CB Performance Strip Dominator Heads

This article details the first major change to the WKR motor since 2002 when we got the first set of CBs CNC Competition Eliminators. Those heads have served us well and have well over 500 runs on them, propelling the blue car to many wins during that time.

With the introduction this year of CBs brand new “Strip Dominator” heads, it’s time to make a change.

The Strip Dominator heads are a work of automotive art. Based on the Autocraft 910 casting, they have been slightly redesigned to accommodate the CNC port configuration that Pat Downs at CB has designed. The rocker supports are also different from my old Comp Eliminators, featuring full support of the rocker shaft all the way to the ends of the shaft, minimizing flex.

The new rocker arm set-up for the Strip Dominators is made by Pauter Machine. I’ve been running Pauter connecting rods and rocker arms for many years and they are the best there is. The only issues I’ve had with my rocker arms over the years can be attributed to flex from the two-bolt mounting. The two-bolt mounting fits almost every VW head made and that is the advantage. The disadvantage, that is well known, is that the two exhaust rockers are unsupported at the shaft ends. The new arrangement eliminates that with full shaft support at both ends as well as the center with a four bolt mounting arrangement.

Along with the heads and the rockers, Pat at CB has recommended a new cam profile. The venerable CB2298 that I have been using for years will be swapped out for something with a bit more lift and a bit less duration to complement the port configuration.

Now, there’s a little more to the job than simply swapping the heads out. They are not what one would consider a true bolt-on. For example, the bottom row of head studs need to be much shorter as they will not protrude into the rocker box area like they do in most VW heads. That's a small amount of work when looking at the Big Picture.

I’ve been waiting to replace the pistons and barrels until the new heads were available. The Strip Dominator has a slightly different valve size and spacing, and the relief notches that are to be cut into the pistons need to match that.


To that end, Ron Barrett of IAP kindly arranged another set of AA pistons and barrels for us, with the barrels honed to my desired dimension. AAs typically come with tighter piston to cylinder wall clearance that what most feel is good for a drag race motor. That is why I asked for a little more clearance honed into the barrel. I did this with my previous set and I believe this is one reason they have performed so well.

With that, we will machine valve notches and cut the barrels to the needed length to give us .045” deck, including the .040” copper head gasket.
We’ll get started with changing out the head studs. All the studs are shorter to some degree with the bottom row now about the same length as the top row. There are four each of two different length studs on each side. The heads have provisions for the “Six Stud” arrangement, but we’ve had good success with the standard deal using 10mm studs, even at close to 15-1 compression ratio. Once I got an optimum length for the short studs and the long studs, I made eight of each size and checked ‘em for length once they were screwed in. I also made it so the stud screwed all the way into the case, leaving no threads showing. The studs have a slightly reduced diameter on the main body, and this makes it so less material have to be removed from the base of the barrel around the stud relief to sit flat on the case.

With the standard K-800 valve spring removed and light checking springs in their place, what I want to do is get a measurement of “Actual Rocker Ratio” and get the total net lift. This is mainly to insure that our new cam will not cause a coil bind issue since it has more lobe lift than my CB2298.
At this point, I discovered that my existing pushrods were too short. So, I cut a spare pushrod in half, ran a tap down the ends of each half so that a piece of all-thread could be screwed in, thus making an Adjustable pushrod.

Upon mocking up and measuring using my new adjusto-pushrod, I found the actual ratio turned out to be close to 1.6, just as it had been with my Comp Eliminators, and put total net lift with the new cam at around .675” and about .050” short of coil bind. With the “Centered” timing washers in the timing gears, the cam installed on a 106° intake lobe center. One degree advanced. I’ll leave it as is.

 

 


While the light checking springs are still installed, A measurement was taken for cutting valve notches in the pistons. Once they were cut, I reassembled and double-checked the clearance. After making the notches .200” deep on the first go-around, then re-measuring, I only had .050” valve to piston clearance on the intake, and .070” on the exhaust. I felt they needed another .030” to be safe, so that much more was machined out. Assume nothing!

