The primary order of enterprise for our junkyard BBC was to switch the manufacturing unit EFI induction with easy carburetion.
In case you are out there for a critical chunk of horsepower hardware, look no additional than your native wrecking yard. Positive, all of us love a critical build-up, or perhaps a crate motor that exhibits up assembled and prepared for motion, however there’s simply one thing about rolling the cube on an unknown commodity that basically will get us going! In fact, there are preventative steps to be taken to attenuate the shock, however even then, you by no means actually understand how properly the junkyard motor goes to carry out till you park that child at WOT!
It took some looking by way of the native wrecking yard, however we managed to find an appropriate big-block Chevy. The important thing was to look within the truck / SUV part of the yard!
We’re speaking concerning the time-honored custom of yanking a motor from the bone yard and flogging it for all its value on the engine dyno. Not simply any motor thoughts you, however nothing lower than a tried and true, pink, white, and blue, big-block Chevrolet! Assume the Rat motor isn’t an enormous deal? Our native LKQ Pic-a-Half put a premium on the 454 Chevy. Solely the 454 Chevy. Even at almost twice the worth of the lesser V8s, that lesser record included huge Fords and Dodges (if you’ll find one), to not point out numerous V10s. What’s to not love a few big-block Chevy for the paltry sum of $500? That doesn’t rely the core cost, nevertheless it additionally doesn’t take into consideration the 40-percent discount that may be had on sale weekends. Rating!
After wrestling it out of the 1997 1-ton 4WD Suburban, we plopped it behind our 2003 1500 Silverado and have been off to the dyno.
Huge dyno numbers are usually not the story right here. In any case, what might we realistically anticipate from a stone-stock, smog motor with over 180Okay miles—even one sporting 454 cubic inches? This story just isn’t about what it’s, however somewhat what it may be, however let’s not get forward of ourselves. Earlier than we even take into consideration testing, we should first find and liberate one, to say nothing of shedding some extra tonnage. Beginning with the “locate” class, don’t hassle in search of a big-block within the engine bay of a Camaro, Chevelle, or El Camino. These days are lengthy gone! Look as an alternative the place all of the big-blocks reside, beneath the hood of full-size vans and SUVs. Used to energy ¾- and 1-ton vans and Suburbans, the big-block we all know and love was used as much as the yr 2000, when GM converted to the ill-fated eight.1L. Although displacing a really fascinating 496 inches, the short-lived stroker BBC was one thing of an anomaly, and carries little or no aftermarket help. Against this, the Mark IV, Gen V and Gen VI big-blocks that pre-dated the eight.1L are as fashionable as ever, with an infinite variety of cam profiles, cylinder heads, and consumption manifolds to select from, to not point out all method of stroker mixtures. That’s why we selected the 454 over the bigger (and later) eight.1L 496.
One of many many causes we favored the Gen VI motor was as a result of they featured manufacturing unit hydraulic curler cams. Notice the spider meeting used to carry the lifters in place.
In terms of big-blocks, there are three major varieties. As we talked about, the Mark IV was the unique motor launched by GM in 1965. This was changed by the Gen V, whereas the ultimate iteration got here within the type of the Gen 6. An entire historical past lesson is pointless right here, however know that the all the Gen V and Gen VI motors featured Four-bolt blocks, whereas nearly all of Mark IV motors have been of the two-bolt selection. Because of this alone we are likely to favor the later blocks. The icing on the cake for us was that GM launched hydraulic curler cams within the Gen VI. Now toss in the truth that the Gen VI additionally acquired larger compression and standard-size oval-port heads to exchange the restrictive peanut ports used on the Gen V, and also you begin to respect the sweetness that’s the 7.4L, Gen VI 454. Due to these upgrades, the Gen VI was additionally rated a lot larger in energy than the earlier Gen V 454, a distinction of roughly 50 hp. Additionally it is value mentioning that the Gen VI heads are a great improve for the Gen V, because the Gen V heads featured not solely the smaller peanut ports, but in addition large 120cc combustion chambers in comparison with a measured 102 cc’s for the Gen VI.
