Opinions on Idle

Some background information. I finally installed my Holley 8007 390 cfm reman carb on a offy dual plane intake. I am running a HEI Ignition set at 12 BTDC plug gap is set .055, with a set of hooker headers and a mild cam. I am now unable to get the engine to idle down to the 600 rpm that was easily achieved before with the stock Rochester 2G. It is idling at 1000 rpm with about 16" of vacuum at the port in the front of the carb. My son and I went for a little drive and I pulled up to a hill and put it into 2 wheel drive low and 1st in my sm420 and proceeded to dig some ditches with the rear tires and it did slow the motor down to 650 rpm or so continued to run like this engine should. Should I be concerned? Or does this sound normal. And what possible direction should I go if needed. Also as stated from installations the engine does like to breathe it certainly freed up some hidden HP.
Thanks in advance Jim C

 

Different engine but my EF 231 idles around 900 rpm with timing right where yours is set. I did this on purpose since most of the trails I run are between 7,000 and 11,000 feet in elevation. It maybe a bit high for around town in SJ but I don't mind.

 

Thanks I just wasnt sure if it would have any adverse effects

 

I guess the only downside would be burning slightly more fuel? I am not sure what an OF normally idles at but they definitely sound unique.

 

If it won't idle below 1000 rpm something is wrong unless you have a race type camshaft installed. Maybe a vacuum leak, vacuum advance hooked to wrong port, etc.


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Nick I do not have a race cam in it. I did check for leaks by spraying carb cleaner around intake and carb and no difference. And with a 16" vacuum at idle this is what has me puzzled if it was a leak. If I grab the throttle blades and really close them hard then it will back down the idle. I do have a dual spring return for the throttle linkage also. This is a reman carb from Holley. I disconnected the vacuum advance during initial set up and then hooked it to the port on the upper passenger side of the carb. The vacuum port at the base in front is where my gauge is connected to. All other ports are plugged or capped.

 

Doh

 

Sounds like your issue right there. Try adjusting the idle. May have the wrong idle cam or something too or the throttle plates are binding/not centered in the bore not allowing the throttle plates to close fully. Might look down the bores without the engine running and see if the plates are centered in the bores. I'd definitely contact Holley on this.
Is the port you have the vacuum advance hooked to ported or manifold vacuum? I'd double check. Should be ported vacuum. Should be weak/no vacuum at idle and increase as the throttle is opened.

 

Is this the gauge you're tuning with? Should tune off manifold vacuum not ported.

 

As for the ports I am connected to here is the information sheet I used when installing this carb. Now something in the picture that is not on my carb is the hose from the bottom of the carb to the top that is shown with no explanation. I believe these ports are just capped at this point should they be connected.

 

That looks right, you have full manifold vacuum there. The hose may be for vacuum secondaries. Just a guess, I'm not real familiar with Hollies.

 

I tested the carb and manifold for leaks today with propane and no effect any place I put it. Then I twisted the throttle closed myself and it idled down nicely. It must be something in the carb. I just hope they are willing to work with me on this. It is at least 4 years since I purchased this through the Holley EBay Site.
Well I am going to call Holley Tech Line tomorrow and see what they have to say.

 

The vac advance should be hooked to the port on the side of the metering block labeled "timed spark vacuum source" in that pic. Vacuum gauge should be hookewd up to the port on the base. The electric choke Holleys use a small metered internal vacuum port to operate the internal choke pull off and to keep the electric element from overheating. The tube runnibg from top to bottom supplies clean air from the top of the carb for this purpose. Not all Holleys have this-some just have a brass fitting at the lower connection by the choke that has a brass screen in it for filtering purposes. Either one is fine, but dont cap off that port on the choke assembly.

 

I just spoke to a Holley Tech back in Bowling Green Kentucky I am shipping my carb back and see what he can do for me. The saga continues.

 

I'm running the same Holley 8007 (4160), Offy Dual Plane & HEI on my 225. I've spent a lot of time tuning it to see how low I could get it to idle. Mine will idle at 600 but I do prefer around 650-700.

To get to 600 RPM I had to adjust the Secondary Throttle Stop which is only accessible by removing the carb (download 199R10013rev from the Holley website). It says back off the secondary screw, turn it back in until it just touches the lever plus another 1/4 turn. I found just a hint less than 1/8 of a turn gave the primary idle adjustment the range I wanted.

 

CJ Joe Thank you very much for the advice it worked like a charm I am able to adjust it up to 650 rpm now. Time to start actually working on tuning rather than trying to trouble shoot this beautiful little gem. And to this whole group there is no better people to turn for help and advice, to you sirs I salute you in my own humble way