The Pre "First Fire" background story...

ScottDate: May 15, 2014

So many of you have asked, what was wrong with the Cobra and what did I have to do to get the engine running. Well ok, only Mr. Jeff Duce asked, so I will tell the story because I like Jeff...

After the initial attempts at tyring to start the Cobra, I was fairly sure it was something electrical, since I don't understand electrical things all that much, plus this car has a computer. Every other car I have ever worked on, the radio was the most complex electrical item on the car. My concerns revolved around the wiring, thus I was checking interlocks, electrical switches, relays, wiring diagrams, etc., thinking I had missed a vital connection to allow the car to fire up. I replaced the ignition coil, spark plus (3X), and still got nothing except a cough or two.

Talking to Mom about the cobra (as I normally do to keep her informed) she asked me if I had done a compression check on the cylinders. Now I know most/all of you are thinking, wow, Scott's mom knows a lot about a car. Well that is true and not true. I'll be the first to say that my Mom is the coolest person on the planet (others will attest to that). When it comes to cars, well, that is from my Dad. Dad always...always...would do a compression check first. Actually, Dad would do a compression check almost anytime something wasn't working on the car. Me -"Hey dad, I think the car may be out of gas." Dad - "Did you do a compression check?""Nope." "Well how do you know you're out of gas then?" (these have nothing to do with each other...) Anyway, I said, "Why no Mom, I did have not done a compression check. Dad would be turning over in his grave knowing that I did not do a compression check." (So instead I went upstairs and shook the urn with Dad's ashes to make him feel better). I also did a compression check and here were the results. Cylinder 1-2-...-8: 115-0-0-0-0-0-0-(did not check). Hmmmm something wrong with this picture. So its time to look at the valve train.

Ya see, Dad put in new 1.6 ratio roller rocker arms (stock rockers are not roller rockers and have a ratio of 1.4). What this means is the roller rockers have a rolling contact point on the top of the valve (less friction) and the increased ratio from 1.4 to 1.6 means the valves open more (not longer), which is one way to allow a little more fuel/air mixture in/out of the cylinder. This will help since we have upgraded from a 55 mm to a 75 mm throttle body (allowing more air into intake manifold). Now, since the rockers are non-stock, you have to adjust them so they open/close properly. Well, it turns out that Dad did not get the chance to do a compression check to ensure that the adjustment he used was working.

To remedy this situation, the first thing I do is get online to find out how do you adjust roller rocker arms. There are a ton of ways to do it and all of them say it is pretty easy. Some describe how to make the adjustments, starting off with,"while the car is running..." Ok, can't do it that way. The procedure is pretty straight forward. Loosen the rocker arm until the push rod is free to move up and down, and then tighten the retaining nut by hand until the rod no longer has any up and down movement. Here is where it gets tricky. Since I have hydraulic lifters, you have to preload the lifters via the rocker arm. Depending upon which reputable data source you are using, the preload is either: 1/4 turn, 1/2 turn, or even 1 full turn of the retaining nut. Hmmmm. That's weird. I first chose 1/4 turn, but I noticed that I did not receive _any_ resistance on the nut, so I figured that was not enough. So 1/2 turn it is. Now you have to turn the engine into 3 discrete positions in order to set all the rocker arms properly. Its like, do the Intake valves on 1,3,7 and Exhaust valves on 2,5,8 (etc.), next position... Once again, there is a lot conflicting information from my reputable data sources on which valves to adjust in each position...great. I use my trusty ole timey book and I adjust all my rocker arm. Now lets do a compression check (Dad was happy). Results were much better: Cylinders 1-2-...-8 : 145-125-150-150 - 145-110-155-150. Now we got somewhere. I readjust cylinders 2 & 6 to see if I can get something more outta them, but no luck. Not to mention my compression gauge decided to start leaking and essentially "broke" on cylinder 8 testing (hence a frustrating moment or two). I switch to using dad's compression gauge which is essentially older than me.

Now let's put it all back together and give it a go. Putting the top part of the intake manifold on and torquing the bolts to 15-18 ft-lbs, I hear a "POP!" Which in automotive mechanic terms means, "Oh F#@&!" It turns out that one of the threaded holes on the lower intake manifold cracked. No worries, I have a helicoil repair kit (since the same thing happened on the day we put the engine in the cobra, see previous postings). So I drill out the damaged threads, tap new threads, insert the helicoil repair insert and let's rock-n-roll. Everything was great except for one thing. The bolt for the repaired hole is too short since I had to sink the threaded repair insert much deeper into the lower intake manifold. I now need a 8.5 inch bolt and the one I have is 7.5inch. These are not bolts you can go to Home Depot and get, so....time to get online. Luckily, I know of McMasterCarr and go straight to the bolts only to find out that bolts are sold in 1/2 inch increments UPTO 8 inches, next length is 9 inches. So I buy 2 9 inch bolts (always buy an extra one) and now I wait 2 days. I get the bolts and have to do some modification (cut it) and away we go.

Now for the final attempt, I turn the key and the cobra almost starts. I try again and lots of coughing and almost starts. Third time, it starts right up and the engine purrs (that is the video). Hey, that was easy, wasn't it! :)

Lesson: If I had performed a compression check before trying to start the car, and found out that I needed to adjust the rocker arms from the beginning, the car would have been running about 2 months ago. Oh well. I think this was Dad's lesson, "Be sure to do a compression check first, like I told you." :)