Phred

Steve: The relief valve is easy to get to. If you installed the pump your self, you had your hands on it. Its the big hex bolt head on the bottom side of the oil pump. Its either a 19mm or 7/8 in. hex. Its actually a cap plug with a spring and plunger behind it. A 1/4 in. AN washer fits perfectly in plunger. Any race shop or aviation supply has AN washers. They come in thin1/32) or thick(1/16) sizes. Mix & match till your happy with the pressure. Phred

As long as were on the subject, I've been looking for a 3.9 R-180 gearset for quite a while now. I found new gears for $428. If a used set is unavailabe, guess Ill have to bite the bullet. To be exact, 3.9 gears with a 115mm ID ring gear. Thanks. Phred

Steve, Your kind of between a rock, & a hard place. If you know your oil temps on the high side, Synthetic will protect your engine better than petroleum. However if your pressure is starting to drop when things get warm, it will continue to do so. If I had to make a decision without any more info. This would be it. I ran 20-50 racing Synthetic (any brand as long as its 100% Syn.) in a turbo motor for eight years. But I live up here where it can be 20 degrees in the morning, and sixty in the afternoon. Its probably more moderate where you live, so you could get away with a straight 40 or 50 wt. I would also replace the oil pressure relief spring, with the Nissan Comp. spring(s). Or Shim up your current spring with a couple of AN washers. 2manyZs hit on the other factor. If your bottom end (rod & main brgs) have even a thousanth too much clr. (.003 instead .002), it will tend to "bleed" off oil when things get warm. This is noticed as a drop in oil press. It should'nt be harmfull, just bump up the pressure with the relief valve spring. If you have an accurate gauge, consider 40lbs. absolute min. when hot. 50lbs. preferred. With your eng. probably a little loose on the bottom end, you might end up seeing 70/75 psi when its cold, and 40/45psi when hot, and 50psi when everthings warm & fuzzy. OK, so syn. costs $4.00 a quart. Your eng. will thank you. Phred

Zvoiture: Too many questions, not enough answers. Guessing is as bad as taking things for granted. Lets assume the SU is good, and the gauge is good. For now. That means the engine is really producing less pressure when certain conditions exist. Why? Oil pressure relief valve not functioning properly? possibly, not likely. Which gets us back to thin oil. If this is the culprit, this may explain why.. General info on tests I performed on an engine dyno using both a 1600 & 2000cc formula ford engines. The tests were performed to evaluate the differences between petroleum vs. synthetic oils. Oil pressure, oil temp, horsepower, and torque, were the main focal points. Brefly, the results showed: At 180 degrees water, 160 degrees oil, the synthetic showed 2 to 3 more horsepower than petroleum. it also indicated 3 to 5 lbs. less oil pressure. (synthetic is thinner than a similar petroleum, producing less resistance within the pump). At 200 degrees water, 200 degrees oil, Horsepower figures were the same. Why? because the petrolium oil thinned, and presented the same internal friction coefficient. At 200 degrees water, from 200 to 220 degrees oil, both oils produced basically the same power. However, at 200 degrees water, starting at 225 degrees oil, the petroleum oil started to show a power loss and a drop in oil pressure. Power loss was notable at 240 degrees. Due to an increase in internal friction. ( the oil was starting to break down.) The synthetic oil did not cause a loss of power. My point being, pressure is directly related to temp. And is directly related to RPM. More RPM, More H-P, More heat. I drove a six hour enduro once, where we had excess oil temp. by dropping the shift point 250 RPM, oil temp was reduced nearly 10 degrees. An oil temp gauge is the only way to know for sure. Good luck. Phred

Clive: right now on Z car.com there is a used set of 40mm webers with manifold for $350. 40mm & 45mm use the same manifold. Also I have a brand new, never mounted manifold I bought for $295. I used the soft mounts on another setup, so will sell the manifold for $200. fly.fred@verizon.net

You stated you were cruising for an hour @ 90 MPH, 4200 RPM. My Guess is the oil heated up, thinned out, with an expected drop in oil pres. After it cooled down, I bet your oil pres. came back up. I've seen this on the dyno many times. Try a straight 40 wt. racing oil. This will tend to foam less, and thin down less than a multi-grade, street blend. Phred

Cuong, Awesome yellow Z. What type of discs did you use with the Brembo 993 calipers? Phred

