Tugs back and forth when downshifting ?

[carmine]

OK good pictures

As i can see in pictures there is rust present around the NIKE shaped weights.

1) Remove the silver springs. (They snap on to protruding posts).
2) lift out nike shaped weights.
3) clean rust off weights using very fine sand paper (Aprox 600 grit) or steel wool. Also use steel wool to clean rust off posts.
4) Wipe all parts clean of any grit.
5) lube post and nike weights with litheum grease.
6) re-insall.

Hope this helps.

[D111]

I will do.

One question though if it's the ignition system wouldn't it also do it upon Acceleration? It accelerates and rides a long supersmooth Even at very slow speeds. it's only upon decelerating

Think you

[carmine]

Not always.

The centrifical force of acceleration is very strong on making the nike weights extend apart.
They only have the pressure of the springs to pull them back, which should be sufficient provided they are clean (no rust) and lubricated.

I generally clean and lube these weights once every couple years.

[D111]

Got the Parts cleaned up And lubricated, just waiting for the drizzle to stop Here so I could take it out and give it a Test run.

[Tomcobra17]

The info that carmine is suggesting is good and could be the issue.

It may or may not fix your problem....doesn't hurt to try and could avoid problems in the future. Try it and see.

The next step will be look at your carb again. I read on another one of your posts where you stated that the fuel level in the bowls of your new carb are at 3/4 of the sight glass. They should be set to the middle of the sight glass. Try resetting the levels and see.

Also, check the vaccum ports on the carb and make sure that the ones you are not using still have the black rubber caps on them.

Tom

[D111]

Just got back from a short ride I would say it definitely improved Both conditions . The idle seems to only Go down just a bit after stopping maybe 500 RPMs which is fine with me.
And the tugging seems to be cut in half but I really didn't go for that Long of a ride because of the weather.

Maybe it's just the nature of the beast and I'm being too picky or Maybe I just shouldn't downshift so much , I barely use the brakes only to come to a complete stop at the very end, someone had told me that it's good for the clutch and I love the sound of the motor.

Thank you very much for your replies and help.

[Tomcobra17]

I missed the post about calling quickfuel.......

I do not think changing the main jets is the issue as the mains are not flowing at idle / coasting.

Your idle feed restrictors (ifr's), idle air bleeds and idle mixture screws control idle and coasting.

I do believe that it is a lean condition and could be fixed by adjusting the idle mixture screws counter clockwise to richin the circuit where the condition you discribe is occuring.

Check the items that were discussed earlier and report back.

Just so you know, I have the same BDR and Roush 342R that you have. I have a quickfuel Q-650 and a wideband. I have spent the last year learning a lot about carbs and tuning every circuit of my carb to run perfect.

Tom

[blykins]

Originally Posted by D111

Just got back from a short ride I would say it definitely improved Both conditions . The idle seems to only Go down just a bit after stopping maybe 500 RPMs which is fine with me.
And the tugging seems to be cut in half but I really didn't go for that Long of a ride because of the weather.

Maybe it's just the nature of the beast and I'm being too picky or Maybe I just shouldn't downshift so much , I barely use the brakes only to come to a complete stop at the very end, someone had told me that it's good for the clutch and I love the sound of the motor.

Thank you very much for your replies and help.

I'm sure having the idle set at 700 was a good bit of the problem. The cam will work against you at this rpm. Setting the idle higher and giving it a little more idle mixture should get you dangerously close.

[D111]

Originally Posted by Tomcobra17

I missed the post about calling quickfuel.......

I have a quickfuel Q-650 and a wideband. I have spent the last year learning a lot about carbs and tuning every circuit of my carb to run perfect.

Tom

Hey Tom what's the wideband?

Dennis

[Gaz64]

Originally Posted by Gaz64

The slow return to idle is typical of a semi-race style carb AND camshaft.

Your idle circuit is a tad lean for idle/ progression conditions.

