Asked by Jul 05, 2009 at 01:27 PM about the 1978 Oldsmobile Cutlass

Question type: General


7 Answers


Hmm this is weird. In 1977 Oldsmobile started marking their blocks with the CID. Double check the block. As for the vin number on the block, one spot is to check between the intake manifold and the timing cover, but I think that is only for older models. Double check the side of the block though, there should be in big letters, "260" if it is the original motor. Hope this helps you out! PM me if you want anymore help.

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well in 78 and 79 they made oldsmobile with 260's i took mine out and put a olds 350 in. the tranny that was connected to the 260 worked for a while with the 350 but it was to hard on the tranny so i bought a b.o.p tranny that witch u can aslo get the bop tranny with universal tranny wholes for a chevy 350 which i did.

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I believe they used the TurboHydramatic 200(Metric),on the 260 2-bbl V8 in that year. it looks like a TH350 but it aint, and it wont interchange(compatible), it will "fit" but Olds. didn't intend you to do that. I'll conferm my answer shortly and get back to you.

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re: 1978 Cutlass motor size and transmission model?" If its a 260 Oldsmobile V8 with a 2 bbl. carb. the '78 specs. are: (general)110 HP @ 3,400 rpm, 205 lbs. ft. torque @ 1,800 rpm. Compression ratio is 7.5 to 1. Bore and stroke is 3.500" X 3.385". Tune-up specs. are [timing] 18B(man.) 20 B(auto.) @ 1,100 rpm. Idle speed 800/500 rpm. Oil pressure is 40 psi @ 2,000 rpm. Spark plugs were R-46SZ. Fuel pump press. 5-6 psi. If it's an auto. trans. its probably a TH200. By bring it back to life do you me "restore" it or just get it running? A brief history of the Olds. 260 V8/TH200 trans. Olds. needed a small V8 for fuel economy reasons in 1975, rather than trying to design a new motor they underbored the existing Olds. 350. This made the 260 a durable if not underpowered V8(2 bbl. only). The TurboHydramatic(TH),200 was a "economy" minded version of the TH350, GM(and owners), had alot of problems with this trans. they did various things to "solve" them, eventually it was generally accepted to replace the TH200(in service), with the TH350 and I believe they dis-continued the use if the TH200 altogether. If I had it to do all over again and I owned a very good condition 1978 Oldsmobile Cutlass Supreme(RWD), with the 260 V8 and AUTOMATIC trans. I would do this: Find a 1978 or 1979 "donor" car, dont get a Cutlass for this, rather find a large full-size Olds. or Buick(Delta 88/98 or Park Avenue/Electra). Get one in otherwise good condition for cheap. make sure it has the Olds. 403 engine, it will also have the TH400 trans.(more on that later). If your going to do most of the work(removal/install), yourself be sure to keep good track of things. Remove the 403 and ship it to a engine builder who is familiar with these engines, Mondello in California is one of them, or contact them they may not need your engine. You will however need alot of the other "stuff", so an inexpensive donor car is a good idea anyways. Olds. only produced this engine for a few years, it is however physically identical in size to the 260/350 and it will fit in your car. After a mild build-up on that engine with the right combo. of parts I'd say 275 HP would be a reasonable number with ALL the factory acces./emissions/exaust with maye the exception of an Eldelbrock 4-bbl. aluminum intake manifold with EGR system(50 states legal). The torque output would be around 400 lbs. ft. Considering what it would cost to get those numbers out of a 350(forget about the 260), you'll be way ahead. I'm talking about a 8.5 to 1 compression(approx.), street legal car that you can get inspected/registered anywhere, that will start right-up and run on regular gas and be reliable, not some "hi-performance" motor that people talk about and dont really know the out-put of the motor to back-up their claims of 400HP Olds. 350 motors. You will have everything you need to install that motor in your car, have the Quadrajet rebuilt with a "Brad Urban" type overhaul and its likely the carb. shop will re-do the distributor to match the motor/trans. combo. Have a reputable(ATRA), tans shop set-up a TH350 to go into your car, the TH400 will be to much hasstle to fit in because I dont believe there is a factory "G" body crossmember. If your car doesn't have that "442" type suspension,springs,shocks,sway-bars), no big deal as alot of Olds./Pontiacs/Buicks were outfitted with similiar parts. Put the Olds. 14 X 7" wheels(SSIV's)or what ever they called the late 70's early 80 version of the 15" SSIII's. Set of BFG P22560R14's on it, keep the sinle exaust, you might have to install the catalytic convertor out of the donor car and larger diam. pipe/muffler. I'd say 0 to 60 times in around six seconds(depending on the rear gearing), and top apeed of around 115 mph. If you want to add a "performance" reart axel use the entire assy out of the Olds.442/Buick Regal it had the larger ring gear(8.2") and was much more durable. Better yet I think you can buy that whole set-up new. Have fun.

