Inside Our Midget Motor

Building a high-powered Midget engine is fairly simple. Making it durable and easy to live with is a bit tougher, as we demonstrated in our September issue.

The wizards at APT helped us create a Midget engine that will provide plenty of power yet remain reliable. For more details on how we did it, including which parts we chose and how much we spent, read on…

Part numberDescriptionEachTotal
HAY ABP-1275Alumininum CNC-machined rear engine plate$159.00
XRN OPA+Metro A+ Slot drive oil pump$53.98
ENG DCC832Clutch cover (3-piece kit)$122.79
CNT CCP601-HDCompetition clutch disc, solid hub, $118.75
XRN RG-1444Ring gear$69.79
XRN PB-474Bronze pilot bush, 5/8” OD$6.35
BEA VPW41-SThrust washer set$19.45
XRN RA572-1Heavy duty lead/copper rod bearings, 1.625” dia., 010$79.00
XRN MA91120-1Heavy duty main bearings, 2” dia., 010$87.00
MSC P73-5-11Mega 73.5mm big bore 11cc dished piston set$583.00
ROM 12CSP-2Degreed crank damper$299.00
SWF HLR-321.5 Ratio roller rocker set with heavy-duty shaft, bronze bushed$698.00
XRN PR1275Push rod, 8.735 OAL$6.49$51.92
ROM AVG-ALightweight vernier cam gear set, duplex$278.49
XRN CTP-1Cam thrust plate$19.99
APT CF-04Super duty phosphate-coated cam followers$118.00
APT SPVP-3-BKPerformance scatter cam$349.00
LAB HED002Hardened valve seat insert$11.00$44.00
TEC 10012521No-lead exhaust seat insert$5.99$23.96
APT CHA-01Fully prepped road spec cylinder head$1,654.00
SRP WPP-AAluminum water pump pulley, 4.75” dia.$73.95
MSC WPA-1Water pump with large impeller and hose take-off$51.86
KNN HP-1002K&N Oil Filter, 3.75” high$12.98
MSC FBA-1Spin-on oil filter housing$98.00
ENG VPC989Cam bearings (not split type)$49.90
Dyno time$600.00
APT SD3-3186”x1.75” round filter for HS4 SU carb$73.98$147.96
HAY MSS4Billet aluminum CNC machined stub stack for HS4 SU carb$32.50$65.00
BFS 2xSUHS4Pair of HS4 SU carbs$797.65
VFS HS169Carb heat shield$81.99
MSC MFA338SU manifold spacer with vacuum fittings$15.29$30.58
MAN SUA4-2Maniflow steel intake manfold$249.00$249.00
MAN EXL9LCB header$299.00
Lighten flywheel$133.00
Remove/Replace flywheel ring gear$49.00
Resize/recondition connecting rod big ends$23.00$92.00
Magnaflux crack test rod ends$7.00$28.00
Remove//replace pistons on rings$18.00
Balance connecting rods$16.00$64.00
Grind & polish crankshaft$151.00
Balance crank/flywheel/pulley assembly$149.00
Plasma ion nitride crankshaft$139.00
Magnaflux crack test crankshaft$39.00
Tear drop shape oil holes in crankshaft$30.00
Remove/install pilot bush in crankshaft$20.00
Wedge crankshaft$295.00
Align hone block$153.00
Magnaflux crack test block$45.00
Hot tank and jet wash block$72.00
Remove/replace A/B cam bearings$48.00
XRN OGPOil galley plugs$3.36$14.64
Remove/replace oil galley plugs$35.00
Remove//replace core (freeze) plugs$38.00
Offset bore block for 1380cc$275.00
Deck block$77.00
Elongate pushrod holes$106.00
ENG EF460Spridget conversion gasket set with timing seal$49.78
SWF CMG-01Manifold gasket$12.95
XRN DK450Head gasket set$49.95
TSI GRS-1Gear reduction starter$269.00
ARP FB900-6A series flywheel bolt kit$32.71
ARP BEB-6001-8A series rod bolt/nut kit$119.98
ARP MSA54A series main stud kit$89.98
ARP HSA9A series head stud kit$136.82
ARP AMS-1Stainless steel manifold stud kit$48.99
ARP THS-1Stainless steel thermostat housing stud kit$29.48
HAY CDB-3Heavy duty crank damper bolt$39.81

So what did all of that get us? On the dyno, our engine maxed out at 107 horsepower and 98 lb.-ft. of torque. That’s a lot of power from the venerable A-series, especially one with dependable street manners.

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View comments on the CMS forums
Seescott New Reader
7/13/09 9:16 p.m.


TJF New Reader
8/16/09 11:08 p.m.

If I were to spend that kind of cash on an A-series engine I would either install a 7 port head or even better do the K-series DOHC BMW motorcycle head conversion. The thing I find frustrating is that with all that money spent, just think how much that would buy you if you building a SBC.

tatekc None
8/19/09 1:33 a.m.

Making a "period looking" engine more powerful takes finesse and skill; not to mention taste. All of these things cost money. There are small block Chevys galore in Hot Rod magazine and others of that ilk. Unfortunately, they lack some of the above qualities.

Trevor Dork
8/25/09 2:27 p.m.

You could subtract many of the parts like the degreed harmonic balancer, extra charge for off set boring, wedged crank, roller rockers, enlongating pushrod holes, nitriding crank, maniflow intake manifold, etc, and come up with enough extra cash to have a supercharged engine. It would be more streetable and have similar power. Of course... I'm biased.

johnsfolly New Reader
8/26/09 11:29 a.m.

It's great to have deep pockets. When a mistress seduces us, we are willing to spend whatever she wants. 11-grand for the motor, plus all that body work. It's got to be for love. Come sale time, it'll still only be worth $7500. -JohnD (who loves his Spridget)

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