All of my Base Circles are Reduced

[Danglerb]

I picked up the cams today for the Euro hybrid motor I am building, .506 lift means that even with welding, to fit through the bearings the base circle on the intake lobes needed to be reduced to 1.360" from the stock 1.415". I think that is still within the lifter tolerance range.

Cams are still in boxes, tomorrow I start playing with them. Picts when I can.

[Landseer]

More description, too, so the less knowledgeable can follow.

[Danglerb]

I just gave a try on explaining, but better to wait for picts.

[rich]

Oh Boy!

[BrendanC]

How much? Where from?

[rich]

Which cams did you start with?

[rhjames]

WebCam.......

or

JME.......






--Russ

[Danglerb]

Here are some picts that should help explain it all.

Stamp on the end with the factory cam grind (173 for US 1980), and the new Web cam grind.


I'm not sure what the finish is, its not something that is going to wipe off.



Side view showing the build up of the weld.





Edge view showing tip of lobe even with bearing





Gear end of the cam.

[MPDano]

Hey Mike, your holding that thing as if it's heavy

[rich]

Oooo.....Beauty!

[Danglerb]

Originally Posted by MPDano

Hey Mike, your holding that thing as if it's heavy

Thats my son.

I told him its a 20 lb $500 egg, and I wanted to see TWO hands holding it at all times. Now its safely wrapped back up in its bubble stuff in the shipping box until time to do something with it.

[BrendanC]

How much for the 2 cams?

[rich]

Originally Posted by BrendanC

How much for the 2 cams?

Well... two $500.00 eggs..

[Danglerb]

Standard price, weld and grind $938 plus tax in Calif, but no shipping since I picked up and dropped off.

Looks like about $100 for two sets of 944 turbo valve springs, one set acquired, one still working on.

Lifters have not been decided on. Could be used I already have, up to buying new and coating the face. Edging toward less complicated, and cheaper if practical.

Stock valves.

Heads I think will get port matched, but I don't plan on a lot of grinding.

Chevy drilling the crank and fly cutting the pistons are the only other things I can think of.

[Landseer]

Are you saying you bought camshafts and had the wear surfaces built-up with welding, then machined to meet Euro specifications? Did you have other choices? Am just trying to learn the ins and outs of camshafts. Guess I need to search and read more on my own.

[Danglerb]

Sort of yes, except the Euro S cam is still a fairly mild grind, and this one is more the classic V8 hot rod grind with the maximum lift and duration the 928 will support without a bunch of other changes.

Since the cam would be welded I picked the lowest performance cam I had, a non S US 80/82. First step was that cam was inspected and measured. How much to reduce the base circle and how much material would be welded on were decided, then they did it.

Part of how this works is that the lifters have a small "automatic" adjustment range, they expand to match the reduction in base circle size, which in turn results in more lift from the lobe nose.

Link below explains terms more.

http://www.webcamshafts.com/pages/cam_glossary.html

Here is a nice labeled diagram (still looking for a good one on the whole heads).



Here is a diagram of the whole engine, from http://en.wikivisual.com/images/4/47/Four_stroke_engine_diagram.jpg




How a hydraulic lifter works "lifted" from http://satikudlu.blogspot.com/2007/07/hydraulic-tappets.html

Hydraulic tappet is mainly consists following parts.

1. Body
2. Plunger Assembly
3. Pressure Check Valve






Working:
When engine runs oil pump supplies oil to the hydraulic lifters body through oil channel, lifter consists a small hole on it’s body and through this hole it gets oil supply from the bore and there after passes inside the plunger through plungers oiling hole. When plunger filled with oil it pushes the check ball against its spring and enters into the pressure chamber.

Now the whole lifter was filled with oil when cam shaft rotates its lobe pushes the lifter body upward with pressure when lifter get pressure from the lobe it tries to move upwards so it pushes the check ball and spring due to this action ball moves upward and closes the oil supply hole of the plunger now the oil stuck between lifter and plunger i.e. in pressure chamber is acts as a cushion. Cam lobe pushes the lifter body further upwards now the whole body acts like a solid Tappet / Lifter and moves upwards and push the valve against its seat via push rod and rocker mechanism.









When cam lobe turn downwards it withdraw pressure from the lifter body now the valve spring pushes the whole mechanism i.e. rocker arm, pushrod and lifters down wards.

In this system there was no need to keep valve clearance or lash because whether engine is cold or hot there Hydraulic lifters always get oil and according to the pressure it self adjust the clearance. So these tappets are called self adjusting tappets.

Merits:
1. Self adjusting Tappets / No adjustment is required
2. No clattering noise at cold engine condition
3. No power loss at hot engine condition
4. Smoother operation

[Barbapapa]

Here's something closer for you. These Porsche lifters are better than the pushrod ones in many ways except for the mass, they move at full valve rate rather than a reduced distance of a pushrod engine.

[Landseer]

Damn.

Thanks!

[Landseer]

Mike, my wife has even sitting here looking at these pictures and understands them.

Once again, great post.

[rhjames]

good info Mike, glad you took the time to let us know how it goes.

new lifters please. it's more money, but why risk the cams with old?

use plenty of cam lube, be sure to run engine above 2500 rpms for at least 15 minutes to properly break in the cams/lifters. you cna shut it down during the break in time, but rpms need to be above 2500 for the duration.



what duration (@ .050 lift) did you have them grind the sticks to?



--Russ