For more than a decade, small-block Ford guys have argued the merits of the 331 versus 347ci stroker small-blocks. For the past several years there's been a clear answer: Skip all that and build a 363. If you missed the debate, here's a backgrounder. The Ford small-block Windsor engine family offers two block-deck heights: 8.2 inches for the 221, 260, 289, and 302, and 9.48 to 9.5 inches for the 351 (there are also aftermarket race offerings in 8.7 and 9.2). The factory-offered deck heights offer two dilemmas for hot rodders. First, the 8.2-inch engines require intakes, distributors, oil pans, and sometimes headers that are different from the 9.5-inchers. Second, the engines with the taller deck heights are also 2 or 3 inches wider and taller, depending on the parts used. That can cause fitment problems in tight, early-'60s Ford engine compartments or in street rods. Those are a couple of reasons many guys stick with the low-deck engines, even though the 351-based mills make it easy to get 408 to 454 ci. Another reason is that many use boost to make up the displacement deficit. So, if you've settled on a 302-based, low-deck- height mill, which one?
THE OLD SMALL FORD
STROKER OPTIONS
A stock 302 uses a bore and stroke of 4.00 x
3.00. By using an overbore of 0.030 inch and
an afermarket 3.250-inch stroke, you get
331 ci-a setup that is most commonly run
with 5.4-inch rods and piston compression
heights of 1.175 inches. Te same overbore
with a 3.400 stroke delivers 347 ci. With
the 5.4-inch rods, the 347 pistons have
a compression height of 1.090. That's
admittedly slim for a street engine (they
require a ring-support rail because the rings
hang into the hole for the piston pin), so the
aftermarket came up with 5.315-inch rods
that use pistons with the same 1.175-inch
compression height used in the 331.
Piston-ring issues aside, guys were already
arguing about rod ratios of the 331 versus
the 347. Rod ratio is the rod length divided
by the stroke, and in theory, ratios around
1.8:1 are good, and get worse toward the
point of 1.5:1, which is really bad. In a 331,
it's 1.66:1; a 347 with 5.4-inch rods is 1.59:1;
and with 5.315-inchers, it's 1.56:1. According
to many web-forum experts, the 347's rod
ratio is a disaster. According to us, it doesn't
mean squat-especially in the world of
street/strip engines under 7,000 rpm.
And, according to the bench racers, the
331 makes better top-end power while the
347 makes better low-end power, due to its
longer stroke. In our world, all that matters
is cubes.
ALONG COMES THE 363
News flash: Bigger bores mean more
displacement. Te 363 stroker has a 3.400-
inch stroke just like a 347, but it uses 4.125-
inch bores instead of a puny 4.030.
This means a bonus of 16 ci (or about 20 hp on
an average street engine), but the larger
bores also add up to more intake airflow-
regardless of the cylinder head used-due to
unshrouding the valves.
The financial downside is that big bores
can only be had with an aftermarket block.
Five or six years ago, aftermarket blocks fell
into the reach of the mid-range hot rodder,
specifically with the Ford Racing Boss 302
block (which is called Boss even though it's
a regular Windsor) and the Dart SHP line of
entry-level iron castings. We used the Dart
unit, which is $1,865.41 at Summit Racing
(the Ford blocks are typically $100 cheaper,
but they are delivered rough-bored, so the
machine work eats up that difference). That's
about $2,000 shipped to your door, which
may have you in sticker shock. But consider
the benefits.
Most important, stock 302 blocks will
literally break in half when you get north
of 500 hp, so if you ever plan on going
there, you've got to go aftermarket. Also
consider the price of rebuilding a stock
block: cleaning, crack-checking, thread
chasing, align-boring, decking, boring,
honing, stroke-clearance-it adds up, and
it's money you usually won't spend on an
aftermarket block. Summit Racing offers a
machined stock block for $689.95, which
is about as cheap as it gets. But it still can't
endure real power.
Engine Specs DESCRIPTIONSPECS Bore x stroke4.125 x 3.400 Rod length5.400 Piston compression height1.090 Piston dish-16cc Piston deck height0.013 down Cylinder head chamber size62cc Head gasket thickness and bore0.041, 4.200 Compression ratio9.26:1 Comp Cams Nitrous HP cam specs232/244 duration at 0.050, 0.565/0.580 lift, 114-degree LSA
AIR-GAP
VICTOR JR.
RPMLB-FTHPLB-FTHP
3,000372.6212.9352.8201.5
3,100380.6224.6355.4209.8
3,200390.9238.2362.0220.6
3,300399.6251.1369.7232.3
3,400408.0264.1377.7244.5
3,500416.0277.3384.3256.1
3,600423.8290.5390.5267.7
3,700431.6304.1397.0279.7
3,800436.8316.0404.9292.9
3,900441.0327.5412.7306.5
4,000444.8338.7419.4319.4
4,100447.3349.2424.1331.0
4,200449.2359.2426.7341.2
4,300450.9369.1428.7351.0
4,400451.7378.4430.5360.7
4,500451.9387.2434.3372.1
4,600451.8395.7439.9385.3
4,700450.8403.4443.9397.2
4,800449.2410.5446.3407.9
4,900447.3417.3447.7417.7
5,000445.3423.9448.8427.3
5,100443.6430.7449.3436.3
5,200442.1437.7447.4443.0
5,300439.8443.8444.5448.5
5,400436.9449.2441.8454.3
5,500433.7454.1439.8460.6
5,600429.4457.8437.2466.1
5,700424.7460.9433.8470.8
5,800419.5463.3430.2475.1
5,900414.8466.0425.4477.8
6,000410.4468.9420.9480.9
6,100405.4470.9415.1482.2
6,200399.1471.1409.5483.4
6,300392.1470.4402.9483.3
6,400386.4470.9395.6482.1
6,500377.6467.3387.6479.7
6,600
We tested both an Edelbrock RPM Air-Gap dual-plane and a Victor Jr. single-plane. The results were predictable: The dual-plane makes more power below 5,000 rpm, and the single-plane makes more power above that point. In this case, we think the Air-Gap is the best choice, even on the dragstrip. On our Facebook page, we play Guess the Power. Reader Mike McDonald won, estimating 477 hp at 6,300 and 450 lb-ft at 4,200.
