70 L-46 drivability issues

[Timothy B.]

Re: 70 L-46 drivability issues

I think at this point it's a good idea to verify TDC with a piston stop, don't do this test with the starter, just turn the motor with your hand.
If you place the #1 cylinder at TDC and the distributor rotor is not pointed at #1 on the cap the chain is suspect. If it's aligned OK but the damper mark is off then the balancer has moved.

[Paul Y.]

Re: 70 L-46 drivability issues

I think at this point it's a good idea to verify TDC with a piston stop, don't do this test with the starter, just turn the motor with your hand.
If you place the #1 cylinder at TDC and the distributor rotor is not pointed at #1 on the cap the chain is suspect. If it's aligned OK but the damper mark is off then the balancer has moved.

That's good advice for the first place to start.

[Jim T.]

Re: 70 L-46 drivability issues

Timothy why do you think the TCS is something you have to use? My 1970 has not been using its TCS since it was a new car 45 years ago. I disconnected it and began using full time vacuum advance in SEP 1970. Better gas mileage in the city/town and no temp rise in heavy stop and go traffic.

[Timothy B.]

Re: 70 L-46 drivability issues

Jim,

I don't want to change the direction of the subject in this post but I would probably use it only because it was originally installed from the factory and the first post states the engine is completely original except for the breakerless ignition.

I would also make sure the system works properly, but that goes without saying. I understand the advantages of full manifold vacuum advance and agree with your results.

[Mike F.]

Re: 70 L-46 drivability issues

Update - The timing mark is mis-aligned with #1 piston at TDC. I made a new timing mark for 0* at TDC and got the car running.
I am not sure what caused the original popping/backfiring at this point. (A slipped balancer should have no affect on drivability until you tried to retime the engine.)
The engine was rebuilt a few years ago and has about 8k miles on it. A Liberty LT98100 timing chain set was installed. I find it hard to believe that the chain has jumped a tooth already. As I dig into it, I'll update.

Thanks for the help.

[Joe C.]

Re: 70 L-46 drivability issues

Agree with verifying TDC with a piston stop. It is very possible that the timing chain jumped as well. When #1 is @ TDC and rotor is pointing to #1 (not #6) both valves should be closed on #1 cylinder

[Mike F.]

Re: 70 L-46 drivability issues

I'm not sure this thread has a final answer? At this time the car is running, but still needs work.

In short, drivability issues most likely associated with an ignition problem lead me down the path of removing, testing, re-installing
all ignition associated components. This trouble shooting lead me to a slipped harmonic balancer which had nothing to do with the initial drivability issues.
The discovery of the slipped harmonic balancer came a key turn too late, as all of the ignition and then secondary harmonic balancer trouble shooting burned up my Restoration Battery.
So, with a new battery, new harmonic balancer installed and most of the original ignition equipment re-installed, the car fired right up and ran like a champ. That lasted about 10 startups as I re-installed the remaining 1970 ignition shielding and parts to get the car ready for the Texas Regional. I would start the car and drive it after each piece was re-installed to confirm I wasn't installing a bad part.
With all original parts back on the car, it sat for two days until today. I went to start the car and back it out of the garage, it started, ran for 30 seconds and stalled. Numerous attempts to restart failed. (From the very beginning I did not rule out a fuel problem and chased my tail on that as well.)
So after verifying spark, I went and bought some starter fluid, I was able to get the car running on the starter fluid only. After numerous attempts I took a soft mallet to the carb. Car started right up. So I’m not sure how many problems that I currently have or had, but it looks like the carb float is one now.

[Rey S.]

Re: 70 L-46 drivability issues

Hi Mike ------
One thing not mentioned in all these great replies is to replace your fuel filter! They do clog up after a while. Use a quality replacement.
Rey S.

[Edward J.]

Re: 70 L-46 drivability issues

Mike, float problems cause flooding, I have never seen a float stick in the closed position. I would rule out a float problem unless your car is flooding. and being that you were spraying starting fluid and it ran that tells me lack of fuel. I would start checking the problems is it there. As Ray says fuel filter first, and if it has one of the check valves in the filter remove it and throw it away and reinstall the gasket only, do a blow test to see if there is a blockage inside the filter. this is a common issue if your tank has a lot of debris. Make sure there are no kinks in the rubber fuel lines that are on the supply side also the one hose that comes of the bottom of tank. also peek into tank and check the sock on the end of sending unit they can also plug. all in all these are quite simple inspections. lastly make sure the pump is still pumping fuel as you did before, pump some fuel into a bottle while cranking engine. if this all checks okay, then remove the top of carb of and inspect the needle and seat, I have seen the seat back out of the air horn so far that it will shut the fuel down when you really need fuel.( this issue is due to not being tighten properly when it was replaced)

[Tim E.]

Re: 70 L-46 drivability issues

Mike - This goes along with what Ed just suggested.....When you look down into the primary venturis and move the throttle to full open, do you see gas squirt into the venturis? If so, this indicates fuel in the bowls. If not (and I suspect you don't see any since you had to use starting fluid), then it indicates a starvation issue and fuel not getting to the carb (fuel tank filter, fuel line blockage, clogged filter, weak or bad pump) or past the needle & seat (stuck needle). If you end up removing the top of the quadrajet (which can be done on the engine), see if there is debris or sludge in the bottom of the bowls which could prevent fuel from getting out of the carb. If so, you will probably need to take it apart, soak it, and blow out the passages.

[Mark E.]

Re: 70 L-46 drivability issues

Mike,

I believe you're local to the Frisco Regional event. If you can somehow get the car there, we can put a team together and figure this out. Bring the tools.

[Mike F.]

Re: 70 L-46 drivability issues

The fuel filter has been changed (more than once), the fuel pump pumps fuel like a race horse, the accelerator pump squirts fuel as it should, the fuel tank is new and clean, the carb was rebuilt by Lars a couple of years ago.
Since using the mallet, the car has started four or five times without any issues. At some point in the near future I'll pull the top off of the carb and look at the float.

[Mark E.]

Re: 70 L-46 drivability issues

Since using the mallet, the car has started four or five times without any issues.

Paraphrasing Jay Leno as he was test driving a new Z06 on his YouTube channel- "The nice thing about the Corvette compared to the exotics is that it's a Chevy. And you can fix a Chevy with a hammer."

[Terry M.]

Re: 70 L-46 drivability issues

Floats often fill with fuel or if foam absorb fuel. Again this will cause flooding, not starvation. If improperly installed float can hang on the side of the bowl. Bring the soft mallet with you to Frisco. C U there.

[Mike F.]

Re: 70 L-46 drivability issues

Car wouldn't start this morning. Maybe next year.