The biggest problem is when the diameter of the valvestem above the keeper groove is not the same diameter as the valvestem below the keeper groove. Check some of valves with a micrometer and you’d be amazed at what you find. I have not had these issues with Ferrea and REV products, which is the reason I use them.
I have found Comp Cams retainers and valve locks to fit well to most components, but it is a good idea to check the fit of all these items together by installing the valve, lock, and retainer in your hand and pulling them together with some force. The valvespring retainer should lock itself to the valvestem and should not fall off without you pushing it off with some force. If you let go of the assembly after pulling the components together, and the assembly falls apart, there is a radius mismatch and a recipe for dropping a valve if the engine goes into valve float.
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Intake Manifolds
Everyone is very concerned with cylinder-head flow, flow numbers, and cylinder-head performance, but many seem to forget the intake manifold bolted to it. In reality, it is just as important as the cylinder head. The intake-manifold runner is an extension of the intake port. Given that, you have to look at the intake runner as a whole, from the plenum where the runner starts, to the intake valve. The biggest problem with intake manifolds (especially older designs) is that the intake runner cross-sectional area is usually smaller than the intake ports, and this changes volume along the path too much. Current casting technology has come a long way and the runner sizes can be controlled much better than years ago.
One of the reasons Oldsmobile engines have a reputation of producing tremendous torque is because their intake manifolds have very long runners due to the tall deck height of the block. In general, equal-length longer runners help produce more torque in the lower-RPM ranges. This is the reason extended runner dividers inside the manifold plenum often make more power. It seems that you can never get the runners long enough in single 4-barrel manifold designs for any application.
The W-30 intake manifold is basically the same as all of the other cast-iron intake manifolds of that era. The advantages are the weight and the ability to cut it up, port it, and weld it back together.
Replica W-30 intake manifolds are available through vari¬ous Oldsmobile vendors.
The old Edelbrock 04B is still very popular.
The brand-new Edelbrock Oldsmobile 455 RPM Air Gap Manifold (PN 7551) has a constant cross-sectional area of 2.94 inches and is a good match for an out-of-the-box set of Per-former RPM Olds cylinder heads.
The Offenhauser Port-O-Sonic accepts a 4150-style carburetor and the Super Sonic intake manifold accepts a 4500-series carburetor. Although these models are out of date, there are some hard-running Oldsmobile engines out there using them.
The Edelbrock Torker for the big-block Oldsmobile engine is very popular. This single-plane manifold is about as tall as you can get and still fit under stock hoods. These are very hard to port as the runners are very long. I have extrude-honed a few of them and it appears that doing so is worth about 15 hp.
The plenum on the Torker has an unusual shape and requires a tremendous amount of work to get it to function almost as good as a new-style Victor manifold.
The 2812 Edelbrock Vic¬tor is only available with the 4150-style carburetor flange and has a constant cross-sectional area of 3.2 square inches. When using the Performer RPM cylinder head on a small-block Olds engine, this manifold is required; most other manifolds generally do not have enough material at the top of the runners.
Dual Planes versus Single Planes
I have never been a fan of dual-plane manifolds for performance applications. To me, I see no reason to make the air/fuel mixture make a bunch of twists and turns to get to the valve. These dual-plane designs typically have very long runners, which are conducive to low-end torque. But the bottom line is that if you want a better ET slip at the racetrack, the ET will likely be lower with a single-plane manifold. Some say that the dual-plane manifold is better for the street, but the way I see it in my world, whatever manifold makes the car faster at the racetrack is the one that is better for the street.
Single-plane manifolds have a reputation of losing low-end torque, but I am not sure that is true. I have competed in the Popular Hot Rodding magazine’s Engine Masters Challenge three times with an Oldsmobile engine, which measures engine performance on a dyno between 2,500 and 6,500 rpm. On this subject, 99 percent of all the entries, including mine, used single-plane manifolds. I found that on these engines, in what I consider a typical street-RPM range, the camshaft and header design had more to do with low-speed power than having a dual-plane manifold. Use a single-plane manifold if performance is the goal. If you are concerned with cruising and rarely go above 3,000 rpm, I guess the dual-plane wouldn’t hurt.
Porting
Porting an Oldsmobile intake manifold is not a simple operation. The runners are very long and it is difficult, if not impossible, to get even the longest of carbide burrs inside to open up the runner size. If the cross-sectional area of that runner is smaller than the cylinder-head runner, it doesn’t matter how much the head flows on the flow bench, the manifold won’t feed it.
