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Sun Jun 29, 2008 10:24 am

Hi I have a 1776 motor built on a dual port with engine block number starting with AK. My oil pressure relief and control valves have the plain stubby cylindrical plunger. Some have said that the grooved plunger is better. Why would this be?

Sun Jun 29, 2008 2:24 pm

The grooved plunger, when used, is put into the valve by the oil pump, by the way. Leave the other one solid. The grooved one is supposed to let more oil flow to the oil cooler and let the engine run cooler.

They added a note in the old VW1200 service manual after that modified relief piston was introduced and here it is:

Sun Jun 29, 2008 2:34 pm

Is it proper to use the grooved plunger in the later dual-relief cases? Or is it just for single-relief cases?

Sun Jun 29, 2008 7:08 pm

Glutamodo, are you suggesting that I replace only the pressure relief valve plunger with the grooved plunger and leave the pressure control valve plunger as is?

Sun Jun 29, 2008 7:48 pm

Well, as Phil said, it might not even be appropriate to use in dual relief cases. I've seen such valves in them before but I'm not sure if they are supposed to be in there. Anyway, to answer your question, yes leave the control valve as a solid plunger. If you change anything just the main pressure relief valve, the one by the oil pump.

Andy

Sun Jun 29, 2008 9:05 pm

Thanks Andy, I'll order one and try it, but keep my current one nearby.

Sun Jun 29, 2008 9:23 pm

I would wait for a definitive answer before buying and installing a part that might foul up a crucial engine function like oil pressure.

Manuals I've looked at recommend the grooved (1500s) plunger for single-relief cases, but none show it installed in dual-relief cases. The diagrams appear to show no place for the groove to dump oil (no relief drilling), so at best it would be non-functional, at worst, it might change the temperature-related flow of oil to the cooler.

Do you really want to be a guinea pig?

Sun Jun 29, 2008 10:22 pm

Well, when i've seen them I think it's been after someone's put a kit like this one in:

http://www2.cip1.com/ProductDetails.asp?ProductCode=ACC%2DC10%2D5326

But I don't really like the stronger springs in those kits anyway, and, the grooved plunger is taller than the stock one making it even tighter in there.

Sun Jun 29, 2008 10:27 pm

Yes, I felt better about it after seeing the kit available at cip1. I also have an oil pressure guage, so i plan to keep an eye on that as well. Thanks for all the help.

Mon Jun 30, 2008 7:50 am

I'll add a final warning and then drop this, since you are intent on trying it.

The CIP kit is a "pressure booster" kit, not a "cooler oil" kit. The springs are stiffer than stock. On a stock motor I see no reason to boost pressure. Do you have low pressure? Change the oil pump out, or consider your bearings may be shot.

I have doubts the grooved plunger does anything on later blocks. It was intended to change the bypass route to send more through the cooler, rather than as a pressure booster.

Mon Jun 30, 2008 9:06 am

VW themselves did not use that plunger with the later dual relief cases, even though they had it available. I am thinking, that it should NOT be used in a dual relief case.

Mon Jun 30, 2008 9:50 am

Thanks for the advice, Phil and Russ. No, my pressure is fine. When I checked my relief and control valves, each one fell out (not stuck) and the springs felt strong when I replaced each plug. Looks like I'll have to keep looking for ways to bring my engine temp down. Got to 215 on my way to work this morning.

Mon Jun 30, 2008 10:31 am

So your motor is running hot? Lots of possibilities, so I suggest you start a new "overheating" thread to get good suggestions.

Mon Jun 30, 2008 11:20 am

Phil, already started ..http://www.thesamba.com/vw/forum/viewtopic.php?t=302865...still cannot figure out why it started running hotter in the first place. I thought it was because I started using a lower octane fuel, but going back to higher octane fuel did not fix the problem. you can see everything I have checked/tried in that post. Thanks

Mon Jun 30, 2008 12:19 pm

Russ Wolfe wrote: VW themselves did not use that plunger with the later dual relief cases, even though they had it available. I am thinking, that it should NOT be used in a dual relief case.
Russ, have a look at Fig.15-7 on page 39 of the engine section of the orange Bentley manual and tell me what you see.

Mon Jun 30, 2008 3:02 pm

I always kind of wondered about that diagram, as it shows a small-diameter oil pickup tube. However it looks like it might just be a retouched photo from the one they used in the 66-69 Bentley. But if you're looking in the Bentley, you should note that the other 15.6 diagram in there shows both of them being solid.

Mon Jun 30, 2008 3:20 pm

It is indeed the same photo as in the 66-69 book, but the plunger has been changed to the grooved one for the 70-79 manual. You gotta wonder why they made this change.

Mon Jun 30, 2008 3:38 pm

I guess a good question, for someone with experience with late model Mexican models, is what did the factory assembled engines use down there? That's a hot climate, after all.

Mon Jun 30, 2008 3:54 pm

Bruce wrote: Russ Wolfe wrote: VW themselves did not use that plunger with the later dual relief cases, even though they had it available. I am thinking, that it should NOT be used in a dual relief case.
Russ, have a look at Fig.15-7 on page 39 of the engine section of the orange Bentley manual and tell me what you see.

I do not have an orange Bentley.
I am just going from experience of building hundreds of VW engines. I have never seen the grooved relief plunger in a dual relief case.

Just checked the T-3 Bentley, and they do not show the grooved plunger in any of their illustrations. They do show the dual relief with the non grooved plunger for 1970 and on. T-3's used the same basic case as the T-1, except for how some things were mounted.

Mon Jun 30, 2008 4:39 pm

Russ Wolfe wrote:
I do not have an orange Bentley.
I am just going from experience of building hundreds of VW engines. I have never seen the grooved relief plunger in a dual relief case.

I've never seen a grooved plunger in a dual relief case either, but the pic in the book is clearly a grooved plunger.