331ci Ford Small Block Engine Build - Power Stroke
Learn how to build the 331ci Ford Engine
From the April, 2012 issue of Modified Mustangs & Fords
By Mark Houlahan
Photography by Panhandle Performance
1 Panhandle was provided...
1 Panhandle was provided a '91 5.0L roller block for the build that had already been machined. Like any good shop, it checked all machining specs and felt the bores were a bit tight. So, on the boring/honing machine the block went. A torque plate, head gasket, and ARP studs were used to pre-stress the block as if it had a cylinder head attached.
Stroker engines and kits are super popular these days. The simple fact is that when you start adding up the cost of a good crank, rods, and pistons, along with the machine work to fit it into your existing or new block, it's just a few bucks more to go with a stroker and reap the benefits of extra displacement without having to deal with an engine swap to a big-block and all the headaches that brings (cooling, exhaust, and so on). The Ford small-block engine has been benefitting from stroker engine technology for decades now. The 347ci stroker has been a popular upgrade and has been built in huge numbers over the years, mainly because it was the first stroker design introduced to the performance-buying public. Over the years, various derivatives of the 347, including the 342, 331, and 327, have been designed, built, improved upon, and made into proven combos that work.
2 The main bores were not...
2 The main bores were not within Panhandle's specs either. But before the main bores could be honed out to spec, the main caps were machined to accept a Panhandle Performance main support and the bottoms of the caps were surfaced to prepare them for the align-honing process.
3 The Panhandle main support...
3 The Panhandle main support system is mocked up here. Like honing the cylinder bores, the main bore will be honed with the main support in place, just like when the engine is in the car and running. The main cap machining allows the support to have greater surface contact with the main caps. The main support is made from 4140 chromoly steel and is 0.375-inches thick. The design clears most oil pans.
4 With the main support system...
4 With the main support system bolted down and the ARP retaining nuts set to the proper torque, the honing machine align hones the main bores to 2.442 inches, plus or minus 0.0001-inch. The remaining block prep included smoothing all of the block's rough edges, tapping the block for screw-in oil plugs, and inspecting the block's deck surface. For this particular block, the surface had been machined previously and Panhandle felt it was better to run it as is, than to cut the deck surface further.
5 Panhandle internally balances...
5 Panhandle internally balances its crankshafts for accuracy and rpm capability. The Scat crankshaft is balanced on this balancing machine using bolt-on counterweights to simulate the Scat I-beam rods and Ross forged pistons this engine is getting. Note the monitor in the background showing the user where and how much Mallory metal to install in the crankshaft.
6 The heavy Mallory metal...
6 The heavy Mallory metal slugs are installed in the crank’s end weights. This particular crank was balanced to within one gram, and received one 7/8-inch slug in the rear counterweight and two 7/8-inch slugs in the front counterweight.
7 With all machining of the...
7 With all machining of the block complete, the block is cleaned and final assembly can begin. Here the crank is installed on a fresh set of King main bearings (King bearings were used for the rods and cam as well), then the main caps and main support are installed and everything tightened to spec. End play and rotational tension were checked at this time as well.
The 347 stroker combination has had teething problems, that's for sure, and while they're sorted out today (This author has 114,000 miles on his personal 347), the slightly smaller 331 stroker was the answer to some of these problems early on. Today, the 331 is as popular as the 347, and some say a better choice of engine package due to its better rod ratio, lighter assembly, and higher rpm capability. A 347 owner will tell you that his engine makes a ton of torque, but the engine is far from a high-rpm screamer. The 331 puts more torque on the table (over a stock displacement small-block) yet still offers the high rpm capability that the original 289 and 302 were known for. Essentially, the 331 becomes a nice middle ground of torque, horsepower, and rpm ability, while offering the potential for longer service life over the 347 of similar build. We must say; that's worth the price of entry in our books.
8 Panhandle rarely uses an...
8 Panhandle rarely uses an off-the-shelf cam grind, preferring to have a custom grind made to match the build parameters of each engine. In the case of this 331 build, Panhandle reached out to Lunati for a roller cam capable of 7,000 rpm with the valvetrain planned for the build. The cam features an Everwear gear, which reduces wear issues induced by oil pump drive loads on the cam and distributor gear. The Everwear gear also allows any distributor gear to be used with it.
9 The rest of the bottom...
9 The rest of the bottom end parts, including the aforementioned Ross pistons and Scat I-beam rods, find their way to the Panhandle 331. Rings are Total Seal with a gapless top ring. Panhandle Performance uses a tension gauge to check oil ring tension in the block's bore to ensure it’s right for the intended application. Lastly, the Lunati custom roller cam and double roller timing set are installed.
10 Rolling the 331 over to...
10 Rolling the 331 over to expose its belly, the oil pump was installed (after being disassembled and having its clearances checked) along with the Canton Racing oil pump pickup. The pickup-to-pan clearance was set at 0.400-inch. The Canton pan has a kick out, as well as a T-shaped sump, along with trap doors to control oil and keep it around the pickup. Note the stock replacement timing cover is installed at this time and the oil pan surface leveled with the block.
We recently got wind of a 331 stroker engine being assembled by Mark Biddle and his crew of craftsman at Panhandle Performance, a well known and respected Ford engine shop in northern Florida. Panhandle Performance is known for its stroker builds, both in race and street configurations, for everyone from NMRA, NMCA, and NHRA drag racers, to road racers and serious street guys. Panhandle Performance built this particular 331 for a customer with a vintage Mustang who wanted the perfect trifecta of power: a road race, dragstrip, and street engine for his early Mustang. The owner wanted the maintenance-free power of a roller camshaft, high rpm ability, and be able to use pump gas for "stop anywhere" fill ups. See this 331 come to life and hit the dyno as Mark Biddle screws together yet another one of his small-block Ford masterpieces.
