kanaric SuperDork
7/11/18 12:34 p.m.

I have an opportunity to buy a '70 cutlass s with a 4 speed w/350. I have workable knowledge of SBC 350 and Ford 351w and 351cl engines but not olds 350. Aside the engine that period of a-bodies is my Dad's specialization, that and Ford Torinos, and he has passed down that knowledge to me. But that knowledge is more on the Pontiac and Chevy side on things. 

What are these engines like? How good is aftermarket for them? Just looking for general input overall. 

My goals for this car would be a restomod but more mild on the power side than what I think most restomod people do. 350 modern crank horsepower would be good enough for me and am fine with buying aluminum heads and doing it a more expensive way. I would actually prefer aluminum heads if there are decent choices for this car. Aside engine I already know what I want/need out of the car.

I am not 100% certain i'm going to pursue this car, I was more looking at 69-73 351 Mustang Mach 1s, but it would be good to expand my V8 engine knowledge anyways. I also think I can get this Olds for much cheaper, which if I can, I would buy it. 

81cpcamaro Dork
7/12/18 10:18 p.m.

Edelbrock makes aluminum RPM heads for the Olds. Aftermarket support is pretty good. Not all that different than the Chevy and Pontiac engines, pretty straightforward engine. 350 crank horsepower is definitely reachable.

7/12/18 10:48 p.m.

If you're not concerned with #'s matching but want to keep Olds engine consider looking for a 455 to build. Cost basically the same money but more cubes = more power. Guys building late 2nd gen Trans Ams into pro touring cars are pulling them out and selling them pretty cheap because of lack of demand to do the currently popular LS swap.

My best friend in high school (mid 70's) had two 70 Cutlass's with 350's. They were like a Chevelle but nicer. Better quality materials used, quieter interior, more comfortable seats, etc.

ClemSparks UltimaDork
7/13/18 7:06 a.m.

My only experience with an Olds 350 was an impressive one.  We bought a Back 40 racer that was a B-body with a 350 olds in it.  It was surprisingly powerful for a junker.  I assume it was all stock (but you know how that goes).  Like I say, it surprised an impressed me.  I considered one for my Buick wagon build...but went SBC for Serpentine Belts and Vortec Heads.

kanaric SuperDork
7/13/18 9:58 a.m.

Thanks for the input everyone. 

I have read a great deal on these engines since posting it. Like you said Edelbrock makes heads but you have to get them milled to get a decent compression ratio because they are made for big block olds engines. I was talking to another guy and he recommended i get flat top pistons as well. 

If I can get this car for the price I want I will go for it. 

455 sounds interesting to me but I like the idea of a lighter engine especially when I add aluminum heads to it. Especially since I am not looking at monster horserpower

ClemSparks UltimaDork
7/13/18 12:49 p.m.

I'm not sure but it sounds like you may be thinking the 455 is larger (heavier, rather) than the 350.  It's really not much larger (just a difference in deck height, maybe?) if my memory serves me right.  Basically, it's hard for the casual observer to tell the difference between an Olds 260 V8 and an Olds 455 V8.

So a 455 will have a hundred cubes on a 350 without an appreciable weight difference.

Now...finding and buying a good 455 to build for a reasonable price is getting tought to do.  So the 350 you have (in the future) may be the best option.

kanaric SuperDork
7/13/18 4:16 p.m.

In reply to ClemSparks :

Oh really, I was under the impression when people were calling the 350 a "small block olds" that there was a decent size/weight difference from the 455.

With the power a 455 makes I wouldn't need to "improve" it much lol. Engines like that if they are pre-smog are monstrous as they are for my tastes lol. So long as they are in good shape. 


ClemSparks UltimaDork
7/15/18 8:47 a.m.

You'll want to do your own research and confirm the differences.  I'm going off memory from when I was interested in these 20 years ago.  But I still think it's not much of a difference.  The external mounting points like engine mounts and bellhouse are all the same.  I can't say for sure, but I'm thinking even headers fit the same.  I think I remember the deck was taller on the 455s making them a bit wider at the top.  I'm sure that has some fit and interchange implications at the top of the engine, but I don't recall how troublesome that becomes.  Like...does an intake manifold fit both a 350 and a 455?

If you want to know how to build a durable Oldsmobile engine, look at the boat guys.  They put lots of these in Jet boats (but not exclusively jet boats) and I'd guess you'll still find as many 455s running around on the water as you do on land.

FSP_ZX2 Dork
7/15/18 10:43 a.m.

The factory made a W-31 option.  Was a very stout motor--I believe it was among the "hottest" of the GM 350s, including the LT1.  They would rev into the mid 6000 RPM range too, which in that day was a lot.  Lots of potential with the Olds 350.   

pres589 PowerDork
7/15/18 11:12 p.m.

From a bit of reading and a bit of memory, Olds V8's like the 350 oil the lifters first, then the mains.  Good to get them quiet at start up, not really a good performance aspect.  Probably more troubling is the center exhaust ports being siamesed somewhat.  The old school method of fixing this was welding iron into one of the better factory heads and then probably a set of headers or whatever manifolds work best with this.  What makes more sense to me, assuming there's budget for it, is a set of new aluminum heads which won't need this work done to improve performance.

For a street cruiser I don't think any of the above matters.  They seem like tough, well-evolved engines, with enough aftermarket support to make living with one or building easy enough.  

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