Well, things didn't get any easier this week. I was hoping to be able to report good dyno results on this entry, but no such luck, and the engine dyno work is going to be set back a couple of weeks as a result of a problem discovered today. I did make some progress on the car, with help from my friend Joel, but still fell further behind schedule overall. Hopefully I can make up some ground this coming week.
Last weekend I'd been ready to dyno the motor with the new intake but problems with the dyno, and then getting a good signal from the crank sensor, kept me from getting the engine running. Those problems continued into the early part of this week, and despite acquiring a new timing light I wasn't able to get a decent signal from the #1 coil to time the engine during cranking. I switched back and forth from the Hamlin hall effect sensor to the Ford VR sensor, and the VR sensor gave me better signal, but was not stable enough to time the engine with while I was cranking it. I spent some time on the phone and via email with Scott Clark, who is an eMS-Pro expert and has dealt with quite a few problems like this in the past. We were both beginning to think that maybe there was a problem with the ECU.
Finally, on Thursday I just decided to hang the Hamlin sensor back on the engine and try to start it without verifying the timing first during cranking. At least with the Hamlin sensor I had a pretty good idea that the timing was set correctly within a few degrees, because I had marked the bracket when I ran with that sensor last summer. I had no idea what the engine would start like with the new intake, but when I gave it a try it fired right up! And as soon as the engine started, the timing light worked like a champ of course, so I was able to check the timing and adjust it to make it match the timing map on the ECU. After getting the timing set I shut the engine off, because Scott was going to be driving up to help with the dyno sessions on the engine over the weekend, so I had decided to wait for him before running any pulls. At this point things were looking pretty good.
Friday night Joel came over to give me a hand with starting to get the rest of the car assembled. Joel worked on building some spacers for mounting the front fenders permanently, and then welded in a framework for the battery box in the trunk, while I cut and welded on the aluminum gas tank. I'd purchased a 20 gallon tank for the car, but it wouldn't fit in the trunk without trimming about four inches off one side. Also, I didn't like the wimpy little sump on the tank, so I cut up an aluminum 3 gallon tank, welded in some bigger AN fittings, and then welded the bottom of that tank into the larger tank. This made kind of a mini-tank sump, kind of like the Aeromotive steel sumps that I've used before on my Mach 1 and my Galaxie. Joel and I worked for three hours or so together on this stuff, and managed to get some work done between BS sessions.
Saturday morning I was up early getting ready for the dyno session. I ran off to the local race gas dispensary and picked up 10 gallons of 110 octane fuel, and then came back and organized/cleaned up the shop a little so that the dyno session would go smoothly. Scott arrived about 11:00 AM and set to work on the computer while I made some final preparations on the engine. Around noon we fired it up, warmed the engine up and started making a few low RPM pulls. Joel arrived next because he was interested in seeing how the engine would do with this intake, and he and I delayed testing for a little while to arrange some ductwork to connect the dyno's air flowmeters to the front facing throttle bodies, so that we had air flow data when we ran the engine again. This effort was complicated somewhat by a shortage of duct tape in my shop; of all the things to run out of! We made do with what duct tape we had, along with some plastic packing tape. Finally this exercise was completed and we began the dyno pulls in earnest.
I was expecting the sheet metal intake to be down on power as compared to the Hilborn setup in the mid range area, but it seemed like it was REALLY down on power. Further, the engine seemed to have a miss in it with this manifold, that was not present with the Hilborn setup. Some A/F tuning helped this situation out somewhat, but it was still present on every pull. We thought we'd found the issue on more than one occasion; for example, we checked the plugs after a few pulls and found the #8 plug had a closed up gap. We weren't sure how that had happened but we regapped the plug and ran the engine again, but saw the same performance. After pulling all the plugs a second time and finding no further issues, I stuck the timing light on each individual plug wire and found that the #2 cylinder was sparking erratically. We felt this could be a number of things but one was the plug, so we replaced the #2 plug, and this solved the problem. The engine ran the same. Next I checked the resistance of the plug wires, and holy cow they were high, measuring something like 600 ohms each. I had a new set of wires on hand, and I checked one of the long ones for resistance; it measured only about 150 ohms. So, I spent an hour and a half building a completely new set of plug wires for the engine. Again, the engine ran the same.
It was becoming harder and harder to dismiss the idea that the sheet metal intake was the cause of the poor performance. Scott had gone over the datalogs multiple times, looking for drop outs in the crank trigger signal that would indicate a problem, or some other issue. For a while we thought it was a voltage problem, because on a couple of the pulls the battery voltage dropped down to 11.5V or so. We let the engine sit while the charger worked on the battery after this, and the voltage came back up to 13+ on the next pulls and still the engine missed and was way down on power. We looked at the exhaust gas temps to see if we were losing any particular cylinder, but the miss did not appear to show up as an erratic EGT. One thing Scott did notice in the datalogs, though, was the MAP sensor that the EFI system uses to monitor manifold vacuum was bouncing around a lot. This indicated that there was a lot of turbulence and buffeting inside the plenum of the intake.
The intake was not set up in the ideal fashion. I had designed it so that I could add internal pieces to increase the runner length, and also add spacers to the plenum, in order to modify the runner length and plenum volume parameters for test purposes. We had reached the point where I would have been ready to add length to the runners, or volume to the plenum, or both, but the machined pieces required for this were not ready; I just hadn't had time to build them yet.
