timing issues

[engineerted]

Jim.

Total advance you want to shoot for is 38deg. So depending on the dizzy you have, this may require some modifications on your part. The 10cr motor i run the dual point dizzy converted to Crane xr3000 with one of the advance springs modified to limit total advance. Per the Croft bible total advance should come in at about 3500rpm, any more advance above this has little effect, and some times can hurt you. Some race engines run with static advance only, due to there high rpm operating range.

Ted

[mdrburchette]

All the twin cam pullies will work for all years as long as you install them on the right cam. Where did you get your cams? do you know if they have 106deg or 110 deg lobe centers? also what size chokes are you running in the idfs?
Ted

Ted, he's got the IAP 40/80s so they're 110 degree.

[troycalm]

I also have a dual point dist with a crane xr3000,I guess nobody has addressed my question about the dist advance springs
if I remove the cap and look down into the dist i can see the springs when i manually retard them by hand i can see that the springs are exltremely loose,will that not cause the timing to advance too fast and abrupt.just checking all avenues.Also a very weird thing happend before,while i was adjusting the timing just my hand on the dist cap sides would cause the engine to try to die,not on the top of the cap but on the sides,when i removed my hand it picked back up ,return my hand and it would start to die out.
Ghost in the Machine i guess
To answer the other question about timing @38 the engine runs great with great response but the valve clatter under a load is hideous.
Troy

[engineerted]

The hand on the dist. cap sounds alot like internal arcing. Did you make sure that the rotor lines up with the cap pickups. When i set up my dist. I broke out a small section of an old cap next to #4 so i could see how they lined up when setting the optical pick up of the Crane system. Do you have a dial back timing light? I am still confused about the valve clatter you talk about? I don't see how you can get pinging from a low compression engine, I run 93octane in my 10to1 cr engine with out an issue. Do you have any photos of the build?

Ted

[ventura ace]

Troy,
The discription of valve clatter is strange. I guess that you're hearing a pre-detonation noise, which would certainly happen if you advance the dizzy too much. You don't want that noise, not at all.

You mentioned that just putting your hand next to the side of the distributor cap would make the engine die. Were you pushing the cap sideways? Did you feel electrical current going thru your body?? Maybe the ignition current is being grounded thru your body, but I would think that you'd feel that, and would want to pull your hand away lickety split. I've heard that some people can conduct high currents thru their bodies and not feel it, and maybe you have that special power!

I did have a problem related to the cap when I first built my 1.8L engine. The car ran pretty good, in fact it screamed at higher rpms, but was not all that impressive at lower rpms. I discovered that it had the wrong cap. The gap between the rotor and contact points on the gap was huge, close to 1/2", and somehow the car ran pretty darn good anyway. I'm serious. The center button didn't even touch the center of the rotor, it just hung down and had a big air gap to jump accross. The same with the verticle spacing on the end of the rotor tip to the 4 electrodes for the 4 spark plug wires. Apparently, there are 2 caps that look identical on the outside, same dimensions exactly, but the inner dimensions are different, to work with a different distributor with a taller rotor, I guess. I found the correct distributor cap, and it immediately fixed the problem.

One thing that was interesting, when I had the wrong cap in place. Whenever I grabbed the dizzy to adjust the timing, it would shock the heck out of me. I had to wear a thick cotten glove to keep from being shocked. It was probably the fact that the ignition current was trying to find the ground path of least resistance, and that was me. Perhaps you have the same thing if putting your hand on the cap will affect the engine idle. Or maybe you have the correct cap, but it is cracked or oily and conducting the current path to ground, or to you, instead of to the spark plugs. You can measure the distances between the interface of the rotor contacts and contacts inside the cap with a good pair of calipers. Will take a little adding and subtracting to get the answer, but it's worth a check. Maybe it's time to try another cap.

Alvon

[troycalm]

thanks for the replies.yes it is prolly predetination.as for the cap if your were to grab your cap as if you were going to feel the temperature and just hold it while its running,I didnt feel any arcing or shorting,felt more like a thermal situation.
Ever have a fuel filter plug up and the car runs great at idle and at cruise. but during hard acceleration it feels like it wants to go, but just cant quite catch up,thats what happening,I really notice it during hard throttle snap.When I advance it about 10 deg too far, the throttle snap problem goes away and is taken up by predetination.
Question: when you set up your timing light is that set on #1 or #4 also could weak dizzy springs be causing a two fold problem(not setting the mech advance back to zero at idle)(and causing base timing to be wrong)and two: Letting the advance actually advance to far under load due to slack)Its just seeming to me that there is a severe problem somewhere in the timing.
I guess i need to get a dial out timing light, mine is static.
I set up my crane ign just like the book said, I dont know how exact it lines up but that sounds reasonable.

[mdrburchette]

My service manual only goes up to 73 so I don't know if the timing curve graph would be the same as for an 1800 but it shows this:
0 deg @ 800
5 deg @ 1100
20 deg @ 2000
36 deg @ 3600

Weak springs can give you irratic timing. Maybe you can map your timing to see what yours is doing.

[troycalm]

Thanks very much that gives me a starting point..

