69 Mach 1 Poor idle

[gt69mach1 10]

So I had a 351 w built with a stroker kit rpm intake 770 avenger carb and a 1000 over stock stall converter, it has around 410 horse power. I have to set the idle at 1100-1200 rpm in park to get it to stay running when its in gear. I think that is to high of an idle. Any thought on what I can do it just seems to run a little rough when at idle:confused::confused1::001_unsure:

[Powershift 19]

When you say "rough" running, do you mean "lumpy cam" rough? Or, rough like a misfire type issue which causes the engine to stall if idling under 1,000 rpms?

 

Most stroker engines have fairly aggressive cams, and that's why I asked.

[Rcodenewf 44]

What are the specs on the cam and what else is in that engine?Timing?JOhn

[Powershift 19]

I would also set the idle speed while the car is idling in gear. Have someone sitting in the car, with their foot on the brake, in gear, while you set the idle speed.

[gt69mach1 10]

Its not a lumpy cam, its pretty mild. Like theres a little miss...I am not sure..it just seems like it should run smoother....What should the idle speed be at when the car is in gear??

Edited March 25, 2012 by gt69mach1

[Powershift 19]

I think stock calls for around 550-600rpm at idle, in gear.

 

You may also have a vacuum leak. Lightly spray some carb cleaner (or something similar) around the base of the carb, and the edges of the intake. If the engine RPMs rise drastically, you have a vacuum leak.

[gt69mach1 10]

It would die for sure at that idle,I have done the carb cleaner looking for vaccum leaks.. I can't find any

[Powershift 19]

I assume you have checked the basics... timing, etc?

 

 

Have you properly set the mixture screws on the Carb?

[gt69mach1 10]

The timing was dialed in on the dyno,and so was the air/fuel.. I did tinker with the air/fuel a little when I got the motor in the car..of course it runs different in the car than on the dyno..I have the dyno sheet in the shop with all the info on it..What do you think the timing should be at?? I am unsure I can only go by what others say.. I have checked fuel pressure its around 6 lbs, the vaccum is 14/15 if I remember right(what should that be?) I can look on the dyno sheet and see what TC timing is set at..New pcv valve installed it has an eletronic accel dizzy with vaccum advance its hooked to full manifold vaccum.. um new coil...good taylor wires..new fuel pump....i am still scratching my head..Timing or fuel I am guessing...by the way thanks for the info..I spent alot of dough getting this thing built..I just would like it to run right:crying:

 

By the way I love the stance of your 70 mach 1..what size wheel/tire combo are you running..I have mine lowered 1 inch in front and stock in back..??

Edited March 25, 2012 by gt69mach1

[Powershift 19]

Hmm, well... if your motor was dyno tuned it certainly should have the basic settings in the right neighborhood.

 

Now, when you say you tinkered with the air fuel mixture... how much did you change it? Sounds like maybe you need to baseline set the screws again. Is the place who dyno tuned the engine at a much different altitude than you? If so, that may certainly necessitate you resetting the mixture once at your house.

 

The wheel/tire combo on my Mach are 17X8 front (4.5 backspace), and 17X9 rear (5.5 back space). Tires are Nitto 555, in 255/40 front, 285/40 rear. My car is probably 2" lower than stock, if I had to guess.

[gt69mach1 10]

Dyno Shop is right down the road from me..I put the motor in and got it going..I set it right back where he had it...I was trying to get it to idle..any thoughts where the timing needs to be at?

Edited March 26, 2012 by gt69mach1

[Powershift 19]

Talk to the shop who built the motor, since they are so close, and ask what they would recommend. If you paid for dyno tuning, they should have a log of what optimum timing should be for your stroker motor.

[gt69mach1 10]

I did talk to the dyno guy...he just shugged his shoulders and said I don't know it ran fine on the dyno. I am going to talk to the engine builder this week and see what he says..thanks again for the input..anything you can think of would help me out

[Rcodenewf 44]

Does it run decent in park and when you put it in gear it runs rough/tries to stall or does it run rough all the time?

 

John

[gt69mach1 10]

runs good in park..when I go to put it in drive it stumbles and dies unless I turn the idle way up:surrender:

[Lemon Owner 11]

If you have no other problems with the engine try advancing the timing by 5 or 10 degrees at idle. The cam in my coupe is so big I have to have some rediculous ammount of timing for it to idle in gear even with a 2700rpm stally. Just make sure to back the idle off a bit because as you raise the timing the engine revs will rise. If it doesn't work then just change it back, easy. :thumbup:

[1969 Mach1 14]

The timing was dialed in on the dyno,and so was the air/fuel.. I did tinker with the air/fuel a little when I got the motor in the car..of course it runs different in the car than on the dyno..I have the dyno sheet in the shop with all the info on it..What do you think the timing should be at?? I am unsure I can only go by what others say.. I have checked fuel pressure its around 6 lbs, the vaccum is 14/15 if I remember right(what should that be?) I can look on the dyno sheet and see what TC timing is set at..New pcv valve installed it has an eletronic accel dizzy with vaccum advance its hooked to full manifold vaccum.. um new coil...good taylor wires..new fuel pump....i am still scratching my head..Timing or fuel I am guessing...by the way thanks for the info..I spent alot of dough getting this thing built..I just would like it to run right:crying:

 

By the way I love the stance of your 70 mach 1..what size wheel/tire combo are you running..I have mine lowered 1 inch in front and stock in back..??