I have milled the carburetor flange on the Edelbrock Victor manifold as much as .625 inch so it fits under a W-30 hood. You have to weld up the vacuum port in the back of the ple¬num prior to doing so.
Think of it this way: Let’s say you have a 3-inch-long piece of 2-inch pipe, and on your flow bench it flows 300 cfm for your baseline reading. After you spend days porting it, use some epoxy on the floor, and flow it again, it flows 320 cfm. Great job! Now add a piece of 10-inch-long, 1-inch pipe on top of your great job and see how well it flows. Get the point? Given that, you need to determine if your intake manifold will feed your cylinder head, and chances are it will not.
Older intake-manifold designs like the Edelbrock Torker, the Offenhauser Port O Sonic, the Super Sonic, and even the new Rocket Racing/ Wenzler intake manifolds have very small intake runners. The only way you can get inside to open up the cross-sectional port dimension is to cut access passages near the runners, cut the manifold in half (or into sections to be able to get inside), and then weld that manifold back together when done.
When using the W31 factory intake in a hydraulic roller application, you must install some of the roller lifters on the inner cylinders with the tie bar facing the cylinders so that they clear the heat crossover underneath the intake manifold.
The good news is that the latest Edelbrock Victor intake manifolds have a constant cross-sectional area so that you don’t have to kill yourself to port the runner of an intake manifold so it can feed the ported cylinder head on which you’ve spent so much time or money. The big-block Oldsmobile Victor (PN 2810 and PN 2811) manifolds are designed with a constant cross-sectional area of 3.4 square inches, which feeds the largest cylinder heads. The small-block Oldsmobile Victor intake (PN 2812) is designed with a constant cross-sectional runner area of 3.2 square inches.
This gasket spacer has O-rings on both sides to allow the intake manifold to fit properly on conventional cylinder heads with intake ports raised to the maximum.
Looking at a big-block Oldsmobile Victor manifold (left) next to a Port-O-Sonic, it is easy to see which one pro¬duces more horsepower.
This reworked 2811 Victor made 820 hp and 725 ft-lbs of torque on a 506-ci big-block Olds.
This “ Gigantafold” is a highly modified Edelbrock Victor manifold made for a high-RPM application. With its short, even runners, it should be a winner.
The Edelbrock 2811 Victor Dominator flange manifold has a constant cross-sectional area of 3.4 square inches. The plenum and runner length are about as optimal as possi¬ble. If I were to design a manifold for an engine other than an Oldsmobile, it would look very close to this.
This reworked 2811 Victor made 820 hp and 725 ft-lbs of torque on a 506-ci big-block Olds.
The plenum area of the intake manifold is important also, but is a secondary concern to the runner volume. Making all edges inside the plenum smooth and increasing the radius from the carburetor-flange wall to the entrances to the runners increases performance. Changing the plenum shape (with bolt-in geometric shapes sometimes known as turtles) and extending the runners should be done on an engine dyno or a racetrack, unless you have already proved that change to work on that particular manifold. I have seen more than one intake manifold with modifications inside the plenum that appeared like it should work well but did not. The modifications you do to the manifold floor affect fuel distribution and you typically cannot predict the outcome. These modifications have to be tested on an engine dynamometer or a racetrack.
Spacer intake gaskets are available through Flatout Gaskets. They are avail¬able in just about any thickness, even for unconventional applications. You sim¬ply glue the standard 1/16-thick gasket on both sides of the aluminum spacer. Flatout Gaskets made a set for me that was 5/8 inch thick.
The Rocket Racing/Wenzler intake manifold is low enough to fit under stock hoods.
Minor modifications to the plenum of the Edelbrock Torker, such as shown, improves power. Make sure your carburetor gasket seals the largest portion of the plenum. Some carbu¬retor gaskets barely seal that area; some are too small and do not seal at all, which causes a vacuum leak.
Often the distributor hits this area of the big-block Victor manifold. Make sure you mock it up before you glue on the manifold. It’s not the time to find out there is an issue when you are ready to fire up the engine.
Offenhauser made a wide variety of manifolds such as this low-profile, dual 4-barrel aluminum manifold. It is a good-looking showpiece, but not good for performance.