THE DART SHP BLOCK
The SHP offers tons of beef beyond a
stocker: priority-main oiling, larger water
jackets, siamesed bores, beefier cylinder
walls (0.250 inch up to a 4.185-inch bore),
0.625-inch-thick decks, and steel, four-bolt
main caps. Unlike the stock blocks, the
cylinder-head boltholes are blind (they
don't go into the water jackets) and drilled
for 1-inch bolts instead of 7/16 inch (the
stock small bolts often require spacers for
use with aftermarket heads). The block is
also preclearanced for a 3.400 stroke with
H-beam rods. All the machine work is done
apart from final honing to fit your pistons
and rings of choice. You'll find many crate-engine
suppliers using this block as the basis
for engines they assemble in their own shops,
though Dart also offers complete short-block
assemblies with cast or forged cranks.
While Dart suggests a limit of 700 hp on
the SHP block-preferring the Iron Eagle
block for real race use-we've seen 'em
survive at least 1,000.
OUR TEST MULE
It's about time HOT ROD had a little Ford to
flog, don't you think? We did, so in this story
you'll see the details of a Dart-based 363 we
built for a number of upcoming tests. In this
first story, we made 471 hp and 452 lb-ft
with just 9.26:1 compression. Why such low
compression? Because the next step involves
something that rhymes with ubercharger
with a catchy chorus of 700 hp. See it in the
next issue.
HOW'S IT DRIVE?
This Dart mill found its way into our
RAUNCHero that you read about a few
pages ago. We can't deny that the application
wasn't right for the car in its current
trim. It was loaded to the rafters with gear,
including an extra set of tires and wheels,
and hampered by a tight converter, 2.80:1
gears, and 27-inch tires. As such, it was a
slug below 4,000 rpm. Approaching the
6,200-rpm power peak in top gear meant
180 mph, and we'd obviously never get
there. There wasn't enough vacuum for the
brake booster, either.
In all, the cam's too big. Our plan is to
solve the bottom-end power with a blower,
but if you want to duplicate our worst-case
scenario, we'd go for something along the
lines of a Comp XR270 with 218/224 at
0.050, 0.513/0.513 lift, and a 110-degree LSA.
If you want to make 500 hp carbureted,
we'd use about a 3,000-rpm converter,
4.10 gears, and a cam with a tighter
lobe-separation angle than the 114 in our current
Nitrous HP cam. Use 10.5:1 compression
and a Comp XR288 with 236/240 at 0.050,
0.555/0.576 lift, and a 110-degree LSA.
Pay Up
Description Part Number Source Price Assembled SHP short-block NA Dart $6,001.80 Black spray paint NA VHT 7.95 Upgraded valvesprings 985-16 Comp Cams 92.95 Lightweight steel retainers 1730-16 Comp Cams 156.95 Nitrous HP Cams 35-560-8 Comp Cams 295.95 Short-travel hydrualic roller lifters 877-16 Comp Cams 239.95 6.450-inch-long Hi-Tech pushrods 7766-16 Comp Cams 145.95 Ultra Pro Magnum roller rockers 1632-16 Comp Cams 386.95 Billet timing chain set with Torrington bearing 7138 Comp Cams 99.95 Lifter spider and dog bones 35-1001 Comp Cams 42.95 Cam thrust plate M-6269-A302 Ford Racing 11.95 Thrust-plate bolts NA Hardware store 1.32 Cam bolt 154-1001 ARP 2.82 Timing cover NA Swap meet 20.00 R.A.C.E. gasket and seal kit Q2718 Fel-Pro 24.75 Rattler damper 870010 TCI Auto 345.95 Damper bolt 150-2503 ARP 23.80 Oil pump 18800 Milodon 63.95 Oil pickup* 18380* Milodon 66.95 Oil pan* 31125* Milodon 292.95 Oil pan gasket 41003 Milodon 32.95 Oil pump driveshaft 22500 Milodon 21.95 Gold oil filter HP-3001 K&N 9.95 10W-30 break-in oil 1590 Comp Cams 35.70 Pro 1 aluminum 195cc heads 13211112 Dart 1,576.52 MLS head gaskets Q1135 Fel-Pro 75.95 Head bolts, 1.2 inch 154-3603 ARP 77.98 M/T valve covers NA Swap meet 60.00 Valve cover breathers SUM-G3401 Summit Racing 4.50 Valve cover gaskets Q1684 Fel-Pro 39.95 Valve cover gaskets Q1684 Fel-Pro 39.95 Air-Gap intake manifold 7521 Edelbrock 254.95 Intake gaskets Q1262 Fel-Pro 21.25 Ultra HP 750-cfm carburetor 0-80803BL Holley 667.95 Ready-To-Run distributor with steel gear 83521 MSD 424.95 Black Super Conductor plug wires 31233 MSD 85.95 Spark plugs R6601-8 NGK 26.99 Accessory bolt kit 554-9501 ARP 215.84 Total $11,959.12
