What was Chevrolet thinking ?
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What was Chevrolet thinking ?
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.
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.
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Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Re: What was Chevrolet thinking ?
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.
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.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Re: What was Chevrolet thinking ?
What is the difference between those Crate motors? 350ZZZ and ZZ2 vs 350 345, ZZ3&4
Maybe Chevrolet listened ZZ top
Maybe Chevrolet listened ZZ top
A balanced person dares to stagger, and modify ports bigger
Re: What was Chevrolet thinking ?
The drop in lc is why the shorter cam works.
Servedio Cylinder Head Development
631-816-4911
9:00am - 9:00pm EST
631-816-4911
9:00am - 9:00pm EST
Re: What was Chevrolet thinking ?
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.
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.
Re: What was Chevrolet thinking ?
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.1980RS wrote: ↑Sun Sep 25, 2022 10:57 am 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.
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."
Jack Vines
Studebaker-Packard V8 Limited
Obsolete Engineering
Studebaker-Packard V8 Limited
Obsolete Engineering
Re: What was Chevrolet thinking ?
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
The ZZ4 was a really nice daily driver performance engine. The earlier setups was definitely lumpier and weak on bottom end torque
Re: What was Chevrolet thinking ?
You're right in your thinking about the full lobe profile.Tom68 wrote: ↑Sat Sep 24, 2022 11:34 pm 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
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.
Kevin
Re: What was Chevrolet thinking ?
Yes well, that certainly explains it.travis wrote: ↑Sun Sep 25, 2022 1:13 pm 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
Only interesting thing then is the 235 cam being single pattern.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Re: What was Chevrolet thinking ?
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?
If I find it, I'll post it here.
Seems to me F-Bird had a hand in it?
Kevin
Re: What was Chevrolet thinking ?
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.Tom68 wrote: ↑Sat Sep 24, 2022 11:34 pm 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
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
Re: What was Chevrolet thinking ?
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 leastrebelyell wrote: ↑Mon Sep 26, 2022 12:12 am
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.
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.
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Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
Re: What was Chevrolet thinking ?
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"?
Re: What was Chevrolet thinking ?
Can you plot that with seat duration values please?Elroy wrote: ↑Mon Sep 26, 2022 9:06 am208-221 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"?
Kevin