This highly modified 2811 Victor with Dominator flange was converted to a 4150 flange with extended runners and a blended-in four-hole BTR tapered carb spacer. It was the manifold used on the 2008 Popular Hot Rodding Engine Masters Challenge 400-ci engine that finished in the top ten.
This highly modified 2811 Victor with Dominator flange was converted to a 4150 flange with extended runners and a blended-in four-hole BTR tapered carb spacer. It was the manifold used on the 2008 Popular Hot Rodding Engine Masters Challenge 400-ci engine that finished in the top ten.
The Offenhauser tunnel ram was only made for the big-block Oldsmobile engine. It is available with a dual-4-barrel top or a single-4-barrel top (shown). You want the long straight runners, but their cross-sectional area is very small and the plenum does not have the best shape for performance. I consider it a show piece more than a performance manifold.
This unique, Algon stack-injection manifold was manu¬factured in the 1960s. You don’t see too many of these around nowadays, but Greg Grubel uses this on his 1951 Chevrolet. An interesting tidbit on isolated runner mani¬folds is that they have wicked throttle response and I have seen them spit fuel like crazy (right out of the top of the stacks) at a certain RPM in a dyno cell.
When a manifold needs to be milled severely to fit an engine properly, or in high-boost situations, we fit it with no gaskets and run a CNC program that machines O-ring grooves so that you never have to scrape a set of intake gaskets ever again. I hate scraping gaskets!
This manifold is a raw, non-machined big-block Batten intake manifold with a 4150 carburetor flange.
This Tech Tip is From the Full Book, OLDSMOBILE V-8 ENGINES: HOW TO BUILD MAX PERFORMANCE – REVISED EDITION. For a comprehensive guide on this entire subject you can visit this link:
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The 4150 flange Batten big-block Olds manifolds can be converted to accept a Holley Dominator-style carburetor with some machining of the plenum open¬ing and relocating the mounting holes.
The 4150 flange Batten big-block Olds manifolds can be converted to accept a Holley Dominator-style carburetor with some machining of the plenum open¬ing and relocating the mounting holes.
Steve at BTR is working on John Turner’s custom billet tunnel ram.
The finished BTR billet tunnel ram helped make 780 hp out of Turner’s 417-ci BTR-prepared DX Olds.
There have been numerous sheet-metal tunnel ram designs over the years for the Oldsmobile. Most of them are on a shelf rather than being used on a race car. The combination of short runners and large plenums are not necessarily a good fit for an Oldsmobile engine with an automatic transmission.
Carburetors
What carburetor should you choose for best performance for your high-performance Oldsmobile? There are many books, much technical data, and varied opinions on which carburetor should be used for what application. Most of the technical data out there is many years old and looks at RPM and cubic inches to determine which carburetor should be selected. I am not sure that this method holds true today. Carburetors are ingenious self-compensating devices. When airflow increases, the carburetor flows more fuel. When airflow diminishes, the carburetor flows less fuel. To a degree, on whatever size engine a certain size carburetor is used, the ratio of air to fuel remains about the same.
The Rochester Quadrajet was a great carburetor as long as it was large enough for the application. When the Rochester products division stopped making carburetors, it sold the tooling to Weber, which made them for Edel¬brock. The original tooling has since been destroyed, so brand-new ones are difficult to find. FYI, the old Roch¬ester Products plant, now used by GM Delphi, just happens to be across the street from my shop.
While messing around on the dyno, I learned that the angle of the throttle blades and the upper air valve make a considerable horsepower difference. The 455 W-30 NHRA Stock Elimina¬tor engine always made more power when the throttle blades and air valve were not set at 90 degrees.
I currently use Cubic Flow Modifications carburetors by Dale Cubic. I don’t know what he does to these things, but each one
My CFM-prepared Holley Domina¬tor carburetor has been highly modified for my small-cubic-inch nitrous applica¬tion. This thing is big! Big car¬buretors can go faster if prepared correctly. I set the record in 2009 at 7.97 at 172 mph at Bradenton Race¬way Park in the National Muscle Car Association’s Xtreme Street class directly after bolting on this new one.
Carburetor Spacers
Whether you have a Holley 4150 or Dominator-style carburetor, I have yet to see a four-hole tapered spacer not increase performance. If you can fit it, use it. I have seen open-plenum spacers pick up power on occasion, but like most items on an engine, you can theorize until you turn blue. The only way to know if there is a net gain from the item you changed is to test it.
