Factory 48 IDF Idle jet size? and another Q.

[Frank]

Hi everyone, thanX for stoping in on my thread!

1) What are the factory Size Idle Jets in my 48 IDF's from Redline. ( Not sure why I can't find this.)
2) Im at less than 1 full turn on most of my Idle jets. How many sizes should I go down. 1/2 or 1 full size? After idle im running good.
3) Im getting the occasional gas squirt up and out from random carbs. Common symptom of being rich or lean? Low RPM condition.

If someone would like to swap or sell me some smaller ones, let me know.

** I have the IDF manifold with no boss in the middle for linkage. I know most of you have IDA's. I worked out my own setup if anyone needs to see it. I also had to modify my valve covers as the acc pump rods hit them.

Thank you, God Bless.

 

[chuck smith]

I would like to see your set up.

standard Idle jets are probably 70
do you mean 1 turn out on the idle mixture screw?

what motor is it? cannot determin jet size needs without knowing cubic inch of motor. What chokes do you have? 37?

IDF's may have very different jets than my IDA's, but I will try to help.

 

[Frank]

Oops, I ran back in remembered I forgot some things, sorry.

331 stroker 9.2:1 Mild build with Iron Cobra heads. 63cc

Yes Idle mixture screw, less than 1 turn till bottoming.

Sorry, but how do I tell choke size.

Heres a pic link http://i18.photobucket.com/albums/b146/mustangII460/331c.jpg

( Forgot to mention its in a FFR cobra)

ThanX,

 

[chuck smith]

look down the venturi and you will see the aluminum choke and a number on the upper rim--probably 37

your gas squirt may be the result of a high overlap cam causing pressure out the carb

try to borrow or buy a LM-1 air fuel analyzer,it is the only way to really check jet sizes. You can usually back off the mixture screw until you hear popping from the exaust indicating a lean condition then screw it out(richer)1/4 turn

 

[Frank]

Heres what I found.
I pulled a tube out. F2 with a main of 150.
On a chart I pulled up on the net. This shows a Idle jet of 55, pump jet 50 and choke 40mm.
Now I atlest have a starting point.

I couldn't see anything on the choke tubes. But while looking I noticed a cracked Auxilliary Ventunri Tube? Looks like a factory defect. That can't help things any. I'll snap a pic tomarrow.

*If I go one size smaller Idle jet, at what point would I change the main jet?

Right now im getting great mid and upper RPM performance.

I do know my timing is still a little off. When I had 15 degrees timing, I didn't have any squirts out of any carb. It was only when I backed it way down.

ThanX again Chuck.

 

[Neal]

Timing will definitely impact performance. Another thing you can do to check mixture is make a wide open throttle run and shut the motor off immediately there after. Then take a look at the plugs. Don't let it idle as they will load up. Platinum plugs help reduce loading during idle. Sounds like you are close!

 

[Frank]

With being at or under 1 trun from bottoming out the mixture screws. Would you guys go a 1/2 or 1 whole size Idle Jet down to start with? I need to order some jets.

.... and how about this picture. Its split from the top to where you can see toward the bottom. Im calling DEFECT. These are brand new carbs that have had NO backfires, ( Flames etc ) out the top. Only the occasional squirt I described before.

Check out the rough casting of everything.

Redline won't speak to me without a credit card number. Thats pretty good customer service.

ThanX guys,

 

[chuck smith]

no doubt a casting defect.

You idle screw mixture seems to be adjusted ok. If it took more than 1 full turn out to be correct it would infer a too small idle jet and vice versa. 3/4 turn out is ideal. If too rich ,you may have to look at idle jet holders .emulsion tubes or chokes as the culpret. give us your symptoms

 

[Frank]

Alright, Im at a stand still until I weld the upper distributor shaft. I barrowed a dial timing light and now have a grasp of whats going on with my timing.

When I bought the dist the total advance is way off of what I need. I'll get back to the Idle jets hopefully by tomarrow evening.

ThanX guys, I'll keep you posted.


*** Heres a mock up of what to do with NO linkage Boss in the middle of the intake. Its rough for now, untill I see how its going to work. I think this manifold is poorly designed in this configuration. I had to mod the valve covers so the accelerator pump shafts wouldn't hit. Everything seems to work great and no linkage binding. The linkage will not work over the valve cover. Zero room.

Hope this helps anyone wanting IDF's or already has them.

http://i18.photobucket.com/albums/b146/mustangII460/DSCN1206.jpg

 

[Frank]

Ok,

Apparently messed up timing can create alot of confusion, more so with these carbs.

After fixing my distributors total advance, initial timing, and when it all happens. I cleared up alot of other problems that were rearing their heads.

My first tune was crude. I knew my timing was out so I didn't want to start making drastic changes until the basic things were right.

After buttoning it up I went out. No popping, no sneezes, no nothing. Just straight out performance. I still need a fine tune, but will need to find a dyno for that. My Idle jets came alive and may end up being about right or a tad small.

ThanX guys for your support.