My dad stopped by again this morning and we wrapped up the engine assembly. We ran the oil pump for about three minutes with a drill and spun the motor over a few times with the starter (without plugs) to make sure oil was nicely distributed throughout the engine.
The moment of truth arrived and we fired up the motor. Success!!! The motor sounds fantastic. Nice and smooth, and no knocking!
We kept the exhaust pipes outside of the garage to limit the exhaust inside. We pushed the RPM up to about 2,500 and let it run for about 30 minutes to help seat the rings.
After shutting down, we pulled the car back into the garage and put the car back on the dolly. Since we’re still in the middle of our remodel, we likely won’t make much progress on the car over the next few months, but I’m incredibly pleased that this is behind us!
My dad and I stopped by Dino’s shop this morning to have him balance our new piston and rod. While our piston was lighter than the old one, we lucked out and the new rod was slightly heavier on the small end. There’s still a small imbalance, but Dino said that it’s more important that the rotating mases are balanced than the reciprocating masses. He also loaned us his tapering ring compressor which makes piston installation far easier than with the traditional ring compressor
We got back to the house and made quick work of getting the piston into the block and installing the bearing cap. We turned the motor over a couple of times to make sure everything was moving smoothly.
We installed the newly painted oil pan, then installed and torqued the heads. I hadn’t yet adjusted the guide plates on the new cylinder head, so we spent a bit of time ensuring that all of the rocker rollers were nicely centered over the valve stems. Finally, we installed the intake manifold and cleaned up the sealant. We can’t run the motor until that sets, so that was a good time to stop for the day.
I cleaned the oil pan and painted four coats of the same Eastwood high-temperature ceramic engine paint that I’ve used on the rest of the engine. I put on some extra coats here because this is likely to take more abuse from road debris than the block or heads.
I received the new piston from Ford Racing (on the right). Unfortunately, it’s 9 grams lighter than the piston it’s replacing. We’ve been told that we need to get the rod/piston assembly within 2 grams, but we’ve also heard that it’s important to get each component as close as possible as well. We’ll check with Dino about whether this will work or we need to order a replacement.
Since our connecting rod was slightly twisted, we decided to order a new one. My dad took care of talking to Ford Racing and Scat about exactly which part to order. That led to an interesting conversation about the piston and connecting rod weight. I weighed the existing rod, and Scat manager to find one that is very close. However, they mentioned that it was important to get the combined weight of the connecting rod and piston assembly within 4 grams of the old weight (preferably with 2 grams).
I was concerned that I couldn’t get an accurate weight from the old piston since I ground some of the damage off and additional wear had occurred on the side of the piston. However, when I flipped the piston over, there was a number written on the bottom that looked like it might be the weight.
I weighed the piston and it was significantly heavier than the number written on the bottom. I figured the weight must be without the piston rings, so I removed as much as I could. There was 2-3″ of the top two rings stop stuck in the piston, but this brought the weight down to 439 grams, so 433.5 grams must be the weight of the bare piston.
While I have the oil pan off, I decided to go ahead and paint it black to match the engine. I spent awhile cleaning out the inside and scuffing the outside with a scotchbrite pad.
We put the Cobra on the lift and dropped the oil pan. After removing the connecting rod bolts, we removed the bottom of the connecting rod and pushed the piston out of the top of the cylinder.
It’s pretty clear that the piston was more damaged that it appeared from the top. This is the bottom edge and it’s pretty well worn above the compression ring. It’s also pretty scored on the skirt. Worse though, both compression rings were pinched in the groooves.
This is the top edge of the piston. You can see wear above the compression rings and scoring on the skirt. The compression rings are also pinched on this side.
In the area the pistons are worn, there is some polishing of the cylinder wall. You can’t feel this with your fingers, so it’s just some microscopic surface polishing. We’ll need to add the cross-hatching back, but that should be pretty straightforward.
It’s pretty hard to see in this picture, but the lower side of the cylinder has similar polishing, but you can slightly feel the polished area on this side. There are no grooves and I think what you can feel is well less that 0.001″.
We dropped by Dino’s shop to have him examine the piston and connecting rod. He showed us how to remove the piston and checked the connecting rod for damage. He suggested we use some 400-600 grit sandpapaer to add the crosshatching pattern back to the cylinder wall. I protected the lower end of the engine as well as I could with aluminum foil and masking tape, then used some 400 grit sandpaper soaked in solvent to add the crosshatch pattern back. I made some good progress on the lower side, but I can still feel the polishing area slightly.
After thoroughly cleaning the engravings with some solvent and a toothbrush, I put some of the of the engine paint over the engravings until I couldn’t see them. After letting it set up for a couple of hours, I used a solvent-soaked q-tip to remove most of the excess paint. I didn’t want do too much at this point since the paint is still soft.
After letting the paint cure overnight, I used more solvent-soaked q-tips to remove the rest of the excess paint. This technique works wonderfully and the engraving really pops.
Even though we’re essentially certain the heads are fine, we still had one head with known damage from the nut going through the engine. It just turned out not to be on the side where he was adjusting the lifter. Since we had already ordered a replacement head, I could either return that or replace the damaged head. I decided to replace it.
I spent a couple of hours tearing down the right side of the motor tonight until it was at the same place as the left side.
I cleaned and masked the new head, then sprayed several coats of Eastwood’s high-temperature ceramic engine paint in gloss black.
Since we’ve eliminated every component of the valve train, the only other place the noise could be coming from is the bottom end of the engine. We know the top of the piston in cylinder #6 was heavily damaged by the nut, and it’s possible that it broke a ring or damaged the area around the wrist pin from the excessive forces of hitting TDC with a nut trapped in the cylinder’s squish area.
We called Ford Racing about this to get the part numbers for the damaged piston and ring set. They needed to have someone from another department look that up and told us they’d get back to us. Today, we got a shipping notice from Ford saying the parts will be here next week! No charge, apparently!
We need to pull the oil pan to remove the piston, and we can’t pull the oil pan with the chassis sitting on the car dolly, so we’re going to move the car over to the lift this weekend so that we can easily access the underside and drop the pan.
I drained the coolant out of the block and pulled the intake manifold…
…then pulled the head. I had forgotten that this head was the one that was originally on the right side of the engine (and not the one that was more significantly damaged when the nut went through the engine). That makes me suspicious that the problem is not in the head. Given that we’ve eliminated everything in the valve train, there’s not much else that could be causing this problem.
Work on our home remodel has taken virtually all of my spare time, but my dad and I have continued to speculate about what could be causing this noise. One thing we wished we had done when Dino got the noise to disappear the first time was swap the lifters between the suspect valve and another one. We got together a couple of times and tried to eliminate the noise again, but were unsuccessful. Dino offered to stop by again, so we took him up on the offer. He adjusted the lifter preload again with the engine running and managed to eliminate the noise again. Not too surprisingly, it was on exactly the same valve; the #6 intake valve.
We pulled the rocker and carefully examined it and the corresponding push rod. Not seeing any issues, we adjusted the #6 piston to TDC and used a spring compressor to remove and examine the spring and valve. Not too surprisingly, everything looked great.
Dino’s pretty convinced now the problem must be in the head. It’s clear that the problem is localized to the valve train and we’ve eliminated everything but the valve and guide (or potentially a crack in the head itself. We have a new head on order, so I started pulling the engine apart.
I didn’t have a lot of time tonight, but I pulled the remaining rockers and push rods as well as the side pipe and exhaust manifold. I also pulled the air cleaner and distributor. Once I drain the coolant out of the block, I’ll pull the intake manifold and head.