 

 

First, the vacuum advance should not be connected to full manifold vacuum. If you want to use a vacuum advance it should be connected to the timed (also called ported) vacuum port on the carburetor. Since the manifold vacuum reduces when you put the car in gear, conneced like you currently have it, your timing may be retarding when you put the car in gear. This can cause the engine to die at idle. Also make sure your mechanical advance is not being activated at idle. I have seen that many times.

 

If your cam is in fact mild and there is not a definite engine miss then I suspect your problems are in tuning it correctly.

[Rcodenewf 44]

Actually i think what is happening is that the idle transfer slots do not have enough exposure. They are situated under the throttle plates.

 

In park the engine can stand to run a tad lean. When you put it in drive there is a load and subsequently the mixture has to be richer.

 

Try this: Take about 2-3 degrees timing OUT . This will bring the idle down of course and you will have to take the idle screw up a bit to get the required rpm in gear.

 

On the dyno the operator was tuning for maximum hp/tq and the engine went from idle to wot. Not from idle to being loaded down with a torque convertor when in the car.

 

You can also remove the carb and have a peek underneath and see how much of the transfer slots are exposed. Usually on a Holley i like to see them 'square' with equates to roughly .020.

 

Keep us posted.....john

[gt69mach1 10]

Thanks for the info guys!!! I will try some of those great ideas...I hope this week or next weekend!!

[gt69mach1 10]

Well just got it back from the guy that built the engine, he recurved the dizzy, advanced the timeing way up..and then tells me to get a 2200 stall converter, he says the motor is lugging down to much in gear at idle and that a higher stall will correct that. Hes the one that told me to get the 1000 over stock in the first place. Dos that sound like it will fix my problem?? I have nothing against spending a little $$ if it fixes the problem but is it just wasting $$? Any thoughts would be great!!

[Lemon Owner 11]

When I first bought my coupe it would not idle in gear due to the cam. I installed a 2700 rpm converter and it did not solve the problem fully. It is the massive ammount of advance at idle that fixed it. I think it would be cheaper to replace the cam, I will be when I get some time off my other project. Or better still get a manual trans. :lol:

[gt69mach1 10]

A stick would be fun but I am really tall and there isn't enough room for my legs and shifting so I will stick to the automatic. Thats what he had to do to get it a little better but now its timed so much I noticed some knocking when I get on it. Not sure if I should waste the cash on a new stall or get a different cam.

 

I am still trying to get the cam card that came with the cam..so I know what I have..the engine shop can't find it, I am calling him today to at least get a part# so I can find out what I have..

Edited May 15, 2012 by gt69mach1

[Monzy 10]

1969 Mach1 and Rcode offered advice that could fix your problems did you check these? As for cam I cant see it being to radical as you still hold 14/15" of vac which is normal for a mild we'll call it cam. I'm with trying 1969 Mach1's advice first. You cant be trying to advance the timing at idle will full vaccum. As for stock idle speed, that may not be possible with the cam you have. You may have to step up to 800-900+ rpm. Someone mentioned 550-600 I think? That would be for a manual trans car also. Auto is higher.

Edited May 15, 2012 by Monzy

[buening 63]

Do you have the vacuum hose connected to the transmission vacuum modulator? With an idle above 1000rpm, it likely is high enough to overcome a vacuum leak. It ran good on the engine dyno because it didn't have things hooked up to the vacuum tree. Double check all vacuum sources, like power brakes, A/C reservoir tank (if equipped - behind rear passenger inner fender), A/C vacuum lines, transmission modulator, etc. In fact, I'd remove all vacuum sources except the transmission one and put plugs on the vacuum tree, then check if you can drop the idle down. When you drop the idle down, you'll likely see a drop in your vacuum readings too.

[gt69mach1 10]

Well I have check all vacuum lines and cannot find anything leaking, got the timing at 35/36 degrees total timing,it runs great in park and going down the road, when I come to a stop sign in gear it wants to die, unless I turn the idle up over 1000, I can feel the tranny pulling,I have been told by a few different people including the engine builder that I need more stall so its not pulling so much in gear at a stop, I think the timing is too high it is pinging alittle when I am getting on it,I called ACC about a different stall converter they said there boss hog21194 2200-2800 stall would do the trick, they said at a stop in gear I could take my foot of the break and it would not move until I gave it some gas?? Any thoughts?