My Best guess is original Minilites. What do I win? Phred

All info above is true. However, even with the proper fixture, the possibility of damaging a piston exsists. If your willing to spend the money to balance your engine, consider replacing the pistons too. After all, at minimum, it needs to be honed, and rings replaced. Pistons wear out like everthing else. they might look ok, but the skirt can wear down slightly, increasing pist/bore clr. Also, more important to horsepower, are the ring lands. If they have any significant wear, which is common with a used piston, performance goes down. Also the piston pin bore will wear, especially with a pressed in type. If your budget will allow, replace the pistons too. Balancing Rods: (never when connected to a piston) Rods are balanced rotationally (big end) and reciprocating(small end) The combination being total weight. First, the caps are torqued on without bearings. They are hung on a fixture which supports the small end off to the side of the scale. The big ends are all weighed and recorded. Then The heavy rods are ground or machined on the cap till they weigh the same as the lightest one. Then the complete rod is weighed. Again the heavy rods are ground or machined to match the lightest one, but this time all weight is removed from the small end, usually around the top of the pin bore. Presto! a balanced set of rods. A good bal. job will have a +/- .5 gram tolerance. The pistons are weighed individually with the pin. As with the rods, the heavy ones are machined till they weigh the same as the lightest. This is usually done as an assembly, which would include balancing the crank, flywheel, clutch, and damper. Good luck! Phred

Danger!!! The Cam Tower bolts you refer to are 8mm dia. x 1.25 pitch. The hex size is 12 mm. IMPORTANT! DO NOT torque ( or attempt to torque) these bolts to 25-33 lbs. You will strip the threads out of the head!! Remember, your head is aluminum, and the bolt is steel. These bolts are the same dia. as those holding the front cover and oil pump on. Datsun Factoty Manual calls for 11.5 lbs. for them. I have assembled many racing Z heads with high lift cams and higher than stock spring pressures, and all have survived with only 15 lbs. of torque on the cam tower bolts. I have heard some engine builders only used 12 lbs. torque. So consider 12lbs. min. & 15 lbs.max. Also never torque bolts into aluminum dry. Put a little lite engine oil on the threads and under the head, then torque. If, when approaching 15 lbs, the bolt feels "soft", STOP. Phred

Also have someone with an adjustable timimg light check total advance (combination of mech.& vac.) should be about 32 to 34 degrees. Also verify the accuracy of your tach. A tune up shop can do the above quickly and cheaply. Phred

Chris, One other thing to do before you pull the head. first set valves. Then have someone familiar with dial indicators and engines check the amount of valve lift at each lobe. This will show how much wear has taken place, and you'll know if the cam needs to be replaced befor taking the head off. Phred

Benn9090, I assume you have already ordered a new set of main jets. The makers of jets have always said never to drill jets. I used to figure they just wanted to sell more jets. But every time I run into drilled jets, they never seem to be running right. Hope that cures your problems. Phred

Benn9090 Hey, those carbs look great! What kind of finish did you apply to them? I used to build airplane engines too, and we used Alodine to protect bare aluminum from corrosion. Looks similar. As far as the poping goes, that could be your distributor. Since you were fiddling around with the vac. advance, there may be something else not right in there. I'm not up on vac. adv. units as we always disable them for racing. However, I have cured some Z track cars that stumbled and popped by going to a locked breaker plate, and using only mech. adv. setting total advance to 34-36 degrees. I'm not advising you do this, I mention this only to point out theres more than one way to skin a Z. More to the point, there are a number of sensor/gauges on the market that will take the guesswork out of what your doing. K&N among others, has a air/fuel ratio monitor, or a device called a Lamda indicator which uses oxygen sensors to indicate air/fuel ratio(ideally around 14.7:1) Or a good old Exhaust Gas Temp. gauge. (EGT) We use EGT and fuel flow to determin proper Mixture settings on an engine dyno. Hang in there. I think your about to become the local Weber expert in your area. Phred

Benn9090 Your Comp. & flow #'s are not uncommon for a street engine with some miles on it. On the downward intake piston stroke, with the throttle plate at idle position, a vacume is created. this is what your reading with the flow gauge. If one cyl. is less effecient than another, or a slight vacume leak exsists, these numbers will vary. simply average and balance them as best you can. You can minimize the difference when setting up the carbs on the bench. With each individual carb, back the idle screw out all the way. Hold the throttle plates closed, and look through the carb bores while holding up to a light. You should not be able to see any light sneeking past the throttle plates. If you see light passing by one plate and not the other, loosen the two throttle plate retaining screws, and lightly tap on them with the back of the plastic screwdriver handle untill they both "seat" into the throttle bore. Retighten, and check with the light. Repeat if needed. This easy adjustment will assure you that both throttle plates of the carb are getting the same amount of movement (flow) when the throttle arm is moved. Now, any differential readings on the same carb will indcate an intake leak or the cylinders inability to draw air equally. Phred

Eric, I've been rebuilding and tuning Webers for years, And I agree with all that Alan (HS30-H) said. For parts and expert advice in your area. go to: www.piercemanifolds.com (408) 842-6667 Gilroy, Ca. Order: Isolator kit #99005.146 (3ea.) Phred