Milling off the carburetor flange allows you to get inside the runners to open up certain areas and shape the plenum properly with whatever carbu¬retor flange you desire.
The old Edelbrock Victor small-block manifold for Batten heads only came in a 4150 flange version and needs a considerable amount of work to make good power. It has been unavailable for many years.
This side-by-side comparison shows an extensive plenum modification (left) on the small-block, old-style Edelbrock Victor for Batten heads for Gene Newton’s twin-turbo small-block Olds.
This side-by-side comparison shows an extensive plenum modification (left) on the small-block, old-style Edelbrock Victor for Batten heads for Gene Newton’s twin-turbo small-block Olds.
This BTR four-hole tapered spacer almost always helps throttle response and horsepower. Throttle bores slightly larger than the butterfly size on the carburetor make more power.
This BTR four-hole tapered spacer almost always helps throttle response and horsepower. Throttle bores slightly larger than the butterfly size on the carburetor make more power.
Carburetor Jetting
The biggest mistake people make with carburetors is that they select main jets too different from the stock jetting. Carburetor jetting is very simple, but is one of the most misunderstood tuning operations. The main jet in a carburetor is selected according to the size of the venturi, which is defined as the tightest area where the main booster is located. Without getting into a long discussion about how carburetors work, I can tell you that the jetting in a brand-new carburetor is already selected properly for you. This stock jetting is extremely close to being optimum for any engine onto which it is bolted.
When at the racetrack or on the engine dyno in normal air, one or two jet sizes up or down is all that is required to make the best power. It takes an air change of approximately 2,000 feet of density altitude to require you to make a jet change in the carburetor. At the local racetrack, I always see guys fooling with jets from week to week. Remember, the carburetor is self-compensating, and that rule applies to any engine.
Another mistake that people commonly make is in the power valve area. The power valve is simply a valve that opens and closes in front of two passages located in the metering block, allowing added or reduced main fuel (depending on throttle position and engine load). These two orifices in the metering block are equal to a certain size of main jet. For instance, a carburetor has a power valve in the primary side, regardless of that power valve’s rating, and the main jet is, let’s say, a pair of 80 jets, and the secondary metering block has no power valve and has, let’s say, a pair of 90 jets. If you want to remove the primary power valve, and block it with a power valve plug, a pair of 90 jets is required for the primary main jet or the same as the secondary side of the carburetor. If the venturi size is the same, primary to secondary, the jetting should be the same. The common misconception is that when plugging the power-valve passages, you must add 10 jet sizes. Remember, the main jet is selected by venturi size.
Off-the-Shelf Carburetors
The average high-performance Oldsmobile street-and-strip enthusiast uses a 4150-style carburetor. The basic 350 engines with minimal modifications always seem to perform very well with the basic 650- to 750-cfm Holley (PN 4776 and PN 4779, respectively). The same-style 455 engines seem to love the basic 850-cfm Holley (PN 4781). If you have a low budget, you can’t beat them. These carburetors work great, until someone puts their hands on them. The Holley HP-series carburetors take the HP Olds engine to the next level if you have extra money in the budget. I have used these in many different applications and they all performed well.
Custom Rebuilt Carburetors restored this old Rochester Quadrajet. It looks great and worked perfectly on David Mendez’s 520-hp 496 W30 restoration engine. It even picked up power over my old “best” dyno Quadrajet.
If you choose to run a high-flow mechanical fuel pump, such as the ROBBMC fuel pump, you have to modify the Edelbrock cylinder head. A portion of the front of the cylinder head is milled out into the water jacket and a new piece must be welded in.
The Holley 950 HP (PN 80496) is the best choice for a 4.25-stroke455-type street engine that spins 6,000 rpm or the 375-ci stroker small-block. On my ever-so-popular 496 pump-gas street engines, I recommend the Holley 1000 HP (PN 80513). Both of these carburetors have downleg boosters and idle beautifully because their calibration is spot-on for these applications. Don’t worry about them not having a choke; you do not need it.
I have dyno tested with these carburetors many times and have found that the calibration is pretty much spot-on straight from Holley. I typically reduce jet size by one number to make it perfect, but it may be different for you.
