Identifying AMC/Rambler Gen-1 V-8s and transmissions

by: Cobalt327, Farna, Jon
(Click here to edit this page anonymously, or register a username to be credited for your work.)

Overview

AMC was formed in 1954 by the merger of Nash and Hudson, the engine wasn't on the drawing board until 1955. There are three generations of the AMC V-8 in all.

Note: "Gen 1" refers to the first family of V-8 engines (1956-'66), also called the "Nash", or "Rambler" V-8s. "Gen 2" refers to the second generation engines (1966-'70), and Gen 3 are the 1970-'91 engines. This is incidental to how GM engines are differentiated.

Bellhousing bolt pattern

The AMC GEN-1 V-8 has a unique bellhousing pattern. 1955 AMC built Nash and Hudson models and all but the 1956 Nash/Hudson Specials used a Packard V-8. The "Specials" were the shorter wheelbase/lighter weight Nash Statesman and Hornet Wasp two-door bodies with Ambassador/Hornet trim to make it easier on the 250/4V V-8, and to distinguish them from the Packard-powered big cars. AMC had a purchase agreement with Packard for V-8s and auto transmissions in 1955-'56. Packard was supposed to buy some parts from AMC but didn't, so AMC got ticked off and started making their own V-8.

The AMC Gen-2 290 cid V-8 appeared in late 1966 in the American, and across the board as a 290 or 343 cid engine in 1967. These use a different bolt pattern than the Gen-1. Pre-1972 inline sixes use a smaller diameter bellhousing (than the Gen-2/3 V-8s) with a bolt pattern shared only with the small 1950-54 Nash L-head sixes. All 1972 and later AMC inline sixes and V-8s use the same Gen-2/3 V-8 bellhousing bolt pattern.

Identifying size

There's only one way to tell from the outside whether you have a 250, 287, or 327 cid engine. The bore is cast into the right rear top of the block just behind the head. The 250 cid block has a 3-1/2" bore, 287 3-3/4", 327 4". Other than that you have to pull the head and measure the bore. Crank and rods are the same in all three: forged steel. The cast-in number is almost impossible to see with the engine in the car, so use a mirror and try to reach back there and clean it off enough to read it. Casting numbers are way over on the side and impossible to see with the engine in the car, but here they are:

• 250 -- 3153077
• 287 -- 3169824
• 327
  • 1956-'62:
    • 3144932
    • 3147230
    • 3153044
    • 3153055
    • 3153677
    • 440275
  • 1963-'67:
    • 3166463
    • 4160275

There may be others for the 250 and 287, but those are the only two I have. If you find another, let me know (farna@amc-mag.com)!!

Engine mounting

All early 250/327 engines have four-point motor mounts. Two in front of engine, two on the bellhousing. 1963-'67 327 and all 287 cid engines have side motor mounts on the block (and one near the end of the transmission) like newer cars. The early ones don't have the side mount bosses in the block, later ones have bosses for both mounting systems, but the forward most bosses may not be drilled and tapped.

Applications

The 327 was used in the 1957 Rambler Rebel, the 1957 Nash and Hudson big cars (no Ramblers) and all 1958-'64 Rambler Ambassadors. It was also available in the 1965-'66 Marlin and Ambassador. All 1957-'59 327 cid engines have Holley 4150c or Carter WCFB 4V carbs and 9.0:1 to 9.7:1 compression depending on application, as do all 1960-'66 4V models. The 1960-'66 base 327 has a Holley 2V carb and 8.7:1 compression. All 4V models also had dual exhaust. The carburetor is rather small at 450-500 cfm, which limits power somewhat.

The 250 was only used in the mid-1956 Nash/Hudson Specials, 1957 Rambler V-8 (other than the Rebel), and 1958-'61 Rambler Rebel models (I know, it can be confusing, but all V-8 Ramblers used the Rebel nameplate 1958-'61). Base 2V models have Carter WCD 2V carbs and 8.7:1 compression. All 4V models use a Holley 4150C carb with 8.7:1 compression and dual exhaust.

