What was Chevrolet thinking ?

[Tom68]

May need a full lobe profile to answer this, the 208 might be an inverted lobe, or extremely aggressive ?

235 235 Equal intake exhaust, they don't know what you're using it in so they can't assume great flowing exhaust system, and it is a 90 degree V8 so the exhaust is always compromised.
So I'm guessing they didn't add Exhaust duration in an effort to keep some idle quality.

208 221 More difference than most, but otherwise normal, makes you wonder what cams with more than 13 degrees difference would perform like.

Chev thinking.jpg

[Tom68]

Rereading that I see there isn't an obvious question.

I guess what I'm wondering is how did Chevrolet come up with two cams so different to do a similar job.

Obviously one is bigger than the other....but like.....wow......Are we all to precious about how we choose a cam if they can throw these two out there....maybe we just go fly fishing and see what we hook.

[juuhanaa]

What is the difference between those Crate motors? 350ZZZ and ZZ2 vs 350 345, ZZ3&4

Maybe Chevrolet listened ZZ top

[Carnut1]

The drop in lc is why the shorter cam works.

[1980RS]

One year I ran 2 cams that the lift and duration was similar
One cam was on a 110° lca the other was on a 106°lca.
Racing the engine the 106 cam just blew the 110 cam away performance wise
On the street though the 110 cam had better drivability, that all that GM thinks about with their cams.

[PackardV8]

One year I ran 2 cams that the lift and duration was similar
One cam was on a 110° lca the other was on a 106°lca.
Racing the engine the 106 cam just blew the 110 cam away performance wise
On the street though the 110 cam had better drivability, that all that GM thinks about with their cams.

For true. I've known guys who chose the wrong/too radical cam and their ride was a bitch to put up with, poor fuel economy, stinky exhaust, but it was their choice and they wouldn't hear anything otherwise.

OTOH, if someone else chooses the cam for them, starts easily, doesn't stink up the garage, decent fuel economy, but they get beat occasionally, they'll claim to any and all "He doesn't know how to built a winning engine."

[travis]

Iirc, the later 208/221 cam was used so they could offer the ZZ motors as an emissions legal package for 3rd gen Camaros. The earlier 235/235 cam wouldn't pass emissions.
The ZZ4 was a really nice daily driver performance engine. The earlier setups was definitely lumpier and weak on bottom end torque

[skinny z]

May need a full lobe profile to answer this, the 208 might be an inverted lobe, or extremely aggressive ?

235 235 Equal intake exhaust, they don't know what you're using it in so they can't assume great flowing exhaust system, and it is a 90 degree V8 so the exhaust is always compromised.
So I'm guessing they didn't add Exhaust duration in an effort to keep some idle quality.

208 221 More difference than most, but otherwise normal, makes you wonder what cams with more than 13 degrees difference would perform like.

Chev thinking.jpg

You're right in your thinking about the full lobe profile.
A better understanding of those two cams would be had if the seat timing was available. And both being GM cams, they'll at least be measured the same way. The .050" numbers give you insight into one aspect of the cam profile but there is information lacking otherwise.

[Tom68]

Iirc, the later 208/221 cam was used so they could offer the ZZ motors as an emissions legal package for 3rd gen Camaros. The earlier 235/235 cam wouldn't pass emissions.
The ZZ4 was a really nice daily driver performance engine. The earlier setups was definitely lumpier and weak on bottom end torque

Yes well, that certainly explains it.

Only interesting thing then is the 235 cam being single pattern.

[skinny z]

Somewhere, someplace, I've had a conversation about those cams. One of them at least. Factory spec seat timing specifically.
If I find it, I'll post it here.
Seems to me F-Bird had a hand in it?

[rebelyell]

May need a full lobe profile to answer this, the 208 might be an inverted lobe, or extremely aggressive ?

235 235 Equal intake exhaust, they don't know what you're using it in so they can't assume great flowing exhaust system, and it is a 90 degree V8 so the exhaust is always compromised.
So I'm guessing they didn't add Exhaust duration in an effort to keep some idle quality.

208 221 More difference than most, but otherwise normal, makes you wonder what cams with more than 13 degrees difference would perform like.

Chev thinking.jpg

The above specs for 10185071 (ZZ4 cam also in x604 (current ZZ6) and CT400 and in defunct x603 crate (L98 aka x113 heads) --- those specs above are different than what I've been seeing for many years for 10185071. All I've known are split on both duration & lift.

That cam is still in Chev Perf 2022 catalog with specs there and at summit below --- same cam & specs in 2006 GMPP cat.
JMO It doesn't need a bronze anything. Some of the dressed crates came with both carb & pump --- look up the GM install guides for those specific crates and it shows pn for the correct fuel pump push rod (it ain't bronze tip); GM specs a melonized gear for both their iron and steel cams --- and melonized works well --- presently, seems Allstar has best price on melonized .491" gears. YMMV

Summit Racing Part Number:
NAL-10185071
UPC:
036666163278
Cam Style:
Hydraulic roller tappet
Camshaft Use:
Street/Strip
Intake Duration at 050 inch Lift:
208
Exhaust Duration at 050 inch Lift:
221
Duration at 050 inch Lift:
208 int./221 exh.
Advertised Intake Duration:
275
Advertised Exhaust Duration:
280
Advertised Duration:
275 int./280 exh.
Intake Valve Lift with Factory Rocker Arm Ratio:
0.474 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio:
0.510 in.
Valve Lift with Factory Rocker Arm Ratio:
0.474 int./0.510 exh.
Lobe Separation (degrees):
112

[Tom68]

The above specs for 10185071 (ZZ4 cam also in x604 (current ZZ6) and CT400 and in defunct x603 crate (L98 aka x113 heads) --- those specs above are different than what I've been seeing for many years for 10185071. All I've known are split on both duration & lift.

Yer I've never seen the 235 cam before, came up on a site when I was looking for the 208 221. But I was always curious about the 208 221, so now I know what was going on with that at least

So many dual pattern cams from Chev which I love the idea of, but they still have a few for single pattern cams (which I have several of) so will put them to use.

20220926_165307.jpg

20220926_165307.jpg

[Elroy]

The drop in lc is why the shorter cam works.

208-221 112LSA 112ICL
IVO is -8.0 ° BTDC
IVC is 36.0 ° ABDC
EVO is 42.5 ° BBDC
EVC is -1.5 ° ATDC

208-221 114lsa 114ICL
IVO is -10.0 ° BTDC
IVC is 38.0 ° ABDC
EVO is 44.5 ° BBDC
EVC is -3.5 ° ATDC

Ok, so its the LSA then? So in this case what specifically about the effects of these 2 LSA's would be the cause of one "working" and one "not working"?

[skinny z]

The drop in lc is why the shorter cam works.

208-221 112LSA 112ICL
IVO is -8.0 ° BTDC
IVC is 36.0 ° ABDC
EVO is 42.5 ° BBDC
EVC is -1.5 ° ATDC

208-221 114lsa 114ICL
IVO is -10.0 ° BTDC
IVC is 38.0 ° ABDC
EVO is 44.5 ° BBDC
EVC is -3.5 ° ATDC

Ok, so its the LSA then? So in this case what specifically about the effects of these 2 LSA's would be the cause of one "working" and one "not working"?

Can you plot that with seat duration values please?

[Elroy]

Can you plot that with seat duration values please?

Were they stated? Seat duration is where the answer lies?