The final pulls we made on this intake were 4000 to 6000 RPM, and at 6000 RPM the manifold would make just over 700 horsepower. My Hilborn setup last summer made 910 HP at 6000 RPM, so this manifold was, apparently, way way down on power compared to the Hilborn setup. I didn't understand how this could possibly be right, but we could find no other problem with the engine. Scott and I had dinner with my family and then he took off to find a hotel; we had decided to switch back to the Hilborn setup on Sunday. I went back out to the shop and took sheet metal intake off the engine, and scraped the gaskets on the engine and on the Hilborn intake to make it ready for installation on Sunday morning. I worked until midnight, hoping that Sunday would bring better results.
I was out to the shop this morning by 8:00 with a big cup of coffee and a fair amount of ambition. After making a final inspection of the engine and manifold I bolted the Hilborn unit in place, using my last set of intake gaskets. Next a spent a couple of hours transferring the fuel injectors and lines, throttle linkage, and all the other bits and pieces from the sheet metal intake to the Hilborn setup. This is always more complicated than it seems that it should be, but about the time Scott arrived at 11:30 this morning I was close to being ready to go. Finally a little after noon we fired up the engine with the Hilborn setup. We noticed right away that the engine sounded a lot better. We had been unable to get it to idle under 1000 RPM with the sheet metal intake, but with the Hilborn setup the engine settled right down into its normal 800 RPM idle. It sounded crisper and cleaner when revved also.
We ran a low RPM test pull and had one minor miss during the pull, which looked like an overly rich condition according to the A/F data. Scott made a minor correction to the map and we ran a 4000-6000 RPM pull. The engine sounded like a million bucks, ran with no misses, and seemed to be its old self. The power data, though, was a huge disappointment; 750 HP at 6000 RPM. What the hell was going on?
We double checked a bunch of things, and then I got the big clue. I glanced at the sight tube at the front of the oil pan, and it didn't look right. A close inspection with a flashlight revealed what I was afraid of - water in the oil! I knew right away we were done on the dyno for the day. I had previously experienced a lot of problems with getting the Hilborn intake to seal properly at the water jacket, and my first thought was that I had an internal water leak at the manifold that was polluting the oil in the crankcase. This might not have been a big deal, except that I had no more intake gaskets for the engine, so I couldn't change gaskets and try again. Of course, the intake had seemed to install pretty well, and there had been no topside water leaks at the intake, which is what I had seen before. Hmmm, maybe a head gasket?
We decided to do a leakdown test. I started at number four, pulled the plug, and the leakdown reading seemed OK. Went to #2, and saw the same thing. Went to #6, and the same thing. This didn't seem to be leading anywhere.
Everything changed when I went to number 3. Leakdown was 30%, which wasn't all that alarming, but I heard another source of air from cylinder #4! I stuck a screwdriver down through the opening in the valve cover and into the spark plug hole for #4, and the pitch of the air leak changed. Sure enough, I was injecting air into cylinder 3, and it was coming out of cylinder 4. I had a bad head gasket.
I continued on by pulling the remaining three plugs from the left side and checking leakdown on #7 next. Here again leakdown was around 30%, and this time I could hear air coming out of the spark plug holes for #8 and #6! TWO bad head gaskets!
At this point we were pretty sure we had found the source of the problem. This engine has a custom bore spacing, 4.700" rather than 4.630" like a standard FE, so it requires custom head gaskets. These are copper head gaskets, and of course copper head gaskets eventually work harden and will start to leak. These gaskets are only a couple years old, but it looks like since the last time I ran the engine things had changed, and the gaskets were no longer sealing the combustion chambers. Obviously they were not sealing the water jackets anymore either, resulting in the water in the oil I had observed in the sight tube. There was no catastrophic leak in the combustion chambers such as what would be found with a burned head gasket, but they were allowing enough crosstalk in the cylinders to rob power from the engine, to the tune of 20% or so. And we were getting fooled because the engine still sounded OK and ran pretty well with the Hilborn setup; it just didn't make the kind of power it was capable of.
So I'm going to have to break the engine down, pull the heads, and replace the head gaskets. This would be no big deal, except for the time constraints I'm under to make Drag Week. Last time I got the head gaskets it took me a week and a half or so to get them specially made. The intake gaskets are also custom, from Cometic, and will take at least a week to make. Plus I should get the heads planed as long as I have them off and am replacing the head gaskets, and that might take a few days. So it seems like in the best case it will be another couple weeks before I can reassemble the engine and run it on the dyno.
Some good came out of the weekend, however. The missing that I experienced from the sheet metal intake indicates to me that I shouldn't proceed with running that intake yet; it needs further development. Also, at only 700 HP at 6000 RPM I was thinking the sheet metal intake was a "steaming pile", but since the Hilborn setup only made 750, the sheet metal intake doesn't seem so bad after all. I had originally figured that the sheet metal intake would make less power at 6000 RPM than the Hilborn setup, and that hopefully it would peak in power at a higher engine speed than the Hilborn manifold and therefore make more average power from 6000 - 7500 than the Hilborn setup. It may still be able to do that, but I'm out of development time, so when the engine goes back together its getting the Hilborn manifold.
I spent the remainder of the afternoon and evening finishing up the welding and fabricating on the car's gas tank; it is now ready for leak checking, and I should be able to install it this week. I'll probably get the gaskets ordered Monday, tear the engine down during the week, and spend next weekend working on the car. I was hoping to get the instrument panel built and installed next weekend, so we'll see how that goes. I'll post another update next weekend.
