Not long ago, we showed the roller cam and valve train components that went into this big block Chevy "rat" motor. What we didn’t show you were the other important parts that are vital to reliability and performance of the engine. Our goal was to make a reliable engine with gobbs of horsepower and torque. It takes major power to get the Swampers rolling especially when you live in Colorado and the altitude is 5800+ feet. The high elevation robs the power of any engine. The engine started out as a basic fuel injection install and has snowballed into much more. Several days were spent just shopping for parts. We actually found some great deals on Ebay for new big block Chevy parts.
Block The block is the foundation of the engine. This is the main part of the engine that everything has to bolt to. The block also houses the crankshaft and the pistons so it’s very important to have a block that’s in good shape. Our block started off as a low powered GM remanufactured 4 bolt 454 that was bored .030 over. Before this block was used on the build up, we searched for another 4 bolt 454 but none could be found without shelling out some major bucks. This would have been ideal since the Blazer could still be driven while the other engine was being built. Another solution would have been to find a 2 bolt and convert it to 4 bolt, which can be easily done by most engine shops. We had to do it the hard way and take the engine out of the Blazer, making the vehicle inoperable. After taking the engine apart, a deep score was found in cylinder number two. It was crucial for reliability that no short cuts are taken so the engine was bored .060 over. Not only does this remove the deep score but it also gives some extra cubes. We also added a cam oiler to the block before the crank and pistons were installed. The cam oiler can be seen here: www.off-road.com/chevy/reviews/bbc_oiler Crank
The stock cast crank would have worked fine but we really wanted to make a torque monster. After doing some searching on the web, we found a source for a forged stroker crank. The longer stroke actually increases the cubic inches. If the engine stayed .030 over bore, it would have become a 489. Since our block was bored .060 over, this crank has now changed it to a 496. Here are the specs on the crank: Triton Engineering's "SUPER-COMP"; Big Block Chevy Stroker Cranks are made of 4130 Chrome-Moly Forged Steel that has been Magna-fluxed, Shot Peened and Multi-Stage Induction Hardened - The Rod and Main Journals are Index Ground and Chamfered with a .125 radius - Cross Drilled Mains - Main Journals are 2.7497(Std) Rod Journals are 2.200(Std) - Stroke is 4.250 - - Cubic Inches are Std=482, .030=489, .060=496, .100=505 - Recommend for 6.385 Rods or Longer.
Rods and Pistons/Rings Along with the stroker crank, new pistons and rods were used to complete the rotating assembly. The new stroker crank can use the existing 6.135 rods but you would have to grind counter weights for clearance and a few other areas. These new Triton forged rods are rated up to 700 hp. Pistons are KB 284’s which are designed for the stroker crank. The KB pistons are a hypereutectic design which are cheaper than forged plus they’re better suited for long-term operation in a high performance engine. The KB pistons also have these features:
More specs on the pistons can be seen here. For long term durability, Hastings PowerFlex Racing rings were chosen. PME Racing suggested the Hastings rings for durability and advised against the Sealed Power rings.
Heads, heads and more heads! Did we say heads? What a nightmare! It started off with the stock peanut port heads, which happen to be worthless for performance. We decided to scrap the small peanut-port heads in favor for some older GM 049 cast iron heads. The 049 heads are a good oval-port head to use for low to mid RPM range horsepower. With a little headwork and some larger valves, they can easily support over 600 hp. Off to the head shop we went to get this done. $500 later and these things were looking real pretty with those larger 2.19 and 1.88 valves. There’s one small problem though. We guessed on the combustion chamber size. We had the 049 heads milled .020" and we figured the chamber size had likely dropped from 113 cc to 109cc. May not sound like much but it really affects your compression ratio. The block was not decked since the heads were already milled. We finally measured the actual displacement of the combustion chambers and found they were now 118cc! What happened? The larger valves required more of the combustion chamber to be removed thus the size went up instead of down. Since the block was already complete with new pistons, rods and crank installed, the next option was new set of heads. This time, we spent a little more cash and got some Edelbrock aluminum heads. After closely inspecting these heads, we only have one word…. SWEET! You can tell just by looking in the ports, these heads are designed for some serious flow. These heads will easily support over 550 horsepower. A totally unique intake port design yields flow numbers traditionally associated with high performance rectangular port heads, but with the smaller runner size and velocity of an oval port for excellent seat-of-the-pants performance and crisp throttle response. The semi-open chamber design maximizes combustion efficiency with street-able compression ratios. The stainless steel 2.19" intake and 1.88" exhaust valves have smaller-than-stock 11/32" valve stems to promote excellent flow and lighter valve weight. The deck surface and water jackets were specially designed to work with all big-block Chevrolet engine blocks. Heads include top-quality ARP rocker studs. With the Edelbrocks being a rect-oval design, they’re actually able to flow more than the cast iron oval heads. Another benefit is you save a little weight. There's a difference of 90lbs between the heads which, means our rat only weights 20lbs more than a small block Chevy. Cool eh?
