Engine will only run above 4000 RPM. Carbs or timing?

[EuroDat]

I just read through pieces of this thread again and I tend to think its a fuel issue.

- If it was spark (HEI, coil, leads etc) and it dies under 4000rpm you could see is on a timing light. If the timing moved you could test it buy turning the dizzy. Also if it dies under 4000rpm because spark fails. How do you get it started?

- The compression is good. Very good in fact.

- Valve timing should be ok because the engine ran good in the other car and hasnt been touched before this started. The good compression also indicate correct timing.

That leaves fuel/air, vacuum leaks etc.

Your going to try the SU carbs. I think that is a good plan. Hope it works

Goodluck with it Chris. After all your good work and effort restoring the car you deserve a bit of luck now.

Chas

Edited May 24, 2013 by EuroDat

[madkaw]

Jeessshhh Wade,

Can't believe there's nothing to learn here for you. I'm quite sure if you were there you would straighten out Chris with your master mechanic knowledge. I kind of like threads like this that make you think 'outside the box'.

I think we have all experienced some kind of anomaly when it comes to mechanical issues. Yes, there are the basics, but Murphy's law is always hard at work.

I remember chasing a spongy brake in a Mustang for weeks. It was frustrating beyond belief-I mean it's just a hydraulic system. In the end I reversed bled a front caliper that pushed the air BACK to the MC. Never experienced this before, and never again. By all regular methods I couldn't get rid of the air.

In the end, it might turn out to be a basic element that Chris missed, or he has 2 things going on at once. This happens when you change several things at once.

I think maybe you(WADE) are thinking you might not get the CDS award. If it's that frustrating for you-how bad do you think it is for Chris. Tune out if it bothers you that bad.

[Captain_Zeros]

Now now, I can see both sides, but this forum is generally one of the most helpful nicest places I've seen on the internet... and many realworld meatspace groups too.

Lets not muck it up by being ****s to each other now.

Personally I'd like to see this thread pop up in the near future with a "EUREKA, IT WAS *obvious thing everybody forgot and should've thought of!!"

[Captain Obvious]

I'd like to see this thread pop up with a "EUREKA, IT WAS *obvious thing everybody forgot and should've thought of!!"

Me too!

And for the record... When I said the below:

If you bring the car to my place, I promise in a weekend we'll have it licked!!

I meant "Two heads are better than one and I've got some diagnostic equipment and some spare parts we can try that would probably help. I can also provide the foot to keep the engine running while another set of hands can check things up in the engine compartment."

I did not mean "My skills are better than yours."

[colinc]

Me too!

And for the record... When I said the below:

I meant "Two heads are better than one and I've got some diagnostic equipment and some spare parts we can try that would probably help. I can also provide the foot to keep the engine running while another set of hands can check things up in the engine compartment."

I did not mean "My skills are better than yours."

Chris,

I agree with the Captain "two heads are better than one". As I mentioned in post #15 there are some great people in our local club that may lend a hand (don't get me wrong,the knowledge base on classiczcar is phenomenal but its hard to fix something you can't see). I spent 6 hours with ont240 the other day while he worked his magic on some crap rebuilt carbs i got on eBay. After stealing parts from my old carbs he actually got these things to run extremely well.

Just a thought.

[grannyknot]

I just read through pieces of this thread again and I tend to think its a fuel issue.

- If it was spark (HEI, coil, leads etc) and it dies under 4000rpm you could see is on a timing light. If the timing moved you could test it buy turning the dizzy. Also if it dies under 4000rpm because spark fails. How do you get it started?

- The compression is good. Very good in fact.

- Valve timing should be ok because the engine ran good in the other car and hasnt been touched before this started. The good compression also indicate correct timing.

That leaves fuel/air, vacuum leaks etc.

Your going to try the SU carbs. I think that is a good plan. Hope it works

Goodluck with it Chris. After all your good work and effort restoring the car you deserve a bit of luck now.

Chas

Chas, I agree, that is one of the reasons I sent the carbs to ZTherapy, even if they were not the problem at least it will help me narrow it down by ruling them out, I'll recheck all gaskets surfaces and any possible vacuum leak.

As much as I hate using silicone sealers and prefer a dry seal I am tempted to try some sealer this time just because I'm getting a bit desperate, would appreciate anyone's input.

Me too!

And for the record... When I said the below:

I meant "Two heads are better than one and I've got some diagnostic equipment and some spare parts we can try that would probably help. I can also provide the foot to keep the engine running while another set of hands can check things up in the engine compartment."

I did not mean "My skills are better than yours."

I knew what you meant Cap'n and at this point I'm starting to believe anyones skills are better than mine.

Chris,

I agree with the Captain "two heads are better than one". As I mentioned in post #15 there are some great people in our local club that may lend a hand (don't get me wrong,the knowledge base on classiczcar is phenomenal but its hard to fix something you can't see). I spent 6 hours with ont240 the other day while he worked his magic on some crap rebuilt carbs i got on eBay. After stealing parts from my old carbs he actually got these things to run extremely well.

Just a thought.

And a good thought Colin, I'll call him and see if he's available.

I called ZTherapy last night and Bruce P. said the carbs should be in the post next Friday and with a week for transit I should get them about the 8th of June, I've also ordered new plug wires and spark plugs to have them on hand if needed.

I'm also going to rig up a gravity feed fuel source so as to rule out fuel pump/regulator and pressure.

[Casey_z]

Hey Grannyknot.

Laverne keeps my 240z tuned.

Give him a call

Casey

[bartsscooterservice]

Hello Chris, how's going so far ?

[Willoughby Z]

I've never seen a more worthless thread than this one.

It only takes 3 things to make an engine run. A combustible air/fuel mixture, compression, and correctly timed spark.

Yet after over 128 posts it has STILL not been determined which of these three items is lacking resulting in this motor not running properly below 4K.

Someone needs to get back to basics.

That was rude. If you don't like the music, change the channel.

[grannyknot]

Hello Chris, how's going so far ?

Hey Bart, still waiting on the carbs from ZTherapy, they haven't shipped them yet. I'm using the time to finish the restoration.

[pacemkr]

ive driven up and down your road about six or seven times in the past couple weeks, hoping to maybe see the front of your car sticking out of a garage somewhere. not sure which house is yours.

actually, beaton road isnt too bad of a cruise, if traffic is light.

on tuesday we cruised by with a couple cars on our way to play hooky from work, out on mono road and hawkley valley road. cruised by but didnt see any sign of you at any of the homes.

looking forward to seeing that beast leaving me in the dust soon.

got a few parts from z therapy a couple months ago, very pleased with their product. it'll be worth the wait.

i have the ztherapy videos if you would like to view them, let me know.

[Patcon]

One time I had a Z I couldn't get running; turned out the valves were too tight, so low compression. I know his compression numbers were good but every one thinks of huge vacuum leak from his symptoms. There are only a few areas for that vacuum leak to occur right?: carb to manifold, manifold to head, internal of head, valve seats, rings, manifold vacuum signals. Any others? I also had a pertronix on my 95 suburban that gave me problems have you tried a stock GM module? I just read all 6 pages of this tonight. I find it intriguing that he couldn't get it to run with the stock dizzy either. I would want to simply like Chris said gravity feed versus fuel pump and keep simplifying until I find the problem. The less variables the better. Both types of carbs have the issue. That seems unlikely. Could still be fuel pressure. He checked valve timing at least once maybe more, not likely. If he feed it from a "baby bottle" I would lean towards ignition issue... my 2cnts

C