Fat Hack
11-24-2003, 09:28 AM
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!
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!