engine and drivetrain Broke a rocker arm, need to find parts

[Hans]

Missed that. HD is cheaper than I expected - makes sense to lash out (no pun) for IE ones I'd say.

[KFunk]

Missed that. HD is cheaper than I expected - makes sense to lash out (no pun) for IE ones I'd say.

I've got about 500 miles on my IE HD rockers so far, and they seem pretty damn good. Of course no real autocross/track testing yet though, stupid winter.

They certainly look way stronger than stock.

[KFunk]

Also for reference, I attached my pics of my old head with original rockers, and new head with HD rockers. Kind of looks unflattering for the old rockers though, because that head is dirty...

[Hans]

So they clamp onto the shaft. Interesting.

[KFunk]

So they clamp onto the shaft. Interesting.

No, they can use the springs too. The IE rocker locks were a separate purchase, and can be used with both style rockers. Supposed to be better at holding the rocker in place. They certainly make it easier to install/change rockers.

[Mike Self]

1. while you have the head off...

--have head & valve cover checked for flatness & planed if necessary (don't forget to have the upper timing chain cover planed if you have the head done)

--grind valves, and if the engine was smoking on the overrun, check valve guides for wear and replace if necessary, and at least replace the stem seals with the E30 style seals--much more long lived.

2. carefully examine the rocker shafts for wear and replace if worn

3. the valve cover nuts should only be torqued to 10-12 ft/lbs; I'll bet you'll find the valve cover is warped around the bolt holes...

I had a rocker arm break on my '69 at 101k some years ago--the cause was a faulty set of exhaust valves (from the factory) whose seating surfaces wore away until one valve pulled through the exhaust port and broke the rocker. These early rockers were un-bushed, and the aluminum rockers wore the steel shafts because grit became embedded in the aluminum and ground down the shafts--in excess of .040 thou.

cheers, and happy mechanicking

mike

[Preyupy]

If you want to see the difference between the cheap aftermarket rockers and the factory ones, look at the picture warmwaffles posted then look at the first picture Kfunk posted. Look at the shape of the rocker, they are tapered and the corners of the castings are rounded. Actually in the picture warmwaffles posted the rocker in the upper left corner of the picture (#3 intake) is a factory rocker and the others are the cheap ones. Look where the #2 exhaust rocker broke, don't you think the BMW rocker looks a lot stronger in that area?

Before there were HD rockers, billett aluminum and forged steel rockers we used Factory BMW Rockers in our race engines. We would buy 30-40 of them, have them Xrayed (it's amazing what you will find) then de-Burr and polish them before we would use them. We then kept records and would not run them more than 35 racing hours before we replaced them. I now only use the steel rockers on race engines I'm going to turn over 7500 rpm and I have some of them that have 7-8 seasons on them and show no wear and pass crack test at every rebuild.

[KFunk]

look at the first picture Kfunk posted. Look at the shape of the rocker, they are tapered and the corners of the castings are rounded..

Hmmm, my old ones aren't all the same either... Looks like I had some good and some bad. I replaced a couple in 2005 with some from Hawaii Import Parts, can't remember which ones.

[TobyB]

With some trepidation, I declare that Febi and BMW rockers seem to be

identical to every degree, with the exception of the logos.

Same shape, finish, and, sadly, quality. As in, I broke 3 or 4 Febis,

and 2 or 3 BMW rockers, and they both had voids, poor reliefs on the

lash side, etc.

the febis were about 2/3 the cost of the BMW rockers.

The BMW dealer at first denied the voids... well, until I brought them in.

Then they muttered a bit, replaced 2, sold me more for less, and were quite apologetic.

For something they really didn't have a lot of control over.

The rockers pictured were very common in the '80's and '90's, and

disappeared from the parts chain by 2002- ish. They must have been

in 50% of the 'junk' head I've picked up...

...things you learn trying to race 'for cheaper'...

t

[KFunk]

The three 'good' tapered ones on my old head, actually I believe are the ones I bought from Hawaii Import Parts in 2005. They always sold me good OEM parts. I remember only buying a couple. One of my old ones was broken, and a couple the machine shop didn't like due to sloppy bushings or abrasions on the inside. The 5 weaker looking ones were likely leftover from the previous owner....

[Preyupy]

I'm with you Toby, I have tossed hundreds of those rockers in the trash over the years, I learned about them in the late 70's. The problem with the voids even in the Factory parts is why we xRay them before we use them.

[TobyB]

Eventually, I hope to get proper rods into the F-prod (yes, it's moving) car,

and spin the Ireland HD rockers to 8500, just to see if they can take it.

They look pretty nice, (for what they are) and things that broke stock rockers haven't popped

'em yet at 7500....

t

[Preyupy]

I have spent a lot of time with stock rockers at 7500 rpm but the extra 500-1000 rpm over thatm raises the failure rate by 50-60% from my experience.

Then you have the Organic variable, the loose spacer between the steering wheel and the seat. Without a tattle-tale tach or or data recorder they will NEVER tell you about the missed shifts and over-revs or how many 5>2 down shifts they had that last session.

Valve float is the biggest problem, if you float them at 5000 rpm you are going to break rockers, and if you control everything correctly you can have very good reliability below 8000.