For a dyno test from Edelbrock click here: www.edelbrock.com/automotive/7161pp.html These heads happen to be the same exact heads as the GM Performance heads and are used on the high performance ZZ502 crate engine. We actually used the intake gaskets from the ZZ502 since they match perfectly for the Edelbrock rect-oval ports. The intake manifold was also ported to match the rect-oval design. Despite having a new set of head bolts for the cast iron heads, we had to order another set of bolts that was designed for these heads. The bolts for the cast iron heads were too short. Edelbrock carries a set specially made for these heads that are made by ARP.
Bearings Even though the existing big block had low miles, new bearings were installed. This includes the mains, rods and camshaft bearings. Our engine shop suggested Clevite bearings. Head Gaskets Long story on these but we went to a .031 thick copper head gasket to get a little more compression and this also achieve proper quench. If we had to do it over again, we would have had the engine block decked (milled) a little and used normal Fel Pro head gaskets. A special sealer must be applied when using copper head gaskets.
Oil Pan The stock oil pan wouldn’t work because of the increased stroke. We had a nice Corvette oil pan with a trap oil door but it couldn’t be used. A Moroso oil pan with the notches for the stroker crank was used. This pan also had a trap door, which helps keep the oil around the pick up tube on steep trails. We got a great deal on a chrome pan so we went pretty. One thing to keep in mind is chrome retains heat so an oil cooler might be next. Harmonic Balancer There’s really nothing wrong with a stock vibration damper except that it’s designed for the engine in Aunt Martha’s luxobarge, which will never see daylight above 4000. At higher engine speeds, stock dampers have been known to fracture and ultimately explode. While such occurrences are rare on a street driven vehicle, they do happen. We wanted to be on the safe side and so we ordered a CAT fluid damper.
Intake Manifold We’ll be talking more about the fuel injection soon but we did end up going with Holley's killer Multi Port Injection (MPI) system with the Commander 950 computer. When comparing to a carb, this will give us more HP and torque throughout the RPM range. The Holley MPI system comes with 8 injectors, computer, 1000cfm throttle body, sensors and a complete wiring harness. The computer is configured through a laptop. The guys at Holley make it too simple to change over to fuel injection. More to come on this later. Distributor Since Holley's Commander 950 computer can control timing, we decided to go with a newer GM distributor that has the proper computer hook-up. The best deal was found at Henderson Chevrolet in Las Vegas and can be puchased online at www.spoperformanceparts.com. Other companies like MSD and Accel offer a similar distributor with the computer harness but will cost more. We already spent enough so we went cheap. Future plans may include a distributless setup so this might be temporary.
Water Pump We were going to stay with the stock water pump until we found a pinhole leak. A new aluminum pump was purchased through Dyno-Flo since they seemed to offer the best prices. Aluminum dissipates heat better plus this pump generates more flow. Oil Pump A Melling high volume pump is used. In most cases a normal pump can be used but with our custom BC cam oiler, a high volume is required. A Moroso pick-up tube is required for the Moroso oil pan.
Motor Mounts The stock 350 SBC mounts will work ok but won't give the strength like a BBC mount will. After finding out the hard way that 3/4 and 1 ton truck mounts don't fit a Blazers frame, we came upon Energy Suspension motor mounts. These are the ticket to any high performance engine and they mount the same way the stock mounts do. Clutch For a serious clutch that can handle the power from this engine, a Centerforce Dual Friction clutch is used. These clutches will grab hard when you want it and you can still feather the clutch if needed. These are great clutches if you have a mechanical linkage since they don't require much force to engage. We have a hydraulic clutch linkage so that wasn't too important.
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