Bearwen

I do intend to turbo it later and yes it's all clocked and good to go. the reason I made the post was so when people are considering a cam upgrade they would have a reference as to where to start with idle and what to expect with different cams sizes and different timing and compression ratios which all factor into how well it will idle at different RPMs. We idle low around 750 ( my sons car and he loves the almost stalling lope sound ( it's cool to the kids)) best idle is closer to 1,000rpm more vacuum ( not much more about 12")smoother idle less rev up off the line and works well with a lower compression motor. with the aftermarket EFI when idle if higher 1000-1100 we are able to get more vacuum and we also go down a little in the manifold pressure Kpa ( low idle speed 750 we are 75-80 Kpa and higher idle speed 1000ish we're in the 68-71 Kpa)

I do have a .460 lift 280 duration cam from comp cams but I just thought it would be good to have a post showing different cams with different compression ratios and idles as well as vacuum so people thinking about a cam upgrade will have a general idea of what to expect from different cams. We are running stock L28 1979 280zx dished pistons and stock compression on a older ( got some miles on her so maybe 8-1 cr ) motor. stock n47 head with port work done and kept the steel exhaust inserts. A 3-2-1 header and we are using modern injectors in the stock intake driven by a megasquirt 3 X. We run a low idle 750 we pull around 8inHg really love the way it sounds at that idle (it is an issue in tuning though ). Edit: forgot to mention we are running a lightened rb25 flywheel and clutch ( using the Godzilla works flywheel shim)

So how many have larger cams in there L28 motors and what is your idle vacuum? Post up your build or at least your cam specs and the vacuum you pull at idle. Also what RPM do you idle at. Thought a list with cam specs and vacuum and rpm might be good info for others considering cam upgrades and what not. Just might help if you do a cam upgrade and end up with low/high vacuum or low/high idles etc you will know it's probably not normal and you have an issue somewhere.

Rossman, you are correct we are going to be running a custom intake and a full megasquirt with modern injectors and LS coils and a 3-2-1 header going MS3X and will probably run the jeep cam sensor mod so we can run full sequential ( not needed but since it's capable why not) we plane to add boost and launch control etc etc so we need the MS3x so figured we would go sequential. The bottom end is all stock with the dished pistons as we plan to boost it later. we are going to be running the comp cams 280/280 .460 lift cam for a nice little lop ( son likes the sound ) and to get a little more out of her but without having to replace springs. Now the intake we were looking at making our own that is basically straight tubes to a plenum roughly like the intake you mentioned. We were planning to add air horns to the ends of the intake runners inside the intake plenum. You mentioned an intake that is wider at the plenum? are you referring to the shape of the plenum being wider on the throttle body side and narrowing towards the rear of the intake or are you referring to the intake runners from the plenum down to the head tapering from larger ID at the plenum down to smaller ID at the head? the current thought was to use a straight tube same inner diameter from the plenum down to the head and match the head port inner diameter at the gasket surface. We are planing to do some port work but mostly deshroud the valves and smooth the rough casting, radius sharp edges, streamline the valve guide bosses and smooth up the valve throat just below the seats. Am I wrong in my thinking of using a straight pipe from the plenum to the head? And if not shouldnt it be the same size as the head port size at the gasket surface? Thats what I have in materials at the moment and because of the tubes and the heads ID being the same at the head gasket surface well the head gasket is a little bigger and that's what got me thinking that gasket matching will change the velocity (but leaving it unmatched leaves a gap from the gasket which might create turbulence) and what not as the air enters the head because we are adding an expansion at the gasket surface and then as it travels down the port to the bowl and short side it will contract and then after the short side into the bowl will expand again and then contract again as it goes through the valve throat and again expand as it goes into the combustion chamber. I am not sure if the extra expansions and contractions will mess with the velocity and the general flow and we're not even thinking about what will happen to the wave when the valve shuts. This is not a race car it is a nice daily that will be given a little something here and there ( my 17 year olds car ) he wanted a cool old school car not a Honda ( and he's a bit of a purest didn't want to do a motor swap) but we want to be able to hold our own with the Honda's ( not the crazy Honda's but what most of the 16-20 year olds daily drive ). Thanks for any help you guys can give.

