Pyro

I'm a little late to the post but I can't believe that with all these motor heads on this site you didn't get the reason why it makes more hp with a vacuum in the crank case. It is called Ring Flutter. Vacuum in the crank case helps the rings seal at higher rpms. Vacuum pumps and vacuum at the header collector are commenly used. Here is a copy paste from a web search of "ring flutter" Ring Flutter Again, many people don’t know what this is. Ring flutter can best be understood by thinking of it as the piston rings going into a float or uncontrolled oscillation due to the imbalance of four forces: ring inertia, tangential ring pressure, compression pressure, and crankcase pressure. Normally the ring seals during the compression stroke by the forces of compression working on top of and behind the ring, coupled with the tangential pressure to seal against the cylinder bore and the bottom of the ring lands. This system functions well until this delicate equilibrium falls apart. As speed increases, the piston tries to get ahead of the ring. If it gets too far, the top ring land stops the ring. During this transition, there is a clear leak path developed around the back of the ring. Another critical point in this balance is the point in the ring travel where the ring is speeding up the bore on the compression stroke and it gets to the TDC where it suddenly stops and changes direction. The mass of the ring can affect this time off the ring land, hence the effort to get lighter ring packages. The tangential load and end gap are other factors affecting ring balance and hence blowby. The bottom line here is that if you have ring flutter, the easiest way to find it is with a blowby meter, whether in the car or on the dyno. When the engine gets to a speed where ring flutter occurs, the blowby will oscillate rapidly for a period, and then, typically, calm down again once the specific set of conditions have changed. Lately, many people have been experimenting with crankcase evacuation systems or vacuum systems, which seem to work. However, like everything that works, there is usually a cost associated with it. The cost here is the work necessary to create the vacuum, and the extra work done by the engine to overcome the vacuum pulling down on the pistons during part of the cycle. Consider that it might just be easier to eliminate the ring flutter and get on with life, rather than trying to create another variable and another subsystem. Accurate blowby measurement will allow you to work on this problem, whichever path you choose to pursue.

Trap speed of 134mph in the 1/4 mile with 26" slicks and 3.90 gear in 4th gear (1:1) at 6800 rpms. Still pulling at the end of 4th gear but don't think the T5 will handle too much HP in 5th gear so I will not use it for WOT. So I guess my top speed is about 138mph with a 3.90 gear at 7K rpm or maybe 152mph with a 3.54.

Well I think Bush is the lessser of two evils. He is not perfect but at least he is not a two faced, limozine democrate and his wife isn't crazy. Plus it is not a good time to change leadership in the USA. At least Bush is trying to thin down the herd of lawyers out there which will save money on EVERYTHING we buy (including medical care). And he knows that other countries also have there own sercet agendas (just like us). So, only ask them a few times for help then move on. And it seems that he is aware that Social Security was NEVER intended to be a retirement plan for america. It is a political death sentence to say that but he is trying to say it by making plans for SS to invest in the private sector. Not sure that is a good idea either but it is better than doing nothing or adding even more money as kerry planned. I don't know how SS turned into a retirment plan. When it first started, it was intend for people over 55, which was the average life span for a man at that time. Therefore, was intended for old women after their husbands died. Now look at the monster it has grow into. Kill it now and everyone plan to work as long as they can. And retire if you can.

I use a 240mm SPEC stage 2 ($305.00) from Nippon Power rated to 455 ft lbs. It has a 1000 mile break in for the kevlar clutch but mine quit slipping at 300 miles. I like it. I run 15 psi of boost and it holds it ok so far. The pedal is light and feels stock and doesn't chatter at all. The spec stage 3 was hard to drive on the street (ceramic, 6 puck, sprung hug) because it chattered badly but rated to 500 ft lbs.

Turbos are different than superchargers. As you know, superchargers get energized from a belt drive and turbos get power from the exhaust. So it makes sense that they would have different cam requirements. And turbo don't like to scavenge. The reason is the pressure in the turbo exhaust manifold can be as high as 35 psi! As compared to the exhaust on a supercharged engine which is like 4 or 5 psi when exiting through headers. So if there is ANY overlap on a turbo it causes exhaust to enter the intake. Therefore, bigger intake duration and smaller exhaust duration is the best setup. The small exhaust duration helps keep the "zero" overlap and increases exhaust velocity, just what a turbo likes. I'm pretty sure Talons and Eclipes use the T3 with a 0.48 housing.

