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Thanks!
Good to hear the nice alu Pauter rockers didn't cause any valve guide issues or broke with your rather high spring tensions

Wally wrote:Thanks!
Good to hear the nice alu Pauter rockers didn't cause any valve guide issues or broke with your rather high spring tensions

Valve guide issues should be non-existent because the roller tip eliminates the sheer force that a standard "wiper" transmits to the valve stem.

Personally, I think Pauter rocker issues are due to the end-user not setting up their valve-train properly. Don Pauter has been using his rockers on 500 lbs of spring in his big-block Karmann Ghia on the street without an issue. I'm confident they would handle even more spring -reliably.

The last internet discussion I had with a guy who broke Pauter rockers revealed some interesting info about a potential mechanism for the failure. He was running K800 springs on a small cam with maybe 400 lbs of spring pressure. That left a LOT of clearance before coil-bind which contributes to spring-surge...essentially, harmonics in the valve-spring that are not damped properly. The 0.070" or so of recommended clearance to coil-bind is NOT a suggestion, it's a requirement to dampen the spring harmonics properly.

This is only a hypothesis based on limited information I've gathered from folks who've had Pauter failures. But when I hear about the running conditions some folks have introduced (e.g. running a heavy spring with lots of clearance to get the seat/nose pressure down), I can only shake my head and wonder if they expected anything different than a failure of some component in the valvetrain.

Good points!
and thanks for the encouragement

Stripped: what are you running for fuel with 12:1 ?

Have you calculated the dynamic compression ratio ?

Unkl Ian wrote:Stripped: what are you running for fuel with 12:1 ?

91 octane.

Have you calculated the dynamic compression ratio ?

Nope. But consider that my cam is retarded 4 degrees (this cam is typically set up with 4 degrees of advance)...this lowers the dynamic compression ratio.

What are the head temps like ?

Unkl Ian wrote:What are the head temps like ?

Hell if I know. I haven't hooked up the cylinder temp gauge. I've got a VDO guage, but I want a temp-compensated gauge, so I've yet to install anything.

I've only hit the heads in different spots with the infrared temp gun...nothing close to "hot", but certainly not valid for comparison with a true, under-the-plug temp reading.

Well, the engine is out of the car and I should split the case tonight to replace the cam. Already seeing some interesting wear patterns on the lifters and I will get a better look at the bores when I get the case-halves apart tonight. So far, nothing alarming, but indicative of the loads high spring-pressures put on your valvetrain.

On that same note, I sent my heads back to Darren at DRD today. The stem-heights of my intake valves were about 1/16" of an inch taller than the exhaust valves. Darren is confident the stems are not stretching (CB Performance RaceMaster valves...pretty stout), but thinks that the seats are sinking in. We *may* be replacing the seats with something larger on the OD so that there is more area under the seat to distribute the load. It's funny that the exhaust seat actually carries more load per square inch, but the intakes are the ones that move around.

I should know what's up sometime next week. Murphy has spent a lot of time hanging around my garage as of late, but what's life without a little challenge here or there?

Interesting report! Thanks for the honest update. I would have never thought that roller lifters would leave any wear pattern on a cam, no matter how stiff the valve springs were..
Pity you have not measured cylinder head temps as they may have given an indication of a possible reason (or not) for the valve seats sinking somewhat.

Disassembling such an experimental engine is almost more fun than putting it together

Wally wrote:Interesting report! Thanks for the honest update. I would have never thought that roller lifters would leave any wear pattern on a cam, no matter how stiff the valve springs were..

The wear that I reported was on the lifters and bores, not on the cam. I haven't seen the cam yet, except peeking through the bore. The rollers of the lifters look fine; there simply is wear on the body of the lifter indicative of the side load experienced by the lifter.

Pity you have not measured cylinder head temps as they may have given an indication of a possible reason (or not) for the valve seats sinking somewhat.

