Was noticing some ignition missing so wanted to do a tune-up.

Replace plugs, rotor and distributor cap. Seemed to run fine. Later, when hitting the gas hard noticed that the missing was magnified and it started running real bad.

Decided to set dwell and timing, since I thought it may be timing related. It has been over 25 years since I did this before. I have a dwell meter and just bought a new timing light. I made a mistake going through the timing instructions on the forum. My problem now is that my idle is very erratic and the engine wants to stall, and will if I don't keep my foot on the gas pedal.

Questions:

1) Will I be able to set dwell correctly with a bad idle?

2) I have a 70 w/350 and automatic, manual says 4 deg BTDC, could this be wrong? I set this with the new timing light, dialed in 4 and set mark to 0 on the timing tab. Engine did not run well.

3) What would be the logical things to do and in what order?

Any good suggestions would be appreciated. Please excuse my lack of knowledge, I would like to solve this on my own if possible.


Regards,
Rich

 

Check your mechanical advance weights/springs under the cap and make sure they're free. Set the dwell to 30*. After that, disconnect the vacuum line from the distributor advance, plug it and then see where your timing is. Just because the sticker says 4, does not mean that's where you have to run it. Bump it up to 6 or 8. IF you swap the springs on the centrifugal advance, then set it up for 30-36* @ 3000RPM.

There's a boatload of info around on timing.

 

before changing anything i would look at the cap and rotor to see what they looked like .while the cap is off check the points ,see if they are burnt and check the gap [about 16 thousands].how do the wires look .if all this checks out then check the timing .

 

Did you remove and plug-off the vacuum line to the distributor before you set the base timing at idle?

 

Yes, I did plug off the vacuum line with a golf tee when getting the base timing at idle.

Cap, rotor, points, plugs, and wires look ok.

thanks for the help

 

When I read this, I thought that I just wrote it! I did the same thing last week and my 350 (LT-1) wouldn't start. It's also been 20 yrs or so since I messed with points and timing also. First I had a new set of Delco points, sealed in plastic, right out of the box that were defective. I could not adjust them to a dwell of 30 without the engine stalling. The engine backfired and ran very rough also. But the forum helped me greatly when a member who lives nearby stopped over to rescue me. We were going to adjust my solid lifter lash, but plans changed.

At TDC, the rotor wasn't pointing at #1 cylinder. That was a clue that something was wrong. So my forum buddy moved all plug wires (which I had installed on the "correct" plugs and distributor cap posts previously) by one post. This worked and the engine fired right up. We were then able to adjust timing, but it wouldn't run well at 4 BTDC. It was better at 12 BTDC with 36 degrees of total advance coming in at around 2500 RPM. So now the only thing left to do, to make this right, is to pull the distributor and reposition it, then put the plug wires back on the correct posts. I just bought my car, so the previous owner must have pulled the distributor at some time, and failed to reinstall it in the correct clock position. When I replaced the distributor cap, I must have put the plug wires on the factory correct posts and changed the modified arrangement that had been done to make the engine run.

 

Answers to questions:
1) If you can get a steady reading on the dwell meter then it should be OK. If the needle is jumping around, then I wouldn't trust it.

2) 4 degrees BTDC should be OK

3) Always set the dwell before setting the timing. Changing the dwell changes the timing.

Some other things to check. You changed the distributor cap and spark plugs. Double check that you have the firing order correct. It's really easy to switch wires if you have them all off at the same time. Surprisingly, the engine will run at idle with wires switched.

When you hit the gas hard, did it backfire? I've seen vacuum lines pop off from a backfire. If that happens, you have a vacuum leak and the idle will be bad.

Good luck.

 

Tried again this morning. Was able to get a fairly consistent idle and set dwell at 30. But had a tough time setting initial timing. It seems that whatever I set it too the car runs bad.

Checked vacuum lines, appear to be ok.

Checked the springs on the mechanical advance, seem to be function ok. Could this be my problem? How do you really know if the springs are bad?

