Pushrod Clatter

[FJCamper]

This is strange enough to put it in front of other VW people. We've been racing on 3/8th chromoly pushrods for many years, always with dual valve springs. We never, ever, experienced the clatter problem we've read about others having with steel pushrods once the engine was warmed up.

This is of course with the "loose zero" adjustment, and 1.25 rocker sets with lash caps, and the adjuster at the bottom of the rocker not the top, 356 Porsche style. On cams from Engle W125 to 140. Straight cut cam gears.

Now, we have built an experimental engine (same 94x78), same pushrods, same rockers EXCEPT for the heads. They are EMPI GTV-2 w/single high-rev springs. Our reasoning is, on an endurance engine, we want the less spring tension possible to do the job. We also reduced our normal 7000 rpm rev limit to 6000. Keep in mind we race 7 and 8 hour days. The less stress the better.

The problem is with the new heads, we immediately got valve train rattle like crazy, on steel pushrods, on start up. Not rattle once hot. And the rattle continues when hot.

Changing to stock aluminum pushrods quietened the rattle. I know I can get HD aluminum pushrods if I need more RPM, buy my questions are why the steel pushrod rattle that seems to be the opposite of the complaints I read about, and can the stock pushrods withstand up to 5500-6000 RPM?

FJC

[Bruce.m]

Did someone on here use type4 pushrods as a HD item on a type1? Needed cut down if I remember correctly. Or maybe I dreamt that one up.

[slayer61]

I'm going to have to keep an eye on this. I have the same heads, same chromoly push rods and rockers. I'm just deaf or ignorant enough to not recognize any valve train noise.

[ONEBADBUG]

I think stock pushrods would be okay with a mild cam. On our Chumpcar Ghia, I used "HD" aluminum pushrods and one of them snapped in 2. Did you check if the pushrod fits in the adjuster alright?

[FJCamper]

We did check the tips of the steel pushrods for malforming, burrs, etc. All good. I was hoping for something as easy to fix as a bad tip, bent rod, etc.

We're running W125 cams in our LeMons engines on 1.25 rockers. Is that considered a mild cam?

[Kafer_Mike]

What 1.25 rockers and shafts are you running? How much side play and offset at the valve?

I'm running a 2332 with a REAL aggressive cam (Engle FK47) and CB Wedgeports with dual springs, 1.4 Autocraft rockers/shaft, and chromoly push rods. They clattered like crazy. I had to tighten up the side play to quiet them down.

[FJCamper]

We're using the pre-assembled EMPI rocker sets. They feel tight. I've had trouble with the old style rocker upgrade kits, so I know what you mean with rocker arm side play. We also have a very anal-retentive engine builder who dotes on valve train geometry.

The only variable here is the new EMPI GTV-2 heads with single springs. The rattling begin on first start. No adjustment on steel pushrods helped. Cold or hot. Stock aluminum rods quietened it.

I don't expect to try and race on stock rods. I've run Aircooled.Net hd aluminum rods in some fierce racing. Loved them. I hate to admit it, but loose zero hot or cold on steel pushrods will spoil you.

[Bruce.m]

Any chance you are getting some weird resonance in the valve springs? Maybe a swap to some known good springs would be a useful check?

[FJCamper]

Hi Bruce,

We are standing by with a set of double springs, on hand. We want to try steel rods again after a race or two on hd aluminum rods to see if the single springs somehow change with use.

For the record, I'm old, old school, and the very idea of a heavy steel pushrod irks me. We used to do everything to lighten the valve train, including filing weight off the rocker arms.

[slayer61]

We did check the tips of the steel pushrods for malforming, burrs, etc. All good. I was hoping for something as easy to fix as a bad tip, bent rod, etc.

We're running W125 cams in our LeMons engines on 1.25 rockers. Is that considered a mild cam?

I use the same cam & rockers on my 2276 street engine. My rockers are Porsche style (adjuster on pushrod side) Berg rockers

[Karlos]

I had chromoly push rods in my 2110 years, the clatter did my head in. When I built my 2276 I got a set of the dual taper HD aluminium push rods, my god I wish I’d done it years ago with my old engine!!! Quieter, lighter, and don’t ever need adjustment. No brainer

[Clatter]

I like the noise!

[Piledriver]

Hi Bruce,

We are standing by with a set of double springs, on hand. We want to try steel rods again after a race or two on hd aluminum rods to see if the single springs somehow change with use.

For the record, I'm old, old school, and the very idea of a heavy steel pushrod irks me. We used to do everything to lighten the valve train, including filing weight off the rocker arms.

The consensus in much of the industry (speedtalk et al) is if you can fit 1/2" cromo pushrods its a win for valve train stiffness.
otoh we arent running roller cams at insane spring pressure, and use very long pushrods. The dual tapered ones get the nod for stiffness.

My t4 rocker setup sounded like a rock concert at idle until I sanded some shims to get the sideplay down. 911 adjusters, cb cromo pushrods sero lash.
not noticable after getting side play down (that was with dual springs supplied by HAM) that was with a near stock web73.

[Clatter]

Is it possible you switched your rockers from one head to the other without re-shimming for end-play on the shafts?

Aftermarket heads will have a large amount of variation in the center-to-center of the two shaft mount studs.
There’s no way a set of rocker shafts all shimmed up for one set of heads will be right for another.

Also,
One of the things VW changed when they redesigned for the type 4 was make the pushrods square to the rocker shafts.
Type 1s and their pushrod angle causes thrust loads which will be exaggerated with big cams and heavy springs.
You’ll see your end-play open up quite a bit with heavy use.
I shoot for a loose zero on rocker shaft end-play.
It’ll open up when run hard anyways so go for as little as possible..