280zzzz Posted August 19, 2009 Share Posted August 19, 2009 I have an l28 with n42 heads and dished pistons. (8.3 compression ratio) Id like to get some good horsepower without turbo or an engine swap, so I am looking at high performance pistons, or an entire head swap. Which would you recommend, and where could I get 1mm overbored, flat top pistons for my engine, without spending 800 for this:http://www.thezstore.com/page/TZS/PROD/PEM04/10-4080 Quote Link to comment Share on other sites More sharing options...
jc052685 Posted August 19, 2009 Share Posted August 19, 2009 This is your best bet http://tiny.cc/d7573 Next to that HP is gonna cost you some money and whole bunch more searching. Quote Link to comment Share on other sites More sharing options...
tyler031734 Posted August 19, 2009 Share Posted August 19, 2009 Why dont you want turbo? you have to pull your whole motor just to get it machined anyways, might as well put a l28et in there! I did in my 240, took me four days, kinda proud on that one or if you are going to bore it anyways why dont you go 89mm? no replacement for displacement Quote Link to comment Share on other sites More sharing options...
z-ya Posted August 19, 2009 Share Posted August 19, 2009 Are you sure you have flat tops? If so, your CR is around 10:1. Does it have a stock cam? Pete Quote Link to comment Share on other sites More sharing options...
280zzzz Posted August 19, 2009 Author Share Posted August 19, 2009 Are you sure you have flat tops? If so, your CR is around 10:1. Does it have a stock cam? Pete Sorry guys i messed up my motor description check it again. Quote Link to comment Share on other sites More sharing options...
z-ya Posted August 19, 2009 Share Posted August 19, 2009 What is your budget? A stock L28 makes around 120HP at the wheels. What are your HP goals? Quote Link to comment Share on other sites More sharing options...
280zzzz Posted August 19, 2009 Author Share Posted August 19, 2009 What is your budget? A stock L28 makes around 120HP at the wheels. What are your HP goals? Were hoping to completely restore the car for 6k plus paint. Quote Link to comment Share on other sites More sharing options...
z-ya Posted August 19, 2009 Share Posted August 19, 2009 Probably the easiest way to get good power is to just do a complete L28ET swap from a running 280ZXT. You can swap in flat tops and a cam and probably get close to 160WHP with the correct tune. Your probably looking at $400-$500 for parts. While you're at it you might as well get a valve job done. So if all goes well and it doesn't need more machining or parts your looking at close to $800 including gaskets. But if it needs a timing chain, and you decide to put a new oil pump in, your looking at another $200 in parts. If it needs to be bored, your looking at around $2000 for machining and parts if you do the assembly. Then after all that you have to be able to tune it to get the most out of it (different carbs, EFI, etc). Another option is to find a good used F54 NA block (flat tops) and swap your freshened N42 head on it with a mild cam. In either case plan on running 93 octane with this setup. Pete Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted August 19, 2009 Administrators Share Posted August 19, 2009 Pistons alone, (compression ratio bump) will not increase your power by a significant amount. That route is quite costly for a very small gain, not enough gain to feel seat of the pants! There are so many more areas to focus on that don't cost as much in time and money that will produce results noticeable. I was able to get my 2750 lb. 280-Z, Naturally aspirated, with dished pistons, ported N-47 head, (all the valve unshrouding dropped the Compression Ratio down even lower to 8.1:1), stock cam, stock EFI, Header, dual exhaust, lightened flywheel, recurved ignition advance, and LOTS of fine tuning, to run 0-60 in 5.7 seconds, and 14.4 @ 97 in the 1/4 mile. The engine was VERY crisp, VERY responsive. Its performance numbers aren't stellar numbers but very respectable numbers for a bone very stock low compression naturally aspirated short block. It is interesting that over the past 8 months or so, there has been a lot of interest in increasing compression ratio as a means to gaining power in the L-6 with not much if any research behind that idea?! (guys reading too many Hot-Rod magazines?) Yes, upping the compression ratio will gain power, but only in very small increments, not anything that is really noticeable, and it should only be done with other mods to capture what a bump in compression ratio offers, (cam, after-market EFI or carbs, free flowing exhaust, etc...) Worst part is, the L-28 is notoriously hypersensitive to detonation and even at 10: 1, it will rattle like a diesel requiring you to retard the ignition advance loosing more power due to the ignition advance retard then you gained via compression ratio. I've personally seen that scenario play out time after time, many have documented the same experience here as well. Also, if you are using the stock EFI, do NOT install an aftermarket cam! The stock EFI does not play well with and aftermarket cam, nor can it be 100% successfully tuned around it. You will need aftermarket EFI or carbs, then a cam is a worthwhile modification. Good luck in your quest for increased performance. LOTS of documented way to gain power here, the search feature is your friend. Quote Link to comment Share on other sites More sharing options...
