HELP! All Mechanical Eliminated- Wont rev past 4K

[Seanw987]

HI, This is my first post here.

I have a 1972 240Z. It's story from my attaining it is chronicled here --> Linkhttp://www.cardomain.com/ride/2977492

The car has been at the mechanics, a Specialty Z Shop, since around Thanksgiving. The car has had a new engine installed and just about everything else one could think of mechanically, has been replaced.

The car won't rev past 4K. Carbs have been swapped, fuel system bypassed(for testing) coil, distributor,points/pertronix, all have been changed out, even the tach.

Wires to and from the coil and distro have been checked/replaced.

My Q: Has anyone experienced this problem before?

Follow -up Q: What was done to correct it?

Or to sum it up, WTF is going on?!?!?

$7,000 later and still no properly running Z wants to know.

Any and All Help appreciated.

Sean:bulb:

[Nigel1943]

Sounds like a timing issue, either the camshaft or the distributor. Have the advance weights in the distributor been checked for free movement? Does the car idle ok?

[ChrisZ]

2nd that, what cam do the motor have ?

Chris

[Zedyone_kenobi]

Was the cam properly installed... meaning was its installed point in the advanced or retarded condition? Also, what happens at 4k. Does it sputter, or just fade off, does it surge?

[Zs-ondabrain]

Or better yet, if it has SU carbs. Check the "Last Chance" filters inside the Banjo fittings (on the float bowls) to see if they are clogged. If so, try and clean them or flat out remove them for testing purposes. Maybe even put the old carbs back on and try again.

What have ya got to lose?

Dave.

[JimmyZ]

Rule out the ignition by hooking up a timing light and revving. The inductive pickup on a timing light can tell you if a plug is fouled or not firing. Observing any "hiccups" in the lights flashes can also tell you that there may be a problem with the points or distributor bushings.

2c Jim

[Seanw987]

This is a new engine and when I took it into the Z shop here in Los Angeles, they checked the timing on the cam, adjusted valves, pulled oil pan and checked/torqued everything they could. The cam is a performance grind and the car idles great and runs great up to 4K when it hits what i think feels like a rev limiter, thats the best way to describe it.

Banjo filters will have to be checked, since i'm not the one working on the car, I am not sure if they have been checked, but i assume that when the carbs were swapped for a known working pair.... it had different filters but same result.

Timing light indicates advance is working and engines firing on all 6.

The mechanics working on the car frequent this forum and i am hoping they will help to elaborate on the issue in this thread. They have had this car since Thanksgiving and i'm sure they would love to see it out of the garage and on the road up to Angeles Crest.

Thanks for the suggestions. Please keep them coming.

[Seanw987]

I need to mention that these symptoms were also identically present when the car had the original 2.4L engine with stock components ie cam.

[Arne]

Interestingly enough, I have been experiencing the same issue on mine. Felt like a 4000 RPM rev limiter. Just today I finally got a change in symptom by advancing the timing more. My current theory is that the timing pointer is not correct, and that I was running it very much retarded. Try advancing the timing about 10 degrees more than what it is now and see if that helps.

[Seanw987]

Thanks, I will try that tomorrow and see what happens

[doradox]

Have you checked the exhaust for restrictions?

Steve

[madkaw]

Fuel tank? If the symptoms were the same regardless of the engine, then it has to be other components. Could there be a partial restriction in a fuel line or pick-up tube that will not allow maximum fuel flow when approaching 4k rpm. If you haven't had the fuel tank out, it is time to pull it and look at things. You said the original 2.4 did the same thing, did you tranfer accessories like the dizzy to the new engine? There has to be a common denominator somewhere.