Engine wont rev above 3000rpm

Have you checked the timing mark is correct, i.e. the marked TDC is actually TDC. I have seen V8s showing TDC at 8 - 10 degrees out. This is how I did it - Sparky's winter/spring/summer/autumn work

Have you checked the vacuum unit on the dizzy ( it turns the plate, and there is a vacuum from the pipe) , the weights move freely, the shaft bearings are ok (try wiggling the rotor arm from side to side), there are no tracking marks on the rotor arm/inside of cap. Try pulling the leads out of the cap and checking for corrosion inside.

Is the wiring ok on the ignition system, check there aren't any of the awful crimping blocks or badly crimped connectors.

What colour are the plugs? If they are very different, is there a pattern e.g. the two middle ones on one bank and the two outers on the other?

All fairly basic stuff, but you never know.
 
If the car is automatic, your problem may be the converter not the engine. If the stator is stuck (failed or jammed one way clutch) it stops the engine revving past the point where the clutch needs to slide.
 
Thanks guys.

TDC certainly seems to be correct - I have had the engine virtually stripped so could see all the moving parts. All ignition parts are new. Distributor has been stripped and rebuilt and definitely advances correctly.

Yes I did wonder about the torque convertor, although the entire trans has been rebuilt including the convertor.

I keep coming back to the unusually unbalanced carb settings. Doesn't seem right to me that they should need to be set so differently.
 
Have you done a compression test on all eight cylinders? Is the 3000 limit in neutral or drive or both? Have you checked all sixteen valves are moving their full travel with the new cam and are the lifters still ticking? did the mechanic put the car on a scope to check the ignition etc? Have you checked the valve opening sequence is the same as the firing order?
 
Just reading through this again...I presume youhave brand new, never used before plugs leads distributor cap condensor and spark plugs. it's pointless doing anything until that is done.

the difference in jet height means you haven't yet looked down the jets at the fuel level. You need to take the bell and piston off to do this, it is also a must and shows you what the needle and seat height in the fuel bowl is. Given what you said about blocking off the carbs I'd say only one is actually being used. You have apparently fixed the air side of the carbs and replaced the needles (hopefully with two identical ones) and jets so the only thing left is the needle and seat adjustment in the float bowl or a blockage in the fuel supply - maybe in the pipe from bowl to jet, it should have room on the inside of the fuel bowl for the fuel to go in, not butted up against the wall which is possible.

Note the carb that kills the engine when blocked off is the working one. If that carb is the first one in line from the fuel filter, which I presume is also brand new, never used anywhere, then the nexxt thing is the fuel pump. If its electric you need to check the built in strainer and see if its blocked and of course that its pumping fuel at the required rate. if its mechanical you need a pressure guage in output line to make sure it is working. What you originally stated does sound like a fuel starvation issue so even after the pump is working ok I'd keep going and check both fuel lines are not blocked, creased, squashed or kinked. Also Try running the car with the Reserve tap all the way out...and check it is working and not stuck half way when knob is in fully.

the more I consider this the more I think that provided all the above must dos are done than inadequate fuel supply is your problem. There is simply not enough fuel getting to the engine past 3000 rpm. This is a very common problem with aftermarket pumps; they simply don't flow enough fuel to provide the necessary pressure to the carbs and return some to the tank but a blocked fuel filter or faulty pump creates the same issue. note that the factory electric pump has a strainer built into the end which needs to be removed and cleaned occasionally...It is placed under the tank and has a tap on it which needs to be fully open (its to turn the fuel off so you can take the end off the pump to clean it (best done with rear of car only in the air so the fuel won't flow back..)

M
 
Thanks Mike. Still looking. Yes all ignition parts are new. Needles, jets, float valves all new from SU supplier here in New Zealand. Have blown air down the jets into the float chambers no problem, and I can see fuel in the jet. Have back flushed the new fuel filter. I have an electric (Facet) fuel pump in series after the mechanical one with a standard filter in between so it should have plenty of flow you would think. I've tried with just the mechanical pump too and it doesn't make any difference.

I had to put new rings in it as there were three broken (honed the bores was all that was needed). Compression is exactly the same on all 8 cylinders - not very high at 135psi, but that could be my gauge.

