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Discussion Starter · #1 ·
I have a stock L28 in my 75 what would be the pro and conson a header system?
Would I notice more change on top end or bottom? Does mileage go up or down(if I can keep my foot out of it). Other than headers what other bolt ons should I get? The motor and tranny are out and I'm changing the bushings on the front end, so If I'm going to change anything else now's the time.
Thank's way in advance.
 

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I have a header and 2.5 exhaust system on my stock '73 Z. The mileage went up about 10% and it sure helps the top end. It didn't do anything for the low end.

There are several postings on headers, so do a search on them and read the various comments on different brands.

> I have a stock L28 in my 75 what would be
> the pro and conson a header system?
> Would I notice more change on top end or
> bottom? Does mileage go up or down(if I can
> keep my foot out of it). Other than headers
> what other bolt ons should I get? The motor
> and tranny are out and I'm changing the
> bushings on the front end, so If I'm going
> to change anything else now's the time.
> Thank's way in advance.
 

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1,610 Posts
> I have a stock L28 in my 75 what would be
> the pro and conson a header system?
> Would I notice more change on top end or
> bottom? Does mileage go up or down(if I can
> keep my foot out of it). Other than headers
> what other bolt ons should I get? The motor
> and tranny are out and I'm changing the
> bushings on the front end, so If I'm going
> to change anything else now's the time.
> Thank's way in advance.
Yes - headers equal improvement in mpg. Anything you can do to improve tne engines breathing (other than a wild cam) will improve it's mpg. Look at a low restriction intake/air filter like a K & N also. It would also pay to put in an '81-83 ZX 5-spd and 3.90 rear end while you have it apart. You will love the difference.
Phantom
 

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Discussion Starter · #4 ·
Thanks for the responce, I forgot to mention that the reason that I pulled the motor and tranny in the first place was to replace the 4-spd with a 24% overdrive 5-spd. Then I got a good look in the engine bay and some rust and the bushings. I'm not sure what diff I have. How can I tell what it is. I like the K&N idea but What effect does rain and snow have on them? Are the flat K&N's that go in the airbox worth it?
 

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> Thanks for the responce, I forgot to mention
> that the reason that I pulled the motor and
> tranny in the first place was to replace the
> 4-spd with a 24% overdrive 5-spd. Then I got
> a good look in the engine bay and some rust
> and the bushings. I'm not sure what diff I
> have. How can I tell what it is.
The best way to tell is to pull the cover and count the ring and pinion gear teeth. Divide the larger by the smallert and you have your ratio. The '75 originally came with a 3.545 gear ration in the differential. If you put a late model '81-'83ZX 5-spd in it (.745:1 OD) without installing the 3.900 differential you will hate the car. The late ZX 5-spd's have lower numerically 1st & 2nd gears. This means you will be super slug off the line unless you have the 3.90's in the rear. If you're building the car to run all the time at speeds over 100 mph this would be good but as a daily driver it will suck pond water big time - IE: late summer algae covered black pond water.
I like the K&N idea but What effect does rain and snow have on them?
Should not affect them unless you eat a wall of sluch thrown by a passing vehicle. Then yu'd be wishing you'd stuck with the flat variety that goes into the existing airbox.
Are the flat K&N's that go in the airbox worth it?
Don't know. I just run standeard filters at this point. Unless you're going to do header/exhaust work too it is probably not worth the investment. What comes in - must go out. Remember hot exhaust gas occupies much more volume than cold intake air so it needs more room to get out.
Phantom
 

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Discussion Starter · #6 ·
I like the
> K&N idea but What effect does rain and snow
> have on them? Are the flat K&N's that go in
> the airbox worth it?

Well, I've never been brave enough to drive my datsun in the snow but I can tell you that driving in rain is pretty safe with the exposed conical filter. I've driven a 300 mile trip in a pouring downfall the whole way doing 75-80mph while passing 18-wheelers as they totally drenched me. Needless to say, the filter was pretty wet by the time I got home. Snow will be even more of a mess, although it's unlikely that you'd get a whole bunch of snow packed in the front of your car(unless you like to plow ;-). The problem with driving in the snow is the cars in front of you that spray up all the dirt and salt, which makes for a messy filter, which equals frequent cleaning.
I guess my past experiences prove that getting the exterior of the filter dirty isn't too dangerous. But the problem is, and Motorsport Auto warns everyone who buys the ram air from them about this, is after you shut the car off and the hot air from engine bay creeps over to the cold and wet filter. This may create condensation in the air ways. Engines hate water.

But on the upside, you can buy the K&N stock filter replacement. They offer superior filtration and airflow. And they eventually pay for themselves in the long run. Just spray it with compressed air, add new oil on it and pop it back in.
 
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