Tech Articles / Tech Projects

Ultra Engine: Hardcore Horsepower’s 781 Horsepower Big Block Chevy 540

(Image/Mike Petralia)

In the past, you’ve had to rev an engine pretty high to make serious power. But the latest cylinder heads and cam designs have allowed us to bring the RPM levels down, increasing engine longevity, and still make really good street power. We built a 540 cubic inch big block Chevy to take advantage of the new technologies.

The 540 Big Block Chevy Build

We started our build using a rather common approach—a 4.500 inch bore Dart Big M Sportsman GEN VI iron block, 4.250 inch stroke Eagle 4340 forged steel crank, and 6.385 inch, 4340 forged steel Eagle H-beam rods with ARP 7/16 inch cap screws. We topped the rods with a trick set of Mahle 4032 forged aluminum pistons with a 13cc dome profile, giving this engine a 91/93 octane pump gas- friendly 10.25:1 compression ratio. (There’s a full parts list at the bottom of this story.)

Oiling a solid roller-cammed street motor should not be left up to a cheap pan and pump combo. Our crankcase was sealed with a six-quart Summit Racing fabricated steel oil pan that features built-in windage controls, but no kickouts so it will clear just about any set of headers. An anti-cavitation Melling Select oil pump and a 3/4 inch welded steel pickup fills the Dart block’s priority main oil passages with Driven DT40 Synthetic Street Performance Oil.

For the top end we drove three hours south to our buddies at ProMaxx Performance in Rainbow City, Alabama to pick up a bare set of their Shocker CNC-ported aluminum heads and one-piece stainless 2.300 inch intake and 1.880 inch exhaust valves. We created a custom spring package in-house using 1.625 inch diameter valve springs (273 lb. installed pressure, 685 lb. open pressure), titanium retainers, and 10-degree steel locks. The springs can easily handle 0.750 inch lift solid roller cams and 7,000 rpm. We backed up the springs with stiffer .135 inch wall, 3/8 inch diameter hardened steel pushrods.

While we only share our custom cam specs with the paying customer, we will tell you that we like to run our springs close to coil bind and had Lunati grind us a billet solid roller stick rated at 0.750 inch-plus valve lift on a 112° lobe separation angle (LSA) to stay EFI friendly on the street. Solid roller lifters and Comp Cams Ultra Pro Magnum XD 1.7:1 ratio roller rockers do a fine job of moving the valves. A stud girdle was added to stiffen the valvetrain and keep the rockers in order.

Induction was handled by Holley’s Sniper EFI Stealth 4500 system. Although Holley doesn’t recommend using a system this big on engines making less than 800 horsepower, we felt it would do OK since we designed this engine with this exact scenario in mind—and it worked flawlessly. The warning is mostly for people who just want the big Dominator carb look or already have a mismatched Dominator carburetor on a poor-running or smaller engine and think EFI will fix everything. That’s not how it works. If you don’t design your engine properly from the start, a big EFI system will hurt more than it will help.

The right intake manifold is also critical to making this EFI package work. We choose a Brodix HV intake for its smaller “cloverleaf” style plenum that reduces overall volume to improve throttle response and mid-range performance on smaller cubic inch engines. Believe it or not, 540 cubes is considered small in today’s world. The manifold’s single plane design helps the built-in MAP sensor in the Holley Sniper throttle body see a more homogenized manifold signal for better bank-to-bank fueling. We’ve tried Sniper EFI on dual plane intakes with full dividers and have seen large variances in left and right bank air-fuel ratios. Since the Sniper EFI uses a single A/F sensor on one side of the engine, we want to give it the best mixture signal we can.

Ignition timing and spark were controlled and delivered by Holley Sniper/Hyperspark ignition components. While we could have run just about any ignition system with the Sniper EFI, using matched components from Holley makes for much easier, plug-n-play connections. The Hyperspark distributor drops right in since we had Lunati fit our cam with an “Everwear” press-on distributor gear. A bronze gear will eventually wear out, causing timing retard and potential destruction of the engine if not caught early enough.

