The key to decent engine performance is moving air in and out of the engine efficiently. O
Brandon Clark, via CarCraft.com: I recently scored a disassembled 305 engine for $50 because the dude said it was junk. I've found a couple of stroker kits for the 305, but some say 334 and some say 335. I've read this is a 400 crank in a 0.030-over 305. I know 305s had smaller bores and most aftermarket heads won't fit without some valve shrouding. If the engine is bored 0.030 over or more, how big would that make the bore, and what heads would be OK on the motor? The main reason I'm bench-building this motor is because I want something different in a sea of 350 and 383 small-blocks. However, if building a stroker 305 is a waste of money, I'd like to know now.
Jeff Smith: At least once every couple of years we review this combination. This stroker package is popular because the 305 small-block is probably the most easily accessible small-block Chevy engine on the planet. As you mentioned, you bought this motor for almost nothing-that's the lure. The 305 uses a tiny 3.736-inch bore and the same 3.48-inch stroke as the 350ci motor. While it's relatively easy to drop a 3.75-inch stroke crank in a 305 block to create a 0.030-over stroker that displaces 334 inches, it's just not a great performance decision for several reasons. If you want to build this engine just to be different, then have a great time. But if you want to build a performance engine to make good power and do all the things a performance engine will do (and why wouldn't you?), then find a good used 350-they're just as cheap-and build that instead. You'll be much happier. Here's why:
We promise to stop running Gasser photos as soon as you stop sending them.
There are only a couple of small-block Chevy engines with a smaller bore than the 305-the minuscule 262ci V-8 is one that comes to mind. In the realm of bore size, the 305 is smaller than the 283 and 307 engines (3.875 inches) and even tighter than the original '55 265ci small-block (3.750 inches). Any knowledgeable performance engine builder will tell you that larger bore diameters create better airflow out of even the weakest cylinder head because the cylinder wall is farther away from the valves. This is why when Chevy decided to build its 302 SCCA Trans-Am engine in 1967 for the Z/28, the company used a 4.00-inch-bore 327 block with a short, 3.00-inch-stroke 283 crank to create the displacement. The engineers went this route because they knew a 4.00-inch-bore engine would make more horsepower than a smaller bore engine with a longer stroke. As further proof, pay attention to any published cylinder head flow data. Most companies will actually tell you what bore size adapter they use to flow their heads. For a small-block, no one ever flows a performance head on a bore smaller than 4.00 inches. Most companies test their heads on a 400 small-block's 4.125-inch bore because the flow numbers will improve.
We talked to Tony Mamo at Air Flow Research, and going from a 4.00-inch bore to a 4.125-inch bore is worth perhaps 2 to 3 percent more airflow. Three percent will bump 240 cfm to 247 cfm without touching the cylinder head. This might also clue you in as to why wider bore spacing engines have an inherent advantage because they offer better airflow potential and bigger intake valves, as with the L92 LS engines that now sport a monstrous 2.160-inch intake valve.
Increasing the 305's 3.766-inch bore another 0.030 inch to allow slightly bigger valves is such a small bore change that it really doesn't help very much. You can't fit a 2.02-inch-diameter intake valve (which is now considered small) in even a 0.030-over 305 bore-it won't fit without hacking on the bore. Your idea is good, it just needs to keep going out to 4.030 inches, which will offer a decent bore size for good airflow. Then you can go ahead with a 3.75-inch stroke cast crank kit in a 350 block and you have a nice little 383 that will make more power not only from the larger bore size, but also the increased displacement of almost 50 ci. That alone is a great reason to build the 383 versus the 334. And if it bothers you to say it's a 383, then tell everyone it's a warmed-over 307-that'll keep 'em guessing.
CJ Strickley, Alexandria, KY: I want to try something a little different for my next small-block and came across some of Smokey Yunick's information on 180-degree cranks. I was wondering if you could shed a little more light on some of the pros and cons of using this arrangement on a street motor.
