As the title suggests, this is my first major engine rebuild. Naturally, I have a lot of questions and want to do this correctly the first time. I got this engine for free and was going to work on it when I had more free time, but the engine in my daily driver took a major **** so I’m getting to this sooner than expected.

As I’m waiting on the camshaft, I started redoing the main and rod bearings. I planned on reusing the OE pistons and installing new rings. However I might have an issue. I’m wondering if I have to get the cylinder walls bored out or if I’m good to go as is. I know these old 7.3s have an issue with cavitation and thus want to avoid boring it out more if I can. I asked the engine builder at my work if I needed to bore or if I could just hone. He told me to hone them then test with my finger nail, if it gets caught then I have to bore them out larger. Unfortunately I don’t have much in the way of finger nails right now. I’d ask him again but I won’t see him for a week.

the first image is the cylinders before honing and the second is after I honed them today. Will this be enough pitting to cause the rings to grab and fail prematurely?

 

I would borrow a mic and snap gauge and measure for out of round and taper or a cylinder dial indicator will tell you the same thing. What type of hone did you use? I am not real impressed with how it looks.

 

I used a ball hone. One of my buddies suggested I try again but this time lubricating with ATF instead of 0W-20.

 

This is the cylinders after I removed all the motor oil and rehoned with ATF as a lubricant. looking much better now. Thinking I should be good to go?

 

that looks much much better.

 

Yes, as @ihc1470 mentioned, you can measure the cylinder with snap gauges and a micrometer, or a dial bore gauge. If you bring it to your machinist and all the cylinders look like that he'll tell you if you can get away with standard sized rings.

 

I got the go ahead for installing the pistons with standard rings. All the rings went on without issue… up until the last one. Last oil ring snapped now I’m waiting on a new set supposedly coming in Thursday.

I went ahead and installed the remaining pistons + connecting rod bearing tonight. When I got to torquing the nuts, the third one snapped. I followed the workshop manual, oiled the threads then torqued to 75ft/lbs then 95ft/lbs. Didn’t even make it to 95 seeing as one broke at 75 so I stopped right there.

Any ideas what went wrong? What am I looking at to remedy this situation?

 

Are these new rod bolts or the old ones? Often it is recommended to replace rod bolts. Did the nut run down by hand or did it take a wrench. What does the service manual say about reusing the rod bolts? I know more questions than answers. Count yourself lucky that it broke now instead of when running.

 

If one of the connecting rod bolts failed you'll need a new one. Use this search engine to find an IDI in a salvage yard near you.

http://www.car-part.com/

You could ask your machinist if he can oversize the bolts for that connecting rod but it might throw off the engine balance.

 

They’re the original bolts, I think they’re pressed into the connecting rods. The workshop manual certainly doesn’t say anything about removing or replacing them before reinstallation. Everything went together smoothly. It broke when torquing with a wrench.

 

If the bolts are part of the connecting rod assembly, could I remove the same cylinder # piston from a different engine, install that rod in my engine, without needing to rebalance?

 

Your machinist is going to have to answer that. You'll have to measure the piston and crank shaft ends of the connecting rod from a parts engine and determine if it can be used in your engine. Did your machinist install oversized connecting rod bearings, or did he even see the connecting rods and pistons since you're assembling the short block,?

 

Just read through a different section and it’s showing some significantly lower torque specs for the same nuts.

 

I was looking at a site this morning that mentioned main bolts with a final torque of 95 ft-lbs they are a 1/2 inch bolt. The rod bolts were listed as 51 ft-lbs final torque. Those listed as 3/8 inch. Does that sound like what you have? If this is the case you better replace all the rod bolts as they will probably be stretched badly from over torque.

Where did you get your information from? Looks like they misprinted main bolt torques on the rod page.

 

That sounds about right. I got those specs from the Ford workshop manual. It’s the digital version of the ye old paper books. This is what we use at the dealerships for all the repairs because, you know, it’s published by Ford themselves. Based on the other page I read this morning, this does seem like it’s a misprint.