Head temp still isn't a concern. At 12:1 CR, if my head temps were excessive, I'd have problems with detonation. However, 180lbs of seat pressure might have something to do with it, on top of the fast closing rate of the valves.

Ah, right, lifter bores; sorry misunderstood originally

You probably did use some silicon-bronze sleeves for the lifter bores right?

I suppose most of this was a learning experience for your supplier of the roller cam too? Would be interesting to learn what his ideas are to make the bores holding up better

Thanks again man, very cool and inspiring stuff!

Wally wrote:Ah, right, lifter bores; sorry misunderstood originally

You probably did use some silicon-bronze sleeves for the lifter bores right?

I suppose most of this was a learning experience for your supplier of the roller cam too? Would be interesting to learn what his ideas are to make the bores holding up better

Thanks again man, very cool and inspiring stuff!

Yes, silicone-bronze sleeves were used.

I should add that the wear patterns are by no means excessive (that I can tell...yet), but result from the fact that the lifters do not rotate in the bores like flat tappets do. There is no wear on the lifters where they are indexed with Rocky's guide-blocks. I didn't split the case last night, so hopefully I'll know more in a couple of days when I get around to opening it up.

Bummer, but experiments go like that.

I recall Jake spent ages thrashing on lifter bore material before he found something that worked long term on T4s.

He also had to find/develop a hard HD thrust bearing to keep the cam from walking and causing weird problems...

I proposed an adjustable thrust button assy that would screw into the cam and run in the cam plug location.

Personally, I think some iron sleeves might work well for the lifter bores...
What does GM use in their aluminum blocks?
I cant imagine they run on the parent metal.. (do they?)

Piledriver wrote:Bummer, but experiments go like that.

Yep. We'll see what Darren thinks of the valve seats and go from there.

Interesting lifter bore wear !!!

I'll have to see if I can take a quality picture of the wear, but until then, I'll simply have to describe it...

...so, every lifter bore had wear at the end of the bore (nearest the cam) on the top side of the silicone bronze bushing. This wear was in the pattern of the "fork" (for lack of a better description) which supports the wheel of the lifter. On a few of the bores, there was 1 substantial groove carved into the lifter bore by one side of that fork.

Now, here's where it gets interesting...I would've suspected this wear to have been on the top side on one case-half, and the bottom side on the other case-half, basically due to the side-load put upon the lifter by the cam's rotation during the valve-opening event. However, this wear is on the top side of all of the lifter bores, so it is occurring independent of whatever side-load the lifter is experiencing due to the camshaft rotation. The best explanation I can come up with is the lifter wear is reflected at an angle opposite from the pushrod angle. So, because the pushrod is exerting force on the lifter at a downward (and sideward) angle, I am seeing wear on the underside of the lifter nearest the cylinder head, and I am seeing wear on the topside of the lifter and lifter bore nearest the cam; e.g. this force is levering the lifter. This may be exacerbated by the tall pushrod-cup of the Isky lifter...the pushrod cup is actually outside of and unsupported by the lifter bore.

More interesting...the wear is worse on the 3/4 side than on the 1/2 side; IIRC, the 3/4 side gets better oiling to the lifter bores than the 1/2 side. Plus, the 1/2 side would be seeing a side-load forcing the lifter upward during valve-opening (the 3/4 side experiences a force pushing the lifter downward during valve-opening...based on the cam's rotation). Yet, despite the levering tendancy due to the pushrod angle, the rotation of the camshaft, and the oiling characteristics, the 1/2 side experienced less overall wear.

I think if I were to go back and measure the deviation angle of the pushrod from parallel to the lifter bore, it would correlate pretty strongly to the severity of wear that I've observed. This certainly is beyond what I would've expected, but what would the Type 1 roller-cammed knowledge-base have predicted? Absolutely nobody has put 16,000 1/4 mile passes on a single set of lifters to demonstrate the wear characteristics.

There you have it. Pictures will follow...hopefully tomorrow evening.