[Jim DeShon]

I would take the dist. out and have a good hard look at everything. Touching the dist. should not cause the engine to die. The "valve clatter" is actually detonation. From what Ted said, I would start by setting full advance @ 38deg. and work back from there. Sounds like the advance springs may be shot. This would cause too much advance in mid-range. I am somewhat suprized that this engine will take 38deg. with 10-1 compression, but I've heard this from several places. The more compression the less total advance. Go with what works though. Once you get the timing sorted out, you can then do some fine tuning with the jets and a exhaust gas analizer. ...J.D.

[troycalm]

Thank you guys very much for all your input,Ive heard a lot things that will put me in the right direction.

thanks again guys

[troycalm]

Ok just got a advanced timing light,cut open a old cap and double checked all my timing issues and all seems fine.
Im still up against the problem with transition.Idles great ,lots of power on snap throttle,but during acceleration it stumbles for a min and then picks up and takes off.
What kind of fuel pressure should I run on twin IDF.
This is gonna drive me nuts. any ideas.

[mdrburchette]

You should have around 3 lbs of fuel pressure for the IDFs. Alvon can tell you they even run well with as little as 1.5 lbs.

[ventura ace]

Yes, I drove several thousand miles this summer with a "low" pressure, high-flow Carter fuel pump (1 to 1.5 psi). I was a little nervous about it at first when I put it on and observed the low pressure, just because it was lower pressure than what I had always been told is recommended (2.5 - 3 psi), but I thought it might be that my pressure gauge was bad, so I continued to drive with it since it was running very well. After arriving in Dallas, 2000 miles from home, Jeff Scheferman and I put a new gauge in place and noticed that the pressure was indeed 1-1.5 psi, so I changed out to another pump that puts out about 7 psi and regulated it back to 2.5 - 3 psi with an in-line regulator, and drove with that combination for the next 6000 miles. However, since there was no difference in performance, I eventually changed back to the 1.5 psi pump several weeks later after we had arrived home from our 8000 mile trip. I still see no difference. The fuel pump's task is to keep the fuel bowl full, so flow capacity is as important as pressure. My experience is that you just need a high flow, low pressure fuel pump.

The accelerator pump circuit may be the source of your problem. I'm not familiar with the term "snap throttle" (what does that mean??), but the stumbling during acceleration is a typical problem of faulty accelerator pump circuit. The rubber diaphram is part of the circuit, so replacing them may help, especially if they are leaking. The other parts of the pump circuit are pump jets and the 'bleed-backs'. When you push the accelerator, the rubber diaphram pumps a volume of fuel at whatever speed you push the pedal. The sizing of the pump jets and bleed-backs determines how much of this fuel is sprayed down the throat of the carbs (the pump jet), and how much is pumped back into the fuel bowl (bleed backs).

Try this: with the car not running, pump the accelerator while looking down the throats of the carburetors. You should see the pump jets from all 4 carbs spraying an equal amount of flow down the throats. It should continue to spray for about one half to one second after you pump the accelerator. Take all the pump jets out and look at their numbers, and do the same with the bleed-backs (bleed backs are in the bottom of the fuel bowl). Be careful not to drop any parts down the throats of the carbs --- there are washers above and below the pump jets (and these must be in place when you re-assemble). If any of them are plugged, you may be able to blow air thru them backwards to clean them out. I can't remember for sure, but I think that I'm running 50's or 52's for the pump jets and 0's for the bleed backs (no bleed back flow). This means that all the accel pump fuel is going to the jets, and none back to the bowl. Other common sizes for the bleed backs are 40's and 80's. You can purchase these from Pierce Manifolds, or possibly your local performance shop. Variations of these carbs are popular for VW's and Porshe, so the performance shop's that cater to those guys carry the parts.

As stated above, the amount and duration of the spray down the throats from the accel pump is determined by the choice of the jets. If there is too much or too little flow, the air/fuel mix will be too rich or too lean, and the engine will stumble. You may need to experiment in order to determine what is best for your engine. I believe the standard jets that were put in for the European Fiat stock 1.6 and 1.8L engines with 40IDF 13/15 carbs were 40's for the pump jets and 80's for the bleed backs. My 1.8L engine has higher compression (10.6:1), 40-80 intake cams, 70-30 exhaust, and the jets I mentioned above seem to work best for me. Opionions may vary. See your doctor . . .

Alvon

[troycalm]

Well I stand before you hat in hand feeling a bit ridiculous.The car has gradually gotten worse and worse to the point of sheer crap.
Its my wifes baby and she drives it ,she has been very very patient while i stand above the open hood scratching my head.
i have put about 10k into this car and it runs like a chevy sprint.
I did this afternoon find the problem
The throttle cable stop on the firewall had broke inside and was only allowing the throttle blades to open about 20 deg.
as she was giving it gas 1/2 the pedal was taken up by slack the other half was actually moving the twin IDF's.i just replaced the cable and now this spider is a screamer.It has not run this stout since I put it on the road.I guess they run a lot better when you actually open the throttle blades.

With hat in hand I thank you all

Troy

Russellville AR

[mdrburchette]

That's awsome! Now it's time to enjoy a few road trips.