Some engines simply won"t walk away. Earlier in the might "11 issue, we brought you the an initial part of our budget-built 400 tiny block Chevy. The idea was to bolt a collection of steel Vortec top on a junkyard 400 tiny block Chevy, add a cam, and also enjoy the torque. Ideal away, us ran right into snags. The block was so nasty the demanded assist while retaining the share crank, pistons, and also rods. The electronic came failed with much less than a week prior to our meeting necessitating one unplanned thrash to rebuild the engine a 2nd time due to the fact that all that dead electronic came metal wiped the end the main bearings. By the moment we were finished, we had actually never operated so hard to develop so small power. The 400 little block Chevy difficulties were multiple: The cylinders waffled prefer ice cream cones, avoiding anything approaching ring seal, and also the compression to be a sickly 8.2:1 because of ugly 0.060-inch piston deck heights. In instance you let go the story, the best power number were got with a set of GM Performance parts Vortec heads provided by Scoggin-Dickey, and even then the 400 small block Chevy managed only 401 hp and also 458 lb-ft the torque. We were underwhelmed.

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Rather than kick the motor to the curb, we decided to construct this engine correctly. The setup was to maintain the initial test"s cam, Vortec heads, Weiand intake, Holley 750-cfm carburetor, and also exhaust headers therefore we might honestly evaluate the power increase from better cylinder sealing and a bang in compression. The distinction was astonishing. You"ve probably already jumped front to the dyno test, however if not, the brand-new torque numbers come in at a tire-shredding 501 lb-ft at 4,000 rpm, and horsepower leaped as much as 466 at 6,000 rpm. That"s a height horsepower bump of 65! us did cheat a small with a pair of new parts, but you"ll need to read the whole story to find out what us did.

While we initially planned come reuse the stock crank, Scat"s Tim Lieb suggested adding an essential option. All production 400 small-blocks were developed as externally well balanced engines. The difficulty with building a performance 400 that can see rpm over 6,000 is the outside weight spinning about on the crankshaft snout; that acts prefer a rock on the finish of a string, including load on the crankshaft the could cause eventual failure of the front key bearing. Lieb said an internally well balanced crankshaft assembly the would call for 6-inch rods and a short- compression-height piston to allow room for bigger crankshaft counterweights. This package expenses a little an ext than the standard 5.7-inch rod and also cast crank system, however it uses much greater durability. One other feasible advantage is the improved rod-length-to-stroke-ratio indigenous the 6-inch connecting rods. Since it"s constantly a possibility that we will lean ~ above this engine harder in ~ a later on date, we opted because that the internally balanced rotating assembly and had Scat balance it for us.

The many obvious adjust to this various rotating assembly is that v a 6-inch rod, the piston compression elevation becomes really short, which move the wristpin up into the oil regulate ring. This needs an oil assistance ring the is gave with the pistons. It"s necessary to note that this support ring comes through a small dimple that have to be inserted with the raised portion facing under so it will not relocate relative come the piston.

Once our maker shop, Barrington Engines, ensured that all the cylinders were correctly bored, the talk plate to be honed, the key bearings were align-honed, and the decks to be level, we had a an excellent foundation. By the moment Barrington finished squaring this block and making the holes round, the thought emerged to us that we had $800 invested. We looked increase the price of a Dart SHP block from Summit. It comes in at $1,499.41 (plus shipping). When this block is an ext expensive, it"s a new casting with four-bolt mains and 350-size main journals, which way slower bearing speeds end the larger stock 400 size. You will still need to hone this new block, so factor in the cost—it"s precious considering prior to investing $800 in a 40-year-old block.

We will certainly not invest too much an are documenting the assembly other than to point out that us did have to mix in rather a few Federal-Mogul 0.001-inch undersize bearing halves with the Scat rods to get bearing clearances to achieve our best 0.0025-inch clearance target. The main bearings were easier due to the fact that Barrington align-honed housing bores, which established much more consistent bore diameters. We likewise mocked increase the engine to measure deck heights and then had Barrington an equipment the deck surfaces to produce a much an ext consistent deck height.

Comp Cams Thumpr 287TH7 hydraulic flat-tappet camshaftCamshaftDuration at 0.050LiftLobe-SeparationIntake2350.490107Exhaust2490.475

See every 14 photosThe Scat rotating assembly came v a forged crank and longer counterweights to do it an internally well balanced system. The forged I-beam rods space 6 inch long.

With an increase of two complete points the compression and good ring seal, we meant some severe power enhancements over the share baseline, and we weren"t disappointed. Ideal at the an initial pull top top the dyno with 36 levels of time (versus 44 levels with the old engine), the 406 grunted out 486 lb-ft of torque contrasted with the previous 458 and also produced between 20 and 30 lb-ft of speak increase across the plank with comparable gains in horsepower with the height of 436 hp in ~ 5,200 rpm. The biggest trouble now seemed to be that we essential some way to make the engine breathe much better at greater engine speeds to make an ext horsepower. The limitation seemed to it is in valve lift, so we thought the simple addition the a set of 1.6:1 rocker arms could help.

