labrat

my 81 280ZX came out exactly 27" center to center on the ujoints, and cost 160 bux. Of course, I had them splice the driveshafts instead of using chebby ujoints on both sides, and it was 50 bux to replace the datsun "non-replaceable" ujoints. 27 inches was also slightly too long, didn't even have enough slip to remove the driveshaft from the pinion flange in the diff without unbolting the tranny and dropping it about 3". no where near enough slip fore and aft, and it vibrates horribly. Fixing that now, though... Bill

I know this is an old thread, and you've probably already dunnit, but here's my $.02... I would run the ground lead from my coil (or batt+ connection for hei) through the firewall and switch that on and off. Let em crank the car, when it doesn't start they will just think it's broke down or something. Actually, i would run it through a series of identical switches of differing up/down orientation with no labeling, that way you would have to set the switches in a certain sequence to start the car. (note to self: inside console would be a good place to put this switch panel) Bill

I gotta second the advice about the head temperature sensor. That is a MAJOR feedback component on the 81's. I think it actually has more to do with the A/F mixture than the O2 sensor. If there is too much resistance in the contacts, or they come off altogether, the motor thinks it's trying to cold start in antarctica or something, even when you're running down the freeway at 80 in the summertime in Texas. Or at least that's what happened to me. Fouled out a set of spark plugs in about 5 minutes...

Sounds like your BCDD is stuck open. Its something that datsun used to reduce emissions. It basically allows air to bypass the throttle body to burn all the fuel that's in the engine when you let off and begin to decellerate. There's a connection to the spedometer that doesn't allow it to work under 10 mph, but when things start sticking, you get a 2k rpm idle or so. I just filled mine with body putty and was done with it. You should notice a tube going from the front (atmospheric side) of the throttle body (on the underside) to the "idle adjust screw", which probably doesn't adjust anymore. I took the hose of on the bottom side of the idle screw, filled it with body putty, then drilled a small hole through the putty with a long drill bit to get my idle adjustment back. Replaced the tube, and it worked like a charm... BTW, this was an 81 N/A, so YMMV. I would send pics, but I got a 350 in there now... Bill

I'm in austin right now, but i'll be heading to mesquite in two weeks with my 81 280 ZX. gonna drop the 350 and a new t-5 in it and maybe paint it if there's time. I'll be at my buddy's house up there, who also has a hybrid Z. He's got a 72 240 with a 327 and ford 9" rear. I'll make a deal with you. You help me drop in my motor, and we'll tune the heck out of your car . I won't promise we'll squeeze all 500 HP out of it, but we can at least give it a good tune up and then go from there. That is, if you can wait two weeks... Bill

All of that was pretty impressive, but the guy in the trans am was FSCKING NUTS! But I guess cruise control and a good alignment go a long way. I need to look into both...

Okay, everyone can breathe again, I found the paperwork for the rings, and got them sorted out. Thank you for your support, you can now resume your regularly scheduled programs. That is all.

Well, if anything happened to the cat, i'd follow right after it. It sits far above me on the totem pole in this house. There are casting dots on both sets of rings, to indicate the top. They are sealed power rings, if that helps. I just wanna figure this out quick without another trip to the parts store, and i doubt they would let me open a sealed box of rings anyway. I was hoping you could tell by the profile of the ring face, or something. What's the worst that could happen if I get them backwards and install them? Just curious... Bill

Ok, My cat knocked an open box of rings off my kitchen table, and they went everywhere. I have my little piles of rings separated, but how do I tell the top ring from the second ring? One pile has green paint near the gap, i think that's the top one but want to be sure... Any ideas? Thanks! Bill

I definitely know the feeling (well, almost). I wrecked my motorcycle two weeks ago and fractured two ribs in the process. I'm just now getting to where I can get comfortable in a sitting position, and i can forget leaning over my engine bay for a while. Just got a new pair of heads to cap off my rebuild, too. This sucks. I either have money and can't find the parts I need, or don't have money when they're falling off of trees. Now I have the parts, and can't install them because of an injury. Life sucks sometimes... Bill

Is all the hype you hear about double pumper carbs really based on fact? Is the vacuum secondary carb mainly for fuel economy like i've heard? I basically threw fuel economy out the window when I did the swap, and my buddy swears by the double pumper holleys. Is there any real difference besides the addition of accellerator pumps in the rear barrels? I'm just curious if it's worth the extra money, i've already got 2 vac. sec. 650 carbs (one holley and one edelbrock), is it worth upgrading to a DP? Thanks fellas.... Bill

It's certainly better than the tire I just used to rebuild my 350. Damn was that a lot of grunting and sweating. Used the 100 bux I saved not buying a stand to buy a cam instead... Bill

For what you are willing to put in it, another supercharger would be the way to go if the motor doesn't smoke or anything. Just with that addition, you should be way over the 450-500 HP mark (or else why supercharge it?). Used superchargers can be had on ebay for about half what you have, or you can go whole hog, buy a new one for a little bit more, and get a killer warranty on it. There are a lot of low-profile centrifigal superchargers out there, and a blown Z would "blow" my mind to drive... Bill

It still won't let me see the pics without registering... You gotta post them somewhere else, man. Bill

well, i had everything all tabled out in 500 rpm increments, then i lost it all, so in a nutshell... 510 hp @5500 528 tq @4000 Nice flat torque curve all the way past 5500 too. Should scoot nicely. In anything. Bill

