Idle RPM?

[tirechip]

Greetings Tiger Fans!

1965 Mk1, with 260 installed. Recently rebuilt carburetor. After being warmed up, RPM hovers in the 1500-1700 range. That sounds and feels kinda high..... What RPM should a stock engine idle at? (sorry for ending the sentence with a preposition)

Chip

 

[pfreen]

It depends on what cam you have. I have a medium cam(lift and duration) and I set my idle at 800 rpm.
1500-1700 rpm might be from the choke is not turning off.

 

[michael-king]

I think your fast idle warmup isn't coming off.. what carb are you running?

650-750 is a decent idle

 

[Austin Healer]

I just had a similar issue and thought it was the fast idle screw on the mechanical choke. If you have a vac. secondary Holley carb,check to make sure that the secondary throttle plates are fully closed. I just had this problem with a customer supplied rebuilt Holley carb. It turned out that the vac. secondary diaphragm spring and diaphragm were not correctly installed and it was not forcing the secondary plates fully closed. As soon as I resolved the problem the idle settled out at 800.
It could also be that the throttle cable is not installed correctly. I have found on both 2bbl and 4bbl applications that the angle where the speedo cable attaches to the bracket on the manifold (or carb for 4bbl) can be too extreme causing the cable to bind in its sleeve. I do have a pattern for the bracket that works best on a Holley 4bbl.

in warm, to warmer climates, I have personally found that idle speeds below 800 don't provide very good cooling at idle...

 

[Austin Healer]

I'd disconnect the throttle cable as a start, that will tell you immediately if the cable is binding or improperly installed. If it's binding, almost no amount of return spring pressure will solve the issue... You will have to apply brute force to bend the throttle cable bracket, or replace it (if you are running a 4bbl). on my own car I replaced the solid inner wire with one from a bicycle derailer cable. Wound wire is a lot more flexible than a solid one! I used cable locks (for the cable) I sourced from Moss, but a good hardware store will have them in their hardware section. Hillman (conveniently enough!!), is a good hardware supplier that usually sells to places like Ace and Tru-Value stores and they supply cable locks.

With the cable removed you should be able to open the choke plate and check the fast idle and main idle screws. if it still won't come off a fast idle, you will have either a massive vacuum leak or throttle plates that are staying partially open.

 

[65beam]

Lubricate the moving metal to metal parts as well as spraying lube into the throttle cable. I use WD 40.

 

[hottigr]

Spray some carb cleaner around the base of the carb- if the idle jumps up you have a vacuum leak.

 

[Austin Healer]

Lubricate the moving metal to metal parts as well as spraying lube into the throttle cable. I use WD 40.

WD40 isn't a lubricant... WD stands for "water displacement"

 

[65beam]

The name WD 40 does mean Water Displacement, 40th formula. It does displace moisture due to the chemical makeup of the product but it's termed a "jack of all trades" used as a lubricant, rust preventive product or as a penetrating oil. I use it to lubricate sticky linkage and throttle shafts and spray it inside the throttle cable housing to lubricate.

 

[michael-king]

Wd40 is not a great long term lubricant. It will fix a squeak for a short time.. then it will start to stiffen again... It's an OK penetrant... .if you were to lubricate things like inner cables you should use an oil or an appropriate grease

 

[65beam]

Wd40 is not a great long term lubricant. It will fix a squeak for a short time.. then it will start to stiffen again... It's an OK penetrant... .if you were to lubricate things like inner cables you should use an oil or an appropriate grease

I just mentioned what I have done with sticky throttles and linkage to cure varied idle problems on my own cars.

 

[65beam]

Wd40 is not a great long term lubricant. It will fix a squeak for a short time.. then it will start to stiffen again... It's an OK penetrant... .if you were to lubricate things like inner cables you should use an oil or an appropriate grease

There are different WD 40 formulations for different parts of the world based on regulations of the country it's being sold in. The product sold in Australia, Europe, Asia, etc. is not the same as what is sold in the states. That could make a difference in the performance of the product. The rest of the story is on Wikipedia.

 

[michael-king]

Robert the thread is about the guys idle speed, everyone was giving answers to what that should be and why it was potentially higher ...

You seem to be trying to hijack the thread. If you really want to discuss various lubricants you and Jean use perhaps start a different thread.

 

[Erich]

Oh this is rich Michael. Calling out 65beam for highjacking the thread when it was YOU who had to say the WD40 was a lousy lubricant. You couldn't let a comment that you disagree with just slide by, could you.

 

[Theorangetiger]

We hadn't had one of these petty arguments for a week or so. It was just a matter of time though.