Generally, rise from 1.5:1 come 1.6:1 rockers is usually worth around 0.030 customs of valve lift, and also since our video camer barely do 0.490-inch lift, the seemed like a an excellent solution. We also tried a 1-inch-tall Wilson tapered spacer that was worth about 3 hp in ~ the optimal with no lose of torque down low. We likewise drained the 10W-30 break-in oil and also tried some thinner-viscosity Lucas 0W-20 gyeongju oil, hoping to push over the 500-lb-ft plateau. All these little efforts really paid off. The rockers alone to be worth almost 20 hp, which helped us excel come 501 lb-ft the torque and upped top power come 466 hp in ~ 6,000 rpm, and the engine comment positively to practically all the changes. All this really proves the quality machine work and proper engine assembly methods really carry out pay turn off with big rewards. Us are already thinking about how to do even much more power with this 406ci, and we might have to start calling that the BFH due to the fact that it brings down the huge freakin" hammer ~ above torque.

This graph illustrates the large differences in torque between the previous combo and also our latest version. Note just how the form of the curves stays basically the same, because we walk not change the cam, heads, intake, or exhaust. But look carefully at how the speech curve dips slightly between 5,300 and 5,900 on tests 2 and 3. The emboldened is more pronounced in check 3, i m sorry is where we added the rocker ratio. Our theory is the the valvesprings are right on the ragged edge and also became "fussy" in this rpm range. The resolve is a various (not necessarily greater load) valvespring that would most likely take care of this. The big news is the huge gain in torque between Test 1 and also Test 3. This would certainly make terrific street engine.

See all 14 photos

Test 1 is the best power us pulled native the original test of the engine indigenous the might "11 issue. Check 2 is through the same Bow Tie Vortec heads, Comp cam, Weiand intake, Holley carb, and also dyno exhaust with no mufflers. Test 3 added a Wilson-tapered carbohydrate spacer and a set of Comp 1.6:1 roller rockers and also performance pushrods.

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Test 1 TQTest 1 HPTest 2 TQTest 2 HPTest 3 TQTest 3 HPTQ/HP Gain

Show All

*Average power numbers were calculated in between 3,200 and also 6,000 rpm to ensure a fair comparison.

Parts List

Used 400 short-blockUsedJunkyard$120.00
Scat crank, rod, piston balancedCall ScatSummit Racing1,496.95
Scat 6.00-inch I-beam rods26000Summit Racing251.95*
Icon forged piston, -51cc dishIC758Summit Racing475.95*
Vortec Bow Tie, large-port25534446Scoggin-Dickey985.70
Comp 1.6:1 roller rockers1016-16Summit Racing351.95
Comp Muscle car 10W-30 oil1594Summit Racing39.75
MSD Distributor, pro billet8361Summit Racing212.95
ARP 400 key studs234-3701Summit Racing77.18
ARP head bolts134-3701Summit Racing108.95
Federal-Mogul cam bearings1404Jeg"s23.99
Federal-Mogul main bearings140MJeg"s65.95
Federal-Mogul stick bearings7100CHJeg"s56.99
Federal-Mogul pole bearings -17100CH-1Jeg"s86.99
Fel-Pro align bore key seal2909Summit Racing23.95
Fel-Pro 400 head gasket1044Summit Racing141.98 pr.
Fel-Pro 1-pc pan gasket1880Summit Racing40.95
Fel-Pro Vortec input gasket1255Summit Racing32.99
Professional commodities balancer, 6.7580000Summit Racing54.95
Federal-Mogul oil pump pickupZ2241246Summit Racing11.95
Federal-Mogul electronic came bearingsZ1235MSummit Racing17.95
Federal-Mogul oil pump driveZ2246146Summit Racing8.95
Sealed strength brass frozen plug Z381Summit Racing18.95
VHT Chevy orange paintDE1620Summit Racing6.95
GMPP self-align 3/8-inch rockers12495490Summit Racing61.95
Weiand rate Warrior intake8501Summit Racing209.95
Holley 750 mechanical-secondary carb0-4779Swap meet150.00
Comp nitrided Thumpr hydraulic cam12-601-20Summit Racing274.95
Comp pro Magnum hydraulic lifters858-16Summit Racing94.95
Bosch at sight + spark plugs7975Auto Zone15.92
Wix oil filter51069Summit Racing5.95
Wilson tapered 1-inch spacer004110Wilson Manifolds128.75
Machine Work810.00
Grand Total$5,739.34

Hot tank block$60.00
Bore and also torque-plate-hone290.00
Align-hone block190.00
Deck block190.00
Install cam bearings60.00
Hone damper20.00
Machine work total$810.00