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Cams--sanitized
https://www.slantsix.org/forum/viewtopic.php?t=11458		 Page 2 of 2
Author:  63Dart [ Tue May 17, 2005 9:53 pm ]
Post subject: 
I have a recent Dutra grind cam in my car. (Thanks again Doug!!!).

IT ROCKS!

The idle is fairly smooth and the car will idle in drive at 650 RPM (it likes 700-725 better, though).

In the zone between 1500 and 3000 RPM where I do most of my driving, the cam is nice and torquey. It will also pull strong from idle just by stomping on the gas, and that's with the stock converter (remember, I have a very light car - 63 Dart).

It pulls *very* strong from about 2000 up to around 4800. It would probably pull higher, but my carbs are not completely synched (I got them where they both open all the way and hit the stops at the same time - but that's not really "synching").

If I do a brake stand and get the engine up to 2000, it pretty much jumps off the line. If I push it beyond 2000 RPM, it starts smoking the back tire.

Even without doing that, I've still got good "off the line," and have put a few cars and SUVs in the dust.

Umm...

I don't really drive like this all the time, by the way. But it's nice to know that I can, if I need to...

p.s. - it's also got a nice lope at idle - with my 6 into 2 flowmaster 40's - it's actually VERY intimidating. The ricers don't even try and race me like they used to. Actually, even the kids with the 5.0 Mustangs, etc. don't seem to want to race.

I did have one guy in a Monte Carlo come up to me and rev his motor. I dropped it into first at about 20 MPH and snapped down the gas pedal for a short second. My car does NOT bog, and the result when I do this is that the entire front end rises very quickly and looks like it wants to do a wheelie. This I guess was also intimidating, so the low-rider turned on the next turn.
Author:  emsvitil [ Tue May 17, 2005 11:09 pm ]
Post subject: 
Quote:
I have a recent Dutra grind cam in my car. (Thanks again Doug!!!).

What are the cam specs????
Author:  gearhead [ Wed May 18, 2005 9:03 am ]
Post subject: 
So I took a look at some cam lobe numbers on the Comp Cams site and the Reed Cams site.

First let me say that I like Comp Cams, I think they make good products, and I have had good success other than a set of springs that kept breaking. But one thing I've noticed about Comp, is that the Grinds they produce for you to choose out of the Catalog, are rather generic, mild, too conservative.

I realize that Cam Companies benefit from being conservative.

That said, if you look at the 252 solid grind for the /6, it has only 215 duration at .050" valve lift, .435 lift, and 110 lobe separation.

There is nothing wrong with this, it is just so mild, that its only good use is for someone who really just wants a driver and step up 5-10 hp over stock...it is a very mild cam grind by anyones standards, and is barely big enough to be considered a stock 2 bbl cam for a V8. Abd certainly not large enough to take much advantage of any head or exhaust work thats been done, or to run with gears shorter than about 3.23.

Now if we go to the Comp Lobe list...we find it hard to find good solid cams this small...not much call for small aggresive cams...but none the less, if we look careful, we find a series of lobes designed for restricted racing. These lobes require special oiling provisions for .842" lifter, but I would bet the tech line would say no problem with a .904" lifter.

257 seat duration, 230 .050" and .425 lift.

This lobe would produce another 10-15 HP more with the extra 15 degrees of duration at .050" (probably) even with less lift.

But what about lobes that are actually in the size range where serious development takes place...

Well go up 10 degrees in seat duration to 260...and a whole new world opens up...

Standard Comp 264 solid cam...264 seat to seat...220 @ .050", .440 lift

Go to the lobe list and find some lobes designed for the .875" Ford lifter (.904" Mopar lifter lobes don't go this small)

First one I found...

264 seat...238 @ .050"....539" lift

Holy Cow!!!!!!!!!!!!!!!

Talk about a difference...for the same seat duration, we get 18 degrees more .050" lift duration...and the lift increases to .534"

This cam would have the same basic drivability and idle of a standard 264 comp "grind" but would produce "substantially" more mid range and top end. I wouldn't be surprised to see 30 more HP and torque over the standard comp grind they would recommend.

