what would a 4.10 do to my M20?

[Danny]

It depends on the condition of the canooter valve along with the willingness of the engine. The engine must be willing to output the extra fifty horsepowers. You must be sure you determine your engine's willingness by presenting it with a questionnaire. This questionnaire may include questions such as "What is your favorite donut?" And "Do you think your mother loves you too much or too little?" Or if you're feeling frisky: "Have you ever touched another canooter valve besides yours and kept it a secret and never told anyone until now?"

I believe in you. Godspeed.

[NeedaE30]

maybe you should just let your local mechanic situate your car for you till you can understand the basics. have you ever changed your own oil before?

It depends on the condition of the canooter valve along with the willingness of the engine. The engine must be willing to output the extra fifty horsepowers. You must be sure you determine your engine's willingness by presenting it with a questionnaire. This questionnaire may include questions such as "What is your favorite donut?" And "Do you think your mother loves you too much or too little?" Or if you're feeling frisky: "Have you ever touched another canooter valve besides yours and kept it a secret and never told anyone until now?"

I believe in you. Godspeed.

[Killacortes]

I love my 4.10 and m20 combo. It's not annoying on the highway at all. At 70mph I'm at 3k rpm. First gear is not useless. It feels torquey in every gear and is a blast to drive

[JinormusJ]

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[htown318is]

always driven e30s with 4.10s and seemed fine at 80 mph. i must be missing out with all this talk of quiet goodness on a highway.

wait... no such thing in an e30. no matter what your ratio is lolol

[AndrewBird]

Just to clear one thing up, an engine's redline is what RPM the engine can safely rev to without damaging internal mechanical bits. It has nothing to do with what chip you are running. All a chip does is provide a rev limiter that cuts fuel/spark so the engine will not rev past a set RPM. M20's in stock form can safely rev higher then the stock revlimiter is set to.

As the RPM's increase, the valves are opening and closing faster and faster (obviously) and the stock valve springs start to have problems closing the valves fast enough. If you rev an engine past its redline, you will get valve float, which is when the valve doesn't close all the way when it should have. This is caused due to the spring not retracting fast enough. When this happens, your valve is open when it shouldn't be, the piston moves up in the cylinder and BAM, bent valve or worse.

In order to increase your rev limit past this mechanical barrier, you need stiffer/stronger valve springs. This is a moot point however as a stock engine makes peak power well before redline and then starts to make less power the higher in the rev range you go. You can change your camshaft (timing, lift and duration) to move peak power higher up in the rev limit, but this is only necessary if you need power up high like that, such as on a race track where speeds are high.

[Bearmw]

I might run a lsd 3.90 168 "small" diff in your car until it fails. A good (as in decent bearings) used diff can be obtained, then maybe replace the clutches and steels and use good oil for it. Check out Metric Mechanic's site for some helpful info as well as many threads here on R3V.

[Eric]

what factors would go in to the 50+ horsepower?

Using racing gear oil in the diff.

[EatsHondas]

in all my ignorance level with me and explain to me what i missed?

Nando was just joshin' ya. A diff will never add or take away power. All you're really doing is giving your engine more leverage by shortening the gears. Remember when you first rode a bicycle with gears? There's the gear that is super easy to pedal but gets you no top speed, and then there's the gear that is hard as hell to accelerate with, but once you get going, you can cruise rather quickly, even though your legs don't change strength. The 4.10 moves you in the direction of the pedal-really-fast-but lose-top-speed gear. Easier for the engine to get you going, but restricts how fast you can actually go.

[AlexHale]

It won't increase wear to a timing belt. Really it doesn't do anything than add an increased wear to a ratio of about 200-300 extra revs per mile, which.. Is really non-existent. Some manual e30s were equipped with 4.10 LSDs from the factory (mostly verts, to help push all that extra weight around).

All a 4.10 will do is shorten your gear ratio, meaning less MPGs, louder ride because you are in a higher rev range per MPH, and your acceleration will be slightly faster. Be prepared to drop 2-3 MPGs, even more on street. Personally, I am against 4.10 in a manual Getrag coupe/sedan. There isn't any point to sacrifice that MPG for a borderline insignificant increase in acceleration


If you want a fast car, build a fast motor

I know I have LSD on my vert, how do I confirm 4.10 or 3.73?

[JinormusJ]

There is a metal tag to the right of the rear of the diff, right next to the speed sensor

If it is LSD, it will have a S, followed by the ratio and then a 4 digit production code. It'll look something like "S x.xx 0000"
You might have to clean some grime off the tag to see the digits though


Should look like:

[AlexHale]

Are the gears inside the cases interchangeable as in Americans?

[JinormusJ]

I would assume gears and pinions are interchangable

[Todd Black 88]

4.10 is a stock diff ratio for m20 automatics. They are everywhere. The difference between a 3.73 and 4.10 on an m20 is negligible. Maybe a couple hundred rpm per gear.

[JinormusJ]

Yes, but the ZF autos are 4 speed and have completely different gearbox ratios with the final drive being .73; which mated to a 4.10, has the same ratio as a Getrag 260 final drive of .81 mated with the 3.73. This is a whole different animal than what we are discussing