Solid Roller Cam and Single Plane Intake Manifold Upgrade for a 427 Big-Block

Here is a quick recap of the motor before we tore it down. The Dart Big M block features four-bolt ductile iron main caps, has a bore range of 4.250 to 4.625, and reconfigured oil passages. The rotating assembly consisted of a forged 4340 chromoly-steel crank and I-beam rods from Eagle, JE 30cc domed 4.280 pistons (10.25:1), Big Mutha Thumpr from Comp (intake/exhaust 0.522/0.507 lift, 295/312 duration, 243/257 duration at 0.050, and a 107 lobe separation angle), Ultra Pro Magnum 1.7 ratio roller rocker arms, Weiand high-rise/dual-plane intake, Holley 750 cfm Street HP carburetor, MSD Digital E-Curve distributor, ATI's Super Damper, Moroso billet spur gear oil pump, and six quart pan. That combo, with 80 primary and 84 secondary jets, put down 507 hp at 6,000 rpm and 471 lb-ft at 4,100 rpm. Not too shabby for a 427, but we found out there was more to be had.

Here is a quick recap of the motor before we tore it down. The Dart Big M block features f

Back in our January issue, we built our own version of the L89 big-block 427 using all aftermarket components. Our rev-happy Rat combo used a Dart Big M block, Dart 275cc Pro 1 heads, Eagle crank and rods, JE pistons, Weiand dual-plane intake, Holley 750 HP carb, and a Comp valvetrain, including a Big Mutha Thumpr cam. The recipe ended up producing 507 hp at 6,000 rpm and 471 lb-ft at 4,100 rpm.

Being the power junkies that we are, the engine wasn't even cooled down before we asked Jeff Strech (Speed-O-Motive's engine guru) "What can we do to make more?" Without hesitation he said, "Your combo is not using the heads to their full potential. We can swap in a bigger cam and a single-plane intake to wake that sucker right up."

While the Big Mutha Thumpr cam sounded very aggressive at idle, the 0.522/0.507 (intake/exhaust) lift was not using all the air flow capabilities the Pro 1 heads provided, just like Jeff had said. The heads flow (per Dart's flow sheet) 352cfm intake and 258cfm exhaust at 0.700-inches of lift at 28 inches of water.

Not needing any more convincing than that, we sat down with Jeff and picked his brain for a cam and intake selection. Jeff said, "The intake is easy-just pick up Dart's single-plane. For the cam, let's go with a custom grind I've had excellent results with." We let him know this better not be some secret grind because we were going to publish the specs.

He was cool with that so we grabbed the Comp Cams catalog and flipped to the BBC solid roller section. Jeff told us to have a solid roller ground with Hi-Tech 0.420 lobes, lobe number 4017 on the intake and lobe number 4024 on the exhaust, that have 0.715 lift specs, a 108 degree lobe separation, and a 4/7 firing order swap.

We will get into specifics of all this in the photo captions. We also picked up a Cloyes timing chain cover from Summit Racing with an integrated cam button to simplify setting the cam endplay. Plus, the stock stamped cover was too flimsy to keep this cam under control anyway.

We did all the work and dyno testing over at Speed-O-Motive in Covina, California, with Jeff doing most of the grunt work. We also have video of the engine making a pull so be sure to check out www.superchevy.com so you can hear it for yourself.

Here is the single-plane oval port intake manifold we ordered from Dart. The high-rise intake is intended to produce power at higher rpm with a power range of 3,000 to 8,500. It is designed for 4150- and 4500-series carbs, features extended runner dividers to equalize port length, and raised water crossover and plenum to insulate the air fuel mixture from engine heat.
Here is the single-plane oval port intake manifold we ordered from Dart. The high-rise int
Our custom ground solid roller bumpstick from Comp Cams was just the thing we needed to wake up our 427. The cams specs are as follows (intake/exhaust): 0.715/0.715 lift, 296/304 duration, 260/268 duration at 0.050, and a 108 lobe separation angle. Jeff not only recommended the cam specs he also told us to use the Hi-Tech 0.420 lobes (PN 4017/intake and 4024/exhaust), which feature a ramp design that is easy on valve springs, yet produces good power. These lobes are primarily used in oval track, bracket, and marine applications where power with durability is a must.
Our custom ground solid roller bumpstick from Comp Cams was just the thing we needed to wa
After tearing down the motor, the new cam was slipped into place with plenty of assembly lube. We asked Jeff what is the benefit of having a 4/7 swap ground into the cam. He said, "On the Chevy motors, the number 4 cam bearing has extra load put on it because the number 5 and 7 valves are open at the same time. Also since 5 and 7 intake ports are next to each other, when the number 5 cylinder valve opens it disrupts number 7's intake charge. The swap cures these issues and makes the motor a bit more efficient."
After tearing down the motor, the new cam was slipped into place with plenty of assembly l

