My V8 has no power and runs as rough as a dog!

[primsil]

looks like six screws to hold the float chamber on. I would think it easiest to remove the carbs from the manifold and do a complete strip and clean.
But before I was going to do that I would spray some easy start into the carbs and see if it fires, just to be sure I wasnt chasing a non existant carb problem.

If it wont start at all, is there any sign of ignition, to be sure it is not an electrical fault.

[nzlromacka]

Gidday Primisil,

I have tested for spark and now have fully charged batteries. I pulled out Number 6 plug and lead and got a reasonable bright blue spark when the engine was cranking. So I am assuming that the ignition system is OK for now...

Another update...

Removed the four screws at the top of each carb and had a good look inside. The diapghrams on both carbs look fine, with no splits tears or perished rubber. (They even look quite new)... The oil filler tube is 3/4 full....could'nt see anything out of order and I used a toruch to have good look! Replaced the covers.....

Awaiting further carburettor rebuild instructions! :p

[primsil]

Awaiting further carburettor rebuild instructions! :p

Disconnect the fuel lines and throttle linkages.
Take off the four nuts holding the carb baseplate to the manifold, remove the carbs and take them to a carb rebuilder

[nzlromacka]

Yeah, reluctantly I think this is the only option. Do the carbs need to be on the vehicle for them to be tuned after servicing?

The wife is going to be extremly pi$$ed, as this truck was boight on the assumption that it was all OK, had a current WOF and reg and needed no work apart form a repaint.....

[primsil]

Once removed from the landy you should be able to remove the float chamber and clean them out, just the usual precautions, nice clean work area and containers for everything.

This was sent me a while ago may be of help;


