JBUGS VIDEO SERIES

JBugs Video Series

VW Super Beetle Setting Rocker Geometry:

Video Overview:

We're almost done with the build of our 1800cc stroker engine and with our compression ratio and deck height set, we can set up the geometry for our 1.4 to 1 Ratio Rockers. We'll use cut to length pushrods which are needed whenever building a stroker engine or when using high ratio rocker assemblies.


Video Tips:

The tools you will need are:
Push Rod Measuring Tool
12mm Wrench
13mm Wrench
3mm Allen Wrench
Pocket Knife
Tubing Cutter
Dial Indicator With Magnetic Base
Angle Grinder With Burr Bit
Air Nozzle
Brass Hammer
2 Used Lifters

The chemicals you will need are:
Assembly Lube
Parts Cleaner

Video Transcript:

Hello, I'm Sam with JBugs.com. We're in the middle of mocking up out top end on our 1800cc engine for our 1971 Super Beetle.

 

In our last video, we just got done setting a cylinder head in place. We're mocking up the top end in preparation for our 1.4:1 ratio rockers. Ratio rockers are an easy way to wake up a VW engine and highly recommended if you have added dual carburetors and a header to a stock motor. The stock cam is one of the limiting factors in getting the fuel and air, into and out of the engine. 1.4:1 ratio rockers increase the amount of lift from a stock camshaft from about 0.320 to about 0.420. That is the equivalent of installing a performance cam and the rockers can be set up and installed in a few hours with the engine in the car.

 

The high lift rockers require shorter than stock pushrods, rocker stand shims, valve lash caps, and testing to ensure that the valve train works correctly. Adding to that, we also have a stroker crank, which requires the same process.

 

At our engine, we first test fit the new rocker assembly and see that it doesn't fit over the stock studs. This is expected as the rockers include new rocker studs so the stock studs are removed from the head, and the new studs are threaded in their place. Next, we install hardened valve lash caps on top of the valve stems. The caps are highly recommended whenever stainless steel valves are used to spread the load between the rocker tips and the valve. High ratio rockers increase the load substantially so consider the lash caps a must.

 

The rocker assembly is set back into place to confirm the fit and we can see the bosses aren't completely bottomed out on the stand. We pull the rockers off and install .0150 rocker stand shims on the studs so the rocker assembly can sit flat against the head. Now we can work on the rocker geometry and pushrod length. A push rod tool is lubed at both endsthe adjusted to the shortest length and placed into the cylinder head into the lifter bore into the case at cylinder number three in the intake valve. The engine is rotated over to top dead center for cylinder number three and we see the push rod drop. The push rod is moved over to the exhaust valve for photographic purposes and the rocker assembly is bolted down to the head.

 

Next, we back the valve adjustment screws, which are located at the pushrod side on the new ratio rockers, all the way out and then screw them in about half a turn and lock down the nut. The push rod length is adjusted so it sits against the rocker adjuster and tightened to zero lash at the valve as we'll be running Chromoly pushrods. Zero lash is where we can spin the rod but there's no play in the rocker. If [you're] using aluminum pushrods, set the valve play to 0.060 of an inch with a feeler gauge.

 

The engine is turned over by hand and stopped when the valve is pressed in as far as the rocker will go. Our magnetic base from our dial indicator is removed, and the post is threaded into the head at one of the intake manifold stud threads. The arms for the indicator are moved and the indicator is positioned over the exhaust valve seat, perpendicularly, and in line with the valve.

 

The indicator is pressed in and set roughly at half an inch, pre-loading the indicator. Then locked in place on the arm. We turn the engine over slowly again, noting the point where the needle stops traveling in one direction and travels the opposite. This is our max lift point and we zero our gauge at this point. The engine is turned over slowly again and we count the gauge as it passes zero. It ends up turning fully four times. It stops at 0.020, giving us a max lift of 0.420 inches.

 

Now we need to rotate the engine over to the half lift point, half of 420 is 210. We rotate the engine back to full lift and continue past zero twice then to the 0.010 marks. The rocker geometry at this point, into the travel, is what we're adjusting. The end result we want is for the rocker arm ends, at the valve and at the adjuster, to be parallel with the head at the half lift moment. This will even the loads on the valves and the adjuster to ensure a long life on the valve train. Without current set up, the adjuster side is considerably lower than the valve so the dial indicator is moved out of the way, the rocker assembly comes off, and we swap out the 0.150 shims for a 0.300 shim.

 

The push rod is lengthened to adjust to the valve and the dial indicator process is repeated and the net result is that the adjusters come up a bit but is still much lower than the valve. The whole process is repeated with a 0.600 shim and finally with a 0.600 and a 0.300 shim stacked together for a total of 0.900. Here, we get a half lift point where the adjuster and valve are leveled. So the dial indicator is moved to the side and the rocker assembly is pulled off.

 

The push rod is removed and brought over to our workbench so we can mark and cut our new Chromoly pushrods with a tubing cutter. The ends of the cut pushrods are cleaned up with a burr bit. The push rods are blown out and cleaned thoroughly. A pair of old lifters is used as a hammer and dolly of sorts to hold the push rod in place at the bench while hammering the opposite end into place into the pushrod tube. The push rods are blown out and cleaned again.

 

Back at the engine, two push rods are lubed at either end and installed as the number three cylinder which is set at top dead center. The valves are adjusted and the engine is rotated over to confirm our geometry. With that, our mockup is complete. We can now pull the head, cylinders, and pistons off the short block in preparation for our top end assembly.

 

Our last two videos have been very tech heavy and whereas properly setting your engines compression ratio should be done for every engine build, setting up rocker geometry is a specific task required when building a stroker engine or installing high ratio rockers. Thanks for watching and keep an eye out for our next video where we'll complete our long block assembly. In the meantime, head over to JBugs.com for all your vintage Volkswagen parts and accessories.