Half a Mouse - Slant Four
Wayne Woodrum; Madisonville, TN: I’ve been buying automotive magazines since 1965, and at times, I’ve run across special engines. The one that really got my attention was a small-block Chevy with the driver-side cylinder bank removed, making it an inline-four cylinder. Imagine a slant four cylinder Chevy. I plan on building one, but I don’t know much about it. Do you have any information on how to do this? I know I’ll need a special crank and camshaft, or can I use parts from an inline engine? I’m old-school so I don’t have any online capabilities. Can you help?
Jeff Smith: This engine was originally designed by Ron Hoettels, who owns Speed Engineering Service Co. (SESCO) in Colgate, Wisconsin. I talked with Speedway Motors’ museum curator Bob Mays, who says there are several SESCO engines in the museum located in Lincoln, Nebraska. Bob told me Hoettels designed the original SESCO engine as an inexpensive, alternative Midget engine for circle-track racing. Up until the SESCO engine, Midget racing had been dominated by the four-cylinder Offenhauser, which was a specific-built racing engine that could trace its roots back to Harry Miller’s ’20s Indianapolis race engines. I then spoke with Hoettels, who said the SESCO plan started with a 283ci Chevy block that was whittled down to just a 6-inch-tall portion of the right (passenger) side of the cylinder block. This machining completely eliminated the original main webbing as well. Hoettels then replaced the main webs with a two-piece aluminum crankcase assembly that then employed the crank from a Chevy II inline-four cylinder. Hoettels told me this worked because Chevrolet engineers pulled the Chevy II four-cylinder’s bore spacing and main web layout directly from the small-block Chevy. Combining a 0.030-inch overbore of the stock 3.875-inch bore with the Chevy II’s 3.25-inch stroke, the SESCO four-cylinder came out to 155 ci. In addition to being less expensive than the Offy, the slant four engine allowed racers to use a ported version of the production iron fuelie small-block Chevy head along with its entire valvetrain, making replacement parts both easier and less expensive to find. The engine did require Hoettels to make his own mechanical fuel injection manifold with 2.1875-inch throttle bores that fed methanol to the 13.5:1 compression engine. Spinning this engine 7,500 to 7,800 rpm would generally deliver around 225 hp, which computes to 1.45 hp/ci.
The SESCO engine was dominant in Midgets with racers like Mel Kenyon and Gary Bettenhausen between 1972 and 1973, but it was eventually supplanted by the aluminum, flat, four-cylinder VW engine. Hoettels then built his own opposed four-cylinder he called the “two by four,” using the center of a small-block Chevy with his own cast-aluminum cylinder heads and the small-block’s Chevy valvetrain. SESCO also built a few four-cylinder Mopar Midget engines using the same half-a-V8 idea, this time basing his four- cylinder on the 410ci Mopar Sprint Car V8. Measuring 165 ci, it made around 300 to 310 hp spinning to 8,500 rpm. This is very close to an impressive 2 hp/ci. Complete versions of all of the SESCO Midget engines can be found at the Museum of American Speed.
If you find yourself anywhere near Lincoln, Nebraska, and you call yourself a gearhead, you need to set aside an entire day to take in the Museum of American Speed. There you can immerse yourself in Speedy Bill Smith’s amazing collection of circle-track race cars and the 300-odd race and development engines on display. Among the plethora of internal combustion artwork are powerplants you never knew existed. This makes the museum literally an automotive pilgrimage for fans of racing history—especially if you think the smell of combusted methanol is just this side of true cologne.
Slant Four - More Info
Museum of American Speed; Lincoln, NE; 402/323-3166; MuseumOfAmericanSpeed.com
SESCO; Colgate, WI: 262/628-4040
The barrels on this PC Carburetors Dominator look like they could swallow magazine editors whole.
It’s All in the V
Larry Webb; Knoxville, TN: Thanks for the in-depth article about camshafts and turbos. The information is very helpful. Being a bit of a geek, I tried to reproduce the numbers you posted for the three cam examples. As I understand, each has a 106-degree intake centerline and an LSA of 110 degrees. If I understand correctly, the measurement of LSA is the difference between the intake and the exhaust at max lift. Since the cam rotates at half the speed of the crank, this value must be multiplied by two to match the two revolutions of the crank. This being the case, I get the following formula:
Intake open = intake centerline – 1/2(intake duration); Exhaust Close = intake centerline – 2(LSA) + 1/2(exhaust duration).