Try 2 T3's. Those turbos litter the junk yards and can be had for cheap! Then you could go for 500 hp! You should also get a "turbo cam" (no overlap please). The compcam 280 is not designed for a turbo. You need a cam with 280 on the intake and 260 on the exhaust with no overlap.

It sounds like you have a pretty nice set up. I think the 650 carb is a good size for a 327. Chevy put 750cfm Q-jets on them from the factory. However, are you sure it is a 650? I don't recall a 4150 offered in a 650. I think it need to be a 600 or 750. It could also be carb power valve issue. What manifold vacuum are you running at idle? Have you checked float levels?? I ending up jetting my 4150 750 cfm carb on a 350 with a rpm intake to 69's up front and 76's in the back. And I used a 6.5 power valve because my engine only make 12 inches of vacuum at idle. FYI, the power valve number used should be 1/2 the idle vacuum. It sounds like your dist. vacuum advance is on the wrong vacuum source. The manifold is not the place to get that. It would be better to not even use the vacuum advance then to use it wrong. Try setting your initial timing up to 20 degrees and disconnecting the vacuum advance to see how it runs.

Is the vacuum advance on the right port? It makes a big difference! I have found a lot of bad running chevys with the dist. vac advance on the wrong port. Use the port on the carb that DOES NOT have vacuum at idle.

Let me answer that one for you Labrat. The answer seem very plain to me. Since I have also performed an over budget/over time V-8 conversion I feel I can answer this one. The 6,000.00 in mods he spent for the V8 conversion could have been done much cheaper for a turbo conversion (1000.00). Then he could spend the "saved" money on the paint, interior, and suspension instead for just V8 conversion stuff. However, I have also done a turbo conversion and it seem to add up also. Maybe 2K is a better estimate.

------------------------------------------------------------------------ Vortec L31 heads. I want 8:1 compression with quench distance of .040". How do you get a quench distance of 0.040" with dished pistons? I think you need bigger combustion heads and/or less stroke to get what you what.

Take it easy on the porting and polishing. It adds up quick and doesn't do much. How and where do you polish a piston? How are they planning to port the intake and exhaust manifold? Extrude honing is the only way to get in there with out cutting it open. Port matching is about the only thing they can do and it does not do much for performance, it just costs a lot. Rings and pins typically come with the new pistons. Use felpro gaskets and C77 bearings. Don't forget to ask for a valve job. I didn't see that on your list. Don't deck the block unless it needs it. With all this porting and polishing what cam/springs are you planning to use? You could pay for a balance job on the rotating assembly but I have never been convinced a L28 really needs it. However, I know people like to say their engine is balanced. I did a 1000.00 rebuild on my turbo engine and I run it hard every day making 15 psi of boost and hitting 6K rpms everytime I get in it. It hit 108mph in the 1/4 mile a few weeks ago and not one thing in the engine is polish or ported or balanced. I also used cast pistons and a felpro head gasket. I think you should take it easy on the engine polish and spend your money on something that will make a difference like a limited slip diff, or a aftermarket efi system, or a good clutch.

Believe it or not I saw some at Pep Boys in their metal brake line section behind the parts counter.

The pulley with the timing marks is rubber mounted around the keyed hub. The rubber gets old and can slip. Plus the pulley is always being twisted because the ac/alt/ water pump is pulling on it along with the spinning/vibration forces from the engine

It sounds like your timing mark has moved? Maybe you should check the timing mark position with a piston stop tool. Now you need to lean out the mixture a little. Check fuel pressure first, if it that is ok, tighten up the airflow meter spring.

Well...According to http://www.geocities.com/z-car/specs/ my car should weigh 2875 from the factory. I think I added about 70 lbs to that even after removing the bumpers and mounts. So I think the car weighs 2974 plus 200lb with me in it for a grand test weight of 3174 lbs. 108 mph in a 3175 lb car should be about 311 hp. ((108mph/234)**3)x2875=311 hp I know that I should get that car weighed!

I'm using the spec stage 2, 240mm clutch (kelar disk, 320.00 delivered). The Spec guy said there is a 1000 mile break in on kelar clutches so they will slip for awhile then hold (so he says). The clutch did slip on me at 15 psi but doesn't slip at 11 psi. So, I'm going to try it for awhile and see if I can turn my boost back up to 15. The spec stage 2 clutch feels great and is very smooth which makes it nice for street use. Before I used the spec stage 3 (6 puck spring loaded ceramic) and it didn't slip at all but the chatter was terrible at low speed. My car makes decent power, hauling a full interior 280Z (AC, big stereo, sound proofing, carpet , and spare tire) and me to 108 mph in the 1/4 mile.

