Too lean, or just needs shielded wires?

[donraye]

Hi all, I just installed my newly built (by me) 418 stroker in my Cobra and today I tried starting it up for the first time. A couple of nasty things happened that made me stop.
One: I had a lower water hose clamp failure that dumped the entire cooling system all over my garage floor when the hose came flying off. That one was an easy although messy fix.
Two: I fixed the hose problem and started the engine again. I planned to run it for about 20-30 ninutes at 2,000 to break in the cam, etc. But after only about 4 nimutes it started to run/miss bably so I turned it off to check it. All the gauges were OK while it was running and oil pressure and temp. were good.
When I checked it out further I was shocked to see that the heat from the exhaust manifold had actually fried three of the plug wires which were closest to the manifold so badly that they were actually turning to dust! One had already come apart and the insulation was gone from about the first 3 inches and the plug boot was almost completely melted/dusted away. The other two of the three were not far behind that point
These are the same plug wires I had only recently put on the 351W I had in this car before the stroker, and they only have a few hundred miles on them. Obviously since the manifold and the wires and their position to each other are the same, it has to be that this engine is producing a LOT more heat than the 351W did.
Is this normal to produce a lot more heat in a 550HP 418 than in the 300HP351 at the exhaust manifold?
I have not changed the carbureter jetting yet as I was going to have it Dyno Tuned next week and leave that up to my engine builder/mechanic friend. But it was actually running a bit rich on the old 351 so I have a hard time believing it could now be so lean as to cause oveheating in only 4 minutes or less!? Could it be that lean, and if so dare I run this engine again at all until it goes to the dyno for tuning?
I am getting a new much better set of wires and I'm getting both "aluminum plug boot heat shields" AND "1,200 degree heat barrier fiberglass 6" boot/wire covers" for them as well.
That should take care of the melting plug wires but now I'm concerned about even running the engine at all until at the shop/Dyno. Should I just pay to have it put on a flat bed and taken over there, or should I try it again with the new heat shielded wires and boots.
I do not want to burn the exhaust valves or put a hole in the piston before I get it dialed in on the dyno.
Do any of you high horsepower guys have to use heat shielding on your plug boots/wires from extreme heat at the manifold? This manifold is VERY close to the wires on those three cylinders but was not a problem in the old 351 at 300HP although one of them was discolored from heat there as well..
This 418 is closer to 550HP and perhaps the old wire set was just simply not good enough for this much engine.
Any thoughts?
Don

[Cobra #3170]

Check your ignition timing if have not already done so, retarded timing will really heat up exhaust manifolds in a hurry.

[Rick Parker]

Pull the plugs if they are "White" or Grey it's too lean. Check the timing if you haven't already done so. The carb may need the idle circuit fattened up too.

[vector1]

ditto on the retarded timing, make sure you have enough advance.

you don't need to run the engine at 2,000 rpm for 20 min for breakin, that is flat tappet units, you have the rollers correct?

you get all your parts fixed, just take it to the dyno and run it in there, it will be broke in after two pulls and the guy will have plenty experience to spot anything amiss. a little run in at home helps to find these gremlins though and save dyno time.

[donraye]

Originally Posted by Cobra #3170

Check your ignition timing if have not already done so, retarded timing will really heat up exhaust manifolds in a hurry.

What I did with the timing was to find TDC on number one.( I also confirmed that by the crank/cam key positions before I put the damper on.) Then I installed the damper which was pointing to 0 degrees on the timing cover pointer after installation.
Then I gently backed the engine up (rotated it counter clockwise by the crank snout) until the damper was reading 10 degrees before that 0 mark on the damper.
Thats where I stabbed the distributor with it pointing to the number one terminal with the rotor.
That should be 10 degrees advance should it not?
I also just pulled a couple of plugs and they look normal, not light , gray, or white.
D.

[Mac VABCH]

Put on wire boot start engine and check timing. If timing is ok just keep going with your run in. Get to a chasis dyno and tune the engine in the car for the best results...Good luck...Mac

[Caprimaniac]

Hi.

Same thing happened to me regarding running in the cam: The headers got so hot that the boots and jacket on the wires melted. Actually, the headers were glowing hot at 2000 rpm, so something was obviously wrong....
And guess what? The head gasket on that side of the engine had been mounted the wrong way around. So, no water circulation. It meant a ruined solid cam and lifters.
After this I changed to roller cam, to get rid of the run- in procedure.

Let's hope you don't have the same problem....

RuneS

[donraye]

No, it was not having the head gaskets on the wrong way (front to back) but it was a combination of two other issues.
>1: The timing was a bit too retarded as I had not set it where I thought I had.
>2: The plug boots actaully contacted the headers on two of the cylinders, so the heat exchange there is direct not radiant. There was no way to avoid the contact

Solution 1: Got the timing set correctly to about 34 degrees total/10 degrees advance.
Solution 2: Bought a set af ACCEL "Shorty Plugs for Headers". They are about 3/8" shorter than standard and this allows the 135 degree bend in the boots to start closer to the heads and further away from the header bend thus avoiding direct contact with the header. Also am using 1,200 heat shield boot covers for extra protection on all 8 plugs/boots, and have the boots on the "problem cyls." wrapped with 2,000 degree "Thermo Shield" reflective material as well. Probably over kill but it can't hurt.
Thanks to all for your input and help. We're now on the way to the Dyno for a tune but the car is driving/running fine now.
Don

[Caprimaniac]

Good luck on the dyno, Don.