Hello All, My son and I are fixing up a 79 280zx and we are putting a medium size cam in it and we are putting a new intake on it. we were looking at the intake gasket and noticed it is about 1-2mm larger than the port all the way around we put it on the the new intake and it's also about 1-2mm bigger than the intake port. My question is should we gasket match the head and the intake? Now the head we plan to do a little clean up on and maybe unshroud the valves. I know the port goes from big to small at the pinch point from gasket surface to just before the bowl and the bowl widens then from bowl to valve seat small again and then into the chamber and the bowl to cylinder we have a Venturi effect with the big little big through the seat. I can taper the head runner from the gasket surface if matched so we keep the port taper to the bowl. The BIG issue is the intake side the intake is a straight tube intake and I can grind the flange area and into the intake runner a reasonable distance but at the end of the day the intake runner at the plenum will be smaller in diameter than the gasket surface of the intake runner. Because of this should I bother to gasket match? I don't want to create weird expansion and contraction areas in the stream. As I understand it the runner should go from big to little from the runner at the plenum all the way to the pinch point of the head just before the bowl where it opens back up. But if I gasket match it will go in the intake from the plenum small to bigger at the head gasket surface and then in the head from gasket surface bigger to smaller at the pinch point and then bigger again at the bowl. The head part probably isn't a big issue all though by gasket matching and shaping to keep the taper I am making the port bigger and it may not really need to be. The part I'm really not sure about is the intake runner being a straight tube and then flairing out bigger to gasket match the head. Maybe I'm over thinking it I just dont want to create any weird air flows or velocity issues that will rob any gains seen from the cam and intake upgrades. I forgot this is a N47 head. we are not removing the exhaust liners in fact I'm good with the exhaust side I know what to do there it's the intake side that's really the issue.

Thanks again for the info. I had forgotten about TCP global and house of Kolor. looks like we are going that route so thanks again.

Gtech very nice the color we are looking at is very similar to what your car looks like. yours is a little darker. so 1 gallon sprayable for every stage isn't to much? base stage, candy stage and clear stage. so a total of 3 sprayable gallons.

So I am looking at spraying my sons 1979 280zx hard top. we plan to spray the exterior the door jams the engine bay the underside of the hood and the engine block. the paint is a red metallic color it is a 3 stage paint The base is a red color then the second layer is a candy red and then the final layer is clear coat. I am wondering how much of each layer will I need to paint this car? I will be spraying over a medium / light grey colored primer. The second layer the candy layer most who have sprayed this color say 2 maybe 3 coats are needed most times. so I am guessing 2-3 coats of base red then 2-3 coats of the candy red and then 3 minimum coats of clear ( we want to wet sand and buff the clear). im guessing a gallon mixed ready to spray of every layer is probably about right since it's 1. Red 2. were painting engine bay, jams, body and the engine block. let me know what you guys think Im looking at a DuPont and a sherwin Williams paint I dont remember the name of the DuPont but the sherwin Williams was there 7000 series. also I will be spraying with a DeVilbiss GPI with 1.4 tip for base and clears and 1.8 tip for primer. This is a regular gravity spray gun it is NOT hvlp Thanks for any help you guys can give me.

That's what I figured but i wanted to double check. thanks again for the replies.

We are debating if we want to do anything as we have another motor and another z car. we are thinking we will just put this one back together for now and just drive it and build the other motor up after we figure out what we want power wise and then we will rebuild this motor to go in the other car. Father and son cars the one we are currently working on is son car so dads can wait. Thanks for the replies I may pull a couple con rods and see how they look. so if the con rods look good and since I took them off should I run a quick bottle brush hone in the cylinders and put it back together ( after cleaning it ) and use the original rings assuming the cylinders are in spec.

So pulling the caps and then retorqueing them is ok? should I put any assembly lube on the bearings when I put the caps back on or just some oil or leave them dry. I have experience with old school chevy and ford motors and well those things when you pull a cap you replace stuff cause it's cheap but these nissans are suppose to be tanks.

Hello all, I have read a lot of posts and have read some say to rebuild some say to leave the factory stuff in the bottom end and I'm wondering what I should do. i have 130,000 mile 1979 280zx it has the 42 block and the 47 head. It ran and drove and didn't really smoke maybe a little we didn't drive it much just around the block brakes have issues. my son did a compression check on a cold motor and did not open the throttle and all cylinders read around 120 give or take 5 lbs. unfortunately We didn't do it warm and with the throttle open also after pulling the motor ( have chassis work to do) we noticed the valve lash was tight all were tight enough you couldn't get a .007 under any of them on a cold motor. Also the timing was a little retarded. Now the head is off and in the cylinders opposite of the piston skirt sides you can still see cross hatch in every cylinder and no big scratches but no cross hatch on the skirt sides on the skirt side you can see wear but not scars. now we plan to put a megasquirt with newer style 20-25lbs injectors as well as a header and probably a custom intake as well as a 236 duration @.050 lift with a max lift of .460 cam. we may boost it in the future at least a year from now. my question is should we mess with the bottom end at all? i read a post that tonyD says the factory stuff is better than anything after market and in that post he said if you do anything pull the rod and pistons and clean the ring lands so rings don't stick and put it back together and only replace anything that is noticeably bad. from the looks of the insides of this motor I think it's in ok shape. So should I bother to pull the pistons and clean the ring lands and do I need to torque the rods with the bearings and measure them out of the motor or should I reuse the rod bearings? this is a street motor and is only getting hopped up a little for street fun and what not it's is NOT a race motor. so what do you guys think leave the bottom end alone take the rods out and clean the piston ring lands and reinstall with original rings and rod bearings or new rings and rod bearings and hone the block. thanks for the replies