When our GMC Sprint damaged the beast of burden stock small block 350, we decided to turn it around with something a little different. Building a stroker is a “no-brainer” for a torquey monster, but we wanted to achieve the extra cubic inches with connecting rod length. A long rod stroker for a long, dependable engine life with the torquey bottom end as a kicker. Using performance parts from Chevrolet Performance, K1 Technologies, Clevite, Canton Racing Products, Victor Reinz and a Fluidampr harmonic balancer, our crew at L & R Engines went to work on creating our newest bullet.
We’ve been known to push the borders, especially with crate engines, just to find out where the edge really is. Company’s like Chevrolet Performance publish safe operating parameters, and we’ve consistently found a little extra beyond the published maximums. Occasionally we find the limits, which is what happened to our GMC Sprint project car recently. After doctoring up a Chevrolet Performance crate engine with a top end rebuild, we set out to perform our version of a stress test.
Obviously the purpose of a stress test is to stress the parts, and we managed to ding a piston in our “anything goes” test session. After taking a look at the damage, which was very minor, we decided to take things up a notch by turning our SBC 350ci crate into a 383ci small-block Chevy. 383ci stroker builds have been around long enough that engine builders know how to build dependable stroked out engines, but we wanted to show how using a longer connecting rod might improve the longevity of the build.
Why Build A Stroker?
An old hot rod adage states simply, “There is no replacement for displacement.” Bigger cubic inches are almost always better in the gear head world, especially when you can build a larger displacement 383ci instead of a 350ci for roughly the same price. Unlike the early 70s when 383ci strokers saw the light of day, there are a large assortment of brand-new, fully machined, and ready-to-install stroker cranks on the market. Why build down when you can supersize without costing more?
“383’s are our bread and butter and we do a lot of them,” said Derrick Rainey of L & R Engines. “A long time ago there was a lot more work involved in the 383 strokers than there is now. You’d have to do your homework and figure out the math where now the parts are available. I’ve been doing this for over 30 years and I can remember guys getting the Oldsmobile 6-inch rods, and get the 400 pistons with the crank and grind the journals down to fit the 350 block. It was a lot more work and a lot more money. Hot rodders want the cubic inch and people would do these things. You’d see all kinds of weird combinations,” he recalled.
A rod’s function is to connect the piston to the crankshaft. Period. – David Reher
The longer 3.75-inch stroke in the 400ci engine compared to the stock 350’s 3.48-inch stroke added some displacement. Most used 350ci blocks required an overbore of 0.030-inch to clean up the bore properly during rebuild. The longer stroke combined with the overbore adds 28 cubic inches to the block’s displacement. Speaking strictly by the numbers, this combo equates to a 382.6ci which is rounded off to the nearest whole number 383ci.
We are reusing several components from our initial parts upgrade:
- Comp Cams Xtreme Energy Cam, Part #12-246-20
- Racing Head Service Pro Action SBC Cylinder Heads, Part #12052-01
- Comp Cams High Energy Hydraulic Lifters, Part #812-16
- Comp Cams Magnum Pushrods, Part #7695-16
- Comp Cams High Energy™ Die Cast Aluminum Roller Rocker Arms, Part #17002-16
- Comp Cams Pushrod Guide Plates, Part #4808-8
- Edelbrock Performer EPS Intake Manifold, Part #27013
- Edelbrock Performer Series Carburetor, Part #14063
- Edelbrock Pro-FloAir Cleaner, Part #1223
- Performance Distributors DUI Street/Strip Distributor, Part #12720BK
- Performance Distributors LiveWires Spark Plug Wire Set, Part #C9054
Converting to a stroker engine, we are also adding several other components:
- K1 Technologies Forged 4340 crankshaft, Part #350-3750BB6F
- K1 Technologies 6.0-inch connecting rod, Part #CH6000ALLB8
- SRP Pistons, Part #268830
- Clevite Camshaft bearings, Part #SH1796S
- Clevite H-Series coated main bearings, Part #MS909HK
- Clevite H-Series coated rod bearings. Part #CB663HNK
- Victor Reinz head gasket set, Part #HS1178VJ
- Victor Reinz lower gasket set, Part #CS1178
- Fluid Dampr CT Gold, Part #62260D
- Canton Racing Products oil pump driveshaft, Part #21-200
- Canton Racing Products standard volume oil pump, Part #21-500
Why Use A Longer Connecting Rod?
