WTB Turbo cam

[zarfnober]

Looking for a turbo cam, nothing bigger than an OTTO OT20, preferably, really don't want to go with a regrind, but whattaya got? Clarks has cams in stock, thought I'd look here first'. The cam that came out of my 55K turbo is in excellent condition, other than it's bent and binds on the high spot, as does an older OTTO 304 with less than 1k miles.

Rocco
65 Turbo Corsa

[joelsplace]

Straighten it. All it takes is a dial indicator, some v-blocks, a dull chisel and hammer.

[66vairguy]

Straighten it. All it takes is a dial indicator, some v-blocks, a dull chisel and hammer.

Yes straighten it, although how to do it explanations vary. Sometimes during shipping they get bent.

I had a brand new Isky cam that was fine in the "V" blocks (used a good dial indicator). The "local" machine shop BENT IT installing the cam gear! I told they to fix or replace it and they sent it to Isky (not far away) and it came back from Isky STRAIGHT, but Isky took off the cam gear claiming it was not on perpendicular! I never sent a cam/gear to the local machine shop again.

After that I sent the cam to Jeff at Calif. Corvair to put one of his billet cams on it and it came back STRAIGHT. So far so good.

[zarfnober]

I've heard of the hammer and chisel technique, but wouldn't dare try it myself. Headed to a local shop tomorrow evening, he's gonna take a look at it and see, fingers crossed, but still looking.

[zarfnober]

FOUND thanks to Kevin Nash, an OTTO TB20 is on it's way.

[jimbrandberg]

Speaking of turbo cams I have 3 Early turbo engines apart and was disappointed to find no 63 turbo cams among them. I have a 150 and a 102 to put together so I was hoping to find one of each cam but I found 2 102 cams and one LM cam yet to be determined.
Is a OT-20 more for naturally aspirated and a TB-20 more for a turbo? If so has a current TB-20 been found to be true to its original design? I haven't actually gotten around to looking at new turbo cams yet.
I also have a 180 with 140 heads that someone never finished, like an oil return and such. I don't know that I've ever held a 304 cam in my hands to see the number.
Jim Brandberg
Isanti, MN
CorvairRepair.com

[zarfnober]

AFAIK, all the OTTO cams are slightly different than they were priorr to clarks buyout, but don't quote me. Here's the current specs on the TB10 and TB20

[kmart356]

...snip...
Is a OT-20 more for naturally aspirated and a TB-20 more for a turbo?
...snip...

Well sir, that's how the Otto cams were designed and intended to be used. OT for non turbo... TB for turbo.
These days, there are many workable options for the turbo engine. Currently running an OT-20 with 140heads and the results are excellent (using programmable timing and methanol injection). here are some comparative specifications to look at including the venerable 304.
.

[Vairone]

AFAIK, all the OTTO cams are slightly different than they were priorr to clarks buyout, but don't quote me. Here's the current specs on the TB10 and TB20

There is something very wrong with the TB 20 exhaust numbers. They can not be the same as the TB 10 while having more listed duration.

[Nashfan]

AFAIK, all the OTTO cams are slightly different than they were priorr to clarks buyout, but don't quote me. Here's the current specs on the TB10 and TB20

There is something very wrong with the TB 20 exhaust numbers. They can not be the same as the TB 10 while having more listed duration.

The exhaust duration on the TB 10 and TB 20 is identical, but the TB 20 has .025" more lift on the exhaust. How? The lift rate (AKA "intensity") is slightly faster.

[zarfnober]

There is something very wrong with the TB 20 exhaust numbers. They can not be the same as the TB 10 while having more listed duration.
[/quote]

The exhaust duration on the TB 10 and TB 20 is identical, but the TB 20 has .025" more lift on the exhaust. How? The lift rate (AKA "intensity") is slightly faster.
[/quote]

Thanks Kevin!

[Vairone]

AFAIK, all the OTTO cams are slightly different than they were priorr to clarks buyout, but don't quote me. Here's the current specs on the TB10 and TB20

There is something very wrong with the TB 20 exhaust numbers. They can not be the same as the TB 10 while having more listed duration.

The exhaust duration on the TB 10 and TB 20 is identical, but the TB 20 has .025" more lift on the exhaust. How? The lift rate (AKA "intensity") is slightly faster.

The advertised numbers show the TB 20 exhaust opens sooner and closes later than the TB 10 so it has more advertised duration than the TB 10. Wouldnt that make the lift rate slower than the OT 10?

To get a rough idea of the lift rate (AKA "intensity"), take the Adv duration and subtract the .050 duration. The lower the number the faster the lift rate. These numbers ..........
TB 10 .... 256 - 208 = 48
TB 20 .... 262 - 208 = 54

The TB 10 has a higher intensity than the TB 20. That is why I think something is very wrong with the TB 20 exhaust numbers.

[jimbrandberg]

I enjoy the comparison sheet above and printed it off for my cam info file.
One thing missing is lift. I'm a lot more careful about coil bind than I used to be.
When comparing something like a Otto 10 and 20 I don't know if we can really speak to the lift rate without knowing the lift.
I'm not complaining about the list, I really appreciate that you posted it.
I've found Isky cams to usually be repeatable with the Specs. Otto maybe not so much although they may be back on track these days, I hope so, the original Ottos were pretty cool with the different intake and exhaust profiles and such.
In my view a cam should come with a Cam Card not a generic link to information about what it very well could be. I'm old fashioned about most things except a coffee percolator.
Jim Brandberg
Isanti, MN
CorvairRepair.com

[Nashfan]

AFAIK, all the OTTO cams are slightly different than they were priorr to clarks buyout, but don't quote me. Here's the current specs on the TB10 and TB20

There is something very wrong with the TB 20 exhaust numbers. They can not be the same as the TB 10 while having more listed duration.

The exhaust duration on the TB 10 and TB 20 is identical, but the TB 20 has .025" more lift on the exhaust. How? The lift rate (AKA "intensity") is slightly faster.

The advertised numbers show the TB 20 exhaust opens sooner and closes later than the TB 10 so it has more advertised duration than the TB 10. Wouldnt that make the lift rate slower than the OT 10?

To get a rough idea of the lift rate (AKA "intensity"), take the Adv duration and subtract the .050 duration. The lower the number the faster the lift rate. These numbers ..........
TB 10 .... 256 - 208 = 48
TB 20 .... 262 - 208 = 54

The TB 10 has a higher intensity than the TB 20. That is why I think something is very wrong with the TB 20 exhaust numbers.

Look at the @.050 numbers, they have the same exact duration, but the TB 20 lifts more. The intensity OVERALL has to be higher, but because intensity is a measure of lift rate, we tend to think of it as being a constant, but it is not. Its variable, and because of that, one cam can look more intense measured one way and less intense measured another way. The variable nature of lift rates, and how sensitive those are between zero lift and .050" shows why its difficult to use "advertised" duration and "intensity" by themselves as some metric to tell you how bad ass a cam is or not!

[zarfnober]

Cam from Nash Fan showed up at my door today, and apparently, I think, it's from the older OTTO stock before Clarks made changes. The specs are slightly different, and the cam "card" is on an old, yellowed sheet of paper with the original OTTO address, etc. and here's the specs, anyone care to compare from specs listed earlier from Clarks current run?

[zarfnober]

OOPS!