For the ultimate in Oldsmobile performance, the Holley Dominator carburetor is always the winner. I don’t know if I have ever seen a 4150-style carburetor outperform the Dominator-style carburetor, regardless of the application. The box-stock 1,050-cfm Dominator with power valves (PN 8082) is a great choice for the street, and the 1,050-cfm Holley Dominator without power valves (PN 9375) is a pretty good choice for strip applications. Both of these carburetors work excellently on your basic 455, where budget is an important consideration, but a custom carburetor for the application brings performance to the next level.
Quadrajet Carburetors
The Rochester Quadrajet carburetor is a great carburetor in the applications for which it was designed. In more serious performance applications, they have their drawbacks. I recommend the Rochester for a restored Oldsmobile vehicle, or if the engine is going to appear stock, as do my 496 W30 engines.
These carburetors have two major problems. The first is that the main body on almost all of the Quadrajets tends to bend from over-torquing the front two 5/16 bolts that mount it to the intake manifold. Because of this, some of the passages between the main body and the top usually do not seal; the carb will never run well without repairing this situation first and it’s not an easy fix.
Some carbs are worse than others, so this would be the first thing to look at when selecting a Quadrajet carburetor for your Oldsmobile build. If you think you are going to keep looking for one with the correct numbers that isn’t warped, good luck. It would be very rare to find a perfect one. Some companies can repair, re-plate, rebuild, and recalibrate these carbs, if necessary.
The second issue is that these carbs have only one needle and seat, and a relatively small float bowl. These units have difficulty keeping enough fuel in the bowl for high-horsepower applications that require more fuel flow. Larger needles and seats are available, but that leads to other issues such as flooding because the float is not able to overcome the inlet pressure. The typical Quadrajet carburetor cannot withstand much more than 6 or 7 psi at idle with the largest needle and seat diameters.
One trick to make these carbs work in high-horsepower applications is to install a vacuum port above the diaphragm on your fuel regulator and run manifold vacuum to it. This modification reduces fuel pressure at idle as the negative pressure (vacuum) increases. At wide-open throttle, the manifold pressure is near zero, which gives the carburetor more pressure than the unit can manage at an idle. This setup is generally for racing only because part-throttle operation generates very high manifold vacuum pressure and lowers the fuel pressure considerably.
The diameter of the diaphragm in the fuel regulator and idle vacuum affect how the pressure reacts, so if you are going to try this, you cannot just hook up a vacuum line and drive around or race. You have to experiment to get it to work well.
I can’t tell you how many Quadrajet “experts” are out there who screw up these carburetors! Do not despair if you plan to use a Rochester Quadrajet for your Oldsmobile build and need an expert to restore it and make it run well. I have sent numerous Quadrajets to Phil Cancilla at Custom Rebuilt Carburetors. I received every restored carburetor in nearly brand-new condition, and they all performed perfectly. I used to get a pit in my stomach every time I had to fire up a brand-new engine on the dyno with a “reworked by an expert” Quadrajet. I don’t have that problem anymore and you don’t have to either.
Custom Carburetors
A custom carburetor is a good investment for the serious Oldsmobile racer who would rather be going fast at the racetrack than fooling with a carburetor. Are they expensive? It depends on how you look at it. Everything of quality is expensive. A custom carburetor built for your application does everything it is required to do: make more horsepower and have a fuel curve as good as a properly tuned, and more expensive, electronic fuel injection setup. Yes, I mean more horsepower and less expensive.
A carburetor that is on the small side for an application performs well and does everything required for the racer, such as have crisp throttle response, go onto the trans brake quickly, and recover off the shift. A larger carburetor makes more power, but lacks those other attributes unless you purchase a larger custom carburetor from someone who knows how to make it work for your application.
A handful of carburetor shops are the real deal, but most of the rest are marketing hype. I bet that most people hear or see very little about these good guys; you want to be skeptical of the guys who are advertising all over the place. In my experience, these quality shops include Cubic Flow Modifications (Dale Cubic), Book Racing Enterprises (Bob Book), Braswell, and BLP Products, Inc. (Bo Laws). I have used carburetors from all of these companies and all of them exceeded my expectations. I suggest contacting one of them if you want the best-performing carburetor to complement your high-performance Olds build.
If you want to make maximum power from your Olds for the street, I recommend having Dale Cubic at CFM build you a custom Holley Dominator. It will be custom cal¬ibrated for your combination and have excellent street manners, which you won’t get from a shelf Dominator-style carburetor.
Written by Bill Trovato and republished with permission of CarTech Inc
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