289 cid Stroker Motor

Oldsmobile "215" Stroker Motor (289 cid) - Part 1

By: Kurt Schley

(This article appeared in Volume XI Issue 3, September 2003.)

Long-time readers of the Newsletter may remember that several times over the last five years or so, I have claimed that I was on the threshold of an MGA V8 project. Due to a combination of increased hours required at my job, a home relocation, assisting my father in building and moving into a new home (400 feet behind mine) and other factors the MGA shell and chassis have been sitting untouched and forlorn. However, circumstances have finally combined to allow the project's initiation. First on the agenda will be building the MGA's engine, as it will temporarily replace the worn out Olds 215 in my '74 MGB. After a season's tuning and break in, the new engine will be pulled and stored until the "A" is ready.

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I had originally planned a stock displacement Olds 215 with longer connecting rods, i.e. Buick 300. There are several advantages to a long-rod engine. I had collected most of the components for this engine when fate intervened in the form of a phone call from Dan LaGrou at D&D Fabrications. Dan had purchased an Olds stroker motor and had everything except the heads available. It seems that the engine was originally built many years ago to power a racing hydroplane boat (for which the 215 engine was a popular mill). The engine was apparently built, run on a test stand or a dyno only once for a short period of time, never installed into the hydroplane, and stored. Eventually the boat and engine's owner passed away and the combination was purchased by a fellow in Arizona. The new owner had no plans to use the aluminum V8 and contacted Dan. When the motor eventually made it to the D&D shop in Michigan, it was pretty much an unknown entity. The heads were found to have been extensively ported and were soon shipped off to one of Dan's customer's, leaving the balance of the engine on the engine stand.

When the heads and oil pans were removed, the long block turned out to be a treasure trove of mid-sixties Mickey Thompson speed parts. A 3-3/4" welded crank (yielding 289 cubic inches), boxed connecting rods, M/T pistons, roller cam and roller lifters, reinforced cam gears, and a block machined for the crank and rod clearances. The main bearing caps are reinforced with massive steel supports about an inch thick. The pistons show just a hint of heat tint, evidence of only a few minutes running time.

Over the next few months, I will be going over each component of the engine, measuring, cleaning and improving where feasible. For instance, the roller cam is an unknown. I will have to have it "mapped" by a cam expert to figure out the specs and whether it is suitable for street use. The progress of this project will be documented for the Newsletter (Actually, I have mixed emotions about even using all these neat vintage parts in a running motor, due to their rarity. They would look great on the fireplace mantle!).

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Being that the engine came to me with no heads, I decided this would be the first problem to be addressed. The Buick/Olds 215, as well as the Rover, V8's, are well known to be head restricted. That means the port size/configuration and the rather smallish valve diameters will not allow sufficient fuel/air flow to make real power. Even mild porting, while entirely worthwhile, will not allow the engine to breath enough to reach full potential. I could have used modified later Rover heads, but this would have created problems with the valve train and with compression. The pistons/compression ratio were set up for the 51cc (casting suffix -746) low-compression Olds heads. Using Buick/Rover heads with their 37cc chambers, would have resulted in a compression ration in excess of 11.5:1. So, the heads would have to remain Olds 215, but would require extensive reworking in order to support 289" cid. One favorable factor is that the long stroke will dictate a rather low maximum RPM, somewhat lessening the flow requirements for the heads.

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Participants of the past MG V8 Conventions know Dale Spooner. Dale has been a V8'er for many years and one of the first builders to have put together a well handling Ford 302 small block MGB. In addition, Dale is the proprietor of one of New England's premier engine machine shops, Motion Machine in South Burlington, VT. Motion Machine specializes in the precision machining required for successful high performance and exotic engine building. Many other machine shops routinely send their difficult work over to Dale, such as four valve/cylinder heads, Ferrari and other exotics, as well as rectification of other's bungled jobs. For high performance head work, Dale works closely with Dwayne Porter, a master porting and high performance head expert. Dwayne has his flow bench and porting equipment in the Motion Machine facilities.

