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Ford Mustang Short-Block Engine Rebuild - Squaring Away Your Short-Block
Our Recession Special Short-Block Takes A Trip To The Machine Shop.
Our recent budget-minded engine overhaul was a smashing success with readers, and we have received plenty of emails and letters to prove it. As this is written, they are still coming in. We did, however, uncover a problem in assembling the engine, and it was one that we had before, but hadn't given thought to until it happened again.
Years ago, our Recession Special bullet resided in project ProCharged Pony. The '90 GT started out with a P-1SC supercharger, and it wasn't long before the high-mileage colt gave up the gasket. It pressurized the coolant system with combustion gases, and even a swap to new gaskets and cylinder heads eventually lead to another coolant eruption. It wasn't until we dropped in a new short-block from DSS Racing complete with wire O-rings that we put our gasket problems behind us.
Six years later, we dusted off the old 302 to breathe new life in it with a budget rebuild at home. We topped it off with a killer set of ported stock cylinder heads and a very nice Crane camshaft with just the right amount of rumble, and it made a respectable 249 rwhp and 293 lb-ft of torque. Problem was it started pressurizing the coolant system after just a couple dyno pulls. The heads had been milled, and the factory graphite gaskets we used should have done the trick, but once we saw it pushing coolant, we instantly remembered the engine's past problems. We weren't sure if we had torqued the cylinder heads to the required 75 lb-ft on the short studs and 85 on the long studs, so we opted to change the gaskets out and proceed with our next plan, which was to add some boost from a B&G Turbo system.
Four dyno pulls later it was spilling coolant on the ground yet again. Enough was enough. As much as we hoped there would be a relatively easy solution to this reoccurring problem, it didn't look like any of the easy answers could guarantee a proper gasket seal.
Ask any number of engine builders and you'll get as many different answers on how to solve the problem, but one thing all of the people we surveyed agreed on was that we needed to start with a level playing field. That being said, the motor was pulled back out and torn down to bare bones so we could have the deck surface machined flat.
From the foundry, production blocks feature a fair amount of leeway when it comes to tolerances. The extra time and money spent in producing a more accurately machined block can more easily and cheaply be made to work through the use of forgiving gaskets. The problem is that when you start to change the hard components, those loose tolerances can become a bigger problem.
To square up our little 302, we dropped in on Scotty Guadagno of Scotty's Racing Technology in Spring Hill, Florida, to see what he could do for our Recession Special. Obviously any time you involve a professional in your project, it's going to cost money. However if you limit yourself to only getting the essentials, you can save money while still getting what you need done. It also depends on your machine shop and how much they are looking to sell you on machine work.
Our man Scotty Guadagno spends the majority of his time assembling 10.5 Outlaw, Drag Radial, and Pro Mod engines, so taking care of our little 302 street engine was fairly easy for him to handle. In fact, he was at ground zero of the New York/New Jersey 5.0L movement when it began back in 1986, and accumulated a wealth of experience as his customers were consistently pushing the 5.0L envelope. When we told Guadagno of our cylinder head sealing problem, he agreed that milling the deck was the solution and suggested we make a slight modification to the cylinder heads as well.
When it came to machining the deck surfaces of the block, that was really only half of the equation. In measuring the deck height between the two cylinder banks, we found a couple thousandths-inch difference from one side to the other. The driver side measured in at 8.208 inches, and we shaved .003-inch to clean it up. The passenger side measured 8.204, so to square up the block, both sides were cut until we reached 8.202-inch.
With the block surfaces taken care of, it was off to the hot tank for a quick bath to clean out all of the metal shavings. Guadagno removed the rearward oil galley plugs to make sure no particles were left hiding in the shadows, and commented that a lot of engines are ruined because people don't remove them and clean that area out. Next up were the cylinder heads.
Prior to deciding on our block machining, we researched the various head gasket options available to us, mostly because we thought-as did some others-that the sealing problems could be remedied by using this gasket or that. Word was that a multi-layer steel gasket should fix it, but that the deck surface needed to be ultra flat, which was something we didn't have at the time. Graphite gaskets had worked for us in the past, and that's what we were running, but the coolant was circumventing the gaskets. Copper gaskets aren't really an option for street cars, so another option was lock-wire-style gaskets. When it came time to decide, we opted to go with what Guadagno recommended, which was the Fel Pro Lock-Wire gasket combined with a machined receiver groove in the cylinder heads.
Fel Pro actually makes two different lock wire gaskets, with each one having a different thickness of wire. The thicker of the two (PN 1006) is designed for use with the machined groove in the heads. After mounting the cylinder head in a fixture and cleaning up the surface with a file, Guadagno mounted the tooling plate and then began cutting the grooves around each chamber. The groove is only .010-inch deep, but when compressed between the head and block, it sandwiches the gasket and lock wire nicely.
As we mentioned before, professional help with anything can be expensive, but by doing your research and setting goals, you may be able to keep costs down while getting the job done. Machining the deck surfaces of our block totaled $175, while the cylinder head modifications came in at $250. Another $50 for the hot tank, which was more than worth it, and we left without our wallet smoking. Keep in mind that most of the machines in an engine shop cost tens or even hundreds of thousands of dollars, and it's easy to see why the work costs as much as it does. If the $475 keeps us from pulling the engine out again, though, we consider it money well spent.
Since our editor was bombarded with emails regarding the Recession Special, we thought we might query our readers to find out what they would like us to do with it. We have plenty of ideas and plans, but we'd like to hear what you have to say. You can send your suggestions to firstname.lastname@example.org. We've noticed that the car is running a little warmer than it used to, and we're thinking that the thick intercooler is restricting the airflow to the radiator, not to mention the air will be a little hotter having extracted the heat from the intercooler and the A/C condenser. So we may be looking for a low-buck cooling upgrade. We're also going to play with our Turbosmart eBoost 2 controller and get the car to the track to see what our 2.73-geared daily driver can do with 420 rwhp and 468 lb-ft of torque.