The 287 appeared in mid 1963. When AMC dropped the 250 there was no V-8 except for the higher priced Ambassador. Dealers complained, and AMC made the 287 available in the Classic in mid 1963. All factory 287s came with a Holley 2V carb, no 4V option. The 4V intake from a 250 or 327 bolts right on, however, and many people have done so.

Factory power ratings

Size	Years	Carb Type	HP @ RPM	Torque @ RPM
250	1956-'57	2V	190 @ 4900	240 @ 2500
	1958-'61	4V	215 @ 4900	260 @ 2500
	1960-'61	2V	200 @ 4900	245 @ 2500
287	1963-'66	2V	198 @ 4700	280 @ 2600
327	1956	2V	210 @ ????	N/A	Late 1956 big Nash/Hudson models only
	1957	EFI*	288 @ ????	N/A	1957 Rebel engineering prototypes only
	1957	4V	255 @ ????	N/A
	1958-'66	4V	270 @ 4700	360 @ 2600	With dual exhaust
	1958-'66	2V	250 @ 4900	340 @ 2600

*Bendix Electrojector. AMC decided it wasn't reliable enough at the last minute and pulled availability after much literature and between two and ten engineering examples were built.

Sources vary on the number built, only two can be verified; they showed up at Daytona Speed week in late 1956 where manufacturers were showcasing their new products. An Electrojector-equipped 1957 Rebel was the second fastest car in Daytona from 0-60 mph. It was beat only by a Rochester FI Corvette. It easily outpaced larger Hemi powered (354 and 392 cid) cars, but it must be pointed out that those engines were also in larger, heavier cars (a 1957 Nash Rebel weighed around 3400 pounds, a Chrysler 300C weighed 5000 pounds).

Performance upgrade options?

Not many! The 4V intake will bolt to the 287, which had no factory 4V option. The intake carb pattern is standard Holley, and because the 4150C used is only in the 450-500 cfm range (about right for the 250), it's easy to bolt a much more reasonably sized 600-650 cfm carb on the 287/327.

There are no intakes made, though I have seen a rare three deuce intake once, I think it was made by Fenton, but not sure. The AMC Gen-2 intake can be adapted by using a 1/4" spacer plate on each side and cutting the water cross-over (use the original cross-over, which is separate from the intake) and the rear section after the runners off. The ports aren't an exact match, but can be matched with the 1/4" plate. A small block Chevy intake can also be adapted, but the V angles are different and the adapter plates must match angle also.

The camshaft can be reground to a more aggressive profile by any of the camshaft manufacturers. Call first, then send in your good used cam for regrinding. In the mid 1990s Crower, Isky and Lunati had a few virgin blanks, they have probably been used or scrapped by now, but it never hurts to ask!

Headers By Doug sells a flange kit, but no one makes headers. The two center exhaust ports are siamesed, coming out of the head like a 1959-'67 Cadillac 390/429 V-8, or flathead Ford V-8. Sanderson makes a Cadillac header that could be converted by cutting the flange and slightly bending the tubes to match. I don't think the tubes are far enough apart on the flathead Ford V-8. Four-tube headers with the two center tubes right together (as seen on Ford Y-block and Chevy small block engines) can be re-worked by removing one of the center tubes and changing the flange/bending tubes. Sounds like a lot of work, but easier than building from scratch! Possibly 3-tube Pontiac V8 headers might be re-worked, but this has not been confirmed.

Transmissions

AMC used GM hydramatic transmissions in 1957 switching later to a Borg-Warner automatic transmission behind their Gen-1 engine. Only manual transmissions were used in the 1956 Specials. AMC called the GM automatic "Flashaway" and the Borg-Warner transmission "Flash-O-Matic". It's a three speed cast iron case Borg-Warner Model 8 with a vacuum modulator valve. The column shift quadrant will read P-R-N-2-D-1-L. The 1 and 2 are small.

