250 2V surging

[71ford]

Had to go out of state for a week, and the car ran beautifully...... until the day of return, as I set off up the high way the car felt a little surgy, as I slow down it gets worse and it cut out at idle. Under acceleration it feels ok, maybe a bit down on power. After getting the car home, its was no better.

It has a 350 holley on it, haven't had much of a tinker with it yet as I have been too busy, but just wondering weres a good place to start? Before I drove back, I checked and cleaned all plugs, dizzy etc. It also has a MSD unit. It ran fine after I did all the checks as well.

Thanks

 

[addo]

Sounds as though it could be a fuel supply/pressure issue. Hard to tell unless you hook in a gauge. Do look under the car for old rubber flex line - tank to steel line connector is one rubber hose often neglected and it may be sucking air.

You could also warm up the motor and perform a regular compression check, just to eliminate any potential troubles there.

 

[71ford]

thought that it may be fuel pressure related, but it felt ok under acceleration and when travelling on the freeway.

 

[71ford]

Well..... after leaving my car for a week to rest as I had other things to do, I started it and it ran fine, no surging, idle was fine as well. Took it for a drive and still fine. Later on in the day, the idle went again and kept cutting out. I rest the idle screw and went ok again. But the idle still isn't perfect, any recommendations on setting the idle screw for a 350 Holley. Also, one of the idle screw seems a little looser than the other????? problem????

 

[aussie7mains]

Sounds to me like dirt in the idle passages, get the carby appart and throughly clean out the jet block.
The idle screws have cork seals on them one might be missing,
1.5 turns out from bottoming is a good start.
A7M

 

[71ford]

I raised the idle a little and played with the idle screws, both have the cork washers on them, but at this stage only seems to idle nicely when the screws are at about .5 turn. Any further out and they seem a little loose and doesn't appear to idle smooth.

 

[prostkxy]

time for a rebuild on the carby, i had a drama with the 350 holley on my 250 2v ever since i put it on 3 years ago,the car would flat spot going round corners and when i went to put my foot down and also on take off. i had enough of it last weekend so i started by putting bigger jets(dint help so i left em on went from 58 to 63), changed powervalve/accelerator pump? (the one in the fuel bowl that runs off a linkage on the throttle shaft) that didnt help, so i thought i'd change the cam on the throttle linkage and this is what fixed the problem. sideways now every corner, launching at the lights, i can now accelerate smoothly from 30m/ph in 4th gear (toploader) to top speed without down shifting. i thought id give my 2 cents worth on my troubles that may help you. the cam on the throttle shaft i got off a 500 holley 2 barrel all i know is its a bigger mofo.

 

[xctasy]

Good info, prostkxy.


The 218 cam (a white or now somewhat off- white colour in any old stock 350 or 500 cfm carb) set in postion 2 does the trick. It's found on all 4412 500's and the 7448 350.

It yields a massive spike in petrol delivery from off idle to wide open throttle when in position two. Something like 15% more at part throttle to wide open throttle is all you need. A 2v has a massive intake plenumb which needs a lot of fuel early on to get the right mixture to the engine.

There are 8 cams,

White 218 (leanest)
Blue 427
Red 240
Orange 466
Black 234
Green 290
Pink 330
Brown 336 (fraken alchoholic Four X or VB leaker)

All except brown are two position items, and the white is like 17 cc's per ten pumps, the brown is like 36 cc per 10 pumps. Being able to spike the fuel delivey through the squirters by up to 100% by just adding an aggressive cam sounds good, but the squirters have to be able to deliver the fuel first. The bare minimum that gets the job done is the right one.


The problem was most likely the set-up on the accelerator pump. Holley specifically say 15 to 62 thou clearance at wide open throttle. At idle, there should be no clearnance.

 

[XDaaron]

It sounds like a vacume leak. Mine was doing the same thing then I replaced the carby because it was the only thing I hadn't changed now 2 months later same thing.

The car would start find warm up find start driving it it'd seem fine then all of a sudden backfring under deacceleration and it wouldn't idle below 1500rpm power wise it felt a big slugish.

At the moment my mixture screw is about 10-15 turns out I lost count. That's just to get it not to stall.