout now? ... And special thanks for detailed documentation on the cam gear. I find accurate documentation invaluable . ... Install may be later this summer. I will document it in my turbo swap thread in "members projects" section when progress is made. ... -Robert When I saw that instruction sheet, I want sure if I should include it or not. For the most part, the torque specs at the bottom are what you need. Actual cam timing will be determined by what the engine wants based on where you want the power to happen in the rev range. The 17-19 N/M converts to 12.5-14 Ft/Lbs. That is the torque value for the Allen head bolts around the perimeter. Quote Link to comment Share on other sites More sharing options...
ozconnection Posted February 12, 2009 Share Posted February 12, 2009 The goal on this project is a quick spooling fast revving street build. Fun to drive is the number one priority on this, not drag times, or impressive dyno figures. -Robert Why did you find it necessary to port the intakes like this for a 'street' car? Haven't you just slaughtered your low rpm , off boost torque by doing this? Please tell. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted February 12, 2009 Administrators Share Posted February 12, 2009 Why did you find it necessary to port the intakes like this for a 'street' car? Haven't you just slaughtered your low rpm , off boost torque by doing this? Please tell. The intake ports were not race ported, though I guess the opening may appear large. A full race port would be larger, all the way to the seat! The entrance was port matched to a particular intake manifold. Floor of the port entrance was just skimmed, the majority of the port match was on the roof, effectively creating a larger C/L port radius from the port entrance to the valve seat. This port matching only extends in approx. 1 1/4" inches into the port. The rest of the port diameter is stock. Valve guide boss was then blended, then spent a good deal of time around the transition from the valve seat to port itself, blending the transition from the 5 angle seat geometry to the port walls. The only polished/smooth region of the port is at the port entrance where the airflow is dry. In the wet flow region of the port, I purposely left as much raw casting as I could, though where I did carve I left the surface less than polished with a fine sanding-wrap finish, as can be seen around the guide bosses in the pics. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.