Engine builders have long debated the connecting rod/stroke ratio in competition engines for decades. Chevy engine expert Smokey Yunick used to say that the longer the rods are, the better. Explaining that with a 5.700-inch connecting rod, the piston would be within 0.001-inch from TDC for 5-6 degrees versus the 6.000-inch connecting rod that would have the piston “dwell” within 0.001-inch from TDC for 10-12 degrees.
According to Yunick, this allowed pressure to build longer in the combustion chamber before it starts to shove the piston down. The result is usually a broader, flatter torque curve than the same engine with shorter rods. An engine’s horsepower and torque curves depend on a lot of variables other than rod length alone, but if everything else is equal, many engine builders say longer rods produce a broader torque curve.
Rainey added, “There are a couple of different combinations that you can use, a six inch rod or a 5.7-inch rod. The six inch rod will give you more torque in the engine and it relieves a little stress on the engine.”
Longer Connecting Rod Facts
- A longer rod will increase piston dwell around TDC and BDC. However it will accelerate the piston faster between TDC and BDC.
- The increased dwell at TDC and BDC from the longer rod results in lower instant velocity changes thus reducing stress on the piston, rod and wrist pin. This is especially notable in tension loads during the exhaust stroke at TDC.
- During the intake stroke the higher acceleration of the piston after TDC to BDC will improve Volumetric Efficiency at higher rpm resulting in higher output. The higher acceleration of the piston from TDC to BDC ‘sucks’ harder on the intake port resulting in a better filling of the cylinder prior to the compression stroke.
- During the compression stroke the increased dwell at TDC may require different ignition timing.
- Throughout the power stroke a longer connecting rod keeps the piston higher in the cylinder bore for any given crank angle, resulting in higher cylinder pressure after TDC and increased output. The angle at which the connecting rod is applying force to the crankshaft is reduced which makes the conversion from reciprocal energy into rotational energy more efficient.
“The longer rods will give you a lot more torque at low end meaning that it will come in a little quicker,” explained Rainey. “Stock torque might peak at 3,000 to 3,500. With a longer rod it might peak at 2,000 to 2,500 rpm.”
Crankshaft And Piston Combination
Stroking out a Gen I SBC 350ci is generally done with a crankshaft that has a 3.750-inch stroke (1.875 radius). We selected K1 Technologies Forged 4340 crankshaft (part #350-3750BB6F). This crankshaft gave us the 3.750-inch stroke with standard SBC 350 main journals (2.450-inches) and 2.100-inch rod pin diameters. Weighing in at 55 pounds, the internal balanced crankshaft supports a six-bolt Chevy flange. K1 Technologies crankshafts are made from 4340 steel that is core hardened, nitrided, mag-particle inspected, and features straight oil holes for oiling to the rod journals. A great combination in our book.
While externally balanced engines have been around for decades, heavy external weights are more likely to put a twist in the crank at higher engine rpm. To minimize this twisting, many aftermarket 383ci crankshafts are internally balanced, as is the case with our K1 Technologies crankshaft.
We’ve already chosen to use a 6.000-inch connecting rod which leaves us a piston with a 1.125-inch compression height for a 9.000-inch stack up. Remember that an undecked block height for a SBC 350 is 9.025, and the OE installs the pistons with a piston deck height of 0.025-inch. Our stack up of 1.875-inch +6.000-inch + 1.125-inch = 9.000-inches, which leaves the piston deck height at 0.025-inch with this combination of parts.
