bigmike409888

Ok I have a 1980 280zx. I just rebuilt the engine with few mods. That engine had dished pistons. I put flat top pistons from the 1981 model in it to up my power. But It don't seem like it did at all. Any ideas on what I may have done wrong or what I need to do that I didn't do.

NismoPick

Welcome to ZDriver!

Flat top pistons doesn't mean you went "bigger" unless you bored out the cylinders and used oversized pistons.
A few more details (specifics!) would be helpful.
-What cylinder head are you using?
-What are the "other mods" you did?
-Have you verified that the timing is correct?
-All sensors hooked up properly?
-Checked compression?

bigmike409888

I did bore it .03 and it has a streat pipe exhaust and a cold air intake i fabbed. its the stock head. and the timing is right i checked it 3 times before putting the engine back in the car. and every thing is hucked up right.

Lazlo

I am definitely not the expert on this but,

You can use one of the online engine calculators
Z-Engine Calculator

to see what you really did, but if you didn't change anything else, I would be surprised if you actually added more than a couple of HP with the bore and piston selection.

Probably not enough to feel with a "butt dyno."

The real power is in the head.

Lazlo

By the way, how did you use stock 81 pistons with an over bore?

NismoPick

Again, please be specific. Help us help you.

Which head? N47 or P79???

And after you put it in the car? Did you check ignition timing with a timing gun? Vacuum disconnected?

These are basic things that you have either neglected to mention or haven't done... Again, please be specific so we can help you.

bigmike409888

Ok If the bore is .03 over then the pistons are .03 over. And yeah the timing is right. And you telling me that taking away a third of my combustion chamber will only give me a few hp.

bigmike409888

And the head is the n47.

bigmike409888

And I'm new to this so forgive me if I sound like a dummy.

audiofreak97

I believe NismoPick is asking what is the timing at? 8 degrees, 20 degrees? Also stock head, stock cam and stock fuel system?

head/cam/fuel, those are probably whats limiting you, unless you did upgrades there too and haven't mentioned. Perhaps with the work you put into the engine needs a new cam and new engine management (megasquirt) too?

bigmike409888

Other then the .03 over flat top pistons and the exhaust and cold air intake it's all stock. I plan on putting in a different cam maybe some bigger valves and a header some bigger injectors that's all I really know how to get more power.

SHADY280

well if you have bored out the block, the pistons have to be the same overbore size as the block, the rings also have to be an oversize ring. if you don't all the compression will just float right by the pistons into the oil pan. maybe check the compression numbers on the engine to ensure that its sealed up. with that setup you should be seeing 170 psi or more. bigger injectors won't do a thing without a aftermarket stand alone system so work on that first, same with a cam, the stock ecu is pretty dumb and doesn't know to change things up to make more power.

bigmike409888

Ok what kinda stand alone do y'all sugjest ? Teach me oh wise ones! I thought the map told told the ecu how much air was coming in and the ecu desides how much fuel to add. But I have big planes for the engine just doing little bits at a time.

SHADY280

as far as stand alone you can go megasquirt, its common, but just about any system will work, each has its benefits. ms3 is pretty nice, fricfrac here has done a few installs with great success and even offers an adapter kit for some things. first things first tho, you need to get the engine running properly before anything else should happen. no point on putting lipstick on a pig

FricFrac

You checked the timing before you put it in the car but you need to check it running with a timing light....

bigmike409888

Yeah well I've been tinkering with it the last few days. I did a compression test on it and iv got around 210 psi on all cyclendres. And had a buddy bring over a timing light. The timing is right its retarded a bit for it to run worth adang. But now if I advance it at around 3000 rpms it chatters I retard it and it gos away.and how important are plug wires. Iv been getting the ones from auto zone. But I do have NGK iridiums plugs.

FricFrac

Use the NGK BPRE6ES-11 (IIRC off the top of my head...) spark plugs - they are the stock ones and they seem to be the best for our engines after 30+ years of testing and experimenting...

What is your timing set at where it runs properly?

bigmike409888

It's about 3 notchs retarded. And ok I'll try those. And what kinda injectors would you guys recommend when I get bigger ones? And would it be smart for me to get the stand alone first?

bigmike409888

Ok those plugs work great thank you very much!