Timing & or Carb Problems?

[cameron.arnott]

Righto guys, need your help again.

Two issues I'm dealing with and I'm not sure if they are interelated.

Firstly the distributor. Just back from being rebuilt and I had a Pertronix installed as well. But I just can't seem to be able to line it up so that I can set the nut in the middle of the slot and get the timing where I need it. Its always at the far end of the slot with the timing on the right spot. Is it possible that the Pertronix is positioned incorrectly altering the timing? I must have pulled the dizzy twenty times today, and moved it notch by notch and its still at the far end of the slot........

The other issue is that I'm trying to tune my newly rebuilt carbs which are Weber 40 IDTP 13C's running 32mm Venturis, 135 mains, 180 air corrctors, 60 idles and F7 emulsion tubes (very close to F3's according to PMO)

The car pulls really well througout the rev range and is a vast improvement on the previous set up but the idle is doing weird things. Setting it at 900, its climbing by itself up to around 1800rpm seemingly at random. It will stay there for a while (minute/s) and then drop back (usually). Its making it bloody hard to tune...

I have set the timing to about 5 degrees advance, checked the manifold & carby nuts for tightness, and used new gaskets all round. All throats are balanced and drawing the same air. I did notice one of the idle air screws seemed to have a slightly bent tip but not by much. Could this be the issue?

Any help would be greatly appreciated, as I am slowly driving myself insane!
Thanks

[cameron.arnott]

Oh come on, where's your sense of adventure...

I should add that yes I lined up the rotor with the slot on the dizzy next to #1 plug each time. I think I might start by pulling the Pertronix and putting the points back in to see if the same thing happens.

Any other suggestions?

[cameron.arnott]

Ok maybe third time lucky.

Ive taken off the pertronix and put the points back in, played with the timing from 5 degrees ATDC to 10 degrees BTDC, changed the mixture screws, and changed the idle jets from 60's to 55's but the idle is still sitting high at between 1500-2000 rpm. I can pull it back down when driving by running the revs right down when the car is in gear as I pull up to the lights but sometimes even then it climbs back up again.

The ignition co. I sent the dizzy to removed the old vacuum advance unit that used to just be plugged off. I am wondering if the old vac unit was still fulfilling some role of pulling the advance back to idle? I.e. was the diapragm acting to pull the advance weights back as the engine came off idle or is this not possible in any way with a plugged vacuum? Its a 010 Bosch dizzy from a '73 'S'.

C'mon guys help me out here...! Please

[shbop]

I'll take a shot. At least give yo a bump. Your last post indicated that you re-installed your points, and then played a bit with the timing. Do you know the timing spec for your car? What year and model? After setting the timing for the last time, did you verify that the mechanical advance works? Is the mechanical advance possibly the culprit for the speedy idle?

[shbop]

Sorry, one last question. When you crack the throttle, from idle, do the revs drop right down, or does the motor hang up there for a while and slowly return to idle. Latter might indicate vacume leak.

[72olive911T]

Hi Cammeron,
I'm no expert, but it does sound like there is something diferent with your distributor.
Also, do you have a float gauge you can use while the engine is running?
Maybe it's a sticking floast that is dumping extra gas into the carbs.
i've heard that with a good CD unit you don't need Pertronix because there
isn't much voltage going thru the points.
Good Luck,
Pat

[cameron.arnott]

Guys,

I've checked the floats yesterday and all are within specs. The engine is advancing fine up to about 35 degrees at 6000rpm.

It's an S spec 2.4. Without the vacuum retard I think they are supposed to be set at around 5 degrees BTDC instead of 5ATDC but I have varied the timing to see if it has any effect which it doesn't......

After revving the engine is just sitting at anywhere from 1500 to 2000rpm and generally not dropping back. I used all new manifold gaskets top & bottom and have tightened everything down as much as I dare.

Any more guesses?

[Fishcop]

Hi Cam

When I started with my tired 2.0 T (now 2.7RS spec), just getting it to run cleanly was my goal. I started with binning the now obsolete Marelli dizzy and replaced with a machined down 2.7 distributor (as per JWW specs) and sent it to Scorcher Ignitions in Melbourne to have it regraphed for crappy Aussie fuel (10 degrees BTDC), this meant the adjustment groove has NEVER been in the middle. I also added a Crane optical ignition unit and Crane XR700 electronic ignition. I then rebuilt the carbies and put it all together.

I initially had the issues you're describing. I had air getting in at the manifold under the carbs - try cheching this by spraying some Aerostart around the seals while the engine is running. If you get rev fluctuations you'll know you have bad seals. I pulled them all off and used some Hylomar. Solved the problems and allowed me to tune the engine.

The differences with the rebult carbs and particularly the electronic ignition were startling! I suddenly went from a cranky pig to an absolute darling

I recently went through it all again with the build of the 2.7RS spec. This time I encountered the issues you get with completely changing all the internals of the carbs, and like you I suspect, I was living in a "regional" location where sourcing good advice and tools is hard (Toowoomba & Townsville). This time my tuning woes were floats and float valves. I had received one dicky float valve in the kit, which took a while to work out.

