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Slant four - Jeff Smith Technical Questions & Answers - Ask Anything

Breathe In

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.

Traction Action

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®.

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.

More Info

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

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