Spark is generated by a Hyperspark coil and amplified with a Hyperspark ignition box, all controlled by the Sniper ECU. NGK resistor plugs and Accel suppression core plug wires were used because EFI does not play well with RFI noise.

Our 540 Chevy Big Block Goes to the Dyno!

Some people fear testing with EFI. Actually, it’s not challenging at all when you know how to properly configure the parameters and can carefully monitor the engine’s vitals during the critical break-in and tuning process. Our in-house Dynomite Dynamometer gives us that ability. We employ dual wide-band air/fuel ratio sensors from Daytona Sensors in addition to the single Bosch sensor included with the Sniper EFI kit. This gives us the ability to “see” both sides of the engine, which often have A/F ratio disparities.

While there’s no easy way to correct bank-to-bank A/F ratio differences with the Sniper system, we feel it’s a small issue compared to the big power it makes. We’ve mostly seen large variances at idle. When you start to get into the throttle, things begin to even out; by the time we’re at WOT the engine’s average A/F ratio is pretty even bank-to-bank.

Our best dyno run of the day netted an impressive 781.6 horsepower at 6,400 RPM and 721.7 lbs.-ft. of torque at 4,900 RPM. Earlier low-RPM tuning showed over 500 lbs.-ft. of torque at 2,500 RPM and 671 lbs.-ft. at 3,000 RPM.

This thing is gonna love the street!