z-ya Posted August 20, 2009 Share Posted August 20, 2009 Agreed. Just bumping CR will not gain you much but potentially blown head gaskets if you don't keep detonation under control. You can increase power significantly by increasing CR AND a free flowing exhaust, intake, and mild cam. A lot of head work is not required. Time on the dyno and good engine management is required. My 180WHP L28 is proof of that. To get much over 180WHP requires a stout cam and LOTS of head work. I'll let Paul elaborate in that area since it is his area of expertise. Pete Quote Link to comment Share on other sites More sharing options...
MONZTER Posted August 20, 2009 Share Posted August 20, 2009 Raising the compression ratio in combination with more duration in the cams can help with controlling detonation, as the increase in duration will lower the dynamic compression ratio. See below from wikipedia: start quote - Dynamic Compression Ratio The calculated compression ratio, as given above, presumes that the cylinder is sealed at the bottom of the stroke (bottom dead centre - BDC), and that the volume compressed is the actual volume. However: intake valve closure (sealing the cylinder) always takes place after BDC, which causes some of the intake charge to be compressed backwards out of the cylinder by the rising piston at very low speeds; only the percentage of the stroke after intake valve closure is compressed. This "corrected" compression ratio is commonly called the "dynamic compression ratio". This ratio is higher with more conservative (i.e., earlier, soon after BDC) intake cam timing, and lower with more radical (i.e., later, long after BDC) intake cam timing, but always lower than the static or "nominal" compression ratio. The actual position of the piston can be determined by trigonometry, using the stroke length and the connecting rod length (measured between centers). The absolute cylinder pressure is the result of an exponent of the dynamic compression ratio. This exponent is a polytropic value for the ratio of variable heats for air and similar gases at the temperatures present. This compensates for the temperature rise caused by compression, as well as heat lost to the cylinder. Under ideal (adiabatic) conditions, the exponent would be 1.4, but a lower value, generally between 1.2 and 1.3 is used, since the amount of heat lost will vary among engines based on design, size and materials used, but provides useful results for purposes of comparison. For example, if the static compression ratio is 10:1, and the dynamic compression ratio is 7.5:1, a useful value for cylinder pressure would be (7.5)^1.3 × atmospheric pressure, or 13.7 bar. (× 14.7 psi at sea level = 201.8 psi. The pressure shown on a gauge would be the absolute pressure less atmospheric pressure, or 187.1 psi.) The two corrections for dynamic compression ratio affect cylinder pressure in opposite directions, but not in equal strength. An engine with high static compression ratio and late intake valve closure will have a DCR similar to an engine with lower compression but earlier intake valve closure. Additionally, the cylinder pressure developed when an engine is running will be higher than that shown in a compression test for several reasons. The much higher velocity of a piston when an engine is running versus cranking allows less time for pressure to bleed past the piston rings into the crankcase. a running engine is coating the cylinder walls with much more oil than an engine that is being cranked at low RPM, which helps the seal. the higher temperature of the cylinder will create higher pressures when running vs. a static test, even a test performed with the engine near operating temperature. A running engine does not stop taking air & fuel into the cylinder when the piston reaches BDC; The mixture that is rushing into the cylinder during the downstroke develops momentum and continues briefly after the vacuum ceases (in the same respect that rapidly opening a door will create a draft that continues after movement of the door ceases). This is called scavenging. Intake tuning, cylinder head design, valve timing and exhaust tuning determine how effectively an engine scavenges. - end quote Again, like the others said, there is no one magic trick, it is careful planning of all of the right parts working together. Quote Link to comment Share on other sites More sharing options...
gira Posted August 27, 2009 Share Posted August 27, 2009 280zzzz, I can make 200flywheel horsepower all day long with all stock internals, including cam, pistons, rods, etc. This is in IT prep, so almost no headwork either. It's race engine knowhow, assembly, cam timing, a combination of all of these. Greg Ira Quote Link to comment Share on other sites More sharing options...
WizardBlack Posted August 27, 2009 Share Posted August 27, 2009 Like they said, just drop a turbo setup in and spank N/A without having to spend lots on squeezing every drop out of it. You are already swapping the motor out. Why the big deal keeping the same shortblock in it? I am not sure how you will find forged pistons without paying close to $800 for a decent set. Ross are pretty good bang for your buck. 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.