1986 mark iv #158

[mike stephenson]

I purchased a 1986, # 158, last year. The car is black with tan. I restored the interior, engine bay, and undercarriage to new condition. The paint and body are nearly perfect.  I have emailed Mr. Muck for help with the cars history recently to know more about the car and modifications made to the motor. The engine appears to be a svo crate motor painted black, non roller cam, casting # e3ae, alloy gt40 heads with roller svo rockers. head serial #sb-188-2-1601. I think it has solid lifters. intake manifold is alloy and COBRA is cast near the front. The older firing order is cast on the intake.(I am using the old firing order)Stainless steel tubular headers to twin mufflers to a chamber over the left rear fender. Twin left side tailpies. Holley avenger 670 vacuum carb.(just installed). The engine does not perform as I think it should- poor idle. poor acceleration. Any advice on the motor would be greatly appreciated. Even more interesting to me would be the history on the car prior to 1993. Thank you. Mike

[Guest]

Where ya located .. I own 1234 green with tan interior .. I'm in NY .. my car has 9k miles and is in bone stock condition .. the motor can be tuned .. probably the holley needs to be jetted down .. a 600 cfm would be more suited .. but rejetting and checking the pwoer valve would get it to smoothen out.
   Ron

[mike stephenson]

I am located in holland michigan. This 670 holley is brand new. prior carb was a holley 750(used with a fresh rebuild kit). before the 750 was a holley 600(also new). The car idled and ran the best with the 750, but not as good as it should. If I can find the owner who redid the motor, Information on the cam, timing etc. would be helpful

[Guest]

You can get the motor running if you take it to some one with a chasis dyno ... they can help you tune it and run it to find its personal best .. cam info is not necessary ... timing play with it.. if your running pump gas ..crank it up to 25 initial and see what it does ??? check the plugs ?? are they black ?? is it too rich .. too bad you werent closer .. I love that stuff.

[mike stephenson]

The plugs are nearly white- indicating a lean condition. With the new 670 avenger carb idle is 1700 at minimum setting on idle circuit. When pushed the engine runs like a motor not warmed to temp. I have tried both firing orders with the older firing order being better. The greater the load-ie third or fourth gear-the worse it runs. I checked the aluminum intake for leaks- found none. while some of the carbs would idle around 1000, all perform the similar under load.

[Guest]

Mike,
   
   If the plugs are white the carb is too LEAN . they should idealy be light brown .. it all is logical ..you say it idles at 1700 , thats too high .. Ok couple things on the HOLLEY ..
   
   1. put a vacumn guage on the port on the carb ( not intake ) the side of the Fuel block there is a plug or maybe a 1/8" vacumn connection .. example if it reads 7.0 then you need a 5.0 power valve ..always 2.0 less then a vacumn gugae at aporx 1200 rpm.  Also if the motor backfired out of the carb ..the power vlave is shot .. dont beleive the BS that the carb has an anti backfire kit in it.
   
   2. the accelerator pump lever .. needs to have .015 play in it .. if not tighten the 3/8 nut on top and hold the bottom until its jingles .. you may be in the acceleration stage causing this.
   
   3.add more timing .. where is it set initial .. push it up .. turn it advanced until the motor sounds like it will stall then turn it back slightly and try it then and make sure you have new fuel, fuel goes bad in a month ... also check the fuel filter.
   
   4. The lifters are solids they should be set COLD at about .021 .. if they are too tight this also could be a problem.
   
   5. fireing order has to match the CAM .. I think your on the new FIRING ORDER if its a crate motor you definately ARE using the new firing order.  Be careful ... you need some history ???
   
   
   To me sounds like you have a hot motor that wants FUEL and Timing ..
   
   Ron

[mike stephenson]

Brought the car to a well respected engine builder in Mich today. At 1st hearing they think the issue is an intake leak or an electical problem. I will report on their findings and results. Mike

[mike stephenson]

The car came back yesterday from the race engine builder-finally. They found the biggest problem to be a bad distrib-replaced. Also they could not get the new Holley 680 cfm avenger to perform just right and replaced with a Holley double pumper 600cfm. The engine now runs cleanly and is strong to 4000 rpm whre it screams to 6500 rpm. I might have a problem dealing with the 4000 rpm rush but the car is now seriously fast. I would appreciate advise on the one remaining drivability issue-clutch adjustment. several times I have had the engagement point adjusted to the center only to have it drop to the floorboard the following day. It drags only slightly down there but makes fast shifts difficult. Why wont it say after adjustment? please help

[Mark IV]

Clutch cable info and adjustments here:
   
   http://www.musclemustangfastfords.com/projectcars/mmfp_0309_mustang_clutch_cable/
   
   and here:
   
   http://www.key-ideas.com/DG_ClutchAdjuster.htm
   
   and
   
   http://www.key-ideas.com/DG_ClutchAdjuster.htm
   
   Any of the cables for an 82-92 Mustang will work a little tweaking.
   
   Rick

[keithjecks]

One of us should have suggested that as the solution. It was standard for SVO 302 engines in cobras for them to put too big a Holley on it. Mine had the same full throttle issue you describe, but not the idle issue which put me off. With a 600 cfm carb it was transformed. The problem was that with the larger chokes you never get enough gas velocity to atomise the fuel.

[mike stephenson]

Rick, are you saying that the cluch cable needs to be replaced? I was hoping there is a way to fix the existing cable, it acts like a slipping cam adjuster or something. The carburater thing is strange. The car last fall ran the best with the 750 cfm holley but maybe a lot of problems were disguises by the bad dist. The two 600 cfm carbs that were tried last fall were the street version. They caused the engine to run the worst.

[Max Allan]

Mike
   
   Have you got your clutch pedal problem sorted?
   
   I own a Brooklands Ace, not a Cobra, so the set-up might not be the same. But it sounds like some of the teeth on the plastic quadrant have stripped causing the pedal to drop.
   
   
   
   Fiore make a smart alloy replacement and a bulkhead cable adjuster, doing away with the need to adjust the clutch from under the car.
   
   
   
   A word of caution – although I'm sure it's unnecessary. I'm in the throws of converting to manual transmission and sourced a manual pedal box from a Sierra, only to find the quadrant is smaller and the pedal shaft bigger, so the Fiore quad. won't fit without modification. I would imagine, however, the Cobra is fitted with a Mustang pedal box, so the parts will interchange without problem. Hope this helps.

[Max Allan]

Oophs - I'll try again
   
   plastic quadrant
   
   
   Fiore quad & adjuster