The Gen VI 454 additionally featured flat-top pistons with consumption valve reliefs mixed with small-chamber, oval-port heads.
There are a few different delicate variations between the varied generations of big-blocks that additionally bear mentioning. As talked about beforehand, big-blocks got here in three varieties, although all will work for many efficiency purposes. Probably the most troublesome to seek out was the unique Mark IV BBC, out there in widespread displacements starting from 396-454 inches. These early rat motors are distinguished by the presence of a mechanical fuel-pump boss on the aspect of the block. Since GM deliberate on phasing in digital gasoline injection to the later Gen V and Gen VI motors, they eradicated the gasoline pump boss on the later blocks. An electrical gasoline pump can be crucial with these later blocks for those who plan to run them with a carburetor. The exception to this rule is a few of the early Gen V motors, as they nonetheless retained the gasoline pump boss. From the manufacturing unit, nearly all of Mark IV motors got here with Q-Jet carburetion, whereas the later Gen V and VI motors acquired gasoline injection. The Gen V motors received the much less highly effective throttle-body injection, whereas Gen VI L29 454 acquired a long-runner, multi-port gasoline injection system.
After checking the situation of the spark plugs, cranking compression, and oil strain, we put in a dual-plane Weiand Stealth consumption manifold.
When selecting a big-block from the junkyard, listed here are few issues to think about. First off, our junkyard would solely promote the big-block as an entire motor, there was no choice to buy a (inexpensive) short- or long-block combo. This was disappointing, since we deliberate to ditch the manufacturing unit EFI instead of easy carburetion for our testing, nevertheless it is perhaps attainable to promote the EFI system, or no less than the injectors, throttle physique, and/or TPS, IAC, or CT sensors off the injection. The identical is true of the accent drive, as this got here with the entire motor. A pleasant big-block serpentine system could be very fascinating for road use, so be sure that to get each half you’ll be able to. We even gathered elements off different automobiles to finish ours. In case you are paying for all the things, you may as nicely ensure you get all the things. We have now even changed the manufacturing unit EFI system with a carbureted consumption, Q-Jet (or Holley if yow will discover one) and an HEI distributor (although you may want a unique distributor gear). When deciding in your big-block, don’t overlook the transmission—for those who want one. Most big-blocks are backed by a turbo 400 or 4L80E, so when you want a drivetrain to deal with big-block energy, snag the tranny too!
The Weiand Stealth consumption was topped with a low-buck—however lots highly effective—Brawler carburetor. The 650cfm carb needs to be one of many best-kept, low-buck secrets and techniques in carburetors.
For this big-block journey, we carried out the spin-to-win check previous to removing. Our junkyard moto is, if the motor spins, it (often) wins. The primary “will-it-run” check is to take away (and examine) the spark plugs and ensure the motor even rotates. If not, cross on it and discover one other candidate. If it does, issues are wanting good. After removing, we shortly pulled the EFI distributor, crammed it with oil, and carried out an oil strain check. Within the photographs, this check was proven on the dyno, however we truly rolled the motor as much as the dyno on the engine stand and plugged into the dyno gauge. After spinning the oil pump with a drill, we have been rewarded with over 60 psi of oil strain, a superb signal that the motor was in fine condition. That the plugs seemed new and have been in fine condition was additional proof of a operating motor. The ultimate step was to carry out a leak-down check, which this motor handed with flying colours. We then tore into the motor to take away all the things we didn’t want on the dyno, together with exhaust manifolds, motor mounts, and the equipment. The ultimate step was to take away the EFI system and exchange it with carburetion.
Although it’s potential to snag an HEI distributor from the junkyard, we selected an MSD unit for our big-block. The billet distributor was teamed with a 6AL amplifier and Blaster coil.
