[ericandape]

Hey Guys,

I'm going to be purchasing a 1955 Chieftain from a my sister-in-law in about a week or so and have a fairly simple question. It has the original 287 in it and I'm thinking that's not nearly enough engine for a car this size. I was checking out the forums and saw that if I upgraded to a 1960 389 engine that it would bolt right in. The car has the original 2 speed Hydromatic trans in it. I have 2 questions, first does the 1960 389 really bolt right in to the current motor mounts and second, would I have major headaches mating the 389 to the current transmission or would I be better off getting a 389 with it's original transmission to avoid any mating problems? Thanks for your help in advance!

[poison heart]

I think most pontiac motors will bolt in IF you use the 55 style mounting. I think the 55s had front and rear mounts instead of the 2 side mounts.

I think all hydromatics were 4 speeds. I think yours is a dual range. Your trans will bolt up to any block up to 1960. 1961 the bolt pattern changed.

You should come up with a lot better answers than I gave but I think most of my info is correct.

[Bill Hanlon]

Putting a '60 model 389 into a '55 is easier than a lot of swaps, but does require a little work. See these web pages about swap problems at the front, driver's side
http://www.pontiacsafari.com/L1Garag...eID/index.html
and rear of the block.
http://www.pontiacsafari.com/EngineCooling/index.htm

[Jack Gifford]

Originally Posted by ericandape

... The car has the original 2 speed Hydromatic trans in it. I have 2 questions, first does the 1960 389 really bolt right in to the current motor mounts and second, would I have major headaches mating the 389 to the current transmission...

Welcome- I hope you'll enjoy that '55!

I've done this type of swap a couple of times. As stated above, your car has a slant-pan DualRange Hydramatic, which is a great transmission if it's in good shape. Do you know the condition of it? They've gotten to be very expensive to repair or rebuild.

Mounts- the two rear mounts bolt to the transmission. The '55 front mount will bolt right up to the '60 timing cover.

If you want the engine to appear original (reverse cooling), use the "front end" of the '55 engine on the '60- timing cover, hoses and elbows to the heads, and distribution tubes in the heads. You'd also need to do a little drilling on the '60 block to make it functionally like the '55- two new holes behind the timing cover, and enlarge a few (six?) coolant holes on the block's decks.

Flywheel- yes, it's a heavy steel FLYWHEEL, not a flexplate like modern automatics use. As the Safari site points out, the '59 and later crank flange weights do interfere with the forward face of the flywheel- only by about 1/16", but it needs to be taken care of. I prefer to trim the crank's weights, rather than cut the flywheel, but this mandates engine disassembly in order to rebalance the crank. When I've done this, I've also given the shop the flywheel and torus cover so they can balance everything. As long as they've got all the pieces anyway, I've had them use their crank lathe to cut a small bevel on the outside-rear of the crank flange, just enough to clear the flywheel.

As if I hadn't already talked too much- here's why I don't like cutting the flywheel-
the whole flywheel and torus cover assembly is cantilevered off its mounting on the crank. This is a totally different concept from other automatics, in which the location of the rear of the torque converter is intended to be provided by the transmission's front pump. Pontiac had good reason for making the flywheel of high-tensile steel approximately 3/8" thick, and I prefer not to compromise the flywheel's bending strength at all.

[stevep]

Just make sure to use sealer (not silacone) on the flywheel where it attaches to the crankshaft or you will have a transmission leak.

[Rocky 389]

I also ran into the crank-flange problem when installing my 60, 389 in my early 56 chieftain with the old dual range 4 speed hydro but I wasn't as smart as Pontiac Jack. I didn't realize the difference until after I had the car together and running.....[I had seen a buddy have the same problem in the late 60s with a 389 in his 55 safari but completely forgot about it]luckily I didn't ruin the front pump in the tranny. I was able to grind the back of the crank flange in the car with the transmission removed. I ground a bit, checked fit, ground a bit until the flange cleared the flywheel. I didn't have the engine rebalanced and was very wary of any engine imbalance....I didn't detect any vibration problems at all....just got lucky but in the future I'll damn sure get my balancing done after any crank machine work...

[ericandape]

First off. Thanks so much for the input! It definitely seems like a project I'm ready to tackle. A couple of answers to Jack's reply. I'm not quite sure what condition the transmission is in. I've driven the car a couple of times and the one thing I do remember is it does shift a little hard. I just chalked that up to the transmission needing adjustment.

