Valve stems and rockers

[Elizabeth Lenkeit]

I have recently torn apart the motor on our '64 356C and will be having a lot of questions over the next few months. The first involves one of the many things I found on disassembling the motor, in particular, the damage to the rocker tips caused by offset on the valve stem. In various other places I have read that, in order to promote rotation of the valve, the tips should not be centered on the valve stem. Somewhere, I think it was in the Maestro's book, I recall reading that the instructions in the Porsche shop manual should be followed on reassembly. I am in the process of having the rocker tips ground and the rockers and shafts reconditioned, and in anticipation of reassembling the lot I looked in the Porsche shop manual for the proper procedure. On both page E38 assembly step 3 for the 1600 and page E40 assembly step 4 for the 1600s it says "insert thrust washers in such a manner the the rocker arms are centered over the valve stems." I don't see anything in the supplemental pages for the C motor. What am I missing?

Thanks

[Greg Bryan]

I don't believe the 616 motor valve gear promotes valve rotation. Others will chime in but, as you pointed out above, the RM has procedures to center the rocker tip on the stem.

P.S. - add your location so people can point you to local resources.

[Martin Benade]

I think the valve tips tend to show wear consistent with them rotating. I wonder if there is any rocker position that would prevent that.

[Harlan Halsey]

I am uncertain what "reconditioning." means with regard to rockers and shafts. I usually just turn the shafts over to put the worn part of the shaft in the low load area. The curvature of the tip is part of the valve geometry. In the old days people used to try to replicate the original curve by hand. And while that was crude, it seemed to work OK. Today there are people who have made a jig to reproduce the curve accurately. As for offset, I think that's mainly a wear issue. I try to get full contact.

[Elizabeth Lenkeit]

I'm having the rockers and shafts reconditioned by PartsKlassik. They bore the rockers, grind the shafts and then hard chrome and regrind them to size. The rocker shaft supports then need to be reamed to fit the slightly oversized shafts.

[Harlan Halsey]

That approach seems worthy of a 1906 Peugeot DOHC engine. I think there are cheaper and better solutions, but I haven't seen your project. If you are not competent to make these decisions yourself, there are a number of reputable 356 mechanics within a few miles of you, some of whom post regularly here or advertise in the magazine. I would urge you not to rely on the internet but to find a mentor in your area. Start with Jack Staggs or Larry Markham and go from there.

[Martin Benade]

Elizabeth, if that job isn’t wildly expensive I see no downside to it.

[Al Zim]

Elizabeth: If the rocker arms are worn so are other parts of the engine. The most critical area is the main bearing area supports, crankshaft and heads.
I am NO longer allowed to post on how to do any repair or their approximate costs. You may call me you are welcome to call me regarding costs and time frame. Al Zim 817-267-4451. Please call early in the day.

[Mark Roth]

I am NO longer allowed to post on how to do any repair or their approximate costs. You may call me you are welcome to call me regarding costs and time frame. Al Zim 817-267-4451. Please call early in the day.

Al,
You have always been allowed to post how to do any repair. You are not allowed to advertise your business in a post in the Main Discussion section of the forum.

[Al Zim]

ZIMZ AUTOTECHNIK cannot risk the loss of communication with the registry members from an incorrect evaluation of a post from a trustee. al zim

[Adam Wright]

Elizabeth: If the rocker arms are worn so are other parts of the engine. The most critical area is the main bearing area supports, crankshaft and heads.
I am NO longer allowed to post on how to do any repair or their approximate costs. You may call me you are welcome to call me regarding costs and time frame. Al Zim 817-267-4451. Please call early in the day.

Al, you don't play the victim well, I would stop trying. You were warned on multiple occasions to not promote your business as the sole answer for someone's question about their car. Only ZIMS has the tools and expertise to fix what ails your car, don't try to work on it yourself, or something to that effect, over and over. That's what you were asked repeatedly to stop doing. Sharing your vast knowledge on the inner workings of the 356 is most welcome on the forum, I would hope to see you continue doing that.

[Dave Erickson]

The repair quoted sounds expensive and unnecessary. Flipping the rocker shaft will present an unworn surface. There are lots of used parts available for rockers. Much more important is the radius geometry they grind on the end of the rocker. The radius center should be on the the axis of the valve stem (averaged between beginning and end contact points). It also needs to be the same on each valve, which hand held grinding is not going to achieve. The size of the radius affects the lift and the wear of the rocker so it may be important to consider. Yes you can ignore that but it takes an informed decision.

[Ted Hedman]

I believe Bob Gilman of Lake Machine in Lakehead CA is still refurbishing rockers, though it's been a couple years since he did mine. He used to do (and maybe still does) a lot of work for Shasta.

[Mike Wilson]

Elizabeth, there are several of us 356 owners in the South Bay including San Pedro. I'm in Lomita. There is a local Cars & Coffee the first Saturday of the month, 7:00 - 9:00 am at the Peninsula Center theater parking off Indian Peak. Hope to see you there.

Mike

[Elizabeth Lenkeit]

Getting caught up here:
Cars and Coffee, good to know. I will be there when I can. It will be a while before the 356 is back on the road, but there are other options.
Regarding advice: Sure I read what I can on the internet but I am relying on a couple of extremely experienced local experts.
Elizabeth: I am actually John, her husband. She is the official car owner and registry member, I'm just the maintenance guy.
Other damaged/worn parts: I have been struggling with how far to take this project. So far I have in my possession or on order: 86mm Shasta P&C, Willhoit heads, Scat crankshaft, Elgin cam and followers. The case, rods, flywheel etc. are going to Precision Machining as soon as I can organize everything. The distributor will likely be going off to Vintage Werks.
The goal of this project, beyond just getting all 4 cylinders functioning, is mid range torque, the kind of thing that gets you out of corners in the canyon and local mountain roads. Maximum HP at high RPM is not what I am looking for. In my youth I spend enough time with high strung 2-stroke road racing motorcycles to realizes that that sort of of power band is suitable only for the track.
My next challenge (at least that I have some visibility of) is what to do for carburation. Other than the dead cylinder, the car started and ran well with the Zeniths.

I'm interested in what the collective experience is with Webers. I know that the available kits come with 28mm venturis, but venturis are also available in 30 and 32mm. Most of the vintage racing guys have lots of experience with Solexes and Zeniths. Has anyone experimented with different venturis in 40 IDF carbs? Willhoit has some interesting dyno results for a comparison of Weber 40IDF with 28mm vs. Solex 40P1

Maybe I should start another topic?