There are a very few engine builders that prefer not to use a 6.000-inch connecting rod, thinking that the wrist pin intrudes into the piston’s oil ring groove, preventing the oil control ring package from doing its job. Sean Crawford, Director of Marketing for JE Pistons cleared up the situation by stating, “JE has literally tens of thousands of pistons in service for that combination. We have not experienced any issues with the oil ring intercepting the ring groove as long as the proper oil ring support (provided) is used.”
Rainey agreed by explaining, “With this combination, it’s a little more torque and the RPM range is better, plus the piston skirts are protected better because of the longer rods. The longer the rod, the less of an angle on the piston when the motor is running. So it does take a little stress off of the piston.”
Crankshaft, Connecting Rod And Piston Combination:
K1 Technologies Forged 4340 crankshaft (part #350-3750BB6F)
- Forged 4340 steel
- Two-piece rear main seal style
- 3.750-inch engine stroke
- Internal engine balance
- 2.100-inch rod journal diameter
- 2.450-inch main journal diameter
- 7/16-20 Balancer Bolt
- Standard crankshaft snout style
- 55.000 pounds
K1 Technologies 6.0-inch connecting rod (part #CH6000ALLB8)
- 6.000-inch length
- H-beam style
- Forged 4340 steel
- Shot-peened finish
- Floating wrist pin
- Cap screw retention style
- 7/16-inch ARP2000 connecting rod bolt
- 220,000 psi fastener Yield Strength
- 12-point connecting rod bolt head style
- 635 grams weight
- 2.100-inch rod journal diameter
- 2.225-inch big end bore diameter
- 0.927-inch pin end bore diameter
- 0.940-inch big end width
- 1.010-inch pin end width
- Magnafluxed, weight matched set
SRP Pistons (part #268830)
- Forged Aluminum
- Flat top with two valve reliefs
- 0.030-inch oversize (4.030-inch bore)
- 1.125-inch compression distance
- 11.1:1 compression ratio
- +5.00cc piston head volume
- Press fit wrist pin
- 0.927-inch wrist pin diameter
- 1.2mm steel top ring
- 1.5mm cast iron second ring
- 3.0mm chrome-plated carbon steel oil ring
It’s easy to understate the importance of engine bearings in an engine build, but a sloppy build with too much bearing clearance can kill an engine quickly. “The design of engine bearings allow for a layer of oil to form between the rotating shaft and the surface of the bearing so that the shaft does not actually ride on the bearing itself but on a formation of an oil wedge that supports the rotating shaft under normal operation. By riding on a layer of oil instead of the bearing itself, the bearing helps dissipate heat,” explained MAHLE Aftermarket‘s Team Leader of Training, Bill McKnight.
When it came to selecting engine bearings for our upgrade, we asked McKnight about engine bearings for higher performance street applications. “Most of our everyday bearings, other than the late model stuff, are still tri-metal, which is steel-backed, with a cast copper lead intermediate layer and then a babbitt overlay,” said McKnight. “A normal passenger car can have cylinder pressures around 1,200 psi range. An 800-900 horsepower race engine may have cylinder pressure in the 2,200 psi range,” he added. “The steel backed, tri-metal bearings work well for these applications.” Our crate engine upgrade build will be in good shape with these bearings.
McKnight added, “Clevite has narrowed their performance rod bearings rather than using a big chamfer. The new effect is the same, but is has created upper and lower shells in many applications so be sure you look on the back of the bearing for a “U” or and “L” and get your bearings in the right place!” Narrower bearings mean less friction and less friction means more power.
