Idle Problems

[tittyman]

Have a BBC, very radical cam (no specs) 2 Holley 660's, tunnel ram, 12:1 compression...carbs needed to be rebuilt and just completed them..boat fires right up..problem is with this cam I can't get to idle consistently at 1000 rpm...at about 1200-1400 it appears to be no problem..when you get to 1000 it wants to fall off. Fuel pump and pressure is good. I set my float level correct while they were on the bench..just can't figure out why they want to fall off at a 1000 rmp..thanks..

[tomcei]

check for a vacuum leak

[tittyman]

The only place I could have a vac. leak would be around the base of the carbs to the manifold...I double checked those and they are snug..there are no additional vac. ports or hoses connected to these 660's...

[Moneypitt]

When it idles at 1200-1400 are the main jets flowing? I would think they would be. Look in the carb and see if the venturi are dribbling. As you back the idle speed down the butterflies will close and the idle will depend on the idle mixture screws...So, it is here where your problem lies. Screw the screws all the way in, gently, and then back out two full turns, that is a starting point and you need to adjust the mixture with the butterflies closed. A vacuum leak will usually raise the idle speed............MP

[tittyman]

The mixture screws were all set at 1 1/4 turns out...this was way too rich after looking at the plugs prior to me rebuilding the carbs...they are now all set at 1 turn out and the mixture appears to be much better..
Another question..I adjusted the float level dry..it's now hard to adjust the level running the motor..I have a holley elect. pump...can I just run the pump and build up pressure to wet set the float level or does the motor always have to be running at idle to do that adjustment correctly...

[nyjetboat]

had the same problem with my 660s i opened up the secondarys alittle more 1/4 turn at atime .I used small screw driver that i bent to reach in the little slot on the other side of the card from the linkage. this way you don't have to take off the card to adjust it . i use a elec pump too doesn't need to be running for the floats. i set mine right at the sight hole ,not running outwith 7 lbs fuel pressure hope this helps

[nyjetboat]

also got idle down from 1100 to 900 on mine

[tittyman]

Spent half the night thinking about vac. leaks in the rebuild of these 660'S..
Question 1. In the acc. pump discharge nozzle there are 2 pieces..the nozzle and the hollow screw that holds it in place..is there suppose to be a gasket under the dis. nozzle and another one on top of the nozzle where the screw holds it in place...I'm not sure if there were gaskets there or not..my diagram is generic and does not give much detail.
Question 2. The idle mixture screws were originally set at 1 1/4 turns. As I mentioned prior I thought this was a little rich and reset them to 1 turn. You guys with experience with these 660'S where do you find you usually end up at....and do you always have the primary and the secondarys both set the same. Holley says they should be..

[nyjetboat]

i found if the primarys are opened too much the idle mixtures screws have no responce because you have gone past the idle slots in the venturi.if they are more than an 1/8 of an inch you lose the signal to the idle circuit.by opening the secondarys this allow to close the primarys to regain the signal.depending on the cams lobe seperation is how much vac you have.as far as the gaskets in the center where the needle is i don't remember if there was a 0 ring in there but there is a flat gasket under the screw that holds the squiters down.some people even drill a 1/8 in hole in the primary butterflys to allow them to close them more but i perfer to open the secondarys more i also changed my needle and seats from the stock .110 s to the spring loaded .097s didn't notice any change in fuel flow but i wanted the spring loaded seats nyjetboat@yahoo.com

[460 jus getn it]

With a 12 to 1 motor and a very ratical cam would 1200-1400 be a good idle. I have a 468 bbf that idles between 1000-1100 and its fine.

[Bow Tie Omega]

With a 12 to 1 motor and a very ratical cam would 1200-1400 be a good idle. I have a 468 bbf that idles between 1000-1100 and its fine.
I second that, with a radical cam and high compression, you are not goint to get your boat to idle at 800 rpm, it will want to stall. Even at 1000 rpm, it will have a rough, very lopey idle. Just my 2 cents. Good luck

[tittyman]

Still looking for a vac. leak..still working on adjusting the idle mixture...can't find a holley diagram (even from Holley) on 660'S to see if I need seals iin the acc. pump discharge nozzle and the screw that holds it in place. It idles at 1500 and then I try to slowly adjust it down to say 1000 and then it just falls off and stalls...really appreciate all the good advise so far..

[Bow Tie Omega]

Still looking for a vac. leak..still working on adjusting the idle mixture...can't find a holley diagram (even from Holley) on 660'S to see if I need seals iin the acc. pump discharge nozzle and the screw that holds it in place. It idles at 1500 and then I try to slowly adjust it down to say 1000 and then it just falls off and stalls...really appreciate all the good advise so far..
Have you checked your timing. Sounds stupid, but I am trying to think of the simple fixes first, rather than the more drastic ones.......

[tittyman]

timing is OK..still working on the problem...Speaking of timing..this motor has a Pete Jackson gear drive system...never heard of it before, but you can hear the thing wind up...don't even know how it works...