In conversations with Dale, it was decided to send a set of Olds heads up to him, so that he and Dwayne could decide how best to make the heads flow to their full potential. I also sent a scrap head for experimental work. A few weeks later, the revamped heads arrived back and they are gorgeous, suitable for display on the living room coffee table! Through extensive machining, component selection and porting, the heads are now capable of flowing enough air/fuel to keep the stroker well supplied. The components are listed below:

• Intake Valves - Ferrea Racing Components p/n F6223 (Ford 2.3L) 1.74" head diameter, 11/32" diameter stem, 4.800" overall length, 0.400" tip length

• Exhaust Valves - Ferrea Racing Components p/n F6224 (Ford 2.3L) 1.500" head diameter 11/32" diameter stem, 4.800" overall length 0.400" tip length

• Valve Springs - Competition Cams p/n COM-901-16 (outer spring with damper) 1.500" O.D. 1.080" I.D. 110 lb at 1.650" load at checking height, 290 lb@1.150" load at open height, 1.110 coil bind height

• Spring Retainers - Competition Cams p/n COM-743-16, steel (Chevy-Olds-Pontiac-SB Ford) 7 lock angle

Dwayne performed a baseline flow-bench test of the stock Olds head with stock valves. He then proceeded to develop the optimal port shape and size, performing three additional flow bench tests at various stages of the development.

• Test 1 - Stock Oldsmobile 8.75:1 aluminum head with stock 1.525" diameter intake valves and 1.350" diameter exhaust valves.

• Test 2 - Basic full port job, intake opened to 1.70" x 1.00", stock valves, 30 back cut on the valves, competition valve job.

• Test 3 - Basic full port job, intake opened to 1.70" x 1.00", 1.620" diameter intake valve, 1.400" diameter exhaust valve, both valves with 30 back cut, re-blended bowls.

• Test 4 - Basic full port job, intake opening to 1.80" x 1.00", 1.620" diameter intake valve, 1.400" diameter exhaust valve, both valves with 30 back cut, re-blended bowls, fully polished runners, more guide streamlining.

The final results showed an approximate 32 percent increase in intake flow and a whopping 54 percent in the exhaust flow (both at 0.600" lift).

EXHAUST - Tests corrected for 28" H2O
Lift Test 1 Test 2 Test 3 Test 4
 % CFM % CFM % CFM % CFM
0.100 69 835 71 36 90 45 91 46
0.150 75 52 80 55 93 64 92 64
0.200 64 65 71 73 75 76 77 78
0.250 72 73 84 85 86 88 88 90
0.300 76 77 94 96 97 99 99 101
0.350 78 80 72 105 75 108 77 112
0.400 80 81 76 110 79 114 81 118
0.450 58 84 79 114 82 119 85 123
0.500 58 84 82 119 85 124 87 126
0.550 58 84 83 120 87 126 89 129
0.600 58 84 84 122 88 127 90 130

INTAKE - Tests corrected for 28" H2O
Lift Test 1 Test 2 Test 3 Test 4
 % CFM % CFM % CFM % CFM
0.100 63 43 69 48 74 51 74 51
0.150 62 63 70 72 76 77 76 77
0.200 84 85 66 95 72 104 72 104
0.250 72 104 76 111 88 128 88 128
0.300 80 116 85 124 81 146 81 147
0.350 84 122 95 138 88 159 89 161
0.400 71 128 83 150 93 168 95 172
0.450 73 133 87 158 93 168 95 173
0.500 74 134 91 165 94 170 96 174
0.550 75 136 93 168 95 173 97 176
0.600 75 136 93 168 95 174 98 178

Disclaimer: This page was researched and written by Kurt Schley. Views expressed are those of the author, and are provided without warrantee or guarantee. Apply at your own risk.

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