Author Topic: Rockers (Read 3884 times)

flat4 · « **on:** September 02, 2004, 08:27:14 AM »

Ok.

It seems like I've hit a wall in the performance of my 2110. I'm running stock 1.1 rockers on heavy duty shafts. According to specs for my cam, this should produce .452 lift at the valve. If I change to 1.4 rockers, .575 lift at the valve. Will this create a noticable differcence in the performance of my engine?

Cameron · « **Reply #1 on:** September 02, 2004, 10:30:37 AM »

What cam?
Was the cam designed to run stock 1.1 to 1 ratio?
Or was it designed to run 1.4 to 1 high ratio?

flat4 · « **Reply #2 on:** September 02, 2004, 11:30:10 AM »

It's an Eagle racing cam I purchased from CB. I'm pretty sure it's 1.1 recommended...the model is 2246-314 duration and .452 with stock rockers.

Cameron · « **Reply #3 on:** September 03, 2004, 07:59:24 AM »

Quote

It's an Eagle racing cam I purchased from CB. I'm pretty sure it's 1.1 recommended...the model is 2246-314 duration and .452 with stock rockers.

I looked up that cam number on the CB Performance web site. The 2246 cam is for 1.1 : 1 rockers. If you use 1.4 : 1 rockers with that cam, you are going to hurt something. I would say \"Don't do it!\"
Also, they recommend that cam for a turbo application.
Check out \"Performance Group 7\".
Click Here

flat4 · « **Reply #4 on:** September 04, 2004, 11:50:03 AM »

I knew it was a recommended turbo cam. When I talked to Marianne at CB, she said this cam would be ideal for the setup I'm running, as it is matched best with flow rates on the heads. Perhaps I cut the pushrods incorrectly. Is there any easy way to check while the engine is in the car? How does a guy know what the maximum lenght of rod should be? I have an adjustable pushrod, and was certain the measurements were done correctly...

Cameron · « **Reply #5 on:** September 05, 2004, 10:05:54 AM »

There are lots of articles in Hot VWs and VW Trends that will help you set up rocker arm geometry. Also, \"How To Hotrod VW Engines\". But that has nothing to do with what ratio rockers a cam is designed to work with. If you want to run 1.4 : 1 rockers, then you will have to install the proper cam first.

flat4 · « **Reply #6 on:** September 05, 2004, 10:52:34 AM »

I'm pretty sure I've got the geometry correct. What I'm unsure of is whether or not I cut the pushrods to the right length. What is the best way to check this? Perhaps my valves aren't opening as much as they should be. From what I understand, I should be running faster than I am now. Any idea of what size jets I should be running? I haven't jetted the carbs yet. Just using what cam in them. Seems to run fine, but I know it's running pretty rich.

Scratchy · « **Reply #7 on:** September 08, 2004, 08:15:08 PM »

Quote

I'm pretty sure I've got the geometry correct. What I'm unsure of is whether or not I cut the pushrods to the right length. What is the best way to check this? Perhaps my valves aren't opening as much as they should be.

This statement tells me you don't understand rocker geometry and pushrod length, as they are both inter-related.
The correct rocker geometry determines the pushrod length;

http://www.superbeetles.com/performance101...formance101.htm

This is one of the most important, and often overlooked, thing that will determine no only the performance of your valve train,
but ultimately the life of your engine. For some reason, most DIY engine builders seem to skip this part ( \"That's too HARD!!!\" )?

flat4 · « **Reply #8 on:** September 09, 2004, 02:20:20 PM »

I think I understand geometry just fine, but there are 4 different areas that I can think of that change the angle of entry for the valves, thus making me question whether or not the pushrods are cut right. The first being the pushrods themselves, the second being the number of shims under the rocker arms, the third being valve height, and the 4th being the type of adjuster being used in the roccker themselves. Swivel feet are larger than the regular adjusters, and would require a higher shim stack, and possibly longer pushrods to ensure that the valve is going in straight at 1/2 lift, no? The amount of travel on the pushrod side of the rocker should be the same amount of travel on the valve side of the rocker, with adjuster/swivel foot contact being dead straight on the valve right in the middle...is this incorrect?

Scratchy · « **Reply #9 on:** September 09, 2004, 07:35:18 PM »

You are more or less correct, so I don't understand your question on the pushrod length. If all of the above is correct, then your pushrods must be the right length. Other-wise your geometry would be off. The factors which determine pushrod length (different from stock) are:
Cylinder shims, cylinder head gaskets, flycut heads, rocker stand shims, swivel feet/elephant feet, length of valve stems, amount of valve lift.

