Porsche tappet adjusters

[tomterrific]

Good point 5T. I wasn't thinking about assembly.

Tom

[crazypj22]

I ordered some last Saturday. They are out of stock until Friday 27th.
I'm expecting to get them by Monday 30th.
PJ

[5twins]

Well, here's an update on my install. Just as the old original posts state, you must remove about 4mm from the rocker bottoms. I tried the drill bit idea to bore the hole and countersink it slightly but no go. That rocker is so darn hard, a drill bit, even in my drill press, wouldn't put a mark in it. I ended up carefully grinding them down on a bench grinder, a little at a time, quenching them in water as soon as they were hot to the touch. I didn't want to overheat them and risk losing that hardness. Here's one compared to an original .....



The end of the stock rocker is 12mm thick. You have to remove about 1/3 of this and grind them down to about 8mm thick. This allows you to back the new adjusters off enough for assembly/disassembly.

I got the elephant's feet from PJ's link. Although advertised as allens, they weren't. They're the plain slotted screwdriver type like all the others. They measure 31.5mm long as compared to 28mm for the stock screws. They don't need to be shortened if you don't want to as there is plenty of clearance under the covers.

Snuffy mentioned the weight factor but it really doesn't change much. Grinding that 4mm off the rocker removes about 2 grams and the elephant's feet weigh about 2.5 grams more, so you're not gaining much. It might even equal out if you shorten the new screws.

I'll report back on how they run in a week or so. I'm hoping they'll be nice and quiet and allow slightly larger clearances to be used.

[crazypj22]

I'm going to try a carbide countersink bit I have on the rocker arm then shorten screws. They are wider than the top of valve so there should be virtually zero wear when the oil fills them. With less side thrust on valve the guides should also last longer.
PJ

[davidrayner]

All,
Mine are Porsche (I think - it was quite a while ago). On the motor they are meant for, they are pressure fed through the rocker and so the oil will circulate around and go into the ball-socket, there is a section of the threaded area that's relieved. This is inside the 650's rocker and as such, not only have you reduced the strength of the valve-end of the rocker, but you have also removed 1/3 of the threads. Added to this, the relieved area of the tappet removes another couple of threads so the tappet is held in place by about 1/2 the threads as it was before.

Imagine that when the lobe of the cam comes around and the rocker starts to bare down on the valve, the tappet wants to pop up through the rocker and the threads are all that is stopping that from happening. Even with half of them removed, they seem to hold up just fine. I've heard that others do not have the relieved area on the threads and I suppose I'll look for those next time, just to make me sleep better.

When I first began riding my bike, I noticed a loud ticking coming from the head. Of course, I thought it was the tappets and I wondered how they could make that much noise when I'd gone to so much trouble to get the correct clearence on them. It turned out to be something under the tank that was rubbing on the tunnel. When I tilt the tank slightly by pushing on the left side of it, the ticking stops and the motor is absolutely silent (mechanically). Of course, I don't have a timing chain and I suppose that helps but even if I did, the tappets would still be silent.
Dave R.

[crazypj22]

Hi David,
I've seen at least 4 different types of ball ended adjusters
The EMPI / Porsche style without the oil feed, the ones you describe with the oil feed (both known as elephant foot) and the ball bearing with a flat which have a smaller head, either with or without oil feed.
They also come with allen head or slotted, allens are slightly lighter in V-Dub
Problem is, I dont remember who makes what anymore and being 4,500, miles from home can't find old invoices/suppliers.
I used to build aircooled VW engines about 20 yrs ago and there is no significant difference between adjusters, mainly personal preference.
I think there could be a problem with a high lift cam and high seat spring pressures but for most of us with relatively stock engines reducing thickness of rocker arm will be as you said, just fine.

[grahamdelooze]

porsche tappets are M7 and not M8

[mashermoto]

I got my rockers ground to accept the tappets. How do I...and what specs do I set the clearance? Some of you guys are talking about zero clearance

[5twins]

Zero? No way. This is a mod that allows larger than stock clearances without the valve clatter. This is supposed to allow more oil in between the rockers and cam and also work better with the old slow rise design cam. I don't know, maybe it's all bull, but mine certainly doesn't run any worse like this.

www.650motorcycles.com/isky.html

This is a bit complicated for the rookie rider to understand. Maybe I have "650 on the Brain" but I went for it. Like I said, the bike doesn't run any worse.

I have to take this opportunity to thank Jack. I did my own little port job with my Dremel following his most excellent tips. Flow, baby, flow.

Most of my buddies can't understand why I'm so enamored with this old 650. They ride new $10,000+ bikes. What? I guess we live in different worlds.

[mashermoto]

650Motorcycles shows .006 for the intake and .012 for the exhaust. So, if I add .002 to both sides to make it .008 IV and .014 EV, is that a good starting point

The 650Motorcycles article sounds like larger gaps are better, but there must be some point that clatter and performance loss become an issue.

Anybody messed with it that far?

[crazypj22]

You shouldn't need an extra 0.002" with the Porsche style adjusters, although the oil getting in there will act as an hydraulic cushion to a certain extent and help to prevent shock loadings breaking stuff (if clearance is too wide you miss the opening / closing ramps on cam and sudden acceleration wears stuff out even when it doesn't break)
From tests I've done the compression pressure varies about 10~20 psi going 0.002" tighter or looser from 0.004"intake 0.010"ex. on 78 motor.
The cam duration will make a difference (you could always use degree wheel to find different opening/closing points with different clearances, after you initially degree it in at 0.040"~0.050"lift)
Just my take on it
PJ

[5twins]

I'm running .002" over my stock '78 specs (.004" int. and .006" ex.). That gives me .006" int. and .008" ex. That .006" int. and .012" ex. is for the early 256 motors. On my later 447 motor, I would try to match that at most, not go bigger. In fact, I guess I'll play with larger ex. settings and see what happens. I don't think I'll go any bigger than .006" on the intakes, though.

So PJ, you're saying you get the most compression at .004" int. and .010" ex.?

[mashermoto]

I emailed David Rayner yesterday about the tappet clearance and his recommendation was to use the stock settings. I have a '79 motor, which my Clymer manual specifies .0024 IV and .006 EX measured in inches. Settings must be on a cold engine.

I did take measurements again since the post above. Cam specs came out as shown below. All readings except center readings are at 0.050.

IV open = 21 BTDC
IV center = 99 ATDC
IV close = 41 ABDC

EV open = 57 BBDC
EV center = 113.5 BTDC
EV close = 8.5 ATDC

Using Web Cams calculator on their website, the results are as follows.

Overlap = 29.5
IV duration = 242.0
EV duration = 245.5
IV installed center = 100.0 ATDC
EV installed center = 114.25 BTDC

So my IV is off center by 1 degree and the EV center is off by 0.75 degrees. From what I read that should be OK.

I was wanting a low to mid range cam, so the 100 degree IV lob center didn't surprise me, but the 114 degree EV lob center did.

Does anybody know how this cam ought to perform?

[5twins]

So you've got an aftermarket cam? They usually use different than stock valve lash settings. They should be listed in the instructions or, if not, I would contact the cam manufacturer for his recommendations. That 650Motorcycles link is about stock cams and the benefits of larger clearances with them. Larger than speced clearances may not do anything for your aftermarket cam if it's a new style design with quicker opening and closing rates.

[mashermoto]

Thanks 5T. Yes, it is an aftermarket cam. They didn't provide any specs, so I'm contacting them for the info. I did notice that Megacycle Cams website does provide the clearances, which are about .004 and .006. That's much different than stock.