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Old 11-24-2003, 09:28 AM   #1
Fat Hack
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Default MOTOR, Small Block OLDSMOBILE Overview...

By request, here is a general overview of the "small block" Oldsmobile V8 engines produced from 1967 up into the mid 80s. This is one of my personal favorites, as I have owned a few of them and found them to be amazingly reliable and deft performers!

The "small block" modern Olds V8 engines include the 260, 307, 350 and 403 engines, and technically the 350 diesel motors as well. (However, the diesel engine uses a different block casting and internals that are beefier to withstand the added compression and stresses of diesel operation.) The small blocks share some general design characteristics with their 400, 425 and 455 big block siblings, but they utilize a shorter deck height, making them a separate engine family.

Oldsmobile produced the several different cubic inch ratings by changing the bore sizes on their small blocks. All of them use a 3.385" stroke, but the bore sizes were unique to each engine...

260 = 3.500" bore
307 = 3.800" bore
350 = 4.057" bore
403 = 4.351" bore

The 260 engines should be avoided, due to their lack of performance potential, although all bolt-on parts WILL fit them if you insist on using one. The 307 and 350 variants are equally as common, and make more sense for mild performance applications. The 403 engines found their way into Trans Ams in the late 70s and surprised many folks by out-performing their Pontiac cousins in the same cars! The 403 can also be found in Delta 88 and other large cars of the late 70s, and represents the best bargain in the small block Olds spectrum...winding up quickly with it's excellent bore/stroke ratio and really responding well to aftermarket cams, intakes and headers!

Connecting rods interchange between these engines, and all but some of the 260 and 307 offerings feature forged rods. The best factory connecting rod for the small block Olds is the 403 part number 555142, but stock rods won't be a problem on the typical street motor.

One area of concern on these engines is the oiling system. It works well at lower rpm levels, but becomes a problem above 5000rpm. A good aftermarket pump, along with the Toronado oil pan (part number 398438) which holds an extra quart is a good idea for engines destined to see much performance use. Don't forget to add the correct pickup for the new pan, too. Serious racing engines will require oil restrictors and other mods for sustained runs above 6000rpm, but that shouldn't be a problem for the typical street performer.

As far as cylinder heads go, the 67-70 W31 heads with their free flowing port design and 2.005" intake x 1.625" exhaust valves are the best factory offerings (part number 405585), but the 68-70 350 heads run a close second, although they do have smaller valves. (1.875" x 1.500"). The bigger valves can be installed in the cheaper, more common heads....and Edelbrock now offers an aluminum head for these engines to open your options up a little more. Additionally, Batten Heads in Romulus, Michigan is a recognized Oldsmobile engine specialist that can help you out with head selection and modification on your small block Olds powerplant.

Camshaft selection is wide open, as nearly every cam company has hydraulic offerings for the small block Oldsmobile. Edelbrock has a complete package in different stages for these motors with cam and lifter kits designed to work effectively with their various intake manifold offerings. Keep in mind that the stock Olds valvetrain is non-adjustable, so selecting a moderate aftermarket grind designed to work without modification is your best bet from the perspective of a backyard bolt-on standpoint.

As far as intake manifolds are concerned, you choices start with the factory four barrel intakes and go from there. Edelbrock can supply you with a Performer, Performer RPM or Torker intake (the latter being a single plane design) for your small block Olds, and their designs are tough to beat! Topped off with either a matching Edelbrock 750cfm carb (or smaller for 260-307 engines), or a Holley equivalent, buttoning up the induction system is a simple bolt-on affair.

Distributor location on the little Olds motors is in the rear, and rotation is counter-clockwise. Firing order is the familiar 1-8-4-3-6-5-7-2, and the cylinders are numbered odd on the driver's side and even on the passenger's side, just like a small Chevy. The distributor will either be a standard Delco points unit, or the GM HEI design, and either works well with good tune-up parts and some advance curve tweaking. A performance coil from Accel or other aftermarket supplier should round out your ignition system mods.