Doing this for the first cam gives me this IO = 106 – 1/2(218), so IO = – 3 or 3 degrees before TDC. EO = 10 – 220 + 1/2(224), so EO = 108 or 1 degree before TDC. This gives an overlap of only 2 degrees as opposed to the 53 degrees in the article. Using the same calculation for the other cams results in the expected 12-degree difference but at values of 13-degree overlap and 25 degrees. What am I missing from my equation?
Jeff Smith: You have a basic understanding of the concept—it just needs to be fine-tuned a little. The intake and exhaust centerlines establish the positions of the lobes, but to determine the amount of actual overlap (both intake and exhaust valves are open at the same time), we must use the opening and closing points as listed on the cam card. In the following example, we’ll use a Comp XR281 hydraulic roller small-block Chevy camshaft (PN 08-432-8) using the published specs on the cam card. Assuming a 1.5:1 rocker ratio and a checking spec of 0.006 inch of tappet lift, the valves are actually already open 0.009 inch. Measuring the true valve opening and closing points would require measuring exactly when the valves actually open (which is hard to determine—do you start with 0.001 or 0.00001 inch?), but those points would still be proportional to our 0.006-inch tappet-lift figure. For the purpose of this discussion, we’ll use the 0.006-inch opening spec because it’s easier. Here’s the formula for determining actual valve overlap:
Overlap = exhaust closing + intake opening
As a further point of reference, the formula for determining the lobe- separation angle is:
LSA = intake lobe centerline + exhaust lobe centerline/2
LSA = 106 + 114 = 220
LSA = 220/2 = 110 cam degrees
The XR282 cam specs are:
Advertised duration: 282/288 degrees
Duration at 0.050: 230/236 degrees
Lift: 0.510/0.520 inch
Intake centerline: 106 degrees
Exhaust centerline: 114 degrees
Lobe-separation angle: 110 degrees
Lobe opening and closing points at 0.006 inch of tappet lift:
Intake opens: 35 BTDC
Exhaust opens: 78 ATDC
Intake closes: 67 ABDC
Exhaust closes: 30 BBDC
Overlap = EC (30) + IO (35) = 65 degrees of overlap at 0.006-inch tappet lift with a 110-degree lobe- separation angle
If we were to widen the lobe- separation angle from 110 degrees to 114 degrees, it would decrease the overlap, and the small triangle in the illustration representing valve overlap would get smaller. To widen the lobe-separation angle, we must advance the exhaust opening and closing points 2 degrees while retarding the intake opening and closing points by the same number. Narrowing the lobe-separation angle would require the opposite movements of the intake and exhaust lobes. Of course, you can also move just one lobe or the other; there are no requirements to move both lobes an equal or unequal number of degrees. One way to double-check your opening and closing points is by adding the numbers together (plus 180 degrees) to ensure the duration hasn’t changed. You’ve simply moved the opening and closing points without changing the duration.
Keep in mind that on a pushrod V8 like the small-block Chevy, the only way these numbers can be moved like this is by grinding a new camshaft. You can move the intake centerline relative to the piston, but this also moves the exhaust. This discussion is aimed at pushrod engines. Now if you had a dual overhead cam (DOHC) engine with separate intake and exhaust lobe camshafts, you could move the intake and/or exhaust lobes separately, which means you could adjust the amount of overlap. That’s exactly what the late-model, variable-valve-timing engines are doing. Factory engineers widen the LSA at idle and low engine speeds to ensure a smooth idle and then generally tighten the LSA by retarding the exhaust lobes. This way, they don’t affect the intake closing point because the intake lobe must be advanced to tighten the LSA, and that is counterproductive for top-end power. It may seem complicated at first, but if you study the relationships for a bit, it will all make sense. Assuming that I’ve explained it properly, of course!
Comp Cams; Memphis, TN; 800/999-0853; CompCams.com
In with the Good, Out with the Bad
Don Mueller; Brookfield, WI: I have a 2,500-pound car that has its original ’69 Ford J-code engine with 48,000 miles on it. It still has the factory cast HiPo exhaust manifolds. I’ve installed an Edelbrock RPM intake, a Holley 670-cfm Street Avenger with vacuum secondaries, a Comp Cams Xtreme Energy 262H cam, a PerTronix Ignitor, a TR3550 trans, a 3.80:1 rear gear, and 205/60R15 tires. I have a set of AFR 1402 heads that I would like to install along with a Comp Cams XE274H cam with a 351W firing order and a 21/4-inch dual exhaust with a cross-pipe.
