Pyro

With a P79 head and a L28 block you have two compression choices using stock components. 7.4:1 cr with dished pistons (stock N42 block). This makes stock turbo compression. or 8.8:1 cr with flat tops (stock F54). This is stock 81 to 83 zx NA compression

I run 14 psi with stock NA injectors and NA ecu on my 75. I just limited the total advance to 26 degrees by welding up the advance slots, Set the initial timing to 18 degrees, Tighten up the afm flap by 8 or 9 teeth, yes tighten Run a FMU to ramp up fuel pressure to 95 psi at 14 psi of boost. I use a 4 psi hob switch to activate another fuel pump in parallel. I'm also running 7.4:1 cr (stock turbo cr). My fuel pressure doesn't even start to come up until 4 or 5 psi due to a bleed valve delay in the fmu. The engine would run too rich when the pressure came right up. I found it easy to run up to 8 psi but after that the fuel pressure curve became tough to get right. Once I got it working at 14 psi, I dare not touch that FMU. If a higher compression engine was used then I would just lock out the timing to 20 degrees, run stock boost (8 psi), and set the fmu to 55 or 60 psi. FYI, I use a bell engineering FMU and msd fuel pumps.

The stock 180 diff and 4 speed will work just fine. However, the clutch will not. You need to install a stock 2+2 clutch (240mm). Nissan sells a clutch kit for 160.00, get a 9 bolt flywheel and 2+2 bearing hub from the junk yard for 30.00, and get the flywheel resurfaced for 25.00. Don't forget to get the pressure plate bolts. You will also need a 280Z tach from a 75 to 78. If you are running stock boost, you really don't need a boost gage. It is nice to have, but not really needed. A simple A-pillar mounted boost gage is all will you need. Swaping a transmission is easy work. If you don't want to change the trans now then don't.

If you are using flat tappet lifters (hyd or solid), then the lifters will be pushing the cam towards the rear of the engine. There is a slight taper on the lifter faces that force the cam back. If you plan on using a roller cam then you will need to use a thick walled timing chain cover along with a thrust button and a roller bearing at the block timing chain interface. And the proper cam back lash must be set with the timing chain cover and the thrust button. Please use diesel engine oil in your engine. BBC are very sensitive to cam lobe damage. I have built many BBC's and have learned the hard way.

I don't want to bust your bubble but 305's aren't know for making that much hp. Especially with stock cylinder heads. So, it is always better to guess low to not disappoint your-self on dyno day. Stock heads, mild cam, holley and some headers will make about a 250hp (200rwhp) 305cid, if you are lucky. The good news is with some better cylinder heads this can be increased to 250hp. Then add a 350 short block for another 50 hp. Back firing out the carb indicates retarded timing and/or a lean mixture. If your diff gear is stock, it should be a 3.54. A 25 inch tire with a 3.54 will make the engine rev 1000rpms for every 21.0 mph in 3rd gear (1:1 in a th350). So, 70 mph will make the engine rev to 3,333 rpms. Sound about right? What tach are you using? Right now you should be able to run a low 14 at 98 mph. I'm trying to be positive here. In JTR V8 manual they say a stock 350 with a 5 spd in a 240 will run 14.5 at 95mph. So, do except much more from a mild 305.

I used a NA efi pump on retro-fit turbo and it worked ok with stock boost. I only upgraded my fuel system when I turned up the boost.

Use the stock turbo exhaust manifold.

I run 14 psi with the stock NA injectors and ecu. However, I have a fmu that jacks the fuel pressure up to 95 psi at that boost level plus a fuel pump system from hell. All you need is a little more fuel pressure. 45 or 50 psi during boost should do it. The higher the boost, the less the injectors will flow. When the manifold is under positive pressure it slows the fuel volume from the injectors due to less pressure difference (boost pressure- fuel pressure). If the boost pressure was the same as the fuel pressure, no flow would come out of the injectors. Maybe all you need is a pressure sensitive fpr.

Should get 14 to 15 easily in the city with a mildly cammed 305 and over 20 mpg on the highway, even with 3.54 gears and a 3 spd auto. What is your set up: gears, cam, heads, exhaust, carb, ect???

It just isn't the zinc they are taking out. There are a few more additives that they have reduced. I don't believe they took out the zinc completely, just reduced it by one half. If there is a zinc-free oil, maybe there are other additives which make up for it. FYI, Chevron Delo is formulated for diesel engines. Here is a copy and paste from there web site. Chevron Delo® 400 ESI Multigrade SAE 15W-40 Chevron Delo 400 Multigrade heavy duty motor oil is an industry leading, super premium quality "universal" engine oil which exceeds industry and engine manufacturers' performance requirements. It is formulated utilizing the most advanced additive technology available to provide outstanding engine protection under both pre- and post-1998 EPA exhaust particulate emissions standards for on highway diesel trucks, using both high and low sulfur diesel fuels. Chevron Delo 400 Multigrade is formulated with ISOSYN™ base stocks, which rival synthetics in critical engine tests and an optimal blend of the latest technology in dispersant, detergent, oxidation inhibition, antiwear, corrosion inhibition, viscosity improver, and defoaming additives. Chevron Delo synthetic SAE 0W-30, 5W-40 Chevron Delo 400 Synthetic heavy duty motor oils are multipurpose 100% synthetic lubricants formulated for use in gasoline and diesel engines, torque converters, gear cases, and hydraulic systems operating in subzero arctic-type temperatures. They are manufactured using stable synthetic base stocks. These oils utilize highly dispersed viscosity index improvers that promote stable viscosities and soot dispersancy between oil drains.