11 Rolling the engine back...
11 Rolling the engine back over, we're almost ready to install the ported Trick Flow Twisted Wedge cylinder heads and the rest of the valvetrain. But first, Panhandle sets a full brace of stock roller lifters into the block and retains them with custom billet lifter dividers. The thought here for dyno testing was use what’s widely available and cost effective and see how much rpm they’ll take.
12 Next, ARP head studs are...
12 Next, ARP head studs are threaded into the block and the head gaskets are slipped down over the studs. We're ready for some cylinder heads!
13 The Twisted Wedge cylinder...
13 The Twisted Wedge cylinder heads begin as stock bare castings that Panhandle builds to the needs of each engine build. In the case of this 331 stroker, the decision was made to use special seat cutters in the Serdi machine to enhance low-lift airflow.
14 Valves are from Ferrea...
14 Valves are from Ferrea and utilize hollow stems to save weight and give the engine an additional 500-1,000 usable rpm. Intakes are 2.02-inch and exhaust is 1.60-inch. Panhandle cracked open the Comp Cams catalog for the 331's beehive springs, retainers, and locks.
15 Panhandle is known for...
15 Panhandle is known for its head porting and these Twisted Wedges received plenty of TLC at the porting bench with Panhandle's Stage III porting and hand finishing. As cast, the Twisted Wedges flowed 249 cfm at 0.600-inch lift. The Stage III porting increased flow to 301 cfm at 0.600-inch lift. The port cross sections were kept small to maintain high velocity through the lift range. Final intake port volume was 185 cc’s and the combustion chamber measured in at 67 cc's.
16 For high rpm stability,...
16 For high rpm stability, a stout valvetrain is a must. Panhandle chose to use a shaft-based rocker arm setup from Harland Sharp. Unlike an FE with a common shaft, the Twisted Wedge uses individual shaft stands for each pair of rockers. Due to the fact that Panhandle used 5.010-inch length valves in these heads versus the standard 4.960-inch length, geometry setup will be extremely critical.
17 To check and adjust the...
17 To check and adjust the rocker's geometry, Panhandle used the rollout geometry method, in which the priority is to minimize roller travel across the tip of the valve. A cylinder head has been installed with checking springs and an adjustable pushrod. This allows the rocker geometry to be checked and adjusted as needed along with the proper length pushrod measurement and piston-to-valve clearance verified. On the exhaust valve tip, you can see the witness mark of the rocker's roller tip on the valve.
18 A set of custom Manton...
18 A set of custom Manton pushrods were ordered at 6.650-inch length once the pushrod length had been verified. These pushrods feature a 3?8-inch id for increased strength, but utilize a 0.065-inch wall thickness to keep weight down. This gives the engine the best of both worlds—a strong pushrod with low deflection. Minimizing the pushrod’s weight also translates to more accurate timing events at the valve too.
19 Panhandle used a Powerbond...
19 Panhandle used a Powerbond zero-imbalance damper for the 331's build up. While most DIY builders don't think (or know) to check it, the damper's press fit id is measured at Panhandle and honed to reach the proper clearance. The damper is then installed with antiseize compound and TDC is set with a piston stop so that the distributor can be installed.
20 Moving along, Panhandle...
20 Moving along, Panhandle finishes off the long-block by bolting down the ported Trick Flow heads and installing the rockers and pushrods. The 331-rpm monster is almost ready for the dyno.
21 For dyno testing, Panhandle...
21 For dyno testing, Panhandle started with a Parker Funnelweb intake. The Funnelweb is highly regarded as a horsepower producer for high-rpm Fords. Panhandle ported the Funnelweb to match cylinder head’s flow characteristics with special attention paid to port balance and manifold fit.
22 For an ignition system,...
22 For an ignition system, Panhandle used an MSD distributor curved for 21 degrees of mechanical advance using a combination of MSD’s blue advance stop bushing and blue advance weight springs. This will ensure full timing is in by 3,000 rpm. MSD's famous 8.5mm Super Conductor wires get the spark to the plugs.
23 Up first on the dyno was...
23 Up first on the dyno was the shop's dyno mule carb, a Demon 750. Timing was set at 33 degrees total for all testing (common combo that Panhandle has built before). Peak numbers were 501.4 hp at 7,200 rpm and 424.5 lb-ft of torque 5,200 rpm.
24 Next to be bolted to the...
24 Next to be bolted to the Funnelweb was a Holley HP Series 750-cfm unit. Yes, this is a vacuum-secondary carb, but Panhandle has used it on numerous builds from small-inch 302s to 408-inch Windsors with great results. The main drawback to this carb is the lack of a secondary accelerator pump for extra fuel on extremely fast throttle openings, but this will not affect dyno testing. When the dyno finished the pull on the Holley equipped engine the results were 515.2 hp at 7,200 rpm and 424.7 lb-ft of torque at 5,500 rpm.
25 The last of the carburetors...
25 The last of the carburetors that Panhandle bolted up to the 331 was a larger 950-cfm four-barrel from Pro Systems. While the Pro Systems carb had the same venturi size as the Holley, the throttle butterflies are larger (1.750-inch versus 1.690-inch). This can affect low-speed throttle response and power, but increase power at the top. The 950 dyno pull netted 514.1 hp at 7,200 rpm and 430.2 lb-ft of torque at 5,300 rpm.
On the Dyno
|Demon Carb 750||Holley HP 750||Pro Systems 950|