A dash mounted push-button shifter mechanism was used in the Rambler 6 and Ambassador from 1958-'62. The American models used a column shifter. The push-buttons were marked N-R-D2-D1-L, with a Park lever under the dash. P-R-N are self explanatory. In D2 the transmission will act like a two speed. It starts in second gear and shifts to third, downshifts only to second. This was mainly used for slippery conditions such as driving in snow or ice. Using second gear prevented excessive wheel spin. Many people think they have a two speed transmission because this is the third forward position on the transmission. Slip it down to D1, however, and you'll find the missing gear! In D1 the trans shifts from first through third and back down. L (low) is first gear only, no up shifts. The trans can safely be shifted into Low at any speed. As a safety feature the trans will not shift down until it has reached a safe speed to do so. If in third it will got to second, then down to first once a safe speed is reached. It will not shift back up until shifted into D1 or D2. To manually shift through the gears start in L, shift up to D1 then as soon as the trans shifts, go back to L. It won't downshift if accelerating. When ready for third gear go back to D1.

1965-'66 models used a throttle valve cable instead of a vacuum modulator to control internal pressure. This is the M-10, internally similar to the M-8 except for the TV cable and valve body. The cable must be connected for the transmission to work correctly! Otherwise it will burn up like a cable equipped GM TH700R4 or a Chrysler transmission without the "kick-down" linkage connected. An electric solenoid inside the valve body controls kick-down (passing gear). A switch on the throttle linkage (usually on the engine) is activated at wide open throttle to force a downshift for passing, etc. It will not kick down over a certain speed, usually in the 60-70 mph range.

These are reasonably heavy duty transmissions. They are equivalent to a Ford-O-Matic three speed, which were used behind their 352 and 390 cid engines. In fact, they are nearly identical. Borg-Warner, Studebaker, and Ford formed a development team for an auto trans in the early 1950s and introduced one around 1953-'54. Ford contracted to buy 50% of their automatic transmission from Borg-Warner through 1958, and built a factory to build the other 50% on their own. That's why the same trans kit will work with Borg-Warner and several Ford auto trannys, BUT it is not a Ford transmission! The Ford transmissions should bolt to the AMC bellhousing, no one I know has tried since the older Ford transmissions and parts availability is about the same as the Borg-Warner units.

The only "problem" with these transmissions is finding someone familiar with rebuilding them, and that there are no performance parts. Most good performance torque converter shops can rebuild the stock converter, and should be able to change the stall speed. Some are busy enough with more familiar/popular transmissions that they don't work on odd-balls like this any more. The only other performance mod is to change the line and/or converter pressure valve springs. There are no springs made specifically for this purpose, but some have either stretched or shimmed the stock springs or replaced them with other springs they have found, but this takes some searching and experimenting, so be careful!

Parts are available from several old auto trans sources. Northwest Transmission (www.nwtparts.com), Fatsco (www.fatsco.com), and Dave Edwards (www.autotran.us) are good sources.

Kaiser Jeeps used a TH400 in Wagoneers and pickups from 1963-'67. It's the "universal" TH400, which was the Buick Nailhead model. Buick Nailhead engines have a deep flange on the back of the block, covering the flexplate/flywheel and require a shallower bellhousing than other GM engines. That shallow bellhousing left room to make an adapter without adding length to the engine/trans, so GM sold it as a "universal" model and continued production a few years after the Nailhead bit the dust. If you get one make sure you get the 1-1/2" to 2" thick cast iron adapter as well as the flexplate and spacer. The crank will need a pilot bushing to match the flexplate. As stated, a Nailhead TH400 will work if you get just the adapter. Rolls-Royce and Jaguar used the universal TH400, among other smaller makers who didn't need enough units to warrant casting a new case. If using another AMC sourced transmission behind a former Jeep 327 with auto, make sure the thin pilot bushing is removed first.

Manual transmissions used were from Borg-Warner. The 250/287 typically used a T-85 three speed and the 327 used a T-89 three speed. Overdrive was an option -- all V-8 overdrive models used the T-85 (even the 327). I'm not positive about input shaft length, but the bolt pattern is the same as other 1950s and 1960s Borg-Warner three speeds. The T-85 uses the same pattern as the T-10 four speed, and there were a few T-10s used behind the 287 and 327 in 1966. The T-85 and T-89 used different bolt patterns to the bellhousing. The T-89 is similar in appearance to the T-85 but is a heavier built transmission.

Resources

• AMC V-8s