Tuning SU CarbsTuning SU Carbs
Courtesy of Roger Garnett
Revised 5 Dec 91
Well, it's not really that hard to set up SU's, just different. Of course it
always gets more interesting when you have more than one...There is a very good
Haynes SU carb manual available, recommended reading.The basic syncing process
also applies to Zenith-Stromberg's, but the adjustment mechanisms are different.
Here is a layman's guide to adjusting SU's (long):
step 1- Tune up the rest of the engine- REALLY! clean or replace, and set the
points, set the timing, plugs, valve lash, and remove the air filters (have new
ones ready) All of these things can affect the setting of the carbs, which
should be done LAST, (if at all). The carbs rarely need to be adjusted, once
set. Also replace/install the gas filter. Of course, it helps if the carbs are
in good mechanical condition as well. But you can consider a rebuild once you
have gotten things working first!
step 2- clean the carbs! use gum-out or similar stuff, clean all external
linkages, shafts, and stuff.
step 3- Remove the float bowl covers, clean the float bowls, remove old
sediment, and check/adjust the float setting. (turn the cover upside down, and
get a *1/8" in drill bit, set the drill bit across the cover, the float tab
should just touch the bit.) Make sure the needle is moving and seating properly.
This is just like *most* floats. Replace the cover.
* This is for HS4 SU's- (1/8-3/16") if you are dealing with 1", H's, HS2's
HS6's, HIF's, etc.- check the spec for your carb.
Note: You can check for matching float settings, after setting the mixture, by
removing the pistons, and peering down at the jets. The fuel level should be
about the same on both carbs, a little below the top surface of the jet. (After
car has been run only)
step 3b- Go get a pint of ale, or something close, and set it nearby.
step 4- Remove the piston covers. CAREFULLY remove the piston, DO NOT BEND THE
NEEDLE. Set the piston down on a clean wadded rag to prevent rolling. Clean the
inside of the carb. Check operation of the throttle. Check the throttle shaft
slop- this is the most common place for wear on an SU, and is often where
air/vacuum leaks occur. The bushings and shafts can be replaced, but it requires
some machining. A small amount of leakage can be tolerated, the car just won't
idle as evenly. Clean the piston. Stare in awe at the odd carburettor design,
simple and effective, (constant velocity). Dump the old oil out of the damper if
you haven't already spilled it. clean. Reassemble, check piston movement, raise
it, then let go, it should fall freely. If not, check assembly again, make sure
the piston isn't binding against the carb body, it should ride only on the
damper shaft. Do not stretch the spring. When all is operating properly, fill
the damper with Marvel Mystery Oil for light damping, or use motor oil for
heavier damping. (I use MMO) If you get "flutter" on acceleration, you might try
the heavier oil.
step 5- Start the car and warm it up, then turn off/disconnect/otherwise disable
the choke mechanism. (Loosen the nuts on the clamps so that the choke stuff
isn't doing anything) This will get set later.(Later Zenith-Strombergs have a
thermostatic choke, not a cable.)
step 6- Check coarse throttle adjustments- make sure the throttle cable pulls on
both carbs equally, and returns completely when released. This is adjusted by
loosing the set screws on the throttle shaft and matching the two sides. You can
also adjust the cable length at this time, using the cable set screw/retainer at
the end of the cable. You can check the float adjustments now by removing the
piston & cover, and looking at the fuel level in the needle seats. Both carbs
should be about even, a little below the top surface of the jet. If not,
readjust one or both floats to match the level.
step 7- Synchronise the throttles- if you have a uni-syn, here's your chance to
use it, (or other air flow gauge), if not use a tube and listen to the airflow.
The Uni-Syn is much easier to use, and can result in better balance. Alternately
adjust the idle screw on each carb, attempt to set the idle as low as possible
(~800-1000 RPM). Adjust until the air flow is *close* to the same at each carb.
The engine may now be running rough, just keep the idle speed high enough to
keep running. Give the throttle a quick snap to make sure everything is settled,
then check sync again. Periodically snap the throttle to make sure everything is
seated. Large differences in where you can adjust the two carbs may indicate
air/vacuum leaks, or other problems, such as a bad valve)
Magic Time- Relax, and shake your voodoo rattle...
step 8- Adjust the mixture- this is done with the spring-loaded hex fitting
under the carb, where the fuel supply tube enters from the float. Turning the
fitting raises and lowers the needle seat. Pick a carb, and turn the fitting 3
flats (1/2 turn), first in one direction, then back 3, then 3 in the other
direction. Note where the engine runs better, idle speed should increase. Turn
to the best setting. Repeat this procedure until you get the best operation you
can, (highest idle speed), keeping track of flats turned will help you remember
where you were. If you get lost, turn all of the way in, then back out 12 flats
and start again. Periodically snap the throttle and push up on the fitting to
make sure everything is seated. Note: Type HIF carbs (With integrated float
bowl) no longer have the hex nut to adjust the mixture. Instead, there is a
screw to twiddle, on front of the front carb, and behind the rear. The screw is
connected to the needle seat through a temperature compensated gizmo, which is
said to make the carbs more stable. Adjustment can be done in much the same way,
by counting turns/flats of your screwdriver. There is less adjustment range than
with the the basic models. When you think you're close, stop, uncramp your
fingers, breath deep,and do the same to the other carb. Then retune the first
carb, and then the second again. This serves to match the mixture of the 2
carbs, and prepare you for the beer sitting over there in the sun. (why do you
think the British drink warm beer?)
step 9- repeat step 7, setting the idle speed as low as possible, and re-syncing
the idles. Now go back and readjust the mixtures. After a couple of iterations,
the engine should be running smoothly (controlled by mixture) and at a low idle.
Repeat as necessary. Set the final idle to 800-1000 RPM, depending on the
condition of the rest of the engine.
This is a standard mixture test, performed AT IDLE:
Under operation, (air filter off) lift the carb piston by 1/16" with the lifting
pin or a screwdriver, which leans the mix a tad.
If:
RPM's rise and stay up, that carb is rich.
RPM's rise briefly, then drop, mix is about right.
RPM's fall, engine gets rougher- mix is lean.
step 11- Adjusting the choke- I won't get into the temperature compensation in
the type HIF, or the Thermostatic choke in the later strombergs. Check the
manual for more info.
The choke is supposed to do two things; the first half of travel moves a cam on
each carb which opens the throttle, for warm up. The second half pulls down on
the needle seat to richen the mixture, for starting.
Start with the choke in the off position (knob in). Adjust so that the cam only
starts moving the throttle after you start pulling out on the cable (adjust with
shafts and adjusting screws). Try to get both carbs adjusted the same, so that
both screws begin to hit the cam at the same time. This is not real critical,
but you can use your Uni-Syn to match air-flow on both sides, with the choke
partly engaged.
After the cable is about halfway out, it should start engaging the lever which
pulls down on the needle seats. Adjust the linkages so both carbs are acted on
equally. You can do this by adjusting for even running of the engine. Of course,
for a warm engine, the richness of this mixture will cause some roughness. Make
sure the needle seats return freely when you release the choke.
step 12- Drink that warm beer (only one, no DWI now...) it will taste great at
this point!, go wash up, and go for a ride.
Notes: These procedures assume that your engine/carbs are in reasonable
operating condition. If something is malfunctioning/leaking, etc, this should
still help, but the results may vary. For instance, if you have leaky carbs,
worn needles, engine modifications, etc, you may find things work better if you
tune for optimum performance at open throttle rather than idle.
The first time through carb adjustments can be confusing, once you've done it,
all of the stuff in the manuals makes sense. Go back and read them again-As
always, I recommend Bentleys, which is a repro of the original factory manuals,
and then Haynes, and throw out the Chiltons. (original factory manuals are to be
read in a clean environment, reproductions are for smearing grease all over,
except, if that's all you got, use it!) Haynes has an excellent manual just for
SU carbs, it covers operation, theory, rebuild of all models, and has needle
charts for hundreds of car/engine/carb set-ups. They also have a manual for
Zenith-Strombergs, which, while similar, are a whole 'nother beast.
-Safety First!
Copyright © 1989-1995 Roger Garnett You may publish this in your club
newsletter, provided full credits are given, and you send me a copy.
<<< Back <<<

[stirlsilver]

But before I was going to do that I would spray some easy start into the carbs and see if it fires, just to be sure I wasnt chasing a non existant carb problem.

