z24i help

[JG23]

I have a 87 D21 that's got a z24i with a bit over 200,000 on it and its pretty tired, I'm replacing plugs and wires doing fluid changes and all that just to get the engine running a bit smoother (it was sitting quite a few years) but does anyone have any recommendations to get a bit more kick out of it? from what I've been able to learn I'm thinking dual side drafts, a cam, and header with a less restrictive exhaust? anything recommended to do with the suspension or tires to get more power to the ground / make it a better ride? (I have some 17s without tires yet I'm planning to put on it) I'm just trying to learn what I can do with this little truck. appreciate it!

[datzenmike]

The Z series engines have very little room for performance increases because of the poor head design. It's perfect for what it was designed to do... lots of mid range torque to pull a heavy truck, and do it with very low emissions. The head design doesn't breath very well when revved up would never need the breathing potential of dual side drafts and no way around this. After market cams tend to be very mild because the valves touch if too much over lap and lift. 

 

I would set to tune up specs. Timing 5 degrees BTDC, valve lash 0.012", make sure both intake and exhaust side plugs are firing, only use NGK plugs BBPR6ES on the intake side and BPR5ES on the exhaust side, gap 0.032"

 

The exhaust manifold flows well enough so save your money on a header. Straight pipe it through the catalytic converter and get a larger turbo muffler but avoid anything you can look right through.

 

In order to run carburetors you have a problem. Right now you have throttle body fuel injection and the ignition is a CAS crank angle sensor. You would have to get an intake and distributor from an earlier Z24 from a 720 and the low pressure electric fuel pump. Then throw away the Z24i intake, throttle body and CAS. Spend money saved on header and put toward a 32/36 Weber carburetor replacement from Pierce Manifolds. There are a lot of crappy Chinese knock off out there so go with Pierce. It's under $300 and has everything needed. Myself I would just leave it fuel injection... too much to look for and change.

 

Don't worry about getting power to the ground it doesn't make enough to worry about that.

 

If a standard transmission it has a 3.70 ratio differential, if automatic it's a 3.889. Both are seriously too low and gearing like this is only for mileage. If you have a standard try to find an automatic 3.889 or even better a 4.11 H-190 third member for it. The older 720 4x4 used 4.11 differential gears.This will increase acceleration at the expense of top speed (who goes there anyway) and a bit of miles per gallon. Differential changes have no effect on the engine, it puts the same power through a shorter distance which increases acceleration.

 

 

17" tires???? Make damn sure that the diameter of the tire is the same as the stock tire at 25.5". If you go taller you will loose gearing advantage and the truck will accelerate slower. That's to be avoided. If you were to put new 28" diameter tires on it this would drop from 3.7 down to 3.369. Like I said that is to be avoided!!!