When it came to coated bearings, McKnight had this to say, “We find our customers have strong feelings about coatings. They either love coated bearings, or wouldn’t use one if it was given to them free!” Almost all bearing coatings provide an anti-friction layer to the bearing and are intended to increase the bearing life in very marginal oil film conditions by preventing the transfer of the bearing face material to the crankshaft. These marginal oil conditions can exist under heavy operation loads seen in racing and performance engines, but also may be present when an engine in a street rod is started for the first time after sitting all winter. Since damage to the face material of a bearing is permanent, this protection is deemed a good thing by coated bearing advocates.
McKnight also cautioned us to use the best oil we could afford in our engine, “Saving money on oil is a really bad idea. Find a good, reputable performance oil supplier and follow their advice on the type of oil, the additive pack and the viscosity for your engine and its intended application. Forty percent of engine bearing failures are lack of lubrication issues.”
It’s a no-brainer to use the performance series bearings from Clevite for our stroked out crate engine rebuild project. There’s no such thing as overkill in protection, so we will always default to performance standards when it comes to engine components.
Clevite Camshaft bearings (part #SH1796S)
- High Performance/Race
- AL-3 Steel Backed Aluminum
- Large Journal
Clevite H-Series coated main bearings (part #MS909HK)
- Developed primarily for NASCAR racing, but are also well-suited to other types of competition engines
- Especially good for engines that run at medium-to-high revs
- Steel backings with carefully selected overlays and a high crush factor, plus a medium level of eccentricity
- TriArmor coating
- Enlarged chamfers at the sides for greater crank-fillet clearance
- Made without flash plating for better seating
- Available with either 180 degree or 360 degree oil grooves, as well as an extra 0.001 in. of clearance
Clevite H-Series coated rod bearings (part #CB663HNK)
- Developed primarily for NASCAR racing, but are also well suited to other types of competition engines
- Especially good for engines that run at medium-to-high revs
- Hardened-steel backings with thin overlays and a high crush factor, plus a medium level of eccentricity
- TriArmor coating
- Made without flash plating for better seating
Victor Reinz Gasket Sets
Most people don’t realize that MAHLE/Clevite is the largest distributor of Victor Reinz gaskets in North America. As long as we were stepping our crate engine build up a notch, we opted to go with the Victor Reinz head gasket set (part #HS1178VJ) and the Victor Reinz lower gasket set (part #CS1178). Our engine builder, Derrick Rainey at L & R Engines, confirmed the choice. “We use a lot of Victor Reinz gaskets here,” he said, adding; “Victor Reinz is a top notch company and they’ve been around a long time. I think it’s a good quality gasket.”
According to McKnight, there are several critical factors that make Victor Reinz gasket sets a great part of an engine build. “You’ll get everything you need in a Victor Reinz set,” McKnight stated. “Parts like the valve seals in the head gasket sets. These valve stem seals are made by Victor Reinz. We don’t out source these offshore in some other country, they are made right here in Avilla, Indiana. For American engines, these are typically the OE seals.”
In addition to maintaining quality by keeping much of the manufacturing in-house, Victor Reinz packages everything in subassemblies. Each subassembly is weighed to ensure that every component is in the subset before it is shipped out to the customer. “The odds of a customer buying a gasket set from us and missing a part is about slim and none,” McKnight asserted.
“We are very committed to following the OE. If the OE has a two-piece stainless steel exhaust manifold gasket on their Chevrolet engine, that’s what you are going to get from Victor Reinz. We think that most technicians are comfortable when they open up the gasket sets and it looks like what they took off the engine.”
“If there is a sealant required to install a gasket, it will be in our gasket set. That is our policy,” said McKnight. “So if you open up a Victor Reinz gasket set and there is no sealant inside of it, none is needed. More gaskets are ruined by applications of sealant than anything else. So, if you need a sealant for installation, it will be in the kit and you can take that to the bank.”
The Victor Reinz cylinder head gaskets for this application were Multi Layered Steel (MLS) type construction. “The MLS is a newer head gasket that everybody is running because it withstands a lot more compression,” added Rainey. ” In the old days people used to O-ring blocks and run copper gaskets to hold up to big boost but the technology of head gaskets these days, especially the MLS, you can do away with the O-ring gaskets. There is less machining that needs to be done with MLS gaskets and they hold up well.”