The lifters were soaked in oil for a half hour or so before being dropped in.
One thing to note on the tie bars. Make sure the arrows are pointing up or bad things can happen.
One thing to note on the tie bars. Make sure the arrows are pointing up or bad things can
Since a solid roller needs more spring pressure to prevent valve float, we changed the ones from our hydraulic cam. The solid roller lobe has a more aggressive ramp rate and opens the valve quicker. We used a Comp dual valve spring set (PN 953) that Speed-O-Motive polished, to keep the valvetrain under control. Here, Jeff is checking install height, along with retainer to guide/seal clearance.
Since a solid roller needs more spring pressure to prevent valve float, we changed the one

With the install height measurement and the cam specs, Jeff can figure out the seat pressure, open pressure, and coil bind. These springs gave us 200-lb seat pressure, 600-lb open pressure, and 0.100 before coil bind with the lift of our cam.
With the install height measurement and the cam specs, Jeff can figure out the seat pressu
With a dial gauge and degree wheel, Jeff checks the piston-to-valve clearance. We ended up with 0.187 on the exhaust and 0.145 on the intake. What is not shown is the installation of the new timing cover. We got so caught up in a bench racing session that we forgot to snap a picture. Just know that Jeff set the cam end play to 0.010 so the cam can move a bit to mesh well with the distributer gear.
With a dial gauge and degree wheel, Jeff checks the piston-to-valve clearance. We ended up
With all the springs changed, it was time to figure out pushrod length. Jeff grabbed a few but just couldn't get a contact patch he was happy with. He installed some lash caps on the tips of the valve stems, and with 8.650-inch (intake) and 9.600-inch (exhaust) length pushrods, he got the contact patch you see here. That little contact patch is rocker sweep on the tip of the valve through full articulation. The idea is to have it centered and as thin as possible. This is the type of attention to detail you get when a professional shop builds your stuff.
With all the springs changed, it was time to figure out pushrod length. Jeff grabbed a few

With good contact patches on the valves, Jeff sets the initial cold lash to 0.14. The hot lash will need to be 0.20 but from past experience Jeff knows that an aluminum head will grow about 0.06. Now if it were an iron head, the cold lash would be 0.18, and if it were an aluminum block and heads he would set it to 0.08.
With good contact patches on the valves, Jeff sets the initial cold lash to 0.14. The hot
The single-plane was next on the to do list and it was installed with a Mr. Gasket intake gasket (PN 107) that we got from Summit Racing. Boy, you sure can tell this intake was designed for these heads; the casting looks like it carries right into the head.
The single-plane was next on the to do list and it was installed with a Mr. Gasket intake
A few of you had asked for a closer picture of the Ansen valve covers we had made for this project. These are the same covers found on Motion and Yenko motors, but ours has a laser-etched Dart logo in the window instead.
A few of you had asked for a closer picture of the Ansen valve covers we had made for this

Now it's time to see if we lit a fire under this rat's butt. After breaking in the cam just a bit and letting the engine come up to temp, it was shut down and all the bolts and such were checked. Jeff set the timing to 32 degrees total and put in 79 primary and 84 secondary jets, which got us to 557 hp at 6,000 rpm and 500 lb-ft at 5,600 rpm. That's a 50 hp and 29 lb-ft gain, but Jeff knew there was more. He inspected the plugs and air fuel numbers and determined the engine was lean.
Now it's time to see if we lit a fire under this rat's butt. After breaking in the cam jus
He put in a one-step colder plug (NGK R5671A-10), went up on the jets by two sizes, set the timing to 36 degrees total, and installed a 1-inch spacer from Trans-Dapt Performance. Since the last pull looked like it had more to give, Jeff also upped the rpm to 6,500. How about 575 hp at 6,500 rpm and 505 lb-ft at 5,600 rpm?...
He put in a one-step colder plug (NGK R5671A-10), went up on the jets by two sizes, set th
...That is a 68 hp and 34 lb-ft gain over our last combo. What is really nice is the fact that at no point did we lose any power or torque compared to the old combo. Now we have even more power and torque to move our heavy Chevelle and it sounds even meaner than before. Remember, we shot video of the dyno pull so make sure to visit www.superchevy.com and check it out.
...That is a 68 hp and 34 lb-ft gain over our last combo. What is really nice is the fact