Way back when the polyspheric-headed small-block Dodges gave way to the “modern” LA engine in the ’67 Valiant, the Pentastar populous could not have known that their little creation was capable of making over 1.4 hp per cubic inch on plain old pump gas. A team of engine builders from SKMFX Racing Engines in Ontario, Canada, recently did that using cylinder heads designed when the LA was only a couple years old. Though much of the rodding community has moved to the cookie-cutter late-model EFI swap, the guys at SKMFX built this LA engine from old-school parts using new-era thinking. Lead engine builder Jesse Robinson ain’t no newbie when it comes to making power to go. As a two-time competitor in the AMSOIL Engine Masters Challenge, he’s done his share of research into what it takes to make power.
Team leader Jesse Robinson claimed that the number-one factor in the engine performing so
“I always liked the stock stroke deals,” he says. “Everybody’s building 408s and 416s out of the 340s with a 4-inch stroke. I built one for myself about eight years ago, and I didn’t like the power curve. It was all done by about 5,500, and it pounded the mains out of it. The caps like to walk, and it kind of turned me off. I built a real budget 360 about eight months after that 408, and bang for the buck it was about the most fun engine I’ve ever had.”
With those experiences in the back of his mind, Robinson decided that for the 2010 Engine Masters Challenge, he’d build a stock stroke 360 to bring back the fun factor. He rounded up an old 360 block, and after a good cleaning, gave it a short fill of Hard Block to stabilize the cylinders. SKMFX offers full machine shop services in-house so it was no biggie to bore and torque-plate hone the block .040 over. Robinson often leans on team member Joe Rutters to perform the machine work flawlessly, and he made sure that the hone job matched the intended ring package. Leaving the cylinder walls too coarse can prematurely wear the rings while some rings won’t seat quickly if the bores are too smooth.
Running an oil line across the lifter valley to even oil flow is not too uncommon for an L
Another of the techniques the team used to make the lightweight “A” engine scream was to mill the deck to an even 9.588 inches. Using that number as a baseline, subtracting half the stroke and the rod length of 6.123 inches revealed a final piston compression height of 1.675 inches. “Diamond [Racing Products] whipped me up some excellent pistons. That was my first time using an .043 inch with a Napier-tapered hook groove second, and low-tension oil rings, and boy, I specify that Napier second ring in everything now if I can.” Besides offering low tension and surface friction, he noted that the pairing of that Napier with the low-tension oil rings really helps keep the oil out of the chamber. “I think there’s something to be said for that second ring doing a lot of scraping and I think the low-tension oil rings are sealing better.”
Having seen previous issues with the two-bolt main small-blocks exhibiting signs of cap walk, SKMFX installed a set of ARP main studs. The extra pulling power of the studs kept the main caps from moving around as the crank spun through its rpm range. An Eagle forged steel crank was chosen and treated to Eagle’s Armor Shield treatment to reduce friction and shed oil. Since the steel crank was denser than the original cast-iron crank, it allowed them to internally balance the rotating assembly. Mopar engines that are externally balanced use a counterweight on the torque converter instead of the flexplate like the rest of the world. That tends to make balancing the crank with a fake converter “substitute” a real pain. Internally balancing alleviates that problem.
The Hughes lifters come with the top of the lifter body beveled to clear the severely angl
After reading some of contributing editor Steve Dulcich’s articles on small-block Mopars and W-2 heads a while back, Robinson decided to give the iron W-2 heads a shot. “We wanted to explore what those had to offer on a stock stroke 360. So we picked up a set in probably around 2000.” They’ve been sitting on them since then waiting for the right project to come along. “They’re very expensive to get going because of the support equipment you need to run them. They take dedicated rockers, a dedicated intake, dedicated headers, and so on.” Those dedicated accoutrements are the result of the engineers at Mopar pushing the envelope. They were designed from a mostly clean sheet of paper with the caveats being that it must bolt to a factory small-block without major modifications and it should be cast iron to meet various class rules. The result was rather interesting.
Obviously the designers looked at the primary restriction of the small-block LA heads—the pushrod pinch—and made that target number one. Anybody who’s worked with small-block Mopar stuff knows how skinny the port entrance is and if you get greedy porting for power it is all too easy to grind through into the pushrod hole. Not good. The solution in the W-2 was to basically make that pushrod hole solid and run the pushrod cocked over at an angle meeting up with extremely offset intake rocker arms. With the possibility now of having a big-ol’ intake port, they also spread the intake boltholes out to match. On the back side, they followed suit by spreading the exhaust port pattern out to maximize pressure relief.
