Some Driving Wierdness

[Bruzilla]

I've been having a recurring issue with the Roadrunner for several months now. Normally, I have the at-temp curb idle at about 900, and it drops to the low 700s when in gear. I can drive the car for quite a while and those numbers stay pretty consistent. But... every once in a while, something flakes out and the idle jumps up to 1,200-1,300.

This happened last night, but it happened while I was sitting in a drive through. The idle seemed to get rough for a few seconds, and then jumped up. I had never felt the rough idle before as this seems to happen while I'm going down the road and I never noticed it. The fuel system is new from tank to carb, so I know it's not a fuel issue, so I'm thinking it's a vacuum issue.

So I'm wondering if I'm having a problem because instead of putting a gasket under the Holley, I used the phenolic spacer that I bought for the Edelbrock. I remember when I put the spacer on, and tightened up the nuts on the carb, I had to retighten them shortly after that when I started getting a vac leak because the spacer is pretty soft and as it heated and cooled it created a gap under the carb.

I'm thinking of putting a regular Holley gasket on tomorrow and see what that does.

 

[idrivemopar]

I have a spacer under my thermoquad, and I run a gaskets on both sides of it. I would keep it and just add the gaskets.

Regarding the increased rpm, could be vacuum leak, but could be the throttle isn't returning to idle position, have you double checked to make sure choke isn't sticking or throttle spring doesn't have enough tension or something else preventing the throttle from returning to idle position?

 

[747mopar]

Yeap, phenolic spacers should have a gasket on both sides. Phenolic is quite hard, we use it for wear guides at work where we drill and tap it with 1/2-13 threads and torque with an impact so yes it's hard and not meant to seal... I've also seen timing gears made out of the stuff!

 

[YY1]

That's the reason I swore off Holley's for quite a while.

Back in the day that happened to me at least 2-3 times per week.

...on every car I ever had that had a Holley.

Simply maddening.

 

[beanhead]

When I had those issues it was the throttle linkage...at a stop light the idle would be 900 or so, and if I just ever so lightly touched the go pedal it would drop back to about 750, which is what I had it set for. Turns out it's where the arm connects to the secondary throttle shaft..on my carb(850 speed demon #1563010 of the 2008 vintage) with the throttle (supposedly) at rest you can push on the throttle arm, and while it doesn't appear to really move the rpm's will drop a hair back to normal...I see how I could fix it but I cant remove the shaft from the body, it's like they squish the retaining nut on the other side..long story short I would double check all your linkage movements

 

[Kern Dog]

That's the reason I swore off Holley's for quite a while.

Back in the day that happened to me at least 2-3 times per week.

...on every car I ever had that had a Holley.

Simply maddening.

Oh man, I love the Holley based carburetors! They can sit for weeks and still start!

 

[oldbee]

Have you checked the throttle plates for looseness?

 

[Bruzilla]

Yeap, phenolic spacers should have a gasket on both sides. Phenolic is quite hard, we use it for wear guides at work where we drill and tap it with 1/2-13 threads and torque with an impact so yes it's hard and not meant to seal... I've also seen timing gears made out of the stuff!

The problem I've found with these spaces is "Phenolic" isn't indicative of what they are made of. These spaces can be made with a wide range of materials, and can be like a hard plastic or a soft rubber.

 

[Bruzilla]

I think I found my problem. I had bought a new starter relay that I thought I needed, and decided to install it anyway. As I was swapping out the relays, I looked at the power brake booster and saw a cap on one of the vacuum ports had split all the way up one side and was starting to crack across the top. That's a vacuum leak right there, and I'm guessing the hotter the engine bay got, the softer that cap got, and the more it opened up.

 

[khryslerkid]

Are you useing the electric idle solenoid on the carb?

 

[747mopar]

The problem I've found with these spaces is "Phenolic" isn't indicative of what they are made of. These spaces can be made with a wide range of materials, and can be like a hard plastic or a soft rubber.

They're made of plastic, aluminium and phenolic depending on which one you buy, if it's advertised as phenolic it should be made of phenolic and nothing else. Glad to see you found a leak but if it doesn't have 2 gaskets I'd get them on there.

 

[Bruzilla]

Are you useing the electric idle solenoid on the carb?

The only electric anything I see on there is the choke.

 

[moper]

Tuning is a balance, and it's entirely individual. So Bruzilla - what is your timing setup? Which ignition and distributor do you run?
re-reading the first post - please give all the info on the engine build too. Compression, cam, intake, carb, exhaust, convertor, etc.

 

[Bruzilla]

Tuning is a balance, and it's entirely individual. So Bruzilla - what is your timing setup? Which ignition and distributor do you run?
re-reading the first post - please give all the info on the engine build too. Compression, cam, intake, carb, exhaust, convertor, etc.

My answer is stock ignition, have no clue about the engine internals, Holley 850, Headman headers, and no idea of converter... 90% of which wouldn't cause this problem. Rough idle is a vac leak 90%+ of the time.