Preparing for Engine Overhaul

Preparing for Engine Overhaul

May 13, 2015 – Engine overhaul decisions

With the body at the blasters and out of the garage, I’ve turned my attention to the motor and transmission.  Because one depends directly on the other, and because many of the components the go with the transmission need to be balanced with the motor, I need to think about them as a unit.  I’ll be using a BorgWarner T5 transmission I bought from Craigslist, which will easily bolt up to my 289 with minimal effort.  I’ve gone ahead and ordered all the transmission conversion kit parts, as well as a rebuild kit for the transmission, so that I can have the essential components ready to go for the engine rebuilder.  Because the Ford 289 is an externally balanced engine, the machine shop will need the flywheel and the clutch cover when they balance the motor.  Balancing is one of the key steps to any engine overhaul; when it’s done correctly a motor will spin super smoothly.  Balancing, in essence the process of making sure that the crankshaft counterweights exactly match the weight of the piston assemblies, doesn’t really affect performance unless the motor is super unbalanced, but it is a huge factor in determining the longevity of an engine.  A poorly balanced motor will literally shake itself apart.

The T5 5-speed swap is a very popular conversion for early Mustangs because it makes them more drive-able.  Unlike the factory top-loader, it’s an overdrive transmission, so the engine will turn fewer revolutions on the highway, which also increases top speed.  And with a high numeric ratio first gear, the car will be pretty quick off the line.  My rear-end ratio change takes into account the gear ratios of this particular transmission, so I’ll hopefully get the best of both worlds— better fuel economy and better performance.  While the engine will be getting a professional rebuild, I’ll be rebuilding the T5 myself.  Stay tuned for that update…I’m sure it’ll be a barrel of laughs and bloody fingers.

When I bought the T5 from Craigslist, the same guy was also selling a complete 289 motor.  I didn’t pay much for it, but I figured even if it’s toast, there’s something salvageable in it, and if nothing else, it’ll be a good practice motor to fool around with.  After pulling it apart, I measured the bores and found the block is already bored .040 over, but there’s still a crosshatch pattern in the bores, so it may be usable as-is.

Unlike the body work decision, I only ever made one call when searching for a rebuilder.  Jim Grubbs Motorsports (JGM) was my first and only choice once I decided I’d have the engine rebuilt professionally.  At one point I’d considered having the block machined and then doing the assembly myself, but after thinking through what I want to do with the engine and how I want it to perform, I came to the conclusion I’d need to deviate from the stock configuration.  Going away from stock is something best left to experts, and Jim Grubbs and his team at JGM are definitely THE experts.  If you’ve read many engine build articles in Mustang Monthly, chances are you’ve followed a JGM build.  George Reid’s How to Rebuild the Small-Block Ford follows a JGM build as well.  Between the Craigslist motor and the already-once-rebuilt motor I pulled out of the car, I’m hoping we can make one good engine.  With two of everything to choose from, I’m thinking we’ll be able to pick the best of both motors rather than having to make do with what comes out of the existing motor.  Of course, the decision of which crankshaft is better, which block is better, which heads are better, etc. is best made by a professional machinist.  With that in mind, I threw both assembled blocks in the back of my truck and headed out to Santa Clarita to meet with the guys at JGM.

Had I spoken to them on the phone first, I would’ve saved a trip, but I wanted to visit the shop and chat in-person, so it wasn’t really a wasted trip.  When I got there, I met with Ryan, who took a look at what I had in the bed, chatted with me briefly, and saved me several hundred bucks right there on the spot.  His first question was, “are you sure you want to have us blow both blocks apart?” I said I was happy to disassemble them myself but that I didn’t want to get parts mixed up.  He smiled and said small block Ford engines are like cookies to a housewife, they could almost put them together with their eyes closed; I could throw everything in a box and they’d be able to put it back together no problem.  So I got to drive right back home with the engines, no big deal.  But what really made the trip worthwhile was that I got to meet Mustang expert Jim Smart while I was out there.  A former editor of Mustang Monthly magazine and now a freelance contributor, Jim was out there working on an article and was following along with a build Ryan was undertaking.  He was totally down to earth, and he seemed like a great guy.  I could’ve talked to him for hours.

So the next task is to pull both blocks apart and then make some decisions!  Since I’m doing the dis-assembly myself, I’ll take the time to carefully measure critical wear areas and really see what kind of condition the engine that came out of the car is in.  Given my findings from the partial tear down (remember, I only pulled one head and the oil pan last time), I’m still not sure this engine will actually be worth spending thousands of dollars to rebuild.  We shall see!