Not much power :(

[Co0kieduster]

Just picked up a 1974 260 with an L24 engine, eventually I plan on rebuilding the car frame up and swapping out the L24 for an L28 turbo, but would at least like to have some fun with it till I get the money and a place to do the rebuild. Unfortunately the L24 with dual weber 32/30 carbs seems to be lacking in power. I know that it at least needs a valve adjustment( a bit of annoying tapping). But other than that it runs great the carbs seem to be fine. When i rev it up it sounds awesome and doesn't flutter has consistent pull all the way through the power band. But just lacks in power all together. My brother has a 4 banger prelude rated at 161 hp and it feels 10x more powerful. In fact, im pretty sure my POS old F150 with the original 4.9iL 6 could beat my Z off the line .....sad. Is this what I should expect? Would timing the valves improve horse power that much? Should i learn how to tune up the carbs? Where should i start?

Any help/suggestions much appreciated.

[Dobber]

There are many, many variables that can affect the power output of a particular engine. You state that it seems to pull smoothly throughout the rev. range. I guess this is without stumbling, missing, bogging etc.. Does this car still have smog setup? Does it have a cat. conv.? If so is it plugged? Is your air intake clear? Have you checked the timing with a light? Your valve lash prob. does need to be set, but I would check some of the easier stuff first. How old is the fuel? Are your brakes dragging?

Its hard to compare older tech. with new. I.e. Honda 4 banger. Even in poor tune it could give the Z a run for the money. Take it a step at a time and systematically check through the systems. You may also want to do a compression and leak down test to get a good base line. Good luck. Anything can be fixed.

[Co0kieduster]

No cat. straight piped. going to check the filters. New fuel. Brakes don't drag. ...will probably change the filters and time the valves....then do a compression and leak down test. wonder how much it would cost to put a better cam in when i time the valves?

[Bruce Palmer]

A lot of these ~40 year old L series engines, good as they were, are just tired. A set of compression numbers will tell you where you need to go next.

It's not a whole lot different than chasing after Hitachi SUs that are 90% worn out. You can chase, but you won't catch a solution you'll be happy with.

Merry Christmas.

[Arne]

Also bear in mind that while these cars were considered quick and responsive compared to the other similar priced sports cars of that time, by today's standards even a healthy (but relatively stock) 240Z is pretty tame. So don't expect too much from a stock-motored Z.

For example, test numbers from 1970 showed 0-60 in 8.7. These days, most any econobox can beat that. (My DD 2010 Golf diesel will do it in 8.6.)

[Co0kieduster]

Ok so, after initially cleaning things up, I think i will try some relatively inexpensive upgrades. I've been told that the camshaft is the best place to start (working from the inside out). The engine will be almost completely experimental for me as it is my first toy. I'm excited to try things and find out what works and what doesn't, of course, a little guidance is always nice.

Merry Christmas

[Dobber]

You need to look at the whole picture in a realistic light. If your expectations exceed the ability of the car to deliver, you will never be happy with the performance. Changing the cam will not force untold h.p. from the engine. That will only come with making the best out of what you have, with proper tuning and attention to detail or a complete rebuild. Remember that even when the car was brand new, there was probably only about 135 rear wheel h.p.. The fact that the car was so light, made it a fun car, of its time, to drive. Out of the box the Z was never and will never, be a super car. Thats why you see so many components being offered by aftermarket manufacturers. Rebuilding any car, let alone a 40year old car, is, expensive, time consuming, skill set reliant and will take up a fairly large area of the shop, yard, house. Not trying to lay a bummer on you, just saying that when it comes to owning these older cars ( unless your rolling in the dough and can just have someone else build your dream car ) is a commitment that can't be taken lightly.

[ajmcforester]

You need to look at the whole picture in a realistic light. If your expectations exceed the ability of the car to deliver, you will never be happy with the performance. Changing the cam will not force untold h.p. from the engine. That will only come with making the best out of what you have, with proper tuning and attention to detail or a complete rebuild. Remember that even when the car was brand new, there was probably only about 135 rear wheel h.p.. The fact that the car was so light, made it a fun car, of its time, to drive. Out of the box the Z was never and will never, be a super car. Thats why you see so many components being offered by aftermarket manufacturers. Rebuilding any car, let alone a 40year old car, is, expensive, time consuming, skill set reliant and will take up a fairly large area of the shop, yard, house. Not trying to lay a bummer on you, just saying that when it comes to owning these older cars ( unless your rolling in the dough and can just have someone else build your dream car ) is a commitment that can't be taken lightly.

I agree just changing one thing does not make power. It needs to be a systematic approach, the whole car needs to be looked at as a package. Even the caliper and rotor sizes can effect performance of the drive-line suspension and braking. Bigger tires can slow cars down, but to small a tire and you can't apply power properly, tire size can also effect turning and torque and hp at the wheel. A cam is like a set brain it tells the engine how long the valves should be open and when, so the cam needs to match potential intake and exhaust flow rates, with how long the valve can be fully open, that deals with piston type valve size the whole nine yards. Even when you want the engine to create power.

Now lets say you hop-up this engine, and you do nothing to the drive line you won't get a lot a power to the wheels the whole drive-line needs to be upgraded to match power-bands from the engine torque . . . Then you need to change the suspention system to match the driveline, and the tires so you can apply the power then the bakes need to be changed to match the new driveline and tires, then the driveline and suspention need to match the brakes and tire forces. the diff will need exsta mods to match the stearing and the stearing needs to be modified to handel the new forces . . . this goes on and on till you get it right.

This is also why I shy away from modified cars usually, because 99.99% of people modify cars don't look at the whole picture, and the adjustments that are needed to match their modifications. This won't mean I'll buy a modified car, I have in the past; it just means I need to see what is needed and think it is worth it to make the adjustments, or the car is well balanced from the seller.

[ozconnection]

Excellent advice here....take heed my friend.

I don't think ANY stock L Series puts 135HP (100kw) to the wheels, flywheel yes but not the wheels. Sooooo atw maybe 100hp or so.

Good luck with your project.

[ajmcforester]

I'd say 120hp on the high end for one in good condition might be right for a 240z that would be about a 20% power loss at the wheel with a good performing engine and drive-line.

These cars have some power, tune the 260Z up you stated the valves need work well how much power is that costing you? How worn is the engine? Do you have good compression? is the drive line in good shape, how are the bearings, hows the clutch, how is the points and wires . . . You don't haft to go crazy to have a good performing car, just good care goes a long way

[TomoHawk]

Just picked up a 1974 260 with an L24 engine

That seems to be the first big problem. It's missing 200cc of displacement. Why did it get a smaller engine than it originally had? Edited December 25, 2010 by TomoHawk

[sblake01]

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Edited December 25, 2010 by sblake01
Violated one of my personal rules...........