Though the price was right online, the bargain-priced geardrive needed a bit of fitting an
As was intended, Robinson ported pretty much all the way through the cast iron where the “old” pushrod pinch would normally be. The W-2 pushrod holes are machined into the head and thanks to the smooth finish on the pushrod holes, Robinson was able to press in a sacrificial aluminum tube. Once he ground to the end of the cast iron and struck aluminum, he’d have something to seal the runner from the inside of the engine. The only downside of that was that he was forced to use a spindly (but thick) 5/16-inch-thick pushrod on the intake side instead of a beefy 3/8-inch pushrod like he had on the exhaust.
Robinson followed the path of his flow bench to get the flow numbers where he wanted them and then fine-tuned them on the dyno. He added about an 1/8 inch of epoxy to the floor to try to shrink up the port and raise the average runner height but said in the end it didn’t pick up over his already hot port work. Another spot he worked the epoxy magic was in the area around the valveguide. Cylinder head experts have been playing with wing designs behind the guide for decades and it seems there is no real consensus as to what works best. Robinson built up a basic straight-on wing to help guide the fuel and air to the spot in the chamber he wanted it entering.
Though the head was designed over 40 years ago, the combustion chamber received only minor
The W-2s require extra-long valves and Robinson went through a couple different valvespring setups in order to control them without wasting energy in friction. Initially running dual springs with close to 230 pounds on the seat, he backed off and switched over to lightweight beehive springs. T&D Machine 1.65 ratio rocker arms were chosen for their consistently high quality. “I can’t say enough about the T&D rockers. They’re pretty much flawless.”
One of the other W-2 deals is that they oil through the pushrods instead of through the block. While building their 360, the team paid attention to the oil system to make sure there was adequate fluid up top. Running a crossover oil line from the rear of the passenger side to the front of the driver side equalized flow to the hydraulic lifters. With oil flowing through the lifters and the hollow pushrods, the oil holes in the deck of the block were rendered obsolete. Some engine builders choose to block the holes while others just let the cylinder head or the head gaskets block them.
With almost ¾ inch of offset on the T&D shaft rockers, it’s easy to see that a stock rocke
While the camshaft controls the attitude of the engine, controlling that cam can be a problem. “The blocks are almost 9.6 inches tall from the factory, and I think the worst thing about them is probably that the timing chain length is quite a bit longer [than other small-blocks]. So the LA series engines beat the hell out of the timing chain pretty quick.” Robinson preempted that issue, buying a geardrive to run the cam. In true hot rodder fashion, he found the best deal for one on the web. “It was like $99 off eBay. Of course, I questioned its quality but I have a hardness tester here [Naturally. What? You don’t have that?] so I tested all of the components, and the gears were like high 50s Rockwell C-scale. Extremely hard, and the bearings looked like good quality. Yeah, there were some fitment issues, but other than that it worked great.” Score one point for the Internet! “The lower gear was one of those eight- or nine-tooth gears to adjust timing, but there wasn’t a 2- or a 4-degree spread. One would be 2 degrees and the other would be five and a half. So it took a little head scratching and careful marking to make it work.” Internet point now removed!
Robinson found the Eagle crank sporting their Armor Shield coating did a great job of prot
Once he had the geardrive sorted out, Robinson set the intake centerline to 101.5 degrees. Combined with a tight 104 lobe separation, the valves tricked the engine into thinking it has more compression than it really did. Here’s how.
As the engine rotates over after firing and the piston is being pushed down from the rapidly expanding flame front, the exhaust valve starts to open up a bit before the piston reaches bottom dead center, or BDC. That period of time is referred to as the blowdown period and fiddling with the exhaust opening point is a balancing act between extracting the maximum benefit of the still-expanding flame and making sure the valve will be open wide and long enough to get all that exhaust out. Of course as the piston passes BDC it can help shove that exhaust out. When the piston starts to approach top dead center (TDC), again is when things start getting tricky. The exhaust valve is on its way to closing and now the intake valve gets a head start by opening up. When both valves are open at the same time it is called overlap, and it’s the second balancing act that the camshaft has to control.