[oldselmn8tr]

Your idle mixture screws have very little to do with your spark plugs reading rich this is more a main jet prob than a idle mixture prob. Idle mix screws are just that, they adjust your fuel mix. at an idle. Once off idle the mains take over, so try adjusting and see if you get an improvement. There should be a gasket on both sides of the accel discharge nozzle, but this will not cause anything but a hesitation on the hit as the fuel doesn't go out the nozzle but dribbles around it. Check the intake to head sealing surface for a vacuum leak. Some tunnel rams don't like to idle worth a crap without alot off tweeking to the carb's.Hope this helps good luck.

[tittyman]

So you don't think it's an idle mixture problem, and the fact that the seals around the discharge nozzle are not in is the problem at all..your more incline to the a vacuume leak between the carb and the manifold or the manifold to the block leak? The jets are the original size, 76. I run the boat at 2000 ft. elevation. When I first got the boat I called Holley Tech Support, he said they are fine...he said every size change results in a 4% difference..let me know what you think about all the above...

[Bow Tie Omega]

timing is OK..still working on the problem...Speaking of timing..this motor has a Pete Jackson gear drive system...never heard of it before, but you can hear the thing wind up...don't even know how it works...
I have the same thing. Here is a pic. It is supposed to whine, I love the sound:D Simply put, it replaces the timing chain.

[centerhill condor]

http://www.***boat.com/forums/attachment.php?attachmentid=28290&d=1176073700
befamoeed..or here ya go.

[tittyman]

Guys...thanks for the info on the Pete Jackson gear drive ...I'm still working on the question at hand...making the boat idle..still can't find any vac leaks..not to say there not there..I've got to get those two gaskets that go into the acc. discharge nozzle, but that wouldn't be the problem of not being able to idle at 1000 rpm????? like I said at 2000 rpm no problem, at 1500rpm it starts to die off until it hits 1000 rpm then I got the throttle it real hard again or it just fades away and stops....

[RIVERTIME247]

Guys...thanks for the info on the Pete Jackson gear drive ...I'm still working on the question at hand...making the boat idle..still can't find any vac leaks..not to say there not there..I've got to get those two gaskets that go into the acc. discharge nozzle, but that wouldn't be the problem of not being able to idle at 1000 rpm????? like I said at 2000 rpm no problem, at 1500rpm it starts to die off until it hits 1000 rpm then I got the throttle it real hard again or it just fades away and stops....
my freind just changed his out..he had the same problem and had those carbs worked up and down and still could get a good low idle.
it was pure hell for him in the no wake zone !

[tittyman]

So he had the same idle problem..idles fast..try to set idle at about 1000 and it would die? He couldn't fix the problem and put new carbs on and then he could adjust the idle down? Did he have some other kind of problem like a vac. leak that he also fixed or just put new carbs on and called it good..

[RIVERTIME247]

So he had the same idle problem..idles fast..try to set idle at about 1000 and it would die? He couldn't fix the problem and put new carbs on and then he could adjust the idle down? Did he have some other kind of problem like a vac. leak that he also fixed or just put new carbs on and called it good..
new 750 holleys ....no idle problem and he was told and i quote ! its was more effective to put new carbs on then to sink money into a carb that is know for that problem. im only passing on what a friend of mine has done and what was said regarding this carb.
good luck !

[oldselmn8tr]

Just stand back and throw money at it till it fixes itself!:sqeyes: It can be fixed but you need to find someone in your area with experiance with those carb.s. You are fighting a lean prob. at idle because of the cam and long runners on the tunnel ram, lots of reversion and fuel hanging on the walls of the tunnel ram, combine this with low idle speed and you get a stall.

[RIVERTIME247]

MAYBE THESE WILL HELP YOU..CHECK OUT THIS POST IN SPAM
650's for sale or trade

[Taylorman]

Whens the last time you took the carb apart and gave it a good cleaning? I had idle problems a while back. Pulled my carbs down and cleaned them with brake cleaner and blew them out good with air. Problem solved.

[Moneypitt]

Have you adjusted the valves lately??? Is it solid or hydrolic lifters?? Try backing each rocker nut off ONE turn, and see if anything changes......It sounds like hydrolic lifters on a solid cam..........MP

[Moneypitt]

Any progress to report?.........MP

[tittyman]

I had a very minor vacuum leak which was not the main problem..had to make minor adjustments to the butterflys (which I had never done before)...will now idle around 1200 rpm...plugs look good. If it doesn't rain this weekend I am going to run it and then pull the plugs to check them out...I'm still not sure about the jets..has original jets size 75 or 76, can't remember which, but when I run it and pull the plugs I guess I can make a jet decision...I am at 2000 ft, usally cool, very seldom hotter than 85 outside. I think I will probably run these 660'S this summer and then change to something else next spring, unless they run like crap and then I will make the change right away...If that's the case what do you think the right carbs should be...not looking for top end speed, more interested in fuel and then performance...what size??? and then vacuum or mech. secondaries..Holley or Edlebrock??? Thanks again for all the useful posts.