If there were an '11 Camaro Z28, this is what the engine compart
Jeff Smith: To get the skinny on this, I talked with veteran race engine builder Ryan Falconer, who has considerable experience with 180-degree crank race engines. There are several advantages to the 180-degree, or flat crankshaft, concept. This crank is called a flat crank because the rod journals are spaced 180 degrees apart as opposed to every 90 degrees in a typical production V-8 engine. In other words, all the paired rod journals are located 180 degrees apart, placing the journals in a single, flat plane. One good reason for this is it creates a stronger crankshaft, but the advantage of the design is it separates each cylinder firing to opposite sides of the engine. A typical 90-degree V-8 crank demands that one pair of neighbor cylinders on one bank fires sequentially. As an example, in the small-block Chevy with its firing order 1-8-4-3-6-5-7-2, cylinders 5 and 7 fire next to each other. In the small-block Ford (1-5-4-2-6-3-7-8), cylinders 7 and 8 are the two that fire in sequence. The 180-degree crank fires one cylinder on the left bank and then one on the right. This also allows some freedom in terms of intake tuning in regard to common-plenum intake manifolds. This 180-degree crank orientation also produces a very distinctive exhaust note, since the exhaust pulses are evenly distributed.
There are also distinct disadvantages to the flat crank concept. Falconer says that while the flat crank idea works well with short strokes, it tends to create a damaging harmonic at higher engine speeds with longer strokes. He was involved with a 5.0L V-8 engine with a 3.00-inch stroke flat crank that created such damaging harmonics with its opposed cylinder firings that the engine destroyed itself in relatively short order. So while there are several advantages, it appears that for anything with a stroke longer than 2.75 inches (which is pretty short for a street engine), this wouldn't be a good idea. Keep in mind that a 180-degree crank would also require a custom camshaft, since the firing order would be different.
Beefing the 7.5-inch 10-Bolt
Al Zak, Dawsonville, GA: The majority of articles published in your magazine are about engines or transmissions. What about at the other end of the driveshaft? I have an '85 El Camino. I've already put a revised engine in it and have a 200-4R ready to go in. The rearend and rear brakes are a challenge. The original 7.5 axle is weak. The 8.5 from a Buick GN or an Olds 4-4-2 are like hens' teeth and extremely expensive. Has anyone successfully transplanted an 8.5 with rear discs from a 9C1 Caprice or Impala SS into a G-body? The rear disc brake and park brake designs are much better than anything the aftermarket has to offer and are standard parts, so if you break down in Thyroid, North Dakota, you have a hope of getting it fixed. Would it make sense to narrow the housing and use G-body 8.5 shafts to keep it standard? A lot of Malibu, Monte Carlo, and El Camino owners could benefit from a project like this. Plus, in a time when money is scarce for many reasons, wouldn't this be a good magazine project for a low budget? After all, isn't that what real hot rodding has always been about?
Jeff Smith: We agree with you, Al, that the low-buck way offers more challenges, and we'll always look for the least expensive way that will produce good results. So to dive into this, your idea of swapping the 9C1 police car or Impala SS 8.5 has potential merit, but the upper control arm angle determined by the cast-in mounts in the rearend will not line up, so this is not a realistic conversion. We've heard the upper control arm angles on the early Chevelle 12-bolt are close, so we spoke to Strange Engineering. The company says the distance between the cast-in mounts and their included angle is different-so it's not a good swap.
If we're approaching this from a budget standpoint, then purchasing either a used or new 12-bolt isn't really an inexpensive deal. Frankly, there is no cheap (meaning less than $500 to $1,000) conversion to improve the strength of the G-body rear axle. Unfortunately, that's the reality. The price for a bolt-in Moser 12-bolt is around $2,800 with gears, 30-spline axles, and a limited slip through Summit Racing. A less expensive alternative is a Strange S-60 rear axle assembly for the G-body that's roughly $1,995. Either avenue is a significant financial hit, so let's examine other options.
First of all, your statement, "the 7.5 axle is weak" has credibility in comparison with the 12-bolt, the 9-inch, or a Dana/S60, but how weak? We've heard of many 12-second G-bodies that employ the existing 7.5 rearend assembly. Let's examine what it would take to beef up this rearend, since that appears to be the best solution within a limited budget. But keep in mind that the parts required to upgrade the 7.5 are roughly the same cost as similar parts for a 12-bolt, so if we invest $1,000 in a 7.5 to make it stronger, wouldn't that same money be better spent on a 12-bolt that you know will live? It's something to ponder. The other alternative is to try and find one of those 8.5s. Yes, they're rare, but if you look hard enough, I think you could find one. The 8.5 is virtually as strong as a 12-bolt, and again, the parts cost the same.
