'76 Bronco 302 Engine Swap
Several years ago, my brother Andy bought a stock '76 Ford Bronco with a 302 V-8, C4 auto tranny and Dana 44 & 9" axles. It ran well for him for a while, and acquired a forest green rattle can paint job after some shoe-polish lettering got baked on for a week after his wedding. Unfortunately, Andy wasn't exactly what you'd call a gear head. He thought he was checking the engine oil regularly, but it turned out he was actually checking the tranny dip stick instead (good thing he never needed to add any oil). Eventually, he ran the engine completely out of oil and it seized up on him.
About that same time, my grandparents had an accident in their '82 Mercury Colony Park station wagon. The vehicle was totaled, but the 302 V-8 was still good, so they said Andy could have it if he wanted to put it in his Bronco. Convenient, huh?
I wasn't much of a gear head myself a year ago, but I've been learning quickly in an effort to build up my '95 Jeep Wrangler. At the time of this writing, I know just enough to be dangerous. Andy couldn't afford to pay a professional to swap engines for him, so I offered to help him do it. My father-in-law repairs motor boats for a living, so I borrowed his engine hoist during the slow season. For some strange reason, we decided to begin the task on our parents' driveway in November '97. Keep in mind this is in Nebraska, where we get real winters. Progress has barely crept along since decent weather, especially after work on weekdays, has been rare.
Before we began the task, I scoured the Net for information on what would be involved. The people on the Early Bronco Report (EBR) mailing list were a tremendous help. I was told that it should be a bolt in replacement, with the following exceptions:
- The oil pan on the Bronco is shaped differently than on most Ford vehicles, presumably due to axle clearance. The pan and oil pump from the Bronco would have to be kept when we brought in the engine from the wagon.
- The exhaust manifolds are tucked closer to the block on the Bronco than on most Fords due to reduced clearance in the engine compartment. The Bronco's manifolds would have to be retained.
- Due to engine compartment clearance issues, all the accessories from the Bronco and their associated brackets should be kept.
- The water pump output hose comes out the left (passenger) side of the Bronco, but the right (driver) side of the wagon, so the '76 water pump should be kept.
- The Bronco used V-belts on the main pulleys, but the wagon used the new-style flat, multi-ribbed belts. Which you use doesn't seem to matter much, but the pulleys on all accessories must obviously match those on the engine.
The first order of business was towing the the wagon from our grandparents' back pasture up to our parents' driveway. The accident had rendered the steering and brakes useless, which made the trip interesting. Tight turns were implemented by jacking up the front of the wagon with my Hi-Lift and toppling it over sideways. I almost learned the hard way that I needed to continuously accelerate when towing downhill so the wagon didn't catch up with me. It came an inch from tagging my rear fender at one point.
Most of the first day was spent stripping all the accessories off both engines. The Bronco was pretty clean & simple and took maybe two hours. The wagon was fully loaded with power everything and took for-bloody-ever to strip.
We couldn't loosen the bolts connecting the exhaust headers to the tail pipes. Since the headers needed to stay in the vehicles, we just unbolted them from the block instead and left them in place in the engine compartment.
We made the mistake of not labeling any of the wires and hoses we disconnected, relying only on our combined memory to hook things up right again. (Our dad has a '75 F-150 with a 302 we can use as a reference if needed.) This was probably a stupid move. The next time I remove an engine, I'll be sure to label everything with little tags of masking tape.
Another step we probably shouldn't have skipped is cleaning the engines before we tore into them. A 20-year-old engine gets pretty messy to work on. Half an hour with a good, spray-on degreaser and a garden hose would have made the job easier.
We hit our first brick wall when attempting to remove the engine from the Bronco. Since the crankshaft had seized up, we couldn't rotate it to get at all four bolts holding the torque converter to the flex plate. We had to lift the engine just a hair (high enough for the oil pan to clear the front frame cross member) and slide the whole engine and converter forward until the converter cleared the tranny input shaft and bellhousing. Be sure to jack the tranny up as well to avoid putting undue pressure on the input shaft and torque converter.