I totally agree it sounds and feels like it isn't getting enough fuel at open throttle settings. It is the first carb that kills the engine, so it could still be a tuning thing I guess. It is strange that each carb seems to tune differently.

Interestingly, you can almost feel a sweet spot at half throttle where there is a bit of a surge which is weird.

Anyway I have a mate coming round next weekend who seem to know his way around SUs so here's hoping.

I have restored a fair few cars in my time including rebuilding engines (Rover 2000TC, Rover 2200TC, Ford Escorts, Toyota 4AGE, Morris Minor, and have never had so much trouble.
 
Do you still have the old float bowl needles and seats? maybe check they are the same as the new ones...I've had trouble with replacements not flowing properly in the past.

You could discount pump issues by running the return line fitting into a measuring beaker with the electric pump on but no engine running. That'll show how much fuel is coming through. Also check the fuel tank breather pipe, which exits at one side of the tank under the car, isn't blocked and causing a vacuum in the tank...

Having said that, It's probably worthwhile getting the car on some old school measuring equipment. That'll point to the problem more clearly.
M
 
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Apologies in advance if it this already been suggested, but I admit that I haven't actually read this whole thread.
I'd just like to point out out that the reserve fuel tap can get stuck midway between normal and reserve fuel supply, which prevents sufficient fuel getting to the engine. This feels like a loss of power above a certain amount of revs.
It happened to me, and I feared some dreadful mechanical problem had occurred, which would doubtless mean a hugely expensive repair bill. My most favoured mechanic diagnosed the issue straight away, lubed the reserve cable, freed off the sticking reserve tap, and the full rev range was once again available.
 
Any idea what fuel rate the pump/fuel lines should be providing? Is there a litre/min figure I could work to into the return line?
 
Is this lack of power a new thing? Has it been better previously? Those compression readings do seem a bit low, is it a low compression engine? What's the engine number? Have you had the carbs off the manifold? Is there a restrictor in the manifold?

Colin
 
So have checked that breather is clear, and that the return fuel line is also clear. I can check the fuel flow if someone can suggest a rate it should be.

Colin - I purchased the car as a non-runner and it hadn't been roadworthy for 15 years. Since getting it started it has always had no power. It had wildly varying cylinder compressions and very little vacuum so I have been working through the engine (after replacing all the ignition bits, clearing fuel lines etc.
Heads replaced with reconditioned ones I got for a bargain (as I thought maybe some of the valves may not be sealing properly if they have been open for years. That didn't fix it, so went deeper - into the cam (which was totally stuffed). Replaced that along with tappets and timing gear.
That didn't fix it so pulled the sump, took out the pistons to find broken rings on three cylinders. Replaced those and honed the cylinders. compression now even over all 8.

So back to the carbs, which have been disassembled, cleaned, and jets, needles, float valves replaced. also replaced the seal in the fuel tap and I am certain that is moving correctly. There isn't much left and it is a real puzzler.

It is definitely better than it was but still doesn't have the pickup I would expect.
 
Had a mini once that was like this - would only pick up if you opened the throttle VERY VERY gradually. Final fix - points plate in the dizzy was frozen to the shaft, so the centrifugal advance was absent......After all the work you have done it should be good, but....
 
... but is right. Yep have had the dizzy apart too.
I'm almost certain it is something really minor...but finding it is proving challenging.
 
Sorry if this sounds stupid, but consider replacing the white plastic vacuum diaphragm unit on the top of the brake servo.

A few years ago I bought a new one from a reputable source, put it on and forgot about it as the car wasn't used for a time.
Car ran poorly at certain speeds, replaced plugs, leads, lumenition rotor all to no avail. Got a reconditioned second servo but put the new unit on it and the problem persisted. Decided to get the original servo reconditioned and sent the new unit off with it, put the old unit on to the second servo and the car ran perfectly.
Needless to say the brake reconditioners replaced my "new" diaphragm unit and again the car ran perfectly.
The exercise cost me a small fortune. The supplier of the faulty unit could not have cared less. Will never buy from them again!
 
Just putting it out there, i would also be looking at major vacuum leak. plug up the brake servo pipe port to rule out servo, if your servo is sucking air it would knock out / reduce power on half the engine, + check for vacuum leaks (I don't recommend propane gas being swept over joints to see if RPM is affected as that would be hazardous, even if it works 99% of the time!)
 
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