From a theory standpoint, the smaller ring-gear diameter does limit durability. What we're really talking about here in terms of strength is the amount of tooth contact between the pinion and the ring gear. With a given ring-gear diameter, one way to improve strength is to make our pinion gear tooth contact as large as possible. That means limiting the gear ratio. As the gear ratio becomes numerically larger from 3.08:1 to 4.10:1, for example, the pinion gear diameter becomes smaller because the tooth count is reduced. A 3.08:1 pinion uses 13 teeth while a 4.10:1 gear has only 10. A 3.42:1 gear, however, has 12 pinion teeth, so the contact area should be almost as good as the taller gear. This will improve strength. So this means you probably would not want to go much deeper than perhaps a 3.73:1 rear gear (its pinion has 11 teeth). Next, regardless of the ratio, it's imperative that you employ a solid pinion spacer instead of the stock crush sleeve. The advantage of the solid spacer is it offers additional pinion shaft support. This also means it must be set up properly by using shims to establish a specific overall length between the two pinion bearings. This creates the proper preload on the bearings. The solid pinion spacer can be purchased through Ratech (PN 4111, $16.95 from Summit Racing). If you don't do anything else to the rearend, be sure to do this.
You're also going to need a good limited slip. The Eaton clutch-type units (PN 19663-010, $519.95, Summit Racing) work well but are pricey. We've had excellent experience with the Detroit Locker TruTrac (PN 912A317, 28-spline axles, $375.95, Summit Racing), and the price is more affordable. It requires upgrading from 26- to 28-spline axles-order these as if they were for the Grand National rearend, since they are the same width. We found a set of 28-spline Mosers (PN A102808, $244.95, Summit Racing) for a reasonable price. Add a set of Richmond 3.42:1 gears (PN 49-0007-1, $205.99, Jegs) and a Ratech deluxe installation kit (PN 3001K, $109.95, Summit Racing), along with an aluminum rear support cover (PN 8510400, $149.95) and you have a complete, upgraded 10-bolt.
Adding up all these parts plus roughly $200 for a professional ring-and-pinion installation, we're looking at just under $1,000. If you are talented, you could do the installation yourself, but it will require some custom tools and significant expertise. Even doing the work yourself, the bottom line is around $800, and you've now invested that much money in a weak 7.5-inch rear axle assembly. But you must spend more to step up to an 8.5 or even a 12-bolt. If your car is only running in the high 12s-we'd suggest upgrading the 10-bolt and trying not to abuse it. If the car has the potential to run low 12s or quicker, then we'd go with the Strange S60-it's roughly 20 pounds heavier than a 12-bolt but has immense durability and torque capacity. It's your choice.
Eaton (Detroit Locker)
Morton Grove, IL;
The Ratech solid spacer gives more support and is more stable than the old crush sleeve. I
Ronald Cooper, via CarCraft.com: I acquired an '86 5.0 small-block Ford with the intent of building a low-buck track car. Upon teardown, I discovered flat-top pistons without valve reliefs and heads with a bad combustion chamber. I was told by my head shop that the valves are sunk in the chambers to provide adequate piston-to-valve clearance. I planned to use the flat tops in a nonroller block with a set of 54cc, fully ported 289 heads. My cam has the required duration and only 0.448-inch lift. The factory roller cam specs out at 0.444-inch lift. Is there enough valve-to-piston clearance with older Windsor-style heads without notching the pistons?
Jeff Smith: There is much more going on here than just comparing valve lifts. If I'm reading your question correctly, what you're really asking is whether you can just bolt together the engine and not check valve-to-piston (V/P) clearance. The short answer is if you're a gambler, sure-why not? But the better question is if you are going to the expense of bolting together this engine with a different set of heads and a new cam, why wouldn't you spend the extra half hour it would take to measure valve-to-piston clearance. The process is really simple-all you need is a little bit of modeling clay and some patience. Before we run through the procedure, let's also touch on all the different variables that can affect V/P clearance.
Ratech also now sells a new design crush sleeve called the Smart Sleeve for most rearends
Clearly, valve lift is the most important change in this situation, and since it's a fairly simple concept, we don't need to spend much time with that. Changing rocker ratio will also increase valve lift, so you need to account for the rocker ratio as well. The idea that sinking valves help V/P clearance is true in theory, but that's not a good reason to do this, since it kills flow-so we'll just ignore that one. The valves on your early heads are still in the same position in relationship to the piston as the later model heads, so little has changed there. Did you increase valve diameter? Larger valves are often culprits. Another point worth mentioning is piston deck height-or how far the pistons are below the deck surface of the block. If the engine has been decked, this will reduce the V/P clearance. Head gaskets are another point worth discussing. A thick head gasket will increase V/P clearance while a thin gasket will reduce it. And, of course, you have the valve pockets in the pistons.