Eric, After cranking, check all spark plugs to see if they are all the same, i.e. gas fouled or dry. Also, with a mirror & light, look down each carb to verify each squirter/accelerator pump is functioning. While peeking down there make sure all throttle plates are opening equally. It won't keep it from starting, but I didn't see any Isolator 'o' ring plates between carbs and manifold. These are part of a mount kit which keeps the carbs isolated from engine vibrations, which keeps the float level from splashing fuel up into the air corrector jets which causes flooding, and poor performance. Let us know what you find. good luck. Phred

Go to: www.rebelloracing.com Phred

I was just about to order one. Does anyone know if all the dash covers are made by the same parent company, and then simply labled with different retailers names? Or does one brand fit better than another? I'm aware of MSA & VB, but I also picked up a business card at the Portland Roadster Show from a place called - Dash-Caps in Paradise, Ca. (www.dashcaps.com) The sales person said they only offered half caps for the 240's because they had problems getting the full cover to fit properly. But also said if enough interest was shown, they would likly work toward making the full cover again. Preferably one that fits. I would like to ask all who have bought dash covers, to reply with place of purchase and quality of fit. Then we could offer a knowledgeable recomendation to those in need. Thanks. Phred 71' 240 Vintage Racer/restoration in progress

Balancing eng. components is part of my job as a racing engine builder and machinist. First, it will not gain you 15, or any horsepower. unless the bal. was so far off that the bal. job allowed the engine rev a bit further than it did prior to the bal job. (highly unlikely) A complete bal. job involves balancing both rotating and reciprocating parts. That means everything that spins around (rot.) and everything that goes up and down. (recip.) The crank, fly, clutch cover, and damper are spun individually, and as an assembly, on an electronic eng. balancer. This machine works somewhat like a spin balancer for tires. An imbalance is detected by a sensor, and with the use of a strobe light, the location is indicated. The required amount of weight is drilled, or ground away, untill no imbalance is indicated. The con rods, pistons, and pins are balanced statically so that all components are equal in weight. A balanced engine may last longer because there is less stress delivered to all areas within the engine. Iv'e had assemblys nearly hop off the machine when a badly out of balance component is bolted to the crank, so you can imagine the hammering the bearings might encounter. Any time an engine is rebuilt with performance in mind, a complete balance job is just as important as the parts you build it with. It is generally not practical to disassemble an engine just to balance it unless a serious internal problem exists. If you are looking for higher revs and higher horsepower, a balance job is worth its weight in gold. Having driven both balanced and unbalanced engines on the street, and the track, I can tell the difference in the smoothness throughout the rev range. And it will theoretically live longer. But, sorry, no horsepower gains by simply balancing an engine. Phred

Racer-19, Do you have weight info on the Lexan pieces? So that I might compare them with their glass counterparts to see how much weight savings can be achieved. Building Vintage Z racer. Phred

I've been reading/hearing about some confusion many home engine builders are having concerning camshaft timing-duration numbers. Such as,"my 300 degree cam dosn't have as much lift as my buddies 280 degree cam, and his seems to make more power. Whats up?" First, understand there are two different methods cam duration is measured. One is the absolute, or advertised duration. The distance in degrees measured from a point where the lobe physically starts to rise from the base circle, to another point where the lobe blends back into the base circle. The second is a standard "checking height" of .050 lifter rise, or in the case of the L series engines, valve lift. Naturally, if you take a degree reading .050 after the the valve starts to rise, and another .050 before the valve closes, the total duration will be less than the "advertised" duration. So, the first rule in describing a cam is to state, " 300 degrees @ .050" or "300 degrees total advertised duration". Without that distinction for comparison, degree numbers are useless. Lastly, valve lift is a seperate function of cam design. Valve lift is also measured two different ways. Advertised lift, is the total physical size of the lobe, measured in thousandths of an inch. This is somtimes refered to as "gross valve lift". Then there is the actual running valve lift which is known as "net valve lift. This is a lesser number, (which is why they don't advertise it) because of the required subtraction of valve clearance values and the amount lost (or gained) because of the rocker ratio. I hope I didn't confuse the issue any more than it already is. Simply be aware of the many ways of the black art of the bump stick. Phred, the Engine Shaman

TWM Induction builds quality parts, but gets quality prices for their stuff. 1999 catalog lists a manifold without linkage for $317.44 !!!!:eek:

Hope I didn't mislead you. The R-180 3.9 is NOT an LSD unit. You have to supply that part yourself. In my case, Im going for the Quaife. However it is a complete rear end, ready to run.

I bought a R-180 3.9:1 from: garykaz@pacbell.net (Glendale, Ca.) Price $200. plus $50. shipping to Portland, Or. Claims to be able to produce one on request. Give him a try, worked for me.