I'm sure you know, but I'll stress it again... Float levels are critical! I was using the PMO tool (gold), but presuming "close enough is good enough" the car was a b@stard.... Be anal about gettng the floats perfect!

Oh, this might be relevant, I had a needle with corrosion that I "sharpened up".... yeah I ruined it So if you have a bent one, change it - it's the same from any weber carbie so a local shop should be able to help.

Hope this helps

[cameron.arnott]

Thanks John,

I'm going to try the leak test tomorrow and see how I go. I might try a new set of idle screws as well.

Have you joined the Aussie 901 Register yet?

Cheers

[Fishcop]

Hi Cam

Yeah I've been thinking of joining the register... Just not sure I'll get value for money, for me it would be $75 for only using a forum.

I try and stay pretty active with the early car owners in the Qld P-car club, and I use the Australia/NZ forum on Pelican - something I've enjoyed for the past 6 years (people know how to find me ). If I was down in Melbourne or Sydney then I'd be in like Flynn.

You must be a bit of a rarity up in Darwin! I know I was an oddity in Townsville

[cameron.arnott]

Yes John, not too many of us up here! The other car in the photo with the spotlights is a '69 'S' that has about 70K original miles but unfortunately he has just moved down to Melbourne.

There is supposed to be a green 'T' up here but I'm still trying to track it down...I need another buddy!

I find the Register a handy tool, and in a recent trip to Sydney met a few of the guys and got to ride in a few other early cars. Always someone who knows the answer to your questions.... Whats $75 these days...!!

[SteveF_911]

Hi Cam,

Guess I will have my 2 cents worth seeing I have spent my whole weekend trying to solve a distributor problems. Long story but I have my engine running better now, shame about the gearbox I broke last weekend.

I would guess that you have some air leak or wear in you carbies.

Have you checked your spark plugs to see if the car is running rich or lean on any cilynders?

John will you be coming to assist with Sheldons diff Tuesday night?

[cameron.arnott]

Cheers mate,

I'll be out with the carb cleaner and a fire extinguisher tomorrow after work! Fingers crossed I can find a leak.

Its frustrating not knowing where the problem is and I'm hanging out to get my carbs tuned properly but its hard with the idle issue.

Thanks

[Fishcop]

Beautiful pair of Tangerines

I get up to Darwin once or twice a year to see family. I'll look you up. Do you get your car out onto Hidden Valley regularly? How does it go with the heat?

If you find yourself in Brisbane, there's a few of us Long-hooders here too.

Steve, yes I think so... I want to have a close look at the Modena diffs.

[Goth]

Just an idea...

Did you already look down the newly rebuilt Webbers to ensure the butterflies are closing far enough? If you have to take the screws loose to adjust, don't forget to use some thread locker (you don't want to screw up your motor ).

[RoninLB]

This is SnapOn. Others mfg sell the same unit for less $.

[cameron.arnott]

Aaaaahhh the fun continues. I have sprayed as much WD40 and then carb cleaner as I dare with the fire extinguisher on hand at all times. No drop in revs noticeable. I think maybe a tiny increase in exhaust popping but not 100% sure.

I think its time to pull the carbs off again and see if there is anything obvious. Butterflies should be ok as I have not played with them I only altered the internals such as venturis etc. Fishcop did you retain your gaskets with the Hylomar or just use the sealer? At least if I use the sealer I can eliminate 1 thing. Hidden Valley is fun and cheap to do lapsprints, and yes the old girl gets a bit warm, I'm on the hunt for an oil cooler set up if you know of anything?! Drop me a line if you are headed up this way.

Steve I'll be checking the plugs tomorrow when the car is cold again to see if anything obvious.

[jtf914]

I had the same problem when I was learning to tune my webers and adjust my timing.

Try checking your fuel pressure, I added a regulator to keep the pressure around 3-3.5lbs, I don't know if this was the real solution as I was changing more than one thing at a time, but my hypothesis was that the pressure would build while the car was sitting there idling which would eventually force gas past the needle valves, flooding the bowls causing the RPM's to start rising.

Good Luck,
Justin

[Fishcop]

Hi Cam

I ordered new gaskets and also added the insulation barriers (bakelite 1cm inserts) and the extra long studs to hold it all together. I don't think it would be wise not to use gaskets.

Justin raises a good point. No more than 3.5psi fuel pressure.

[keitho64]

I know some of this may be repetive but here are my thoughts, in no real order:

Float level / needle valve - make sure the needle valve is not allowing fuel to bleed past and that the float level is right.

throttle linkage - make sure it is adjusted - disconnect all linkage and see if it will idle steady - if so verify the linkage

Advance weights - make sure the advance weights are not rusted / binding and that the springs are not weak. (I had this issue on my Marelli - car would idle first and as soon as you bllip the throttle it would never idle back down. I took the weights out, cleaned them and installed new springs)

vacuum leak - besides the usual places check around the throttle shafts

I would suspect the dizzy advance or something in the linkage hanging up.