The car is used for show and shine, cruising, taking my son to school and practices, the occasional stoplight GP, and just plain driving enjoyment, always with the top down and pipes roaring. Its weak links are the original 5/16-inch rod bolts. These prevent me from running more than 5,500 rpm. What is the redline on these bolts? I’ve researched online the question of whether they will go 6,000 rpm, but the only answer I got was “at least once.”
We’ll spare you the guessing as to what this is. Just imagine spoiled milk, a cupholder, a warm car, and plenty of time to ferment. Channeling Gordon Ramsay, the Meguiars guys did their own trash-can barf routine after pulling this out of one of our cars. Details about this calamity will also be in December’s issue.
Of course, money is tight. Can I replace the rod bolts with 3/8-inch bolts when I change the heads, without having to totally tear everything down to have the whole rotating assembly rebalanced? If I am stuck with a 5,500-rpm limit, will the XE274H cam be too big? Your articles say big heads need big cams. I don’t need a lot of low-end torque because the rear trailing arms limit the rear tire size to 225. When I look at the dyno charts for the XE262H and XE274H, from 2,500 rpm to say 3,500, they look pretty much the same to me. The XE274H has about a 20hp and 50 lb-ft advantage at 5,000 rpm.
Finally, I’m told that the cast HiPo manifolds are my power restrictors. My frame prevents the use of standard, equal-length or block-hugger–style headers.
Jeff Smith: There are a bunch of things going on here that all relate to engine power. The heads and the camshaft should work well together, but the exhaust manifolds are certainly a restriction. Based on the fact that you really don’t want to spend the money to upgrade the rods (better rods would be stronger and cost about the same as new ARP bolts and resizing the big end of the stock rods), you’re limited in several areas. Engine durability should limit the rpm to certainly no more than 6,000, and your self-imposed 5,500 rpm is very safe. It’s not horsepower or cylinder pressure that kills connecting rods—it’s rpm. Weak rod bolts with heavy pistons are a poor combination. What happens is that as rpm increases, the rod bolt is subjected to higher g-loads that try to pull the rod cap off the rod as the piston travels across top dead center (TDC). Heavy piston and more rpm combine to create increasing g-forces that will eventually stretch the rod bolts. Soon after, the motor comes apart.
Since you have both a 3.80:1 rear gear and a good Tremec five-speed, you have plenty of gear to accelerate the car, so you can go with a bigger camshaft without giving up too much. Acceleration and throttle response below 3,000 rpm won’t be stellar, but the deep rear gear and the fact that your car only weighs 2,700 pounds are reasons you can make this work. But the big limitations are the exhaust manifolds. Good cylinder heads like your AFR 165cc castings not only have high flow intake ports, but they also match the intake with excellent exhaust flow. One way to look at this is from a comparative-flow standpoint (i.e., the relationship of the exhaust flow to the intake). If the exhaust is around 70 percent of the intake at the same valve-lift points, you have a good head. Your AFR 165cc heads calculate out at 77 percent at 0.550-inch lift, which is excellent. The problem is that the exhaust manifolds restrict the flow from the ports. This creates backpressure in the manifolds, requiring the engine to use horsepower to push the exhaust out of the cylinder. Worse, a direct result of this backpressure is a larger percentage of exhaust gas that remains in the cylinder after exhaust stroke is complete. This mixes with the fresh, incoming air and fuel, displacing and diluting them and ultimately reducing cylinder pressure because the exhaust gas won’t burn a second time. If the backpressure stack-up in the cylinder is severe enough, the exhaust gas will even travel up into the intake manifold. If you’ve ever seen an intake manifold in which the inside of the plenum area is black, that is direct evidence of exhaust carbon residue coating the inside of the intake manifold. The more overlap and duration the camshaft employs, the worse this situation will become. It’s a guarantee that there will a lot more overlap with that XE274 cam than with the smaller XE262.
Did you like the color of IMM’s 360 Stroker? Get the same look for your engine with a can of DupliColor’s Low Gloss Black. “It looks like the Batmobile,” Brian Hafliger told us.
