SteveK

There is an argument that says inlet runners shouldnt have a high degree of polish as it can lead to the fuel dropping out of suspension, having a slightly rougher finish can help prevent it by creating turbulence. The stock Nissan FI unit is not known to be a performance part (in NA form anyway) so it is questionable as to the payback. Just my humble 2 pence worth

Compare the size of the bolted, side bearing journals of the 180 to the 200 Nuff said

Fair comment :classic:

It isnt a mandatory "upgrade" because most Z owners have more common sense than to lower the performance of their engines, and the term "upgrade" implies improvent which it most certainly isnt. If you find a performance gain by moving to a 4 barrel carb on a 90 degree manifold, either your SU's were poorly set up in the first place, or you woke up realising it was just a bad dream.

Currently running an N42, shaved by about 25 thou and cam tower shims, using stainless valves and race springs on a 300 duration cam, chambers are matched to 40 CC Car pulls very well, has a nice torque and HP curve, topping out at 250 Hp

You can be as confident as you want -- doesnt mean it will happen Where are the flow figures comparing this to say the stock manifold and AN other make such as a JDM unit or even an off the shelf canon "plain jane" manifold High compression means jack if your fuel atomisation, spark, cam, squish, head, header, collector -- et al dont all work together. That manifold is designed to take big pressure, look at the design its a pressure vessel, the plenum inlet is way to restrictive for a NA application Measure the diameter of your plenum chamber inlet -- how big is it I found that on my airbox that anything under 80mm began to compromise performance and at 65mm it ran like a Honda (thats on an engine making 250 HP at the fly) NA performance is reliant how much volume of air/fuel you can get into the cylinders, with as little resistance/effort as possible the smaller your main tract is, the harder the engine has to work to pull it in. Its an unfortunate car tuners trait that they sometimes assume HP by the hole left in their wallet

Bubbleguinea Nice as it is Do you intend to use that in a normally aspirated set-up I ask because A. Surely its built primarily as a forced induction set-up which doesnt neccassarily make it good for normally aspirated and B. Your target time of the high 13's is fairly unambitious for a turbo, but highly ambitious for an NA car with single throttle body. I base my data on the fact that I have run a 13.7 1/4 in an 240Z which is an NA set-up using individual throttle bodies and a fully mapped distributorless, ignition system. High to mid 13's in an NA car are significantly hard to achieve and it took 8 months of engine/head/header/collector configuration, building and tuning/mapping to get the 200 Hp at the wheels (250.5 @ the fly) needed for a car weighing 1150 kilos (car, me and fuel) to break into 13 seconds (its a UK record thing we dont get out much :stupid: ) That is unless your US 1/4 miles -- like your gallons are differant from the rest of the world

Ohhhhh that is absolutely sweet, and pretty much direct port injection too. Man if I ever did my dream short stroke L6 on a supercharger then thats the induction set up for me. Good find

The stock Nissan plenum manifold was built primarily with economy and emmisions in mind and it is only when it is used with forced induction(turbo , Supercharger etc) that it begines to work. There is a guy in the UK with a twin turbo'd L6 kicking out the best part of 400 Hp, using the stock plenum (trouble is he drives like a girl and wont come out to play (sorry Mark). I have some pics of it at a show, I will put a couple in my gallery(subject to approval) his are the ones in the sunshine, mine is the one with red throttle bodies.

Sideshowbob You call a compression of "140-150" bad! why?

I had exactly the same issues as Dogma when I did my 2.8 conversion even though I had used 280zx parts right through (flywheel, clutch, throw out collar, fork, release bearing, slave cylinder lalalalalalala).Clutch wouldn’t release completely even at maximum pedal-rod adjustment (reverse would crunch and had I to declutch to get it in) I tried everything, braided lines, new piston and seal kit, new slave cylinder etc. I was only when I did my fuel injection project early this year that I got around to fixing the issue good and proper by using a bigger bore master cylinder from Wilwood, I had too as the ACT clutch that I also put in is a pig to use.

Your wish is my command sir I have just uploaded some to my gallery dont know how long it takes to approve I will scan in the dyno sheet tonight (its 14:30 here) the torque curve is interesting its more like a set of peaks and troughs than a curve but thats work in progress and hopefully that will flatten out with a new exhaust set up

Making 225 -250 with a 2.8 -- will be difficult enough, with or without SU's To give you some idea how difficult. I have just spent 5 months and a zillion pounds, designing and building a custom individual 40mm throttle body injection system with fully mapped ECU, distributorless ignition with a custom flowbenched head, 40 cc chambers and stainless big valves sitting in 3 angle seats and a big duration cam. The engine has custom flat top pistons machined and lapped to 8 thou under deck, ARP bolts, lightened flywheel ACT big clutch, balanced everything, total seal gap-less rings, state of the art exhaust, running a static compression of nearly 11.1 We mapped it the other day on the rolling road and 4 hours later I was pleased with the 230 HP (flywheel) we achieved, I could possibly get a little more with cold air induction and a differant exhaust config but not much say another 10 or so at best. I would be suprised if SU's flowed as well -- still we live and learn, who knows, there are people who have made big HP on SU's but with some seriously serious engine mods.

Considering there is considerable confusion around this area (someone thought the tool was for re tensioning the chain) I thought it worthwhile pointing out, because so far, non of the posts (including yours) had. But if we are all so educated as to how to do this why is the thread 2 pages long and several differant drawings shown.

Rob, give Dave Jarman a ring he's rebuilt a few in his time and he kinda knows what he's doing

Doesnt even need to jam the tensioner (ie touch it), as long as it traps the chain on either side of the guides the tensioner will not pop out as the chain cannot move

Nice one Thank for the advice guys -- muchly appreciated This project has turned into a bit of an epic, and I have had more issues than you can shake a stick at Wrong injectors, wrong throttle bodies, wrong crank sensor, wrong everything at some point still it will all be worth it when we get it fired up.

Cheers Mike, I am led to believe that there are quiet a few dynamics that can affect things. Plus I have read that even if the gap were safe it is unwise to have it too small as the squish area becomes inefficient -- 40/50 thou being optimum I have sourced differant pistons now with the correct pin height (one was a little iffy on the bottom ring groove--- shame cos with the skimmed dished pistons, I was using the longer L24 rods that gave me a small torque gain, now I have to go back to the 130.2 L28 rods Its all fun --- only thing left is to get the multiple throttle bodies mapped and hey presto

Mike, the diameter of a 2.8 piston is 86 mm, the diameter of the combustion chamber is less than this at the sides, with thermal expansion, directional change lalala there is an area under the head that could be impacted (squish area ramp) any impact at these speeds is disasterous. The valves do not worry me as I have machined cutouts on the piston heads

Thanks guys, its not really the compression ratio that concerns me (the chambers are cc'd at 40) its the potential for the piston to hit the underside of the head which is far more worrying