The idle feed restrictions need to be a little bit larger.

Have you got access to a wideband O2 sensor?

Originally Posted by D111

Hey Tom what's the wideband?

Dennis

A wideband O2 Air/Fuel ratio gauge.

[twobjshelbys]

Originally Posted by D111

Just got back from a short ride I would say it definitely improved Both conditions . The idle seems to only Go down just a bit after stopping maybe 500 RPMs which is fine with me.
And the tugging seems to be cut in half but I really didn't go for that Long of a ride because of the weather.

Maybe it's just the nature of the beast and I'm being too picky or Maybe I just shouldn't downshift so much , I barely use the brakes only to come to a complete stop at the very end, someone had told me that it's good for the clutch and I love the sound of the motor.

Thank you very much for your replies and help.

Using downshifting to slow down is a practice that can get you into trouble. I grew up believing it was a good practice. I practiced it on several occasions on my Cobra and found it to be the best and quickest way to get the car going down the highway sideways and backwards.

Here's the problem. At higher RPMS the engine does what is called compression braking. Depending on weather and tires, this sudden braking can cause the tires to lose traction and when they do you're going to go around in a circle. A friend who used to vintage race Cobras and rebuilds the originals said there are 2.5 modes involved in driving a Cobra. Mode 1: Foot on the gas. Mode 2: Foot on the brake. Mode 2.5: Foot moving back and forth between gas and brake. Or as he put it "Engine go, brake slow"... The event is also called trailing throttle oversteer and can even happen when just letting off the throttle. So his rule applies also on the track with the advice, "never coast".

Your driving style may work with engine braking to slow down. I still use it on occasion, but only when coupled with heel-toe downshift throttle blip going into turns. I don't try to do it on a straight line stop. Note the heel-toe maneuver fits exactly to the modes - braking with clutch down, increasing RPMs and reengaging when engine RPM makes up the difference. It all fits.

Sticky tires are a big help.

You know all of this but I've had lots of discussions with others on this.

Drive Carefully!

[Tomcobra17]

Dennis,

As Gaz64 stated, it's a wideband 02 meter that measures the airfuel ratio of the engine. I bought the NGK AFX meter and velcroed the gauge/control box to the bottom edge of my dash. The large LED readout is easy to see and allows me to monitor my air fuel ratio under all conditions. The o2 sensor is installed at the collector on the passengers side sidepipe. I can easily remove the system and just use the supplied plug for the sidepipe.

It's easy to use, accurate and works great!

Tom

[D111]

Tom by chance do you know what your idle mixture screws are turned out at? I have mine currently at three quarters of A turn out on all four corners.

and by the way we have the same color combination also.except I have black Side pipes and rollbar.

[Tomcobra17]

Dennis,

Mine are about 1 turn out, but my carb is different than yours and is probably setup differently from quickfuel as its a q-series 650. I have also changed the ifr's (and many other things as well) as it was too rich in certain areas when i received it. The q series is more of a race carb and your hr-650 is more street oriented. Im sure the metering blocks are different as well.

I was hoping that you had a card included from quickfuel that listed the specs of your carb so I could see how it's setup.

The best way to tune a carb for best performance is with a wideband. The hardest
Part of installing a wideband is having the o2 sensor bung welded into the collector of one of the stainless side pipes. I had a local welder do it for 40 bucks. Tuning takes time as well to make sure everything is right under all conditions. Going to a tuning shop would have cost a lot.......been there and done that years ago.

If you're willing to take a drive one day (where in Jersey are you located?) I'd be willing to make sure the carb is setup correctly and can show you how it works. If you had an o2 sensor bung welded into your exhaust, we could hook up the wideband and check the tune.

