69 RR engine miss/stumbling when warm

[Bcamp69]

When I'm driving in warmer temps 70 plus, the car seems to develop a miss and will backfire (sounds like from the carb) when I mash it down. If I gently press the throttle and slowly accelerate up to 50mph plus and then mash it, it seems to get more responsive with less missing but still backfires a little. If i let the car cool down it seems to run fine. The temp gauge never goes above halfway and I doesn't smell hot. If I'm gentle on the throttle it will get up cruising speed with no issues.

When I bought the car they told me it had a stumble that was corrected using a spacer underneath the carb. I'm by no means a gearhead. I don't have a strong background in motor but I do have a FSM.

Any thoughts?

The carb is Edelbrock stamped #'s 1806s 2566.

 

[Bcamp69]

This is an intermittent problem. Also, it doesn't want to downshift from 2nd to 1st. It will downshift to 2nd from 3rd at about 45-50mph.

 

[Bcamp69]

Here's another photo of the linkage.

 

[moparjohnny]

Here's another photo of the linkage.

View attachment 366840

have you checked your spark plugs and wires lately?

 

[727]

Have you checked your coil? Do you have points or electronic ignition?

 

[oldbee]

First thing your kick down linkage slotted rod should be touching the throttle stud; get out ur fsm.Second, could be fuel or ignition for the stumble. What's total timing now?

 

[Bcamp69]

Could the hot wire being off the choke cause the backfires and stumbling? I've got the manual out reading the throttle linkage adjustment. Looks like I should be able to tackle that.

I have a couple plug wires (2) that are REALLY close to the headers.

 

[oldbee]

Fix all of above. Choke not opening all the way when hot OR not partially closed when cold could do it. If you get the carb/choke all set right you should be able to drive away after a start in cold weather right away(normal driving); that's the way I always knew I had any carb set right. I'm talking not more than 10-15 sec warmup.

 

[lewtot184]

the vacuum advance hose is hooked up to full manifold vacuum. this could crate a stumble in a high vacuum engine. try swapping the hose to the ported vacuum connection on the opposite side of the carb. also try using the top hole on the accelerator pump arm.

 

[oldbee]

lewtot184 and others--- the OP is only 35yrold. Some of us have to remember that a lot of posters on here are still learning... But Lee tot still has it right.

 

[Bcamp69]

Thanks guys, I'll correct up to this point and report back!

 

[Dennis H]

I'm in the choke camp. Spacers are good, but not related to stumbling.

 

[oldbee]

a camp-looked closer at pics; definitely get acc. pump rod in to middle hole on arm as a starting place.

 

[Bcamp69]

have you checked your spark plugs and wires lately?

I'm going to pull the plugs and check them. I haven't yet. I'll prly just replace them while I have them out.

 

[Bcamp69]

Have you checked your coil? Do you have points or electronic ignition?

I believe it's electronic. How do I check the coil?

 

[Ron H]

Ya got a lot of good tips here and could jump in by wondering if you have a vacuum leak and check the spacer that was added as vac leaks have been notorious around carbs. You could also do a vac check wanting a steady needle. An intermittent miss or stumble doesn't make it sound like plugs...but certainly a logical check on the hunt. Another culprit can be build up of carbon deposits internally which if not bad can be cleaned out with good engine cleaner and/or additives. If you find a bouncing needle carbon build up can be a source and hope nothing more serious. Not sure if your motor has been rebuilt or what general shape it's in where this could be a source. You can also check your fuel/air carb adj using the vac gauge as another easy check while yer at it. You mention plug wires really close to headers...if so look at routing further away or if need be buy wire heat insulators. Yeah, there's still some other things that can be checked but see what luck you have given all the tips you have received...

 

[Ranger16]

My vacuum advance is plugged into the full vacuum port (right side as shown). The left (ported) side an early crude attempt at emission control by removing all advance at idle. Personally, I'd leave it where it is and make sure that the timing is set correctly. That said, I'm thinking choke as well.

 

[oldbee]

Vacuum leak is always a possibility. Spray a quick spurt of carb cleaner at all areas,if it speeds up you found it. It could be anywhere, even a leaking pipe plug thread or hose close to intake.

 

[Bcamp69]

So today I took at look at my car. I drove it a couple days ago and noticed some ticking that doesn't appear if I just let it run and warm up/idle in my driveway. If I take it out on the road the ticking begins.

Lifter or exhaust--I don't know. I put a 7/16 wrench on the header bolts and I found 2 loose bolts, maybe 1/2 to 3/4 turns loose. These bolts are opposite each other and the third bolts counting from the front of the engine on each side. I think torque specs are 30lbs but I don't think I can get my torque wrench in there.

I also noticed my spark plug boot on #3 is touch the header pipe and is very slightly melted from contact. There's a lot of white residue on the plug boot and header pipe where they've contacted each other. Ticking source?!?! How do I correct this. It appears there just isn't enough room.

I also ordered some new valve cover gaskets in case i need to pull the covers and check the lifter preload? That's gonna be a first for me.

I'm also planning to check out the mopar swap meet in indy tomorrow so maybe I can just pick up a new intake there and pull the old. I think it would make adjusting the valves easier if I can see the lifters rise.

I know I'm reviving an old thread here but I also just got an innova timing light with tach and picked up a vacuum gauge to tune my carb and check the timing. It looks like Sunday if I get everything straightened out I'll be able to take it for a spin.

 

[dieseldazzle]

So many things wrong in the old pics and most of them are mentioned, did you remedy any of these?