Even with a long rod and a 1.7 rod-to-stroke ratio, the tall deck height of the LA engine
If this overlap period is short (wide lobe separation), that means the intake valve is opening late and so, especially at low rpm, the exhaust tends to keep going out the tailpipe and not back up the intake valve—good for emissions and a smoother running engine. Nevertheless, by opening up the intake valve early and closing the exhaust valve later, the inertia of the exhaust going out the header can actually pull some intake charge into the engine and increase its efficiency at higher rpm, but it could also contaminate the intake with reversion at low rpm. Definitely a balancing act.
The final piece in the bumpstick puzzle is determining when to close the intake valve. The piston has now gone past TDC, all the way down the cylinder and is now moving past BDC. Since the piston can’t compress the air it just gulped until the valve is closed, it would make sense to shut it right at BDC to get the maximum compression. But wait, there’s more! Since the air and fuel coming in have mass and inertia, they are still pouring in even when the piston is back on its way up again. So, that last trick is to find the exact point to close the valve that is a perfect balance between the last few tidbits of air and fuel coming in versus shutting it and compressing what you got. That mother-of-all balancing acts is what top engine builders like the guys at SKMFX deal with in every engine they build.
For the Challenge, the team built this custom pan in hopes that it would pick up power ove
As a side note, astute readers will realize that both valves are going to be a little bit open when the piston is at TDC in overlap, but the piston is halfway down the hole when at max valve lift. That is why lots of overlap (aka tight lobe separation) and not maximum valve lift is what causes piston-to-valve clearance problems.
Hughes Engines is a name known in the Pentastar circle, and that was who provided the hydraulic roller cam and lifter set here. “I really like the hydraulic rollers. I’ve been putting them in everything,” Robinson says. He pointed out some things he was really impressed with on the Hughes lifters: “They were a true drop in, they oil through the pushrod, and they have the oil band in the right spot.”
SKMFX is attached to a larger industrial manufacturing facility and so has access to full
Once Robinson had decided where he wanted the valve timing events to occur, his next fight was trying to determine when to light the fire. The team had decided that though they typically run an MSD 7AL3 on their shop dyno, they would use MSD’s digital 6AL2 programmable ignition box. “What I did was mess around with the curve. I took timing out near peak torque and put it back in at the top and that was a solid 10 hp and 10 pounds of torque. Just with a little jag in the timing curve. I was really impressed with that.”
Once they had their tune-up perfected, they loaded up their creation in the back of the modern-day equivalent of the Little Red Wagon and headed to the University of Northwestern Ohio in Lima for the AMSOIL Engine Masters Challenge. Having tried several viscosities of oil in testing to see if one was better than another for a hydraulic roller cam, they selected six quarts of AMSOIL Synthetic 20W-50 oil to protect their baby, and strapped it to one of the university’s two DTS dynos. They fed the Holley carb a steady stream of Rocket Brand 91-octane pump gas and let her rip. As the rpm climbed, there was a sudden jump in the torque as the cam, intake, and headers all reached their happy spots and the horsepower gauge skyrocketed. The final number peaked at 519 horses. The torque was a stroker-motor-like 476 lb-ft. All from parts that were designed before man walked on the moon. Considering those ancient origins of their engine, Robinson, Joe Rutters, and Ron MacLean could not have been happier with their valiant effort.
Using out-of-the-box Shoenfeld headers, the guys were quite happy with the results. Time p
Using a Performer RPM intake manifold along with a four-hole-tapered spacer was the trick
The team had not used one of the 6AL2 boxes before and were stunned how they were able to
During dyno tuning, changing overall timing with their MSD Pro Billet distributor was a si
The SKMFX team used the NASCAR staple 830HP Holley carburetor. No super-trick billet hoo-h
With their race faces on, the SKMFX team showed up ready to turn up the wick. Once they pu
By The Numbers
SKMFX 360 Mopar
Displacement: 368 actual cubic inches
Compression ratio: 11.5:1
Camshaft: Hughes hydraulic roller
Cam duration: 238/242 degrees at .050-inch
Valve lift: .642/.642-inch
Rocker ratio: T&D Machine 1.65 ratio
Top ring: .043 Mahle
Second ring: .043 Mahle Napier
Oil ring: 3mm Mahle low tension
Crankshaft: Eagle Armor Shield treated
Rods: Scat 6.123 inch
Cylinder head: Mopar Performance Iron W-2
Intake valve diameter: 2.08-inch
Exhaust valve diameter: 1.60-inch
Intake manifold: Edelbrock Performer RPM
Carburetor: Holley 830 hp
Header: Schoenfeld 1¾ to 17/8 stepped
Ignition: MSD 6AL2
On The Dyno
360ci LA-Series Mopar