Sluggish bottom end question.

[nismo300zx1990]

So I have a 1990 300zx na and have increased the cams Jim wolf technology and have bored out my block 60 over. However I am having bottom end performance issues. When I take off its not a strong as it use to be bUT when I get to 3500 rpm it takes off. My question here is I have two bad o2 sensors that coded out that I haven't replaced yet and I have disconnected then from the harness. Could this be my issue with bottom end power?

[nissanfreak12]

Yes, the O2's need to be plugged in, they help regulate the air/fuel ratio. You are probably running very rich and when the VTC's kick in it levels it out.

It also could be because of the JWT cams, depends on how the lift and duration are and is the ECU tuned for it? My money is on the O2 sensors though.

[evildky]

I'd double check the cam timing, the vtc and the ignition timing.

[nismo300zx1990]

So I will replace my o2 sensors first bit I do not have my ecu tuned. It is stock. As for my timing I will have to check. If my ecu needs to be tuned where do I go?

[nissanfreak12]

You can contact conceptzperforamnce, Z1, or specialty Z. Ask them if you need a tune for the JWT cams, I am not 100% sure if you do, but it will make a good difference.

As Evil said with the timing, did you do it or have it done? IS your ignition timing set at 13° +/- 2°? Did you just rely on the marks for the timing belt or did you actually count the cogs?

[nismo300zx1990]

When I put my head back on I just lined up the marks on the belt with the marks on my engine. When I purchased the car the timing covers were missing like the who ever owned it took them off to make it look cooler.... so I haven't really put a timing light on it. I guess I need to find a cover? Or is there another way to time with out the cover?