And this grind is still only a .875" lifter design.

If you get to 270 degrees the differences are even greater between designs.

Once you hit 280, you can get as mush lift and .050" duration as the solid roller in my GTO...the .904" lifter is the deal in a half...and all you guys need to start thinking about this if you want your slants to respond to the money you spend.

Yes...Doc is right and you can go off the deep end...and people do often choose too big a cam for what they want, which is why it is important to know just what you want.

But my solid roller in my Goat...runs just as well on the street as my much less power producing old Comp Hydraulic, which actually had 6 more degrees of seat duration than my roller, but 12 degrees less at .050" and much less lift.

Again, I have installed many solid cams in street cars, using this same principle of getting as much lift and .050" duration as possible while keeping the seat duration as short as possible, as long as you target the seat duration to what you want for drivability...you will be a happy camper. :D

Gearhead aka Karl
Author:  panic [ Thu May 19, 2005 3:50 pm ]
Post subject:  VW grinds
You mean the Type I air-cooled flat four?
That's a 1" tappet.
Author:  gearhead [ Thu May 19, 2005 5:49 pm ]
Post subject: 
I don't know what size lifter the VW engines have, but I know the grind isn't excessive for the .904" lifter.

I am not even certain that those numbers were for a VW...just my lame memory remembers Ken at Oregon Cam Grinding saying that to me...but heck...could have been another lobe he was talking about...this was well over a year ago.

oops, my buds here with his truck so I can take my slant block to the machine shop.

Karl
Author:  panic [ Mon Feb 12, 2007 7:34 am ]
Post subject: 
Re: "allows the use of very aggressive profiles without durability issues"

Fundamental error.

The maximum velocity is proportionate to lifter contact area (less a very small safety margin, UDHarold says .020" is safe).
This means that the lobe's point of initial contact with the lifter can be in a different place if the lifter is wider. If the lifter is not wide enough, the lobe strikes the edge and both are destroyed within minutes (if not seconds). This is hardly a durability issue.
The loading on the tappet and lobe are not reduced by using a larger lifter at all, and the more aggressive (higher acceleration) lobe that must use a wide lifter will have as much wear as the most aggressive cam that can use a narrower lifter. It will simply provide more lift.

This is not a subject that may be mastered in 20 years.
I still have things to learn after 40 years.
Author:  Doc [ Mon Feb 12, 2007 8:23 am ]
Post subject: 
Quote:
...This is not a subject that may be mastered in 20 years.
I still have things to learn after 40 years.
I hear that!
I do enjoy the opportunity to discuss and think about how the basic principals of cam design can be applied to the Slant so keep the ideas coming.
DD
Author:  gearhead [ Mon Feb 12, 2007 8:55 am ]
Post subject: 
You are correct Panic. Durability issues however, are not based on the cam lobe only. There is also the valve seat, and valve springs that are affectet by acceleration rates. These also need to be considered for long term durability.

It is completely obvious that the lifter to cam lobe interface is based on the surface area of the edge of the lifter that contacts the cam lobe. But of course, the amount of force applied to this interface goes up quickly as you purchase springs that will control an aggressive lobe. Also, there is the angle at which the lobe rides against the face of the lobe. This angle changes constantly during the rise of the lifter along the profile, however, the smaller the lifter diameter, the more severe the angle, and the farther along the profile it remains severe...and the force from the springs and of accelerating the mass of the valvetrain parts increase.

Also, the larger diameter does change the contact area. The larger diameter allows more of the edge to span the contact area of the lobe during initial acceleration. This is a small difference, but as a percentage change in surface area it is significant.

So there is a difference in how aggressive you can go on any given lifter diameter before durability issues arise. This is why there are better profiles available for larger lifters.

I have a UD solid cam with 13 wiped lobes in 5 minutes. When put on a cam doctor and measured, there was no clearance ramp designed into the profile. It went straight into full acceleration. This was one of the trick "tight lash" profiles they promoted as the hot new way to make power in the early 90's.

I think UD Harold needed a few more years of learning as well.

I am always learning. I haven't mastered anything ever.

Gearhead
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