The basic way to setup a carb is to make sure the primary throttle blades are set such that the transfer slot opening viewed from underneath is square. Install the carb and set the throttle mixture screws to 1 turn out on all four. Start the car and adjust the idle speed using the secondary idle speed ajustment screw. Then adjust the floats so the fuel level is in the middle of the sight glass. Now fine tune the idle with the 4 idle mixture screws. Most people say to achieve highest vacuum, but performance engines with single plane intakes like a richer mixture in my opinion. Once the mixture screws are set, then you may need to go back and adjust the idle speed again with the secondary idle speed screw. The primary idle speed screw should not be adjusted once the tranfer slot is set correctly because it will negatively affect cruise and transition to the main jets if set incorrectly (too much of the slot uncovered at idle). It will also make the primary idle mixture screws insensitive to adjustment.

I know this is probably confusing ( it was to me in the beginning), but this needs to be done to make sure the basic settings are correct before the bulk of the tuning begins.

The link below is a very good article that does a great job of explaining "carb tuning":

Http://members.tccoa.com/392bird/tuning.htm

Tom

[Tomcobra17]

Here is some great tuning information with the use of a wideband that Wayne Presley wrote on ffcars.com some time ago. He used an Innovate LM2 wideband with data logging.

Carb Tuning 101 - FFCars.com : Factory Five Racing Discussion Forum


Tom

[D111]

Very impressive device didn't realize There was so much Tuning ability to these carburetors.

Tom you have a PM

[D111]

took the car to a local High-performance engine builder that's been in business for Almost 30 years, after a short ride he experienced The slight tugging condition off throttle.

He checked my timing which was off he adjusted from 37 down to 34 In hope this would solve it but No.
He wanted to see my sparkplug so when I got home I removed all eight and brought them Back to him which he examined and said they All looked good . He said he,s stumped he's never had this exact problem before.

So yesterday I went to a Local car show and was speaking with a gentleman that seemed pretty knowledgeable Made a suggestion I'm going to try as soon as my neighbors wake up.
He wanted me to check the baseplate butterflies on my primary if they are set totally closed it could cause a Air starvation When cruising off throttle. Which kind of make sense to me as if I give it the slightest amount of throttle the condition disappears. He said just to set them slightly cracked. Not sure how to do that Exactly than turning up the idle Screw slightly and adjusting the idol mixtures to get the RPMs correct?

Wish me luck

[blykins]

Originally Posted by D111

took the car to a local High-performance engine builder that's been in business for Almost 30 years, after a short ride he experienced The slight tugging condition off throttle.

He checked my timing which was off he adjusted from 37 down to 34 In hope this would solve it but No.
He wanted to see my sparkplug so when I got home I removed all eight and brought them Back to him which he examined and said they All looked good . He said he,s stumped he's never had this exact problem before.

So yesterday I went to a Local car show and was speaking with a gentleman that seemed pretty knowledgeable Made a suggestion I'm going to try as soon as my neighbors wake up.
He wanted me to check the baseplate butterflies on my primary if they are set totally closed it could cause a Air starvation When cruising off throttle. Which kind of make sense to me as if I give it the slightest amount of throttle the condition disappears. He said just to set them slightly cracked. Not sure how to do that Exactly than turning up the idle Screw slightly and adjusting the idol mixtures to get the RPMs correct?

Wish me luck

If its idling at 900 they are slightly cracked. Watch about raising the idle too high and exposing too much of the slot, you'll get the carb into the transition circuit prematurely and you'll get some bad results from that.

[AKA EDDY]

D111, another method is to drill a small hole in the primary butterflies.

[D111]

Originally Posted by blykins

If its idling at 900 they are slightly cracked.

messed around with it a bit turning up the idle screw And then Fattened up the low-speeds to then reduce the idle, it did get rid of almost all of the tugging but it just doesn't feel like it's running That well Then.

"idling at 900" this thing is like trying to hold onto an eel, it Idles at around 1100 while driving if I let off the gas than when I stop It's about 950 Then if I sit there for a few minutes works its way down to 750 so I Can't actually say where the Idle is at. :-)

I may just put my Holley back on and see Where I'm at.