To prepared the big-block for dyno testing, we yanked the EFI higher and decrease consumption and changed it with a Weiand consumption manifold. The twin-plane Stealth consumption provided the right mixture of low-speed torque and peak energy. Keep in mind, this motor was nonetheless sporting a wimpy manufacturing unit cam. The Weiand consumption was topped with a Holley 650 Brawler carburetor. Earlier than all you big-block followers come unhinged concerning the considered operating a 454 with such a (seemingly) small carburetor, know that the carb was sized completely for the airflow and energy potential of the in any other case inventory motor. The carbureted induction system was mixed with an MSD distributor, although a inventory HEI would carry out simply as properly at this energy degree.
Run on the dyno with the Weiand consumption, Brawler carb, and MSD distributor, the 1997 454 produced 378 hp at Four,700 rpm and 482 lb-ft of torque at three,500 rpm. Clearly the delicate cam was designed with low-speed torque manufacturing in thoughts, because the torque output bettered 450 lb-ft from 2,500 rpm to Four,300 rpm. Now our Hunk-o-Junk was prepared for a cam, heads, and perhaps even some nitrous!
The fascinating factor about these small-chamber, Gen VI heads is that they needed little or no complete ignition timing. Although we swept timing from 25-35 levels, the motor made greatest energy and torque at 29 levels. Outfitted with carburetion and long-tube headers, the junkyard Gen VI 454 produced peak numbers of 378 hp at Four,700 rpm and 482 lb-ft of torque at three,500 rpm. Clearly designed with low-speed torque manufacturing in thoughts, the 454 provided over 450 lb-ft from 2,500 rpm to Four,300 rpm. Much more necessary than the numbers was the truth that we now had a cheerful, wholesome Hunk-o-Junk simply begging for some superior upgrades!
On The Dyno
Regardless of large mileage, and (possible) minimal upkeep, this 1997 454 thumped out factory-fresh energy numbers. After removing from the native junkyard, the 454 acquired a Weiand Stealth consumption, a Holley 650 Brawler carb and MSD distributor. Outfitted with these elements, Gen VI BBC produced 378 hp at Four,700 rpm and 482 lb-ft of torque at three,500 rpm. Torque manufacturing exceeded 450 lb-ft for almost 2,000 rpm—from 2,500 rpm to Four,300 rpm. This Hunk-o-Junk was now primed and prepared for motion!
As soon as mounted on the engine stand, we proceeded to take away the gadgets pointless for dyno use. These things included the entrance accent drive, motor mounts, and manufacturing unit exhaust manifolds.After removing of the most important exterior elements, we unbolted the manufacturing unit EFI consumption and put in the big-block on the dyno.The manufacturing unit long-runner EFI system was designed to reinforce trailer-towing torque manufacturing on the big-block.The cross-ram type consumption featured central-mounted injectors to feed the person cylinders. Every of the 2 ports within the decrease manifold have been siamesed collectively within the higher manifold and fed by a single (bigger) port opening on the other aspect.Earlier than trying to run the motor, we made positive it had enough oil strain. After filling the crank case with six quarts of Lucas 20W-50 oil, we used our useful, dandy Milwaukee drill to spin up the oil pump. Utilizing a recent Okay&N oil filter, we gave the big-block a brand new lease on life. It was the least we might do, given our intentions.Like most late-model big-blocks, the Gen VI featured a non-adjustable valvetrain, however did embrace information plates for the 5/16-inch manufacturing unit pushrods. A valvespring improve might be obligatory when putting in a brand new cam sooner or later.Maybe overkill for our delicate motor, the 454 was run with 2.25-inch, long-tube dyno headers feeding collector extensions.We made positive to dial within the combo with changes to each jetting and timing. Although we swept the timing from 25-35 levels, these small-chamber Gen-VI heads ran greatest with simply 29 levels of complete timing.