Headers are available for popular A and G body chassis, as well as the F body chassis for the Olds engines, and may fit into some older rods and customs, especially if a GM subframe is used. Stock W31 manifolds work well if space is tight or headers are not available for your custom application, and 68-72 manifolds will do the trick as well. Avoid the later design which employed a cross-over style exhaust manifold system...these are prone to exhaust leaks and do NOTHING for performance or mileage! (Earlier manifolds can be swapped onto newer 260 and 307 engines with no problem).

If you're considering a small block Olds for your project rod, you will find it to be easy to fit. It weighs in at about 530 lbs, or just under the small block Chevy weight, and is 28.25" long by 26" wide. Mounts are the same for all of the small block engines, and they use the standard B-O-P bellhousing pattern, meaning that TH-350, TH-400 and GM manual trannys will bolt right up (as well as later overdrives). The rear sump design is similar to the small Chevy, and the rugged Olds motors will generally fit anywhere the Chevy will.

With it's impressive reliabilty, strong performance potential, and low cost to obtain (THOUSANDS were produced and they can be found anywhere!), the small block Olds engine makes an attractive and sensible alternative motor to the backyard builder on a budget. Complete, running beaters with good 307, 350 and even 403 engines can be had for as little as $60 (what I sold my last one for!)...making the donor vehicle stratgey an ever more viable means to keep costs down!


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Old 11-24-2003, 09:58 AM   #2
Anderson
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Default Re: Small Block OLDSMOBILE Overview...

a few little nitpickings:

You forgot the 330! The 330 Olds engine was the very first 'small block' olds motor. Starting in 1964, it had a shaft style rocker arm system, which was ok for '64, but otherwise isn't very good for any kind of performance. Mid-64 or early '65, they switched from the shaft style to regular stud mounted rockers. The 330 went away in '68 when it was replaced by the 350. One very good thing about the 330's however, is that they have a forged steel crankshaft. These are highly sought after, and are great for high performance engines.

On 403's, I should mention that if you want to improve its performance over stock (very low compression), the best heads to use are '72 350 heads. These will raise the compression ratio a lot. The only thing needed to be done is enlarging the head bolt holes in the head, because the 403 uses larger bolts. And I'll second the use of the 403 rods. They are high revving motors (higher than a 350), but they have a weak block. The main webs which hold the crank are WINDOWED. They are prone to breaking there. There are aftermarket main cap girdles which I've heard good things about. Do not listen to any rumors about a solid web 403, it does not exist, anywhere. I garuntee it.

As far as headers go, yeah, you can find them for '68 and up easilly enough, but i DARE you to try and find a set for anything earlier that fits. Stupid aftermarket. Make some headers for my car! ARGH!!!!! Anyway, yes, the W-31 exhaust manifolds are very good because they are in fact true dual exhaust manifolds. They are commonly known as W/Z manifolds, and are very hard to find. They are reproduced, but at a high price, not worth it in my opinion. Also, as far as the exhause crossover being a 'later' thing, that started in '64. Every oldsmobile engine came with the crossover style exhaust manifolds with the exception of the W-31's. They simply capped the crossover on the passenger manifold and ran the exhaust out the back from the factory.

If you're going for a budget build, the Olds isn't nearly as cheap as the small block chevy. You could spend maybe an extra $500, and still not have the same performance. BUT, these engines have a lot of torque, and simply AREN'T A SMALL BLOCK CHEVY!!! I highly reccomend using them. Thanks FH!!!
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Old 11-24-2003, 10:06 AM   #3
RileyRacing
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Default Re: Small Block OLDSMOBILE Overview...

Thanks, Hack! I know how well they perform, I had one in a mulletmobile T/A! Oh yeah, they take abuse too! My buddy Tim had a Delta, and went to Northwestern College in Lima Ohio. He ran it out of water one time on the way home, and they didn't notice until the heat quit. Pulled off at a rest area, let it cool off for 2 hours, add some water, make it home. Gotta love the Olds!