An American product, built in America for an American engine, with the added bonus of including everything you need for the assembly. Another “no-brainer” as far as we are concerned.
The first 383ci strokers that used SBC 400ci crankshafts taught engine builders about external weights and different engine harmonics than they were used to. Initially, engine designers added this external weight at the flywheel and harmonic balancer ends of the crankshaft to create the externally balanced engine. The 400 is the only Gen I small-block that requires offset balance weights on both ends of the crankshaft. Externally balanced crankshafts are more likely to put a twist in the crank at higher engine speeds. There are many internally balanced 383ci aftermarket crankshafts on the market to help solve that issue.
Engine harmonics-here is where it starts to get fun! A 383ci will have slightly lower harmonic frequencies than a stock 350ci due to the increased stroke and reduced journal overlap. Most harmonic balancers are manufactured for a specific range of harmonic frequencies. This might be at lower rpm for street driving, mid-range RPM for higher performance driving, or a higher range RPM for competition purposes.
“As soon as your engine fires, torsional vibration is present,” said Fluidampr’s Ivan Snyder. “The torsional vibration energy created with every power stroke of your engine is repeatedly ‘punching’ the crankshaft damper. When you hit a light weight punching bag it does not absorb much force. It swings away then comes right back at you. In the instance of a crankshaft, it sends the torsional vibration right back through the crankshaft to do damage.”
Snyder explained how Fluidampr engineers design their dampners for torsional vibration control across a broader RPM range, “In a Fluidampr the inertia ring mass is free floating within the housing. Once the crankshaft starts rotating, centrifugal force and torsional vibration takes the weight of the internal interia ring off the crankshaft.”
“No damper will compensate for an out of balance condition. The vibration damper is designed to reduce crankshaft torsional vibrations, not to balance the motor,” he reminded us. “Only a professional balance job will solve that problem.”
Our crew at L&R Engines balanced the engine’s rotating components then assembled the engine including a Fluidampr damper designed for internally balanced engines. These dampers are completely neutral balanced and there is no counterweight on the damper. Rainey stated, “A good damper will dampen the vibrations in a motor. It’s just gonna enhance the motor and make the longevity better.”
Fluid Dampr CT Gold (part #62260D)
- Internally Balanced
- One-piece damper design
- Steel housing
- Gold-zinc Chromate finish
- 6 1/4-inch outside diameter
- 8 pounds
Oil Pan And Pump
While we were making improvements to our crate engine, it only made sense to shore up the lubrication system during the rebuild. “When it comes to oil systems, Canton is one of the top notch companies in the field,” claimed Rainey. “Canton is top of the line.”
Canton Racing Products have years of extensive testing on all types of engine configurations which enables them to guide consumers to the right products for the specified applications. Our stroker was certainly a specific application, so we sought out Mike Zeranski Jr. of Canton Racing Products to get us pointed in the right direction.
“Our wet sump pans are designed to provide the best oil control and power savings possible,” said Zeranski. “These wet sump oil pans are available in several chassis configurations and are available for all levels of performance with most being available in steel and aluminum.”
When it comes to Canton’s balanced oil pumps, Zeranski says, “By reworking the pump housing and providing feeder grooves, these pumps bleed some of the high pressure back into the gears, providing smoother operation and more constant pressure. This allows for high-rpm operation on race engines and limits oil pump cavitation.”
Having stepped up to performance engine bearings with an eye on running higher RPM, we like the idea of having smooth operation and constant oil pressure in our engine. Our performance improvements in the engine build just begged for upgrades in the oil system. We were more than willing to comply by adding Canton Racing’s oil pan, oil pump and oil pump driveshaft.