 

With that segment of the changeover complete, most of the machine work is done, and the shortblock can be assembled. I am using the bearings over again, because they were nearly perfect. So, the case and the parts to be assembled were cleaned once again, and the bottom end was buttoned up in typical fashion. I then ran a "Dingle-Berry" hone though the cylinders to clean off any residual rust and give the rings a nice "nap" to seat into. The cylinders are then cleaned with Simple Green and hot water one at a time, dryed with compressed air and immediately coated with WD40 before rust begins to form. Believe me, it will happen in seconds right before your eyes once the oils have been stripped out with strong detergent. That's the only way to get 'em squeeky clean tho.

The Total Seal rings were gapped and installed onto the pistons, also cleaned with soap and water. Using a JayCee tapered ring compressor, the piston are then slid into the barrels. A light bead of Loctite 515 flange sealant is applied to the base of the barrels and they are slid over the studs. The wrist pins with my own buttons are oiled and pushed into place, and the barrels are slid home. Since Loctitie 515 is an Anaerobic sealant, I like to slide a head on and snug a couple of the nuts down to press the barrels against the case right after both barrels are on each side. This ensures that the barrel finds "home" and isn't held off the seating surface of the case. The heads are removed after the sealant cures, and new copper gaskets are placed in the heads and then they are torqued down. I had to make a "Special Wrench Socket" to torque the head nuts as all except for two head nuts are behind some part of the head and not reachable by a conventional socket. The big advantage is that there are no longer any head nuts in the rocker box, so they no longer need to be sealed and can no longer be a leak source.

Before these heads, I used to install the spring loaded JayCee pushrod tubes before cinching the heads down as, I had found it was easier to put them into postion when the head is being installed just like stockers. That is no longer do-able with these heads as the tubes block access to the bottom row of head nuts. A minor complication actually.

That completes the longblock. The next challenge is fitting the motor into a stock engine bay.

What turned out to be the major challenge there was the intake manifolds. Making the manifolds fit was semi-painful as it required some clearancing of the engine bay floor. I had just this winter refinished the engine bay after doing the chassis work and wheel tubs, and now it was necessary to make further modifications. It's a good thing I know a fella named Bob Welker that is willing to help with that! Bob was instrumental in finishing the engine bay this winter, and will be called upon again when we have time to finish the new modifications.

Forging ahead, I installed the motor, marked the locations (bottom red circle shows where the manifold hit the floor, top red circle shows how much further down the manifold needs to go before being able to line up the bolt holes) where cuts were necessary, and then dropped the motor back out.

The cuts were made and the motor went back in. Bob and I will go back later and refinish those areas.

With the motor back in and with everything "fitting", the rest of the externals were bolted on. Some work was needed to my throttle bodies to fit them to the intake manifolds and this too will have to be refined later. The throttle bores in the manifolds were big enough to where my throttle bodies wouldn't seal all the way around. I built up the areas needing attention temporarily with JB Weld so they would seal. Everything else fit OK except for the linkage rods. I made longer ones, as they were just barely too short.

The intitial fire-up went pretty smooth. It lit right off, and checking the timing, it was right on at 28°, so I left that as is. The idle fuel ratio seemed pretty lean as it was "hunting" a bit and getting warm. I ran it in three five minute intervals. A couple more times and it was ready to rock 'n' roll!

Our first outing with the new combo didn't allow us to tune it to it's full potential. I ran it in actual competition the very first time out at an American Nostalgia Racing Association event. I had three qualifying attempts to get it dialed in. With the motor tuned very rich, our best time of the day was 11.53 at 117mph. It was so rich, the head temp barely topped 100°. I was out in round one due to a redlight start, so further tuning efforts would have to wait.

As it turned out, I had to pull the motor to fix the leaking pulley. It seeped before, and due to time constraints, I put it back together without changing the seal. While we had it out, it was a good opportunity to run it on CBs dyno to get the jetting and timing closer.

On the first pull, the number was 246hp. This was jetted one step leaner than it was on the 11.53 run. After two more pulls and a step leaner on each one, along with a small timing change, brought the HP number to 288hp!

A Very Special Thanks to Rick Tomlinson at CB for making this happen, and to Pat Downs and Mark Lawless for all their help with this project. These heads are Pats design and they are straight from the CNC machine with no additional porting or blending. This will bring the cost and build time of a super high performance engine package way down.

Thanks also to Ron Barrett for supplying the piston and barrel set.