455 Oldsmobile Fuel injected “Stump Puller”
The goal with this build was to create an engine with exceptional low RPM manners, run well on 91 octane, and have muscle car performance
“Getting to the bottom of the 455 Olds build”
A stock “F” 455 block, stock iron crankshaft, and stock connecting rods was used. All the parts were magnifux’d, the block was bored and honed .030 over with a torque plate, the connecting rods were resized and had ARP bolts installed, the crankshaft had the oil holes chamfered, and the journals polished.
455 Oldsmobile engines have a poor oiling systems with a history of low oil pressure and bottom end oil starvation so a Mellings standard pressure/standard volume oil pump was used. it was blue printed to ensure proper clearances and an .080 shim was added to the relief spring for more low RPM oil pressure
Many people try adding a high volume pump to address the Olds 455’s oiling issues but in stock form these engines have a very poor oil return from the heads to the pan. A high volume oil pump increases the problem by pumping more oil up top and potentially draining the oil pan in the process.
The oil passages in the Olds 455 block are quite large. Because of the way the oil flows in the block more oil is directed to the camshaft, push rods, and rockers arms leaving less at the bottom end. So I added oil restrictors to the # 2, 3, and 4 main oiling passages between the main and cam bearings which limits the oil up top increasing oil to the mains bearings.
The rule of thumb is .001″ of clearance for every 1″ of crankshaft journal diameter. However, the Olds 455 has a 3″ main journal diameter and 2.5″ diameter on the rods, making for .003″ main and .0025 rod clearances which is too wide for a street engine. So the clearances were closed up to .0025″ mains and .002″ on the rod bearings.
The return holes in the heads were opened and radiused. A slight groove was ground in the lifter valley below the heads oil return holes to get the oil back in the pan quicker. The lifter valley was polished aiding oil returning to the pan
Before
After
Before
After
A 5 quart oil pan along with a crankshaft oil scraper was installed to keep as much oil in the pan as possible and freeing up horsepower in the process.
The rest of the bottom end
Olds 455’s are not known for their robust main caps so ARP main cap bolts were added. Sealed power forged pistons, moly piston rings, and clevite bearings completed the bottom end along with balancing everything before installation.
“Cylinder heads and valve train”
Cylinder Heads
We used a set of 455 “G” cylinder heads, they already have harden exhaust seats which is needed with unleaded pump gas
The “G” heads have small 2.00″ intake valves so we upgraded to stainless steel 2.072″ intake valves and 1.625″ exhaust valves. The seats received a 3 angle valve job and the intake valves were back cut to 52 degrees which proved to increase the low lift flow numbers quite a bid. The heads were pocket ported under the valve seats and the intake and exhaust ports were cleaned up. With the 80 cc combustion chamber and dished forged pistons the static compression ratio is 9.25/1 which works well with 91 octane pump gas.
Before
After
Olds 455 cylinder have a history of running hot and cracking the heads between the two center exhaust ports because of the exhaust crossover port that runs under the intake manifold. To reduce heat and help direct the hot gasses out of the head I filled the crossover with zinc. This reduces the heat absorbed in the head and increases power eliminating the potential for heat related cracks
Camshaft and valve train
The car will be a freeway cruiser with 3.20 rear end gears and an overdrive transmission so the camshaft had to be pretty conservative. A hydraulic flat tappet Comp Cams XE256H with Comp Cams lifters, push rods, valve springs, locks, retainers, and double roller timing chain was used.
Olds 455’s have pedestal type non-adjustable rockers arms, so a set of adjustable roller tip rocker arms, ARP rocker studs, and Comp Cams push rod guide plates were used
Induction system and ignition
For low RPM drivability an Edelbrock Performer intake manifold was used matching the camshafts RPM. A FAST EZ fuel injection system was installed for better drivability.
The FAST EZ system was by far the best and easiest system I have ever use and tuned!
Ignition system
The ignition system is a basic HEI distributor with an upgraded coil. The distributor was recurved adding higher initial timing but keeping the total timing at 36 BTDC this helps low RPM drivability.
Finishing off the ignition system was a set of MSD 8.5 mm plug wires and Autolite sparkplugs.
Exhaust system
A set of long tube 1 3/4″ x 3″ headers and a pair of Magnaflow mufflers were used during the dyno session.
404 HP – 521 Ft-Lb Torque
Big Block 455 Oldsmobile Judgement Day
On the dyno connecting the FAST EZ EFI system was actually easier that I had anticipated. I ran the engine for 20 minutes to break-in of the flat tappet camshaft and to allow the EFI to learn what the engine needed. We began tuning with a couple of quick low RPM pulls to find the best timing at 36 degrees and ensure proper oil pressure. The oil pressure at idle was a solid 30 PSI and climbed to a stable 50 PSI at 2500 RPM
After 8 pulls the engine made 404 horsepower @ 5200 and a “stump pulling” 521 Lb- Ft torque @ 3300. It made 460 Lb-Ft torque at 2500 and never dropped below 400 Lb-Ft torque from 2500 to 5200 RPM!
Click on the link below to view the dyno pull
455 Oldsmobile 404 Horsepower – 521 Ft-Lb Torque
With that much low RPM torque this engine will make any Street Rod, Muscle Car, or Ski boat run extremely well!
Contact JMMcKindley990@gmail.com if you’d like more details on this engine build.