- 2-piece rear main seal style
- Driver side dipstick location
- Rear sump
- Stroker clearance – Maximum stroke with OE rod: 3.875-inch
- Wet sump
- 5-quart oil pan capacity
- 8.000-inch oil pan depth
- Steel construction with gold iridited finish
- Baffled with windage tray and crank scraper included
Canton Racing Products oil pump driveshaft (part #21-200)
- Hardened shaft for use with high-volume oil pump
- Steel sleeve included
- Pinned sleeve for correct alignment
- Direct replacement for stock Chevy shafts
Canton Racing Products standard volume oil pump (part #21-500)
- Balanced and modified to provide continuous flow throughout the rpm range
- Wet sump style
- Standard volume, standard pressure
- 0.625-inch pickup inlet diameter
When it came time to perform the assembly of our crate engine, we went back to one of our favorite custom engine building shops in the local area. L&R Engines has been servicing automotive enthusiasts in Southern California for 37-years after opening in Larkin Ranney Jr.’s home garage in 1977. Now operating out of a 10,000-sq/ft building in Santa Fe Springs, California, the family owned and operated business continues to serve the automotive community.We explained to Derek Ranney, son of founder Larkin Ranney, what we were trying to achieve with our simple 383ci stroker build. His crew performed all the measuring and weighing, rotating assembly balancing, and engine assembly for the project. Without fail, the engine showed up on our doorstep, under-budget and sooner than expected.
We’ve heard all the theories, both good and bad, about rod/stroke ratio. Based on what we found out in this engine build, much of the conversation about not using longer connecting rods is much ado about nothing. If clearance of the components or checking camshaft clearance is an issue in using 6.000-inch connecting rods, consider that using the stock 5.700-inch rods require the same clearance checks.
It’s been proven that rod/stroke ratio has a direct effect on the amount of the rod angularity and its ability to increase the side loading of the pistons when the ratio is too high (with shorter connecting rods and a longer stroke).
Some engine builders believe that the horsepower gain is too small to justify using longer connecting rods. If it costs the same and produces any increase at all, isn’t it worth it?
Finally, consider this: All NASCAR engines producing 800 or more horsepower use 6.000-inch or longer connecting rods. They make that much horsepower on flat tappet cams. So…you tell us: Is there an advantage in using 6.000-inch rods over the stock 5.700-inch connecting rods for a 383ci stroker rebuild?
We bolted the engine into a GMC Sprint – GMC’s version of an El Camino – and fired the freshly rebuilt stroker up on the chassis dyno. Without spending any extra time dialing in the fuel curve, our first couple of runs proved the point we were trying to make. Coming in at 298.94 max horsepower at 5,100rpm and max torque of 345.01 at 3,750 rpm with an off-the-shelf carb (red line on the graph above), was a pleasant surprise. We did some adjustments like adding a larger carburetor with larger jets to get 319.53 max horsepower at 5,120 rpm and max torque of 352.38 at 4,270 rpm with size 89 jets (blue line of the graph above).
Watch the dyno run here:
Making comparisons between a chassis dyno and engine dyno are difficult because a chassis dyno isn’t really designed to measure flywheel output. A chassis dyno is designed to measure the overall performance of a vehicle’s drivetrain. While there are accepted loss percentages for drivetrains, they are still only estimates. These estimates can vary from one dyno run to the next and it is important to realize that drivetrain losses vary with RPM as well. However, if you are using the common range of drivetrain loss estimates, these can range between 15% to 25%, depending on who is making the estimate. Ultimately, when it comes to comparing dyno types, the only thing that really matters when you are behind the wheel is how much power can you get to the ground.
Given that 15% of 319.53 is 47.9295 and 25% of 319.53 is 79.8825, this would put the estimated power at the crankshaft between 367.46 to 399.41hp. Using either chassis dyno or engine dyno, the original truth of our story remains: a 383ci long rod stroker will produce a powerful and torquey little engine that will last for years.