***

Short Block Parts

Oiling System Parts

Valvetrain Parts

EFI and Ignition Parts

Misc. Parts

***

This 540 cubic inch big block Chevy was built to handle 7,000 RPM thanks to an internally-balanced 4340-forged steel Eagle/Mahle rotating assembly with ARP hardware. The Dart Big M Sportsman block features 4-bolt iron main caps at all five positions. Dart offers upgrades to main studs and billet caps, but neither are necessary for this power and RPM level. (Image/Mike Petralia)
Aftermarket blocks like our Dart Big M have vastly improved oiling systems compared to factory GM blocks. We don’t use traditional oil restrictors in our street engines because we like to have full oil supply at the lifters as they (or sometimes the pushrods) become the final oil restriction. The solid roller lifters we used limit the amount of oil flowing up to the heads, keeping more oil in the bottom end for the crank and bearings. We installed a single restrictor at the very end of the passenger side lifter galley right before it dumps oil into the distributor hole. The aluminum restrictor is drilled with a .030″ hole and pressed into the oil galley from the back of the block using a simple drive mandrel made from a 7/16″ bolt. We add red Loctite around the plug to ensure it won’t back out. Setting the proper depth of this plug is crucial otherwise you won’t be able to get the distributor in the block. (Image/Mike Petralia)
The rings are included with the Mahle piston kit. We use a Total Seal ring grinder to file-fit them to the proper gap for the engine’s application and type of fuel used–street/strip and unleaded pump gas in this case. (Image/Mike Petralia)
The Mahle forged aluminum pistons require proper side clearance. We measure every bore and piston with more precise gauges, but you can use a stack of feeler gauges to do a quick and easy clearance check at home. Our stack of gauges measured 0.0045″ and the piston just slipped by. This means we have at least .0045″ clearance. The Mahle catalog specifies minimum clearance of 0.0041″ and a maximum of 0.0049″, so we’re within spec. (Image/Mike Petralia)
We only reveal full cam specs to our customers, but we can tell you our custom Lunati solid roller has close to .750″ net valve lift (with 1.7:1 ratio rockers) on a 112° lobe separation angle (LSA) and a 110° intake centerline. That means the intake lobe has 2 degrees advance ground into it that cannot be changed without regrinding the cam. We degreed the cam straight up. (Image/Mike Petralia)
The solid roller lifters we used provide the final oil restriction, keeping more oil in the block and not pumping the pan dry. They also provide high pressure pin oiling to the roller bearings to make sure they live on the street. They are designed to work with valve springs rated at 150-275 lbs. seat pressure and 400-700 lbs. open pressure up to 7,500 RPM. Traditional oil restrictors are not recommended with these lifters. (Image/Mike Petralia)
We picked up a bare set of “Shocker” CNC-ported aluminum heads, stainless 2.300″/1880″ valves, and hardened pushrod guideplates from ProMaxx. The intake ports are 340cc and exhaust ports are 135cc. (Image/Mike Petralia)
The chambers spec out to be 121cc, but we measured them at 123cc. We ran a slightly thinner Cometic MLS head gasket to make up for the small loss of compression the larger chambers would have caused. (Image/Mike Petralia)
The Mahle pistons measured 40cc at .200″ down the bore, which calculates to just over 12cc actual piston dome volume. We ended up at 10.28:1 compression, which is perfect for this combo. (Image/Mike Petralia)
ProMaxx Shocker heads feature an extra hole underneath to add one more head bolt. The bolts must be installed and torqued from the lifter valley, and cannot be torqued to normal torque specs because they’re pulling on soft aluminum threads. We torque the bolts to just 50 ft.-lbs. using a special offset wrench adapter. The extra head bolts must be ordered directly from ARP. (Image/Mike Petralia)
Another part we special order from ARP are the rocker arm studs. The ARP stud is on the left. Since these engines experience higher spring pressures on the exhaust side, we like to run exhaust rocker studs with longer threads to help prevent them from pulling out of the head. This requires measuring the stud holes to be sure they’re deep enough and running a bottoming tap in them before assembly. (Image/Mike Petralia)
We like to run lash caps on solid roller engines to prevent the valve tips from getting beat up. The lash cap will affect overall pushrod length, so we measure and install custom pushrods and check geometry at full lift (shown) to be sure the pattern is correct. (Image/Mike Petralia)
We’ve had great success with Brodix HV intake manifolds. This one needed just a little bit of cleanup in the plenum area. The ports were fine so we didn’t touch them. (Image/Mike Petralia)
Since we always recommend running a functional thermostat on a street engine, we had to modify the Brodix manifold to fit one since they’re not cast for that option. (Image/Mike Petralia)
We’ve found that even quality intake gaskets need to be re-torqued several times to get a final set. 3-4 reps will usually do it after the engine heat cycles a few times. We do this on the dyno, but you can do it in the car as well. (Image/Mike Petralia)
It’s difficult to install stud girdles on big block Chevys and other engines with canted/splayed valves due to the compound angles of the valves and rocker am nuts. We’ve found it best to run the girdles as close to the top of the rockers as possible and check lash as we tighten the girdles. Otherwise, things can move around a bit and change your lash settings considerably. They certainly are not a set-and-forget option, but the girdles do help build power and reliability if done correctly. (Image/Mike Petralia)
Running roller cams can kill a distributor gear. We had Lunati install an “Everwear” cam gear on our camshaft so it’s compatible with any distributor. We pull the distributor occasionally during testing to be sure they’re OK. This is the cast Holley Hyperspark gear after many dyno pulls. (Image/Mike Petralia)
On the dyno, peak horsepower was right where we expected it to end up. But torque was higher than expected, most likely due to the Holley Sniper EFI’s mixture efficiency. Check out the air-fuel ratio numbers. The Holley A/F sensor was in the left side of the engine (A/F L) and it was holding our commanded 12.5:1 A/F ratio perfectly. We run our dyno tests at a realistic street water temperature of 180° F since the Holley ECU doesn’t start learning until the temperature reaches 170° F. Beware of shops showing street engines with dyno runs around 150° F or lower; your street engine doesn’t run there, so those power numbers are misleading. (Dyno Chart/Mike Petralia)
We ran Hooker Super Competition passenger car headers with 2 1/8″ primaries during our dyno testing (HOK-2287HKR). Another misleading power tactic other dyno shops will use is to run dyno-specific headers designed to extract more power. But your passenger car headers might not perform as well, so we run ‘real’ headers right out of the box. (Image/Mike Petralia)

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5 Comments

  1. Would love to know the 2021 cost for the completed package! Parts, labor & dyno tuning?

  2. Robert sheehy says:

    What’s a price of this beast $ looking for my 57 chevy one

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