The problem with the stoker is than it is hard to get the compression down to 7.4:1 (besides costing money). Yes, more compression can be used but the L28 is prone to detonation. One t3/t4 turbo is enough to make over 500hp plus it keeps the tubing down to a minimum. Smaller injectors please. 500 hp needs 500cc in L28. Intercooler piping can be small. 2 to 2.25" from turbo then 2.5 from IC to throttle body is enough for well over 400hp. Too much HP is about as fun a too little HP. Aim for 300 to 400 hp with a turbo Z/ZX street car. Don't try make too much power because you will run into a bunch of walls (diffs, driveshafts, clutches, transmissions, and axles).

Years and years ago. And way before the internet. I used a dish piston L28 with an E31 head, SU's, 6 into one header, 2.5" exhaust, 5 spd, 2+2 clutch, R200 3.90 gear, holley electric pump, and a 290/.500" clifford research cam 6=8, in a 71 240. And the engine pulled hard after 3500 and pulled up to 7K rpms. It ran low 14's at over 100 mph. Thinking back......that was a low compression set up also and it ran pretty good with a big cam. A lot of ignition timing will help and advance the cam. IMHO A big cam in a low compression L28 engine: Will not work so well with a stock EFI manifold Will not work so well with a 3.54 gear. Will not work so well with a heavy car.

I had good luck with my Mallory pumps. In fact, I just bought a comp110 last month and I'm using it as a feeder pump to my EFI pump on my turbo Z. However, you should run a filter before the pump. I also have a Mallory comp140 on my V8 Z and it has been work well for a few years. FYI, you need a low pressure pump, not an EFI pump.

I like the simple Holley 3310 750 vacumm secodary. Cheap, durable, and easy to tune. But don't get the silver version or the street aveger series. An old fashion 3310 can be had for 260.00 from summit. A double pumper Holley works nice on an automatic transmission cars with a 3000+ rpm converter. But, whatever you do, DO NOT buy one of those crapy edelbrock/carter carbs. Those are vapor locking, throttle sticking, peices of shit. The Q-jet carb works great but is ugly.

thanks for the write up! Don't forget to write on the Rod/Stroke ratios and how it effects piston speed and how it changes ideal cam timing. Lower maximum piston speed good for higher rpm use and longer dwell time at TDC with higher ratios which works better with smaller Lobe Seperation Angles. Higher ratios are also less prone to detonation, and so on.....

I use the black magic fan on my V8 Z and I happy with the results. Not to loud and fits nicely. However, The two speed tarus fan sounds pretty nice. Especially since you can get those fans cheap from a pick-n-pull.

Well, my G-tech meter just measured 271 hp with a car weight of 2800. I'm 200lbs, I have a full interior with AC, 2 amps, 2 subs, 2 woofers, 2 tweeters, custom speaker box, sound proofed and fiberglass floor boards, R200 diff, and a spare tire. I'm sure the turbo and IC add weight but I did remove the bumpers and bumper mounts. And all those fuel pumps and FMU add up to! LOL. So, most likely a little heavier than 2800 pounds. At 85 psi (100 psi fuel - 15 psi boost) a 17 lb injector will flow like a 28.6 lb injector. From RC Engineering web site: New flow rate= Square root of (new pressure/old pressure) then multiplied by old flow rate. In this case: new pressure =85 psi, old pressure = 30 psi, old rate= 17 lbs ((85/30) **1/2) x 17 = 28.6 lb to convert lbs to cc: 28.6 x 11 = 315 cc 315 cc injectors should be good for 315 hp in a 6 cylinder. 315 x 0.85 (15% drivetrain losses) = 267 hp at the wheels. This works as long as the injectors I have flow at 17lbs at 30 psi. Sparky, Unfortunately, I'm a little to busy for car clubs. Maybe one of these days I can make it out there. But thanks for the heads up.

I saw it. The red Z was a 70 to 72 judging by the SU carbs. The white one (i think it was white) was a convertible with some front end body molding.

Sorry for any miss-understandings. I have a T40b with a H3 wheel on the intake compressor side and a T3, 0.63 a/r with a stage 3 wheel on the exhaust turbine side.