When I did my first clutch job (at 16 years old), I put the clutch disk in backwards. Also made a funny sound.

Neal, We need a bunch more information about your engine. Maybe you should start your own post.

I wouldn't worry about the quench too much since there is nothing you can do about it now. However, I would get a EFI system that has ignition timing control. Being able to shape the timing curve will do wonders for power, anti-detonation, and mpg. The timing curve is just as important as the fuel curve, especially with a high compression turbo engine. 8.6:1 is high compression for a turbo as far as datsuns are concerned. You should be able to easily run 10 to 12 psi on 93 octane with 8.6:1 cr with a good efi system. And even more with some racing fuel when you take it to the track.

I'm not a Q-jet expert but I would find the adjustment that controlls the opening rate for the secondarys. On a Holley it is simple, just put in a stronger secondary spring, there are about 7 to choose from. Do a little research on the web to find out how to tune a Q-jet. Q-jets are great carbs, and your should learn them if you are going to run one. Could also be a lean condition. I'm sure there are more than a few books out there about Q-jets. The beauty of a properly tuned vacuum secondary carb is the engine will only use as much as it needs. A 750 carb will not flow 750cfm's until the secondarys are completely opened, and that doesn't happen as often as you think.

P90 and P79 have the same combustion chamber size and shape. With the piston 1mm below the deck there will be no quenching effect, so there will be no extra detonation protection. You should had made a piston that had a D shaped dish to allow the flat top of the piston to come out even with the deck height where the head is flat. 0.040" is the the biggest distance that quenching will work. And 0.040" is the head gasket thickness, so you need a true flat top, even with the deck height, to get it to quench. FYI, stock turbo engines or any dished piston Z do not have any quenching either. A P90 or P79 will make 8.6:1 cr a N42 or N47 will make about 10:1. Use a P90 for a turbo or a N42 for a NA build.

Carb tune is also very important. Most people just throw on a carb and expect it to work. There are a bunch of things to tweek on a Holley to make it run right. Front and rear jets, power valve, accelerator pump squirters and cams, and vacuum secondary springs to name the most common. And just because the carb is a 750, doesn't mean the engine will use all 750 cfms. Vacuum secondarys seldom open all the way on smaller engines or on carbs with heavy secondary springs. GM put 750 Q-jets on 283's, but that dosen't mean the 283 would suck open the secondarys all the way. That 600 may just run better because it just happens to have a tune on it that complements your engine combo. Do you know what power valve is in your old carb, or what jets and squirter it had, or what secondary spring was in there? Do you know what vacuum your engine is pulling at idle, part throttle, full throttle? Did you read a plug and change jets?

For a cheap and simple turbo you could use a stock turbo exhaust manifold, stock turbo, stock wastegate, stock down pipe, stock oil feed and drain lines. Then install one carb on the front of the turbo and fabricate a throttle cable. Finally build a connection from the turbo output to the stock intakes. This will consist of some kind of box connecting the two intake with a round input hole for the boost pressure. All thses parts can be found at a pick-n-pull or orders from the web. I get used T3's for 40.00 at the junk yard. A stock T3 will make plenty of power on a 240. However, in a draw through system the turbo will need a carbon seal since gas will be flowing through the turbo. Any turbo shop can do this for you. Gas flowing though the turbo acts like an intercooler which is nice but will have problems to operate under 50 degrees ambient (outside temp). Fnally, lock the mechanical advance in the distributor and set the timing to 24 degrees. Use the vacuum advance normally, the boost pressure will shut it down. They built kits like this for the 240 many years ago. I believe the kit also used water injection to prevent detonation. But I think locking the timing at 24 will do the same thing. I'm pretty sure a stock 240 would run 14.0 in the 1/4 mile with a T3 turbo and one SU carb.

draw-through or blow-through?

I have been using Rotella everday and my oil seems to stay cleaner for much longer periods and also stays much "slicker". My old gas engine oil becomes black and feels like water after a few thousand miles.

Yes, use the vacuum advance. Don't worry about the advance being too much. At low engine vacuum (open throttle and under a load), the vacuum advance will be zero. Reving up the engine in neutral doesn't reproduce a driving condition. With those heads and flat top pistons you should be able to get by with 32 degrees of total timing. However, you will need to run 15 to 20 degree initial timing for that cam. So you will need to limit the amount of advance in the distributor by welding up one of the advance slots just a little.

What pistons are you using, flat, dished,? What heads are you using? How much advance in the distributor? How much initial timing are you running now?

