TheSamba.com :: View topic

Tue Jul 07, 2009 8:54 pm

No story, Russ has mentioned it, and I have heard many others using it. I was not going to delve into it, but since it has come up...

Basically, dealers where setting valves to .004, and having valve issues. To combat this, Volkswagen created fans to blow air backwards though the tin to further cool the heads, and changed the specification to .006 inches. I know not the benefits, but I will has P.A..

Set them to .004 inches at ambient, or .006 inches up to 122 degrees/below hand touch temperature. If you are not sure, or close minded, set them at .006 inches. As I said, better safe than sorry.

Tue Jul 07, 2009 9:20 pm

REALLY a 73 only has 52 HP and 77 lbs of torque

ok :?

70 says
65hp
86 torque

as well as most of the 1600s from 65' up

whats the difference

Tue Jul 07, 2009 9:54 pm

sharkskinman wrote: REALLY a 73 only has 52 HP and 77 lbs of torque

ok :?

70 says
65hp
86 torque

as well as most of the 1600s from 65' up

whats the difference

The difference is that the way horsepower is measured (in the US) was changed in 1972. The older "SAE gross" method gave way to the "SAE net" method, which is a more realistic measure of the engine as installed in the car. If you compare the post-1972 figures with the DIN figures, you'll see that the Germans were always more honest about rating their engines. :wink:

Hope this helps.
- Scott

Wed Jul 08, 2009 11:06 am

I adjust all my valves on type 4's....raging hot.

The qualifier here.....is that I have taken the time to find out what the differences are. There is a very ver y very good reason for setting initial cold (factory .oo6")...and then readjusting when hot. This is because you don't actually run your car with cold valves for more than a few minutes at a time. And...ay cold temps they have all the space they need in the world to keep from damaging themselves.

But....many valves are two piece in constrcution. Also..every single one or two piece....valve is made from a different piece of metal. They have different expansion rates....some significant...most just slight.

Don't beleive it? Take 4 clean intakes and four clean xhaust and bring them up to just about any temp over 200F in your oven. One at a time...take them out one at a time and run them through a comparator....allowing time for the gauge to cool back to standard room temp and re-zero.

In a given set of intake or exhaust valves...usually one or two have an expansion rate that is average .001 different...and often as much as .0025" difference. You can argue whether one pair is not eexpanding enough and the others are expanding too much...but it makes no difference.

Typcially ....(on type 4's for sure...I have never done this on any of my type 3's when I own one) ...a .006" cold setting closes up to between .002" and .003" when the head is at running temp of about 280-300F. I have seen extremes of .0015" to .004" at temperature.

Take a little time to do some hot checking and write down your results. You will find after break-in that the valves settle down to a consistent level of expansion per each valve.

I readjust all of my valves..... individually to.... .002" hot. This takes away teh ragged +/- .001" variances I find. The valves run silky smooth....the car runs much better. This is especially critical if you are doing very tight D-jet system tuning.
D-jet injection is very sensitive to valve adjustment....because it changes the vacuum signature.

Most Porsche air cooled race teams adjust their valves hot for these very reasons. So....its not quite accurate to say that adjusting valves hot is not good.

I think adjusting valves warm....is not great. The definition of warm may be 122F by factor ystandards...but unless you are using factory valves...you have no idea what expansion rate that will get you.

Adjust cold or hot. But thats just an opinion. Ray

Wed Jul 08, 2009 11:39 am

This brings up something that I have noticed at various car shows that I have been to.
I have heard VW's drive past that is sounded like the rocker arms are getting ready to fall off. Like they adjusted the valves with the engine up on the wrong cylinders.
I wonder how these people are adjusting the valves.
Yes, when I adjust valves, I adjust them to the factory cold spec, but I adjust them to a tight .006". I use go and no/go feeler gages. .004/.006". The .004 goes freely, and the .006 just goes snugly. When I am done, I can just barely here the valves. No valve clatter.

Wed Jul 08, 2009 11:45 am

Interesting post, Ray. I have not yet taken the opportunity to measure my valve lash when the engine is still hot -- might be eye-opening!

- Scott

Wed Jul 08, 2009 12:21 pm

bear in mind...on type 1 or 4 based busses and on 411/412's....its really easy to do this. Lots of room. 914's?....kinda hard. Type 3's? Not sure.

But basically drive for 20 minutes, pull over and open the hood first . Letting it sit for about 5 minutes gets the best heat soak and maximum temperature. Turn engine around to marked position for cylinder #1....pull that valve cover...check valves lash.

Whan analyzing...I do one cylinder at a time with 10 minutes driving in between to make sure temp stays stable and hot.
Once you geta baseline you can do the adjusting one whole head at a time. In a type 4....I can do one head properly in about 5-8 minutes. Ray

Wed Jul 08, 2009 2:44 pm

The question just came to me -- is there much of a difference in valve expansion between, say, 300° and 400°F? Intuitively, it seems that if you're going this route, you'd want the valves to be as hot as they'd possibly get in your engine. Or does the rest of the engine grow enough between those temperatures to make it a wash?

Thanks,
- Scott

Wed Jul 08, 2009 2:48 pm

Ray, is desired valve lag on the seat based on hot-zero clearance? Or does the extra gap provide some more valve cooling time on the seat by design?

Wed Jul 08, 2009 4:54 pm

i have thought that for a while (wasnt sure)
adjusting when hot because the gap matter When Hot

i thought that the germans would have thought about that

but with books and people saying .004 to .006
i guess i didnt want to be shot down

ray ... do you know how to fine tune a F.I.
i only live over in Arlington :lol: