Is it worth it to keep my 350 Rocket, or....

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midwestls

Royal Smart Person
Aug 15, 2007
1,497
13
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Bismarck North Dakota
That an XJ right. Nice choice. Like the look of that body style.
 

jae

Master Mechanic
Oct 11, 2006
460
2
16
I guess to get back on topic, if I were you I would price out everything you'd need to get the 383 the way you REALISTICLY want it. What I mean is, build up the 383 on paper the way you'll be installing it in the car, with the intake, carb, dist / ign, all the parts for the motor for your hp/torque wants. Then add the accessories, like the pulleys, belts, fan (regular clutch or electric), or serpentine system, motor mounts, starter (remember the starter on the Chevy is passenger side, the Olds is driver). Then determine the transmission; do you have the dual-pattern TH-200-4R? - if not you're looking at a new transmission. Also the torque convertor. Yes, you can probably get the pulleys and the brackets for the Chevy from a junkyard / swap meet and save some cash but add in the time.

Do the same for the Olds 350 you have now. I woud definitely add in the cost to get '68 - '72 heads on it - #7a are the same as the #7 heads except they have hardened seats for unleaded fuel. You can also check into putting bigger valves into the too, like on the W-31s. Then you can do the same with the 455 BB, again needing to add in the brackets, exhaust, mounts & either transmission upgrade or performance rebuild (rear-end as well?). As Joe_P and others stated you may not come out that much more $$$, if at all, upping the ante on the Olds 350.

Oh, also add in $$ for the "oh yeahs", "damns" and "WTFs" that are bound to come up. And be ready for something else to take a dump after you get all the engine stuff squared, like the radiator, brakes or something.

Funny, I did the same swap on my '81 Calais, replacing the puke 260 with a 350 out of my brother's coworkers' 76 Cutlass (the transmission in his car went out, my motor was dropping cylinders). My current '86 has a 68 -70 Olds block w/ '72 7a heads, Performer RPM intake, 750 carb and Hedman headers and some good internals. It's nice :twisted:
 

Larryg

Greasemonkey
Jun 6, 2008
131
0
0
western Mass
The 10 pound difference is between an olds sb 565lbs and a chevy sb 575lbs, with the olds being lighter. Going to the olds 455 (605lbs), would only gain you 30 pounds over a small block chebby. Noticable, but still not very much. I found that pretty shocking. How fat is a big block chevy? 685lb. How about that 765 lb hemi elephant? No wonder they didnt road race those motors!

I would say an olds 455 isnt that heavy, but a light, quick revving fast breathing 403 small block would likely feel very frisky in the corners and still have the cubes to torque your way around town as well. Running examples out of T/As with 403s can be found with trannys for very little dough. I'm also finding running 455s for less than a grand as well. I havent been convinced to build a 350 Olds yet. This spring I want to drive a few cars and see what I like best.

If I were building with the thought that some day I might want 6-700 horse, I would bite the bullet and go chevy and go LS and start down that path. I dont think there will be any limits on those motors. I think even finding a budget LS1 you will be into the swap for at least 4K without touching your transmission or rear. But then the skies and your imagination is the limit. 8)

Myself money is the limit and I'll be going Olds either 403 or 455, lightly modded yet still making way fun power I can use everyday. When I get the dough for an LS it will still be in the camaro or vette it came in.
 

supercrackerbox

Master Mechanic
Dec 29, 2008
385
2
18
Lincoln NE
Like everyone has said before, right now your biggest restriction is those '76 heads (and likely your cam and exhaust manifolds). They are from the darkest of the dark ages of the smog era. Swap that stuff out and you won't believe the difference. Every single 4-stroke engine, I don't care who built it, how big it is, or how many cylinders it has, relies on the same basic principle- The more air you can flow, the more power you'll make.

And on the topic of big blocks and their weight- Olds 455 is 30lbs more than an SBC, Buick 455 is 50lbs. more. Aluminum intake and heads will MORE than make up for that.

Also, correct me if I'm wrong, but I believe the Olds 455 and 350 will use the same mounts, bellhousing, and possibly even accessories . . . .
 

Blake442

Geezer
Apr 24, 2007
6,866
2,011
113
Minneapolis
supercrackerbox said:
And on the topic of big blocks and their weight- Olds 455 is 30lbs more than an SBC, Buick 455 is 50lbs. more. Aluminum intake and heads will MORE than make up for that.

Taking off the A/C compontents would make up for that.

supercrackerbox said:
Also, correct me if I'm wrong, but I believe the Olds 455 and 350 will use the same mounts, bellhousing, and possibly even accessories . . . .

Mounts and bellhousing are the same.
Many, but not all accessories are interchangable between SBO and BBO.
 

shotgun

Royal Smart Person
Nov 12, 2007
1,067
81
48
Nort o Philly
Not an Olds expert by any means.

How about a nice build (9.5:1, Comp XE Cam, headers etc) on what you already have (why rebuy) and a small 150 shot.

You can have the best of both worlds, a balanced driver that will have decent power and some decent MPG then turn on the bottle when needed.
 

justG's

Not-quite-so-new-guy
Jul 29, 2011
8
0
0
you should never get rid of the rocket.I myself have one sitting in the garage and dont know what to do with it but they are a verry desired block to those that know much about them. as mentioned before it all depends what u want out of it. The thing with the rocket blocks is there are many more stroke options and bore choices with them due to there tall deck height and and cylinder walls unlick a 350 chev bloc, they are prety rare and can be made to produce obscene amounts of power due to to fact they can be made up to a 468 ci small block, but its up to you. Be carefull though the "rocket block" was only made for a short period and some people that say they have one dont it just turns out to be an olds 350 the rocket blocks that im refering to which are the ones people want and pretend to have were only availible 66-72,73 and after that a few were put in production cars just to use up older stock but some minor changes were made. hope that helps
 

GP403

Administrator
Site Admin
Moderator
Feb 25, 2005
4,517
4,940
113
Rolla, MO
The Olds "rocket" thing is just a marketing name, like the Chevy big block "Turbo-Jet"....
 

justG's

Not-quite-so-new-guy
Jul 29, 2011
8
0
0
yes it was a marketing thing but it originally applied to the blocks that are such high demand, but the whole marketing theme just kept going this is why so many people think they have a rocket block. technically they do but not to often is it the large small block "rocket block" that so many people would like to have.
 

Blake442

Geezer
Apr 24, 2007
6,866
2,011
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Minneapolis
justG's said:
yes it was a marketing thing but it originally applied to the blocks that are such high demand, but the whole marketing theme just kept going this is why so many people think they have a rocket block. technically they do but not to often is it the large small block "rocket block" that so many people would like to have.

It has nothing to do with the block.
The "Rocket" title is 100% meaningless and had been in use since the '40s.
There is simply no such thing as a 'rocket block'...
 
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