If you are not willing to add headers because of clearance problems, it will be difficult to make any kind of decent power by adding the AFR heads and bigger camshaft. What will happen is that in the midrange rpm (under 4,000 rpm), the engine will probably make decent power. But above 4,000, exhaust gas backpressure will begin to cause cylinder pressure to decrease, and that means less horsepower. So at the exact rpm that those heads and larger cam should really be working, the engine lays down because of a restricted exhaust. The net result is it’s entirely possible that this combination will make less power everywhere. We tend to take headers for granted, but they are an essential component of the engine performance package. All the systems have to work together for the engine to make decent power.
So it appears you have several choices. The first would be to remain with the smaller XE262 cam but go ahead and bolt on the better AFR heads. Better heads will still make a little more torque with the small cam and perhaps a little bit better peak power. It all depends on how much flow restriction is present with the manifolds and exhaust system. You could go this route, but absolutely add the 21/2-inch mandrel-bent exhaust and cross-pipe. One way to measure exhaust gas backpressure is to weld an 18mm oxygen sensor bung into the exhaust pipe just downstream of the exhaust manifold. Adapt a copper 1/8-inch line to a 10- or 15-psi pressure gauge and run the engine at WOT in Third gear to see what the pressure gauge reads. If you see more than a consistent 2 to 3 psi, the system is restricted. The real test would be to place a pressure sensor in the exhaust manifold right near the exhaust port, but that’s not easily accomplished. Other ideas are to modify a set of full-length headers to clear the chassis interference problems. I’ve run into this situation myself and find that often the solution isn’t that difficult to achieve. It may require changing the location of one or more tubes to clear the obstruction. The cost is reasonable, and the difference in power—even with your current combination—would be noticeable. This is the best way to go.
“Imagine how much power we could make without the rag in the intake.” Don’t worry, all the dyno numbers in the 360 Stroker article are rag free. Brian Hafliger just used it to cover the intake opening while changing carburetors.
I have a last suggestion. Once the header question has been resolved, why not consider retaining the stock engine and building a whole second engine? Start with an affordable 5.0L engine that will have better seals and would allow you to run a hydraulic roller cam with the stock lifters. Make it a 4.030 bore and 3.25-inch stroke crank from Scat along with good I-beam rods, and you’d have a 331ci. Our buddy Tim Moore built an admittedly stout version of this bore/stroke combo back in the Oct. ’08 issue (“495hp at 7,400 rpm,” pg. 44), and it rocked. He used CNC-ported AFR 205s, but your smaller heads would make more torque and a little less horsepower than Tim’s version. Bolt on your AFR heads with about 10.5:1 compression and an XE274 hydraulic roller for a 5.0L engine. This cam delivers less duration (224/232 degrees at 0.050, 6 degrees shorter on the intake and 4 degrees shorter on the exhaust) and 0.555/0.565-inch lift, roughly a 0.030-inch increase, and it will allow you to run those AFR heads right up to their max lift-flow potential. Now you have a thumpin’ small-block that will impress the hell out of your son when you take him to school. Just don’t tell Mom!
Comp Cams; Memphis, TN; 800/999-0853; CompCams.com
Scat Enterprises; Redondo Beach, CA; 310/370-5501; ScatEnterprises.com
Brian Cornelius; Elk River, MN: Since no one seems to know the answer to a pressing question I have had for quite some time, I am hoping you can provide an answer to this vexing issue.
I have a 350ci small-block Chevy with a two-piece rear seal that came with breathers in the valve covers. What I would like to do is simply use the valve covers without any breathers on them. I have installed an early intake so I can add oil to the engine at the front of the intake where a breather/filler tube was standard in earlier years. The earlier blocks had a provision for an oil separator and dumped engine fumes out of a hole at the rear of the block behind the distributor.
I have seen engines that have no openings in the valve covers and with unknown modifications to accomplish this, but I’ve never observed how it was accomplished. How can I make the necessary modifications to accomplish this on my engine? Thanks for any help, and for the detailed help you provide in the Ask Anything section of Car Craft.
Jeff Smith: The simple fix would be to use Edelbrock’s oil fill tube and breather (PN 4803, $13.95 from Summit Racing). This will allow the engine to vent crankcase fumes. The problem with this simple solution is that it won’t take long for a thin film of oil vapor to make a mess of your nice, clean engine. Plus, you will have to put up with the smell every time you run the engine. While it might seem car-guy cool at first, it will get old very quickly. This is why the older engine used the vapor separator you mentioned. It was connected to a road draft tube that vented the oil vapor underneath the car. If you look at photos of the Los Angeles freeways from the early ’60s, you can see these amazing, thick, black stripes in the middle of each lane. That was oil being dumped on the freeway from all these road draft tubes! Imagine what happened to the first guy who drove on that oil slick after it rained.
