I am sorting out my recently built 2056 specs below:
2.0 Heads were done by Len Hoffman
CR 8.56:1
Full Raby valve train kit
Stock L-jet throttle body, air cleaner, and intake runners
stock 2.0 heat exchangers
pertronix ignition


It has a miss under hard acceleration.
All the vacuum lines and oil cap gaskets are new and I can't seem to find a leak any where.
So I decided to recheck the timing.
Pulled vac lines off the vacuum diaphragm and plugged, set idle to 800 rpm
timing was a little more advanced than it should be but not dramatically, but I did reset to factory setting.

Drove it and it is even worse than before.

Would the new engine combo warrant a different timing?

Fuel filter is new but my next step is to check fuel pressures and injectors.

Anything else I should be looking for?

I only suggest this because I have done it

Not saying anyone else would.... But be sure you use the correct timing marks on the impeller.

I am running a 2056 with D-jet and have been struggling with timing for a while. But the stock setting when dome correctly seems to be acceptable. There is some good info in another thread I started. Most of it was added by others more knowledgeable than me and who know which timing marks to use.

I am adding a AF gauge to tune it a little better and adjust the MPS.

You should have a Wideband O2 sensor in there before doing much driving.

He has L-jet not D-jet.

Can I assume that this L-Jet system was working fine before you did all the engine work?

A couple of things... If it had a bad vacuum leak it would not idle at 800rpm, so that leads me elsewhere.

I'd keep looking into ignition as L-jet is pretty solid once you verify the vacuum leaks are gone. Do you have anything to swap out the pertronix to test?

And I agree about the wideband 02 given the amount of money you spent on that motor, it is cheap insurance and a great tuning aid. Just avoid going lean at Full Throttle.

Good luck and post the progress.

For the wide band O2 do you weld that into the heat exchanger or how does it get set up?
I assume you use that with an AF gauge correct?

the L-jet was working before the idle does some funny things.

On start up it idles well below 800, probable 300-500
once warmed up and you come to a stop the idle won't drop till you start to let the clutch out and hold the brake to have the load pull it down then it idles around 800.

Don'tr know if this is a separate issue or linked?

I have other non pertronix distributors I could try, but this worked great before the rebuild

on the wideband! I played around for a long time and made a little progress but it was just trial and error. Mostly error!

How does it perform on a cold start?

Also check your injector seals. I had a pretty good leak on one of mine. Installation error! Wish I could blame it on McMark but everything he did to my engine seems to work. Just wish he was on the east coast!

Sounds like it might be something (the advance mechanism) sticking in the distributor.

--DD

Cold start performance is pretty much the same I just don't notice the miss as much since I wait to get on it till it warms up.

injector seals are all new but I'll check the installation just to make sure.

How did you install you o2 sensor?

Did you buy some sort of kit that included a weld in bung and gauge to read what the o2 sensor is reading?

Yep on the weld in. I got a AEM 30-4100. May not keep it in all the time as I hope to get things set and the remove the gauge and sensor. Will replace the exhaust O2 sensor with a plug but leave the wiring in place so I can quickly replace the sensor if I need to.

The AEM air fuel gauge I bought included the O2 sensor and the bung to weld onto the exhaust.
I started out using the no weld clamp (you have to drill a hole in the exhaust) and it works ok but
in retrospect, I'd get it welded if I did it again. That was on a Bursch muffler....if you're using heat
exchangers, it's best to install the bung on the muffler pipe after the collector merges. I'm not sure
there's a way to do it very well using a stock muffler....you could only use one side of the exhaust.
What's your setup, exhaust-wise?

I have a Bursch exhaust. There is a good location on the passagners that allows the O2 sensor to be angled to avoid water collection on the sensor. If my back holds out I will run the wires tonight and have it going tomorrow. I lift weights 3 times a week and never had a back problem. Sneezed hard this morning and tweaked my back

I hear ya on the back crap, I didn't start having issues until last year. Of course, I get the adrenaline all
up working on the car and don't notice much until after the fact.....it's usually the next day that kills me.
I get to replace the clutch cable this weekend!

Stock heat exchangers with a Thunderbird exhaust which is similar to Bursch as far as how the plumbing runs.

Any pictures of your O2 set ups?