The only thing that matters is that your valve/rockerarm geometry is correct. If your pushrods were too short or long, you would not be able to achieve the correct geometry (if they were too long, you could add a lot of rocker stand shims to correct this, but then there would not be enough thread on the stud to fully engage the nut). I wouldn't worry about the pushrod length if you know your swivel foot is centered over the valve and in alignment with the valve stem at half lift. Did you take a dial gauge and actually measure this at half lift?

flat4 · « **Reply #10 on:** September 09, 2004, 07:41:24 PM »

Couldn't get a proper dial gauge, so I used a slide caliper. More or less, the same measurements, and less to attach to the heads. My real concern is, now that the heads/valves are broken in, the adjustment on the swivel foot was significant (had to make it longer) and when we are dealing with such fine measurements, I wanted to be sure I was getting max lift from the pushrods.

flat4 · « **Reply #11 on:** October 01, 2004, 04:58:09 AM »

Ok.

So last night, I switched to 1.25 rockers. I was on the CB site, and according to their engine dyno charts, all the engines that CB built that use the same cam as mine, they all use 1.25. According to the specs, the cam should have .411 lift at the cam, .452 lift at the valve with stock 1.1 rockers, and .513 with 1.25 rockers.

Cool.

Or not so cool.

I measured the lift (using a slide caliper) at the end of the pushrod, and it was only .403. With the ratio rockers, I'm only getting .452 at the valve. Something doesn't add up. There are 3 shims under the rocker arms (to get the geometry correct), which may be causing a lack of travel in the rocker arm. If I cut longer pushrods, I lose the adjustability in the swivel feet. If I remove shims and use the existing pushrods, the same thing. No adjustability in the swivel feet. When the engine was assembled, all the numbers added up. Now that it's broken in, things don't seem all that right.

I'm stuck and looking for suggestions.

I was thinking of removing the shims, and chopping the pushrods.

Help?

Cameron · « **Reply #12 on:** October 01, 2004, 08:16:36 AM »

Quote

There are 3 shims under the rocker arms (to get the geometry correct), which may be causing a lack of travel in the rocker arm. If I cut longer pushrods, I lose the adjustability in the swivel feet. If I remove shims and use the existing pushrods, the same thing. No adjustability in the swivel feet. When the engine was assembled, all the numbers added up. Now that it's broken in, things don't seem all that right.

Get rid of the shims, under the rocker blocks. You will get your maximum lift when the rocker blocks are sitting directly on the heads. This means you will have to grind the rockers down so the swivel adjusters don't back up into the rockers. And shorten the pushrods.

And a word of warning! Make sure you clearance for extra lift. You don't want to open the valves so far, that they start to hit the guides. Ouch!

flat4 · « **Reply #13 on:** October 02, 2004, 02:22:28 PM »

Yesterday afternoon, I tried removing the shims under the rocker arms and setting up the rockers directly on the heads using an adjustable pushrod. Without grinding down the rocker arm ends by 1/2 (the end where the swivel feet screw into), it doesn't seem possible to make this work...I don't know why, it just doesn't seem like it's possible. I think the next step will be to try longer pushrods with the shims in. There is lots of room for adjustment (on the swivels) with the shims in, so I think it will work. The only bad thing is I'll have to wait for next season to find out. Is Mission raceway open during the winter? You guys don't get a lot of snow, do you...

On a positive note, I ran my best time of the season last night in less than desireable conditions...it must have been 0 degrees at the track, and I managed to whip off a 15.4@84 mph. It was pretty cool to whoop a new Mustang in the process....

Chris · « **Reply #14 on:** October 02, 2004, 03:34:23 PM »

check the website, the schedule is on there.

missionraceways.com I think?

flat4 · « **Reply #15 on:** October 13, 2004, 03:27:34 PM »

Well Well...

I decided to look into my geometry issue again. This time, I thought I'd back up a second, and start looking at part numbers that I received. It turns out, that there is conflicting information regarding my camshaft. the box says it was a CB 2242, and the cam tag says it's a 2242, however, the duration and lift say it's a 2246. The 2242 is VERY similar to an FK-8.

This being said, should I be moving to a 1.4 rocker instead of a 1.25?