There is no excuse for losing traction at the strip anymore.
Another important item is cam phasing. This is why it's important to degree the cam when it's installed so you know where the intake centerline is, for example, in relationship to the pistons. Advancing the camshaft opens the intake valve sooner and closes it sooner, so this move generally decreases intake V/P clearance and increases the room for the exhaust valve. Conversely, retarding the cam usually decreases V/P clearance for the exhaust valve and increases it for the intake. The best procedure is to degree the cam so you know it's installed properly and then check the V/P clearance.
This is what the clay looks like after testing this engine for valve-to-piston (V/P) clear
The easiest way to check V/P clearance is to lightly oil the valves and lay down some modeler's clay in the piston valve reliefs. Then install the head gasket you will be using and cinch down the head. If the engine is using hydraulic tappets, use a solid lifter, since hydraulic lifters tend to bleed down and produce a false reading. Set the lifters with zero clearance on the rockers and slowly turn the engine over about four complete revolutions. Then remove the head and carefully cut the clay in half. The section width of the clay will indicate the total V/P clearance. If the clay is squished completely out-or worse, the engine doesn't turn over-then, as they say, your problem is obvious.
Randy Yauck, Flin Flon, Manitoba, Canada: Is there a way to modify an LS engine to priority oiling like the GM cast-iron LSX and the aftermarket blocks? Can piston oil squirters be added also? A friend gave me a 4.8 out of a wrecked pickup. I will pull it out soon. If it needs work, I'll stroke it with a 5.3 crank.
Up close on the 4360 engine, the arrow points to a roller lifer that rides o
Jeff Smith: There might be a way to modify the block, but why would you want to? Unless you plan to spin your LS-series engine into the stratosphere, there's really no reason for this modification. If you look at the following illustration of the stock LS oiling circuit, once it travels up the pickup and through the crank-mounted gerotor oil pump, the oil travels down a large oil gallery on the driver side of the block all the way to the rear of the engine to the oil filter. After the filter, it runs uphill to the main oil gallery located in the center of the engine. This gallery feeds the crankshaft mains and rods as well as the lifters. From the lifters, the oil runs through the pushrods, up to the rocker arms, and to the valve-springs before returning to the oil pan via drain-back areas at the front and rear of the block intended to avoid the crank as much as possible. To get the skinny on these engines from a guy who has built dozens of them, we talked to Kurt Urban of Kurt Urban Performance in Commerce, Michigan. He says the biggest issue with lubrication for these LS engines is that high rpm can suck the pan dry, especially if you are using a stock, 4-quart oil pan. Many engines have a tendency to pump large a volume of oil up into the valve covers. Limiting oil drain-back prevents the oil from quickly returning to the oil pan. A quick fix that Kurt says might work is pushrods with smaller 0.035-inch feed holes that act as restrictors to keep more oil in the pan. This was a trick GM used in some spec-series racing when lubrication modifications and restrictors were not allowed. Of course, the best solution would be an aftermarket pan with more capacity and a deeper sump, assuming you have the ground clearance. Another good idea would be to retain the factory windage tray that Kurt says works very well.
OK, we give up. How many plastic recycling bottles can you fit in an Escort?
As far as oil squirters are concerned, Katech sells a piston squirter that requires block modifications, but these are only for Gen IV engines. A very low-cost alternative would be to have the stock rods milled with a small V-slot cut in the upper portion of the big end of the rod on the side of the rod shared on the same journal. This slot will be aimed directly at the bottom of the piston that could shoot oil from the rod directly into the bottom of the piston. According to Tom Lieb at Scat, this is a common trick for Honda engines that he's been doing for years.
This illustration reveals a relatively unrestricted path to the mains. The biggest issue i
In terms of bolting the 5.3 crank (3.62 inches) in place of the shorter 4.8L's 3.26 arm, that's an easy way to bump up the displacement on the little iron motor. Why not go a little further and find a rotating assembly for a 5.7L LS1? This assumes that the 4.8 block can handle a bore increase from 3.780 to 3.898, which is 0.108 inch. As long as the thrust surface of the cylinder wall has about 0.200 to 0.240 inch of wall thickness, you're good. Then you'd have a 5.7L engine that looks to the rest of the world like a 4.8. You supply the misinformation about its displacement, and we'll back you up-how's that?
The trick of modifying the connecting rod to oil the bottom of the pistons can be accompli
Kurt Urban Performance
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