Jay
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Old 11-24-2003, 10:08 AM   #4
Fat Hack
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Default Re: Small Block OLDSMOBILE Overview...

True, the 403 engines had low compression from the factory...but as you stated, the head swap will help bump it up a little!

(I seem to recall MANY 403 Trans Ams being equipped with Paxton superchargers and various turbochargers in the early 80s...taking advantage of the low static compression to make big gains with a little boost!!!)

Yes, I forgot the 330...my mistake, but I try to keep my engine overviews centered around late 60s through mid 80s stuff...simply because they make for great bargains in used engine purchases! (Nobody wants smoggers, but they can be "de-smogified" and work out well for low buck builders who don't mind being a little different)!

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Old 11-24-2003, 12:16 PM   #5
56olds-ERDY
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Default Re: Small Block OLDSMOBILE Overview...

i belive your thinking of the 301 pontiac motor for the turbo charged version.there wasnnt a 403 with a turbo.the 403 is a good motor,but like what was said has its limits.it can only be built soo far.i would build a 350 if you where going all out.i personally wouldnt build anything with windowed mains for my personal use.i have beat the crap out of them though,and held up fine.i just wouldnt through money into it.also the 77-80 350 olds is a windowed main block.and the 307 is a windowed main block.they do take plenty of abuse,just cant take as much horse power thrown at them.ive had nothing but good stories to tell when it comes to smakll block olds.my first real car had one.it was my first rebuild,and ive seen them do amazing things at the track.
eric
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Old 11-24-2003, 12:27 PM   #6
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Default Re: Small Block OLDSMOBILE Overview...

[ QUOTE ]
Thanks, Hack! I know how well they perform, I had one in a mulletmobile T/A! Oh yeah, they take abuse too! My buddy Tim had a Delta, and went to Northwestern College in Lima Ohio. He ran it out of water one time on the way home, and they didn't notice until the heat quit. Pulled off at a rest area, let it cool off for 2 hours, add some water, make it home. Gotta love the Olds!

Jay

[/ QUOTE ]

They love abuse
My neighbor moved down to Florida from Buffalo NY in his 76 Cutlass towing a uhaul trailer ran so hot it stopped - not once but twice - on I 95 made it to Sarasota had the thermostat changed and drove it another 5 years! No smoke or problems
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Old 11-24-2003, 12:56 PM   #7
Scotch
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Default Re: Small Block OLDSMOBILE Overview...

One more lil' note of recommendation...If you want to get serious with a SBO, start with a Diesel block! The 350 Olds was offered as a Diesel, and wasn't popular. However, the block cannot be much stronger, and I"ve seen them spun over 8,000 and make 900+ hp. Killer block to build on.
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Old 11-24-2003, 12:58 PM   #8
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Default Re: Small Block OLDSMOBILE Overview...

Thank you very much for taking the time to write this up!
Now I just gotta make this whole thing work!
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Old 11-24-2003, 01:31 PM   #9
56olds-ERDY
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Default Re: Small Block OLDSMOBILE Overview...

ok
how far are we going wih this? if your looking for a desil build up go to realoldspower.com go to the search function.they had a server crash there not too long ago soo it might have gotten lost.it has been discused many times.there is alot of factors to take into acount before building a desiel motor or any olds motor for that matter.also the desil motor is not a givin for performance.its usually better to use a gas block for most applications.depending on what you want to do or your preferances.check out the website i posted .
eric
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Old 11-24-2003, 03:52 PM   #10
Fat Hack
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Default Re: Small Block OLDSMOBILE Overview...

Yes, the diesel blocks can be bored out HUGE, too! With a custom crank and rods, you can obtain 451 cubic inches out of a diesel Olds 350 block....although if you're going THAT route, you might as well start with a 455 big block!