Thanks for the replies!

 

Don't worry about initial timing. Set your timing light to 36 degrees and run the engine up to 3000 rpm and see where the timing is. It should be at 0. You want toatl timing all in by 3000 rpm and set at 36 degrees toatl. Then just let the initial fall where ever it is and see how it idles. The initial timing is really the wrong way to set your timing. It is just a reference point. Find out your total timing and post the results.

Vettes4evr, glad I could help out. We have to set up a time when I can come over and put the dist in the right place and set the valve lash.

 

I cannot get the engine up to 1500 rpms without it stalling to set total timing at 36

Any other suggestions?

Thanks

 

Does a slipping timing chain or one that has skipped explain my problem?

Has any one had any experience with this.

Thanks again.

 

You said you haven't used a timing light for 25 years. If you had a Ford, the number one cylinder would have been the front passenger side. On a Chevy, the number one cylinder is the front driver's side. Are you using the correct spark plug wire? Since number one is first and number two is last they are right next to each other in the firing order and the engine may run but it wouldn't run very well.

If you are on the correct wire then you can try this. Bump the starter until you stop the timing mark at 0 degrees (pretty close will do). Then remove the distributor cap. The rotor should be pointing to either the number one or number six spark plug wire on the cap. If it isn't then you need to look at the reason it isn't.

The other thing you can try is to set the timing by ear to see if you can get it to run OK. If you can do that, you can then put the timing light on it and see if you can figure out how far off it needs to be to run OK. If it runs OK anywhere between 4 degrees BTDC up to around 16 degrees BTDC you can follow the timing instructions on the forum.

If the engine runs good at any other timing then you will need to find out why it is so far off.

 

The "find it first and fix it later" method is sometimes required. Did you also adjust the lifters prior to restarting? If so, perhaps the lifters were not set properly. Otherwise, get it to fire, then very slowly and gradually turn the distributor CW, then CCW to find the area where it runs best. Lock it down and then see where the timing mark shows on your damper. It may be way off the timing indicator.

If there is no spot where the engine runs well, you have another problem [in addition to timing]. It could be the carb and/or a big vacuum leak into the intake. There are lots of possibilities. Try that and report the results back so we can try to help you.

 

Thanks for the input.

I bumped the starter, timing mark is at 0 degrees and the rotor is pointing to #1 at the distributor.

What is the best way to find a vacuum leak? Where do they typically develop?

I have some carb cleaner that I can spray at base of carb and other connections, is there a better way?

Thanks,
Rich

 

Once you get the car running, that is an easy method to find [excess] air leakages into the intake system. But pull off any vacuum hoses (headlights, wiper door, power brakes) and seal off those sources so that leaks in those areas can't affect you with that testing. Also pull the distributor vacuum feed and do the "suck test" on the distributor diaphragm to make certain that it isn't damaged. You should not be able to draw air from the vacuum can. If you do, it is defective and needs to be replaced before you go any further. You just have to eliminate any intake leakage points before you can properly set up your carb and idle conditions.

Spray small puffs of carb cleaner at a specific spot on the intake system (base of carb...several different spots, intake manifold gaskets and end seals) and listen for engine speed increase immediately after each shot. If you find no such speed changes, you are leak-free and have other problems...likely carb related.

 

My 70 is running great now and I am having fun! Timing all in at 36 degrees at 2650 rpm.

My main problem was a vacuum leak at the carb and some questionable points.

The forum is great!!!!! Thanks guys especially 7T1vette, vettes4evr, Gordonm and my 76 ray

 

Glad to hear you got it running.

 

I like things simple - and this approach is straight up.


I am replacing the HEI, plugs, wires, ignition module.

My question is: do I need to adjust the DWELL before this process?

I have a 1977 and the manual does not list a dwell setting.

 

Dwell is for distributors with points/condensor. HEI doesn't have points/condensor so you don't have a dwell to set. So your already one step closer to being finished.

Roger