240z runs but sounds like absolute crap

[angry_dave]

I have a 72 240z and i got it running for the first time today(bought it two days ago) It had been sitting for about 6 months. I hear a knocking noise coming from the engine, I think it could be valves, or possibly, hopefully not, but a rod or main bearing. Maybe after sitting for so long,a hydraulic lifter collapsed. Does this engine have a hydraulic lifter? I am just afraid to run it because of the noise, but i would like to adjust the carbs. Thanks guys.

[Mr Camouflage]

No hydraulic lifters on these cars. Could be that your valves clearances need adjusting.

[FastWoman]

Could be that the valves are gummy and sticking. No rods, no hydraulic lifters. Single overhead cam design.

[angry_dave]

So I took your guys' advice, and popped off the valve cover. I found an absolute mess. turns out, four rocker arms, were not on top of the valves, a couple had not even been installed, so I proceeded to start putting them back on top of the valves, per the manual directions. Then I came across a valve that would not compress, move, even budge. A bent valve i am assuming. So the head needs a rebuild, i am positive after this fiasco. But amazingly, non of the rocker arms, springs, or the cam, suffered so much as a scratch. cool huh. So this brings me to a question, will the head off of a 1981 turbo engine work on my 1972 engine. I also have access to the head off of a 1975 z (a p 90 head i believe) engine. what will work, and what will be the difference between using either of these cylinder heads. thanks guy, sorry i had no pics of the carnage that unfolded. my camera is broke

Edited November 18, 2009 by angry_dave

[GreenZZZ]

I found an absolute mess. turns out, four rocker arms, were not on top of the valves, a couple had not even been installed, ... I came across a valve that would not compress, move, even budge.

Surprised Angry_Dave didn't turn into Homicidal_Dave...

[Mr Camouflage]

So I took your guys' advice, and popped off the valve cover. I found an absolute mess. turns out, four rocker arms, were not on top of the valves, a couple had not even been installed, so I proceeded to start putting them back on top of the valves, per the manual directions. Then I came across a valve that would not compress, move, even budge. A bent valve i am assuming. So the head needs a rebuild, i am positive after this fiasco. But amazingly, non of the rocker arms, springs, or the cam, suffered so much as a scratch. cool huh. So this brings me to a question, will the head off of a 1981 turbo engine work on my 1972 engine. I also have access to the head off of a 1975 z (a p 90 head i believe) engine. what will work, and what will be the difference between using either of these cylinder heads. thanks guy, sorry i had no pics of the carnage that unfolded. my camera is broke

I thought maybe you may have popped a rocker arm off the valve. Both heads will fit, though you will probably end up with a different compression ratio, and may need to notch the block for the larger valves. The P90 is the turbo head, and will give you a poor compression ratio. Use the head off the 75. It's probably an E88, N42 or N47.

Edited November 18, 2009 by Mr Camouflage

[angry_dave]

thanks that helps alot, i had a 1975 280 head, i think it is the n 42, but which head would be the best to use? I have a guy in tennesse willing to trade me p 79 pistons, with rods and pins and rings, with an e88 and n47 head for the turbo z engine i currently have. if the pistons rods, rings and head are in good shape, is this a good deal. thanks for you guys input, really helpful.

[Walter Moore]

What are P79 pistons? And is the engine you have an L24, L26, or L28? (displacement)

The L24 and L26 use the same piston, but the L28 takes a larger piston, which will not fit in the older engine.

If you have a 280Z cylinder head there is a good chance that it is an L28, but you need to check the serial number to be sure.

[angry_dave]

the gentleman said its p 79 flat top pistons, i wanted to raise compression on this engine to about 10:1, i want to see 250 hp at the rear wheels. is this possible with an L 24, or should i just use the L 28 out of the 280. The engine i have now is an L 24. I am just trying to get an idea of what to do, to see the power results i want. 250 hp, but 300 hp would be preferrable. i have also toyed with the idea of the ls1 swap from jags that run. i know it is blasphemy on this site, but i really want power, and dependability. Really i want this car to run mid 12's to low 13's in the quarter.

[Weasel73240Z]

the gentleman said its p 79 flat top pistons, i wanted to raise compression on this engine to about 10:1, i want to see 250 hp at the rear wheels. is this possible with an L 24, or should i just use the L 28 out of the 280. The engine i have now is an L 24. I am just trying to get an idea of what to do, to see the power results i want. 250 hp, but 300 hp would be preferrable. i have also toyed with the idea of the ls1 swap from jags that run. i know it is blasphemy on this site, but i really want power, and dependability. Really i want this car to run mid 12's to low 13's in the quarter.

You aren't getting 250 or 300 hp out of an L6 without some serious cash, probably 5K to start, at least. If the rest of the car is in great condition, and worth that kind of investment, go for it. If you can get the turbo L6 going, that would get you in the 200's and pretty fast. If you want 300 hp and mid-12's, I think the V8 swap is the easiest and cheapest way to get it.