Yes, PRODUCTION turbo Trans Ams used a 301 Pontiac motor with a small turbo...but I was referring to performance cars on the street and featured in magazines. Turbos and Paxtons were a natural for the low compression 403 Olds!

They shore do take a beating, too....rugged and responsive!!

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Old 11-24-2003, 04:23 PM   #11
56olds-ERDY
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Default Re: Small Block OLDSMOBILE Overview...

oops sorry must have read your post wrong.when i said it is usually better to use a gas block i mean its usually better to use a 350 gas besides a desil if your going mild performance since the desil has the extra weight heavier crank bigger main journals(most have the .921 lifter) so forth.and also clearancing the injector pump boss in the front for use of a decent timming chain.they are deffinatly the way to go besides a nascar block for all out though.
eric
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Old 11-24-2003, 08:24 PM   #12
MercMan1951
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Default Re: Small Block OLDSMOBILE Overview...

Hack, I thought Batten went out of business a few years ago?
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Old 11-24-2003, 09:42 PM   #13
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Default Re: Small Block OLDSMOBILE Overview...

2-questions

1. what year Toro pan and pick-up are you saying will enhance oiling capabilities @ rpm?

2. is there a cast crank/ forged crank issue in addition to the rods? I was told once that I'd be ahead to use the crank from my '68 350 in my '79 403 but I don't remember why anymore.

Also, 1 correction...

Early 80's Toro uses a passenger side(rear) exh. man that doesn't have the crossover going through it.
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Old 11-24-2003, 10:49 PM   #14
Fat Hack
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Default Re: Small Block OLDSMOBILE Overview...

I think the Toronado pan is the same from 1968-76. It holds an extra quart of oil, and is still able to fit many chassis with little or no mods.

Batten was in business last time I talked to them...but that WAS a few years ago! Didn't realize that they may have gone under!!

The crank deal puzzles me, unless one is a forged crank and the other cast, I'd say they'd both work equally as well.

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Old 11-25-2003, 12:18 AM   #15
56olds-ERDY
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Default Re: Small Block OLDSMOBILE Overview...

yes batten has been out of buisness for many years now.you can stitt find there heads for sale,but they use a custom intake,and exhast.bulldog has a prototype head,and is suposed to be releaseing one sometime.never know.i think rocket racing racing has there new heads out too.there based out of wisc.of couse theres edelbrocks.ive seen them perform well,but ive seen stock ported perform equal or better.you can get alot out of a stock olds head.a stock N crank (350) will be fine for most jobs.the 403 has a plain cast,and the 68-72'ish have a high noudular cast iron crank.identifyed by a big N at the #1 counterweight.i think some have a cn also.
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Old 09-06-2009, 08:31 AM   #16
Paul
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Default Re: MOTOR, Small Block OLDSMOBILE Overview...

I received this pm from MAD MIKE this morning:
---------------

Good morning Paul.
I would like to ad a bit of tech to the archives. http://www.jalopyjournal.com/forum/s...ead.php?t=5009
There is some confusion with parts.
The Toro pan does indeed hold an extra quart, but its in a front sump that does not drain to the main sump. At worst the sump fills with oil and the crank can hit it. Aerating the oil, and creating windage.
Crankshafts.
64-67 330 was forged, and uses a unique bolt pattern from the later SBOs. Although the counterweight/flexplate/flywheel itself is the same.*besides the smaller Toros*
68-70(known)350 with an 'N' are Nodular.
'71-'75 unverified. Look for an 'N'
'76-90 SBO are Cast.
PMD took over casting the engines and started to use thinwall and windowed main webs. 350-260-403-307.
Most, if not all, cast cranks are drilled for pilot bushings. Nodular will not be unless original application was M/T.

There are other differences but it would probably be better to just look up all the info needed on SBO/BBO and early Rocket engines at http://www.442.com/oldsfaq/oldsfaq.h...0of%20Contents

Thank you for your time.
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