If it wont start at all, is there any sign of ignition, to be sure it is not an electrical fault.

I'm still skeptical that it is the carbies... I would do what primsil suggested and see if the spray makes it fire... Since there is two carbs they would both have to be completely bunged up to bring the engine to a halt.

You say you have checked the ignition system, unfortunately the spark at the plugs behaves differently inside the cylinder when it is surrounded by a compressed mixture of air and fuel. It is possible that the spark is going elsewhere in you distributor cap or leaking at the coil onto something metallic nearby.

Do all the simple checks first before committing yourself to the carbies.
Stirling

[nzlromacka]

Morning (or evening!) guys,

Well I tried some CRC engine start directly into the manifold with no success, the truck just continued to crank and crank (at least the batteries are getting a good workout!)

So I pulled a random selection of plugs from boith sides of the engine. Not a single plug was the slightest bit wet with fuel after extensive cranking. Would this indicate that there is no fuel flowing through the carbs to the cylinders?

The plugs were all in normal condition with no oil/carbon deposits etc.

[Larosto]

Hi,
The overhauling of the carbs is not as difficult as it seems. You should take them out of the car, and then dismantle them step by step.At first remove the big black srew, the damper. Open the four scews on the top and pull out the diaphragm and the piston with the needle. Now you must control the diaphragm, wether it has split, or whether it has got hard. In both cases the diaphragms should be renewed. Look at the sprins, they mustn`t be broken.
The needles must look as if they were polished, no sharp places or damages.
While doing so, you will recognice that it is rather easy job, you only have to pay attention that you don`t loose anything, and that evrerything gets to the place it has been.
Then open the bottom of the carb, there you find the needle valve and the swimmer. Remove the needle valve, and make sure, that it opens easyly, when you try to blow through it from the upper side. When you lift the pin while blowing through, it must close. If you llet the pin go down, the needle valve must open at once, when you are blowing through it.
Look that the swimmer doesn`t have a hole. Then clean everything inclusive the jets, and reinstall everything. Use new seals.
With my carbs, I`ve got a problem with the temperature compensators.
When the car got hot, the engine began to run bad and smoke. I removed the temperature compensatores and cleaned them. Then I adjusted them new. I overhauled my carbs completely, inclusive new jets , needles and so on.
So, now I hope you understand all I tell you, and wish you good luck

Horst

[onno wielinga]

maybe one of the needles is stuck.
turn the engine on and take the elbows of the carbs.
lift with a big screwdriver a needle and see if it will rev up the engine. do this on both sides. I once had a SU carb that was stuck; it had no pulling power and top speed was lower than 60 km/hour with full throttle.
if one of the needles does not lift the diafragm is leaking. also check if the hole in the damper is open.

[nzlromacka]

Thanks for all the awesome advice guys, I'll be working on the truck over the weekend (NZ Time!) and will let you all know how progress goes... fingers crossed aye! Thanks again, I really appreciate the input from you all.

Cheers
Andrew

[primsil]

Hi Andrew. If it did not fire at all with engine start I would be looking at electrics first. The carbs tend to be a lot more forgiving than the ignition.
Not sure which dizzy you have, most of the RF screened ones seem to have been removed before they left the army.
I have just bought an MSD to put on my 110 with the points for a trigger, could have used an electronic dizzy but wanted to have a fallback to points if ever needed.
Caps and rotors are very sensitive in rover v8s.

[nzlromacka]

Gidday guys....

Well it was a frustrating exercise but the V8 is running again! In the end, I called upon a "real" mechanic mate who looked up the correct spark plugs in his book for the Rover V8 as the ones installed in the engine were not the correct type. With a set of new correct replacement plugs the truck started and ran albeit she was very rough at idle. The next stage was to remove both carbs and clean the float chambers of a lot of accumulated sediment. Still the truck started, but ideld like a pig. So,I removed the Army ignition system (the mesh enclosure inside beside the radiator overflow tank) and resoldered the all of the dry joints....and...

This time the truck started and idles sweetly. A quick blat around the block revealed all to be well!! And so a long story ends!!! I reckon it was a combination of factors, bad fuel, wrong/fouled plugs, blocked float chambers and dry joints on the ignition module. With all of these replaced/checked/fixed or cleaned, the truck seems OK again....fingers and toes now crossed! I'll be doing a full oil change this week so hopefully that takes care of the servicing for a while.

Thanks heaps for all the suggestions, I really appreciate all the help and as always excellent advice you guys have given me!

Cheers
Macca
NZLROC Group Moderator

[stirlsilver]

Glad to hear that it has been sorted!!! Great feeling to nail these sort of things on these cars. Here's hoping it's the end... But in my experience I think these cars were designed to keep you on your toes!

All the best
Stirling

[stephen]

Mate Mate Why bother with all that pipeing etc on the carbs swap to 2bbl Holley no more farting &powerless driving fuel up abit BUT more power instant accleration & 140 kph

[stirlsilver]

Don't the holleys have some issues running rich/lean when the car is off road sitting at large angles? I'm pretty sure that was one of the major benefits of the zenith/SU's
Stirling