I'm not stuck on keeping the appearance original so if I don't have to do any of the work to keep the "reverse flow" cooling intact then all the better. I'm mostly after two things, increased power and a better availability of aftermarket parts and going to site's like Jegs and Summit Racing I see much more availability in performance aftermarket parts for the 389, even the early ones.

Thanks again,
Eric

[Pontirag]

You will find that with a more powerful engine the factory tranny adjustment settings cause the tranny to shift kinda hard. there is a range of settings to which you can adjust your tranny to have it shift. You will want to read and understand the adjustment procedure very carefully. This is important because with a higher performance engine the tranny will have to be serviced and adjusted at more frequent intervals. Arnie bestwick used one behind a supercharged 421 and it lasted all season (the early 400's only lasted thru about 2-3 runs). Military tanks and trucks used themthru WWII and Korea. so they are pretty stout and durable but they need to be adjusted according to the manual and how you drive (or wish to drive ) the car.

[Safari Larry]

Here's a couple more things to consider.

If your '55 has power steering and you want to keep the original power steering, you may want to find a '59 engine rather than a '60 engine. The 59/60 difference is only in internal water flow through the engine and the front cover (timing chain cover and water pump housing). A '58 engine (370 cid) would also be a good choice if you find a good deal on one.

The power steering pump will not bolt up to either '59 or '60 front cover. But with a '59 (or earlier) engine, you can use the '55 front cover and be able to bolt up the power steering bracket. You must not use the '55 front cover on a '60 block -- unless you modify the engine block.

Another issue to deal with is exhaust. Your '55 exhaust manifolds will bolt up to the 59/60 engine and will work fine -- but the manifold inlet ports are smaller on the '55 manifolds and will degrade performance. The cheap way to match exhaust ports to the exhaust manifolds is to use 1957-60 manifold on passenger's side and 1957-58 manifold on driver's side. You'll then need to replace the exhaust pipes with larger pipes. For dual exhaust, you'll need to cut holes in the frame to route driver's side exhaust. Bolt-on headers are not available because of the tight clearance on drivers side between engine and steering box. Custom headers can be made but it is not an easy task.

Once you get your hot-rod going, the weak point will be rear axles.

[Rocky 389]

"Once you get your hot-rod going, the weak point will be rear axles"
But luck is with you again!..a '57 Pontiac/Olds rear axle will bolt in place in your 55 and it's really stout. There are a lot more gears and parts available for this axle also. You'll need to change the rear U-joint to the '56-57 style and it's possible the driveshaft may need to be shortened to compensate for the bigger rearend but I'm sure some guys who've actually done this swap will chime in with part numbers and info.
'57 axle shafts are not bullerproof tho. I broke a left axle in my 57 Pontiac with a '59 389/4 speed combo. Still a lot stronger than the 55 parts.

[MOJO Catalina]

I too have found a 1955 Pontiac I may buy. I have a 1960 Engine and trans that I may want to drop in it. My question is about the entire package. Will the 1960 389 and 4 speed SH trans and all mounts line up? The '55 engine and trans are still in the car but have not run in 28 years so I want to go with the engine and trans that I know are good. This is a 2 door post car that needs alot of work. I'm probably going to make a cool red and white Fire Chief type hot rod out of it if I can get the deal done.

[Bill Hanlon]

The '60 engine is designed to use two side motor mounts and a single tranny mount in the rear. The '55 used a single front mount (the holes are still there on your '60 timing cover) and two side mounts from the bellhousing. So it isn't a "drop in", but would be doable with new mounts.

[MOJO Catalina]

Since I would still have the 1955 engine and trans, can the mounts that are on that engine be transferred to the 1960 engine (provided they are useable)? Are the holes still in the bell housing on the 1960 like they still are in the timing cover? No transmission hump issues, trans mounting alignment or linkage snafu?

[poison heart]

The mounts won't be on the trans I don't believe but you should be able to transfer the front mount.

I know the '59 GMCs used the bellhousing and front mounts. I don't think it would be that hard to fab up a cross member to use for the rear and fab up some side motor mounts instead of the front mount.

[MOJO Catalina]

'Nother Question: Will the power steering unit that's bolted to my 1960 engine plumb into the 1955 steering box and make it work OK?

[Pontirag]

Most likely but even if not a good truck hydrualics shop can fab up a set. be sure to get the fittings correct and make sure the hose length and fittings are angled correct for your application. dont use aluminium fittings and braided stainless hoses they are not rated for that pressure.