Once out, the nuts refused to come off the converter connecting bolts, so we initially left it on the old engine while we dropped the new engine and converter (which were trivial to remove from the wagon as separate pieces) into the Bronco. Swapping the oil pans on the two engines was simple--just unbolt the pans, remove the pumps, scrape the old gaskets off the mating surfaces, and then reverse the process with new gaskets. Be sure you drain as much oil as possible before you remove the engine from the vehicle. Because the old engine had been run dry, there was merely a thick layer of tar-like crud on the bottom of the oil pan. We used WD-40 and some flat sticks to scrape the old pan and pump as clean as possible before putting them on the new engine. Since the old pump was so messy, we tried hard to use the new pump in the old pan on the new engine, but it just wouldn't fit. The old pump hand to be thoroughly cleaned and reused.
We had originally planned to make the new engine V-belted to match the alternator and power steering pump from the Bronco. Unfortunately, the flat-belt pulley on the new engine bolted to the balancer wheel with four bolts, while the old V-belt pulley only used three bolts. We could have hunted down a four-bolt V-belt pulley from a junk yard, but since the alternators were otherwise identical, we decided to swap pulleys on the power steering pumps and make the whole engine run off the new flat belts. We haven't verified yet if things will still line up, so we may have to switch back later on. Removing and attaching power steering pump pulleys requires a special tool. Most large auto parts places (like Parts America & Pep Boys) will loan these out for free with a refundable deposit ($50 in our case). Andy found an interesting position from which to remove the pulley from the wagon's power steering pump.
This is where our automechanical ignorance started to show through. We got the new engine almost completely bolted in when we noticed that manually turning the crankshaft produced a nasty clunking sound inside the bellhousing. After yanking the new engine from the Bronco again, it became obvious that the wagon had an entirely different tranny than the Bronco's C4, and the torque converters weren't interchangeable.
After lots of liquid wrench and elbow grease, we finally removed the nuts connecting the old converter and engine. When we tried to put the old converter on the new flex plate, we found that the newer converter and its corresponding flex plate bolt circle were an inch wider than the old converter. No problem, we figured we'd just grab the old flex plate with the correct bolt circle and put it on the new engine. It fit fine, so we dropped the new engine back into the Bronco a second time.
For some unknown (at the time) reason, the engine wouldn't get closer than a quarter inch from the bellhousing. Andy thought the two flex plates were different distances from the engines, so we yanked the engine a third time. It turned out that the flex plates were identical depths, and that the converter just wasn't shoved securely against the tranny. Rotating and pushing a bit made it drop back where it belonged.
Since we had the engine out and accessible again, we swapped the water pumps at this point. The gaskets and mating surfaces were identical, but since the output hoses were on different sides, not all of the bolt holes were in the same places. We just put in as many as we could and called it good. We also had to permanently remove a useless-looking plate that covered part of the balancer wheel (we did reinsert the bolts), and we had to temporarily remove the crankshaft pulley in order to slop part of the water pump back in behind it. Be careful you don't tighten things down too hard or you may crack one of the bolt mounts.
Things looked good finally, so we dropped the engine into the Bronco a third time. It fit flush against the bellhousing, and there was no nasty clunking when rotating the crank shaft (yeah!). It was starting to get dark, so we didn't bother bolting it in yet. Unfortunately, up on consulting the EBR list that night, I found that the two engines had a different imbalance (Ford switched from 28 oz to 50 oz in '81), so the flex plates were not interchangeable after all, which means yanking the engine a fourth time. It looked like we'd have to either redrill new converter bolt holes in the '82 flex plate or have the '76 flex plate rebalanced to match the 50 oz weight from the '82 engine. We opted for the latter route, and had it done for $50 by John Larson, a retired machinist that was recommended by several local parts stores.
We put the flex plate back in and partially assembled the engine yet again in January, only to find that the water pumps were somewhat different between the two engines, and had their intake & exhaust hoses on opposite sides. One pump & pulley was also longer than the other, which caused clearance problems with the radiator. By this point, my brother had lost interest in the project, and was planning to move out of state soon anyway. We abandoned the project (and the funds that I'd put into it thus far) and left the Bronco to sit on our dad's driveway. In June, my dad sold the Bronco and the bin of parts to someone for $500. I wish him luck on the restoration.
Costs involved (most from Parts America):
|Water pump gasket||$1.69|
|Oil pan gasket||5.00||+/-|
|Exhaust manifold gaskets||5.00||+/-|
|Five quarts of motor oil||5.00||+/-|
|Pulley puller||49.99||refundable deposit|
|Flex plate rebalancing||50.00|
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last updated 15 Jun 98 Obi-Wan (firstname.lastname@example.org)