A more elegant solution involves using a positive crankcase ventilation (PCV) system. A basic PCV system pulls filtered air from the air cleaner into the valve cover. Then the air travels through the engine to the PCV valve located in the opposite valve cover. There is generally a vapor separator located inside the valve cover that helps to shed as much oil as possible from the vented gases before they travel through the PCV valve to the intake manifold, where the vapor is burned. The PCV valve is a restriction, but it uses a manifold vacuum to pull the crankcase vapor.
Since you desire clean valve covers with no connections, you could vent the engine differently. One idea would be to use a custom vapor separator located on the backside of the valve cover, where it is less obvious. This could be plumbed to a vapor separator canister located elsewhere in the engine compartment (like under the open area between the inner and outer front fenders). It should be located high enough that oil will drain from the can back into the valve cover. This line would be plumbed from the valve cover to the bottom of the canister, and near the top of the can would be a second line that would be plumbed back to the vacuum source location in the intake manifold. The system will require a second fresh inlet source on the driver-side valve cover, but that could again be placed at the rear of the valve cover and could use a -6 or -8 line plumbed to a small K&N–style filter that would filter the fresh air going into the engine and is pulled out of the engine on the opposite side. There are probably several other ways to do this, but this method will vent the engine without spewing oil.
This is a gratuitous big-block photo of Jefff's Rat in his Chevelle because it's cool.
Jeff Paulin; Ventura, CA: I have put a big-block in my late grandmother’s gold ’72 Chevelle, along with a TH400 and a Ford 3.90 spool rearend. First time out at California Speedway, it ran 10.38, 10.39 twice, and 10.41 at 128/129 mph. The 60-foot times were 1.47-1.52. It has a six-point rollcage that meets all the NHRA safety rules and launches up higher on the driver side. Do you have any experience with the BMR suspension kit (PN XSB006)? I am thinking of buying one and installing it. I have heard good things about the kit helping 60-foot times and launching the car even and straight. I’ve also included a link for the car’s first time out: YouTube.com/watch?v=R_K2OPKXh2s. Your thoughts? I really do read all your articles and have been a big fan, even though Frank Saenz pushed back my ’66 Chevelle’s completion date to get your El Camino ready for the ’99 Hot Rod Power Tour®.
Here’s a shot of Jeff Paulin’s Chevelle launch. As you can see, it likes to yank the left
Jeff Smith: I watched the YouTube clip on your first time out, Jeff. The Chevelle looks very strong. Because you included a front suspension photo, I noticed the front sway bar was missing. While my orange ’66 Chevelle is only a mid-11-second car, I was experiencing the same situation in which it picks up the left front and squats the right rear. I installed the stock front sway bar on the car and noticed this helped the car launch more evenly. You might try this, as that tiny 7/8-inch front bar weighs very little and will help keep the car square.
I recently spoke with Brian Rock, who has a very-low-10-second ’65 Pontiac GTO, and we were discussing this same scenario. He has also installed the stock front sway bar, but additionally uses a rear antiroll bar from a company called HRpartsNStuff. Brian believes this type of bar is far superior to the stock rear sway bar, as the OE bar mounts between the lower control arms. While this is convenient, the pivot for the stock rear bar is actually at the front mounting point for the two lower control arms. This creates a very long lever arm that produces a ton of leverage that requires an unusually large (and heavy) diameter bar to produce the desired effect. The HR Parts, BMR, and Dick Miller bars all employ a frame mount. This ties the antiroll bar directly to the frame after clamping it to the axlehousing. This style of antiroll bar produces additional leverage on the rear suspension but also has the effect of helping to limit body roll in the front. The Dick Miller Racing kit comes in two different applications. One is adjustable from underneath (PN NOS-7413, $318.00) and a second (PN 7413T) uses links that extend through the trunk floor that allow adjustment through the trunk.
BMR Suspension; Thonotosassa, FL; 813/986-9302; BMRSuspension.com
Dick Miller Racing; Hernando, MS; 662/233-2301; DickMillerRacing.com
HRpartsNstuff; Atwater, OH; 330/947-2433; HRpartsNstuff.com
This BMR antiroll bar kit is PN SXB007 and sells for $399.95.
Ask anything— We’ve got solutions!
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