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re: "1978 Olds. 260 V8 motor/trans. specs.". Some more stuff about my previous reply to the topic Olds. 403/TH350 engine build-up and swap. Not sure if anyone is interested in doing this. The 403 got a "bad" reputation early on because of its thin web(bottom-end), casting design, it was regarded as unsuitable for racing/street performance. I recall seeing a build-up of this motor back in the 80's where they installed Mopar 360 rods, "turned" the crank and I think they put Chevy Mark IV(396), flat-top pistons on them to lighten things up. I guess the reasoning was that less recip. mass equaled better bottom-end life. In retrospect I dont believe all this is really needed for a street engine connected to a auto. trans. with a stock type torque convertor(1,800 - 2,100 rpm stall), and stock final drive ratio. With a rear gear ratio of say 3.42 or 3.23 and a outside tire diam. of 22" or so. I doubt over-revving a basically stock quality rebuilt 403 would be a big problem. And keeping the camshaft grind around .410" lift on the intake and .425" on the exaust, with duration around 205 degrs. and centerline around 112 degr., this is probably close to the Olds. 350 W-25 cam. The 403 has larger valves than the 350(slightly smaller than the 455). Also the fact that it's in a 3,200 # car being street driven. I'd say my HP estimate is probably coservative so I'd install all the emission equip.(A.I.R. pump, other vacuum accys.). All that steel plumbing for the "smog" that connects to the exaust ports in the heads ought to clear the "A" arms/steering column. Maybe if someone reads this and has one of those computer programs they could "plug-in" the #'s and post the results. If power loss is a concern in regards to driving a "extra" pulley(accessory), it shouldn't be a factor because the 403 in that car will have a excess amount of power anyways. I believe all of that will fit under the hood and behind the radiator. As far as radiators go I'm not sure if the big GM radiator(Harrison 4-core),the one used through out the 70's in most of their vehicles will fit into a "G" body. I,d use that one and a seven blade fan w/clutch/shroud. Also I'd install an AGR 12:1 ratio steering box for a more modern feal, positive response. I dont think GM offered an optional steering box if a 350 was instaled in the Cutlass(due to weight/durability concerns, not "performance"). I think the 403 was the same weight as the 350, maybe slightly lighter. With an aluminum intake manifold it probably weighs about the same as the 260 V8. All the pulleys and brackets from the 403 should work/fit, if not the 260 ones probably will, and the A/C ought to fit without modification, I doubt any fabrication will be needed. The exaust manifolds and X-over pipe should fit/clear cross member and the header pipe to the cat. conv. should clear frame/line-up, if not the full-size donor car one should work. I'd install the HD front/rear coil springs. I think the Rochester Quadrajet carb./air cleaner assy. will clear the hood on top of that Edelbrock manifold and as far as emission/vacuum hose routing goes I'd set it up like the donor car. I've never done this swap before however by what I've done and seen with Olds./Buicks over the last thirty years it looks like it would work. The end result would be a car that would out perform most of the seventies cars and have a drive manners. In 1979 Olds. offred a Cutlass with a 350/TH350 engine combo., it almost out performed the Chevy Corvette, and it was the only "G" body that year with a 350 motor available. I,d keep the H.E.I. distrb. pretty much the way it is, stock coil, add a good cap a descent spiral-core wires and run it all in the factory wiring loom. Get a 64 amp altenator and dont change it to "1 wire".


what is the idle timing specs for a 1979 olds 350 rocket. like how to time it and what degrees before TDC do you have the number 1 cylinder at

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Im in need of a answere to my question. I have a 260 v8 78 cutlass supreme i recently blew out my trany out wich was a th200. I bought a 350 turbo and instaled it hopeing to get a faster feel but my car is slower and takes very long to catch speed. What could be rong? Is it that the trany is to big for that engin size or what? Please i new an answere.

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