I can't believe a turbo pump didn't increase oil pressure at idle. Are you sure it is a turbo pump? My low pressure idle issues were solved/improved by a turbo pump. The turbo pump has longer rotors than the non-turbo pump. I forgot the exact amount but it is around 1/4 inch (6mm) longer. Maybe you should measure the new pump rotors versus the old pump rotors. I run 15w-40 diesel engine oil in my Z. The next time you get an engine rebuilt, tell the machine shop to install each bearing then mic the bearings and then turn the crank to get exactly 0.0020" clearance on all the main and rod journals. Cost a little more but worth it.

Here is a copy and paste from CompCams website. COMP Cams® Engine Break-In Oil Additive Extends Engine Life New COMP Cams® break-in lubricant provides missing additives no longer found in current motor oils Time marches on... and generally that’s a good thing. But unfortunately, over time, some of the good stuff can get left behind. COMP Cams® Engine Break-In Oil Additive brings back the good stuff, delivering a specially engineered blend of extreme pressure break-in additives that have been removed from current off-the-shelf motor oils. Delivering added protection during the break-in process and beyond for all engine components, including the camshaft and lifters, COMP Cams® Engine Break-in Oil Additive is compatible with any petroleum, synthetic or blended motor oil. COMP Cams® Engine Break-In Oil Additive extends the durability of internal engine components, protecting against premature camshaft, lifter and valve train failure. Best of all, COMP Cams® Engine Break-In Oil Additive has proven to deliver long term benefits with new or rebuilt engines through continued usage. Simply pour in a bottle for initial break-in, run the engine for approximately 1,000 miles, drain the system thoroughly and then refill with clean oil and another bottle of COMP Cams® Engine Break-In Oil Additive at each oil change. For more information about the COMP Cams® Engine Break-In Oil Additive or any other COMP Cams® product, call us at 1-800-999-0853, or visit us online at http://www.compcams.com. #225 TECH BULLETIN: Flat Tappet Camshafts Recent changes in oil and engine technology are likely the cause of premature camshaft failure; here’s what you can do to protect your engine! Premature flat tappet camshaft failure has been an issue of late and not just with one brand or type of camshaft. In almost every case, the hardness or the taper of the cam lobe is suspected, yet most of the time that is not the problem. This growing trend is due to factors that are unrelated to camshaft manufacture or quality. Changes in today`s oil products and “advanced†internal engine design have contributed to a harsher environment for the camshaft and a potential for failure during break-in. But there are several things you can do to turn the tide on this discouraging trend. Proper Camshaft Set-Up & Break-In Proper flat tappet camshaft set-up and break-in, as any engine builder knows, are keys to how long a camshaft will last, both short and long term. Making certain that the camshaft and lifters are properly lubricated will guarantee that the camshaft and lifters are protected during the critical initial start-up of your newly-built engine. COMP Cams® offers the right product for this job (Part #154), and it is available in several different size containers for engine builder convenience. To further enhance this “relationship,†we strongly recommend the use of COMP Cams® Camshaft Break-In Oil Additive (Part #159) during the break-in. While this additive was originally developed specifically for break-in protection, subsequent testing has proven the durability benefits of its long term use. This special blend of additives promotes proper break-in and protects against premature cam and lifter failure by replacing some of the beneficial ingredients that the oil companies have been required to remove from off-the-shelf oil. These specialized COMP Cams® lubricants are the best “insurance policy†you can buy and the first step to avoiding durability problems with your new flat tappet camshaft. Adequate Lubrication Another major factor in the increase of flat tappet camshaft failure is your favorite brand of engine oil. Simply put, today’s engine oil is just not the same as it used to be, thanks to ever tightening environmental regulations. The EPA has done a great job in reducing emissions and the effects of some of the ingredients found in traditional oils; however these changes to the oil have only made life tougher on your camshaft. The lubricity of the oil and specifically the reduction of important additives such as zinc and manganese, which help break-in and overall camshaft life, have been drastically reduced. In terms of oil selection, we recommend Shell Rotella T oil for the break-in procedure. Most often used in diesel engine applications, this higher lubricity oil works in gasoline engines as well.

Engine oil has been reformulated over the past few years. They removed or reduced some of the antiwear additives that they demended bad for the environment. This reformulation didn't effect cam wear on stock engines due to mild cams and light valve springs. Wear problems started to occur when this new oil was used with high lift cams and heavy valve springs. The good news is that diesel engine oil still has all the antiwear additives in the oil. So, use diesel engine oil with your new cam for some extra protection. Go to compcams web site and check out their tech section on cam install. They talk about this problem and also recommend diesel engine oil.

You can check it the way racers are checked after a race to match sure they weren't cheating. Remove the rockers off one cylinder and screw on a compression tester hose with the valve removed. Then attach the hose to clear 2 liter tube with a light piston in the tube. As the engine is rotated, the piston in the tube will rise and fall with the piston in the engine. The volume sweep in the clear tube is the volume of one cylinder.