What kind of steering setup do you have in that ZX? In my 81, the toughest part is finding an exhaust manifold that will clear the power steering gearbox on the driver's side. If you have the non rack n pinion power steering, you may have trouble with those lt1 manifolds. The best mount I found was for a 69 chevy truck, they are about 6 bux from autozone, have good stiff rubber, and bolt right up to the datsun crossmember. They should work OK with your block. Just put about 3" of spacer on each side (keep adding spacers till the mounting holes line up) between the motor mount and block. I think I used 3" on the driver's side, and 2 1/4 on the passenger side, but YMMV. It was really a lot easier than I expected it to be. I would advise you to buy the JTR manual, but you can't follow it like stereo instructions with this car. It focuses on the earlier models, and we are a little different. If you do a search on my member number, i've tried to document the swap pretty well, as we ZX's are in the minority here... Bill

Well, from what you gave, and assuming those pistons actually deliver 10.2-1 (prolly higher though, I think), with small tube headers through mufflers, the numbers I got were: Rpms H.P TQ 2000 122 321 2500 162 340 3000 206 361 3500 259 389 4000 312 409 4500 360 420 5000 401 421 5500 423 404 6000 431 377 6500 421 340 7000 368 258 And downhill from there. Hope this is what you were looking for, sounds like a good combo! (btw, formatting these columns is a B&*%$! when the BB software edits out extra spaces for ya...) Bill

Well, I bought an inside mic (one of the cheap autozone dial ones) and measured the ridge, and it was 4.040, but my mic won't fit further down in the cylinder, hence my roundabout way of measuring the cylinder wear. I'm tearing the motor down because: 1.) it ran like crap, smoked, and used lots of oil. (had 5 broken top rings) 2.) I just bought the donor car and swapped drivetains without really knowing what I had. 3.) the rear main seal was leaking and the easiest way to get to it was with the motor out of the car. While i've got it out, I might as well... 4.) I just bought a motorcycle, it's summer out, and while I have the time and alternate transportation, I might as well... I was able to mic the outside diameter of the pistons (at the skirt) and judging by my crazy way of getting cylinder diameter, determined I have .002 piston to cylinder clearance at the widest point. .0015 at the narrowest. The old bearings looked good when I took them out (only 1 was scored, and i suspect it was ran low on oil once), and there was still a suggestion of crosshatching on the cylinder walls, that's how i'm getting the fact it only had a few thousand on it. I was also told that by the "original" owner (the guy who had it before me, but not original by any means), but I didn't know for sure. If nothing else, it was 200 bux and 30 or so hours worth of peace of mind. I also got a nice new lumpy Crane energizer cam in it, so at least I know what I got now. That was worth it, if nothing else. Bill

You would probably be a little better off if you find a farm truck somewhere with a 350 that runs good but has a beat up body. I found one complete with motor for 400 bux. That was the way I found my donor. I even drove if from dallas to austin after I bought it. (well, drove it with no brakes, broken windshield, and had to add 2qts tranny fluid every 45 minutes...) but it did run! With the extra 800 bucks, buy a new cam, vortec heads, and rings/bearings and you will have a beast of a motor.

Well, i wasn't so much as looking for what I needed, as what I already have. The motor I tore down only has a couple thousand miles on it, so I'm reusing pretty much everything (pistons, rods, crank, etc) just freshening it up with new bearings, rings, cam, and heads. I just wanted an easy way to "check" how much wear I had on the cylinder walls. What I did was measure the ring end gap with the piston on the ring ridge at the top of the cylinder with a feeler guage. I then measured the same gap with the ring slightly lower. The ridge should still be 4.040" (bored .040 over) as no wear occurs here. I took the difference in end gaps, divided by pi, and got the cylinder wear in thousandths. With .002 difference in the end gaps between the ridge and cylinder wall, that means less than .001 wear, or increase in piston to cylinder clearance. Basically just checking to see if it needed punched out again and new pistons. If there is a flaw in my logic here, please point it out! Thanks for the input, guys. Bill

Thanks for the information, it was fascinating reading, but not exactly what I was looking for. I'm looking for something along the lines of "if your piston ring end gap is X, then your piston to cylinder clearance is X" basically trying to measure my exact bore dimensions without an inside micrometer. That's what it appeared Datsun75 was doing in the previous post. On second thought, it kinda looks like he just measured the difference between the ridge circumference and the circumference lower in the cylinder (using the ring gap as a guide) to determine the wear for the cylinder, not the exact dimensions. Hhmmmm... Bill

"We took a measurement of the ring gap on and below the ridge and did the little formula the "how to build chevy small blocks" book explains. Measuring with a feeler gauge, I came out with a difference of .0073 The book indicates that a difference over .006 is saying that you need to punch it out " Does anyone have this formula for finding piston to sylinder bore clearance handy? I know this is an old thread, but its just what i'm looking for... Thanks

Well, i didn't drive it too far when this happened before the beast got parked (just a few miles), as at the same time I bent a few pushrods... I thought i had tightened them down too tight when i replaced the head gaskets, but the detonation explanation is making more sense. The lands on the piston look okay, still nice and flat, but damn are those rings tore up! Good thing I pulled the motor and tore it apart, instead of trying to keep it running this way. Oh well, now I at least know I have a 4 bolt main with a nice balanced rotating assembly and chamfered oil holes on the crank with new clevite bearings and new rings. Now I just need a new cam and heads and i'm in business...

Thanks, that's entirely possible. I rebuilt the carb right before this happened, and had problems getting the gasket to seal on my spacer... that makes sense now. I was just trying to avoid going through this again...

Well, i finally figured out my oil consumption/blowby problem. Pulled my 350 last night and tore it down this morning, and found 5 broken rings. The top ring seemed to give right about in the middle (although one broke into 4 pieces)... At least they didn't score my cylinder walls. My question is, what could have caused this? I'm thinking it was either improper ring gap, or just crap building up in the ring groove, but before I reassemble this thing, is there anything else I should look for? I don't want this happening again... Bill