I made a little progress this evening

Vacuum diaphragm on dizzy was bad on the retard side thus the not coming down to idle.

Didn't get a chance to run it on the road as it was raining but I did shave the grommet for the wires running form the pertronix as they were mighty close to the plate that rotates for advance, just incase that was making the plate hang up on advance.

Hopefully I will get a chance to try it tomorrow.

Have not welded in the bung yet. Have just done the mock up. Will be tomorrow before I can get to it but I will post some pictures. The AEM AF gauge seems pretty well made. Looks like the spent the most on the O2 sensor but the wires don't look like they were done cheap and the connectors seem to be of good quality. The actual gauge is a little cheap feeling though.

Well the new diaphragm on the distributor didn't fix the miss under hard acceleration.

So I tried another distributor with points no success, so I advanced the timing a little just to see and no difference.

So do I still keep looking at ignition or is there a possibility is is just to lean that there isn't enough fuel under hard accel.?

I know this is what the AF gauge and O2 are for but that isn't going to happen in the next two days, and I really wan to run it at the autox this weekend.

Did you ever get a check on what your fuel pressure is running at? You mentioned it in the first post
that it was on the list but if you haven't, I'd check that first. I don't have any knowledge of L Jet as my car still has D Jet but I'd think that the only real way to proceed would be the AFR gauge.
On D Jet, one can disconnect the Temp Sensor 1 on the plenum to richen it slightly but I don't think
L Jet has that sensor. After looking at the manual for L Jet on Jeff Bowlsby's site....it looks like that sensor (Temp 1) is built into the air flow meter? This has some great L jet info: http://www.google.com/url?q=https://bowlsb...RPW3jnJpjKbZiwQ

I should get the pressure checked tonight so maybe that will shed some light on it.

Fuel pressure was 35psi at idle and dropped to 30psi if I opened the throttle.

I pulled the vac line on the regulator and the pressure raised to 40psi so My understanding is the pressure is in the correct range and the regulator is working.

I did notice the idle sped up when I had the vac line off the regulator which I assume the increase in pressure richened the mixture enough to over ride the vacuum leak leaning it out?

3 and 4 injector spray looked good form what i could see. Didn't have time to do 1 and 2

Ok here are the pics of my sensor location on a Bursch type exhaust.

Click to view attachment

Click to view attachment

This is from the passangers side. Sorry about the poor photo quality.

Thanks
Does the kit give pretty good instructions for installation?


I checked all the injector sprays today and everything looks good but I still have the bad miss.

Does anyone know how the vacuum diaphragm on the distributor works?
One side is to retard the timing correct?

does the other side advance it as the vacuum drops or changes? Should I have noticeable vacuum on that hose when i pull it of the diaphragm?

See the Cap'n expiation in post 18 here.

The kit is less than detailed. But it does say where to mount generally but it does not say drill a 21 mm hole.

I had something similar and found I had a poor connection on one of the injectors. Get your multi meter out and trace down all of the injector leads from the brain (ECU) to the injector connection. Move the injector wires around while checking continuity and see if you have a break.

Sorry the picture I posted was useless to you with the L-jet as the all fire at the same time.

What year car do you have? I have a '75 and had similar idle problems, all due to the decel valve never closing due to the increased vacuum of the bigger engine. The idle would never drop until I did exactly what you are doing, applying load, that dropped RPM and then idle dropped. I have not put on my O2 sensor yet, although at a local shop we tested while not under load and found just slightly rich. I would suspect that many switch to carbs in this situation due to L jet being set up for 1.8 L engines. I have pertronics in a SVDA distributor, runs real strong

It's a 74 but I put the L-jet on because I knew it was working with the 1.8 and i didn't know the state of the D-jet that came with the engine.

Wondering if I should do a new L-jet harness if I can establish there are bad wires in this harness or try the D-jet system on the engine.

If everything thing is setup correctly and no vacuum leaks then you have to adjust the Air Fuel Ratio in the Air Flow Meter via the wiper setting as you are running too lean.
You must use a O2 setup like the LM2 to do this and its not hard to do.
Read this adjustment article-
http://www.itinerant-air-cooled.com/viewto...f=50&t=7761

First mark the setup setting with white paint ! so you have a reference point.