128 my take, anybody see it like this ?

[ClassAct]

Most of my stuff is 11-12:1 pump gas and I haven’t used over a 108 LSA on any of them. My own engine is on a 105 in at 105. None of them are bad or hard to drive on the street. They idle clean and will idle down to 700 if I let them.

That’s GM, Ford and Chrysler small and big block. My engine will go on the pump late this winter or early spring. I’ll test it with some other cam if someone wants to pay for the cam and lifters. I’ll do the dyno for free and post the results here.

I'd like to know what CID and cylinder head/ intake valve size (or any trick valve job)?
Those are the 128 inputs and kind of the centre of attention with this thread.
Thanks.

The smallest is 340 inches (mine) and up to 572 (BBC). Everything I do gets a 50 degree valve job. I don’t use 128 because I don’t adjust for compression ratio and shit like that. If it’s on race gas and over 13:1 I open the LSA a bit, or if the RPM is over 8k I’ll open the LSA a bit. Nothing trick about it.

[skinny z]

I only mention 128 because that's the OP's thread title.
Obviously, everyone has their own approach to specifying their cam specs.
128 is just one example. And a very narrow one at that so much as it's only offering up an LSA.

[Stan Weiss]

Most of my stuff is 11-12:1 pump gas and I haven’t used over a 108 LSA on any of them. My own engine is on a 105 in at 105. None of them are bad or hard to drive on the street. They idle clean and will idle down to 700 if I let them.

That’s GM, Ford and Chrysler small and big block. My engine will go on the pump late this winter or early spring. I’ll test it with some other cam if someone wants to pay for the cam and lifters. I’ll do the dyno for free and post the results here.

Tim,
Have you looked at what TMC recommended for these engines verses what you have used?

Thanks,
Stan

[ClassAct]

Most of my stuff is 11-12:1 pump gas and I haven’t used over a 108 LSA on any of them. My own engine is on a 105 in at 105. None of them are bad or hard to drive on the street. They idle clean and will idle down to 700 if I let them.

That’s GM, Ford and Chrysler small and big block. My engine will go on the pump late this winter or early spring. I’ll test it with some other cam if someone wants to pay for the cam and lifters. I’ll do the dyno for free and post the results here.

Tim,
Have you looked at what TMC recommended for these engines verses what you have used?

Thanks,
Stan

Not yet but soon. I have to get excel so I can run it. I’m trying to get my dyno plumbed and wired so I can test all that. Then I’m on it.

[digger]

When i looked at this in ENGMOD4T this seemed to be reasonable provided you were only looking at WOT maximum average power in the 3-7k rpm range.

I think this is also fundamental to the rule.
Although, peak torque may be more of an emphasis. The average would fall into place. Of course, there are exceptions.

I think the first thing people need to do is to create a histogram rpm plot on how they drive. We use 104-106 LSA (104/104 centerlines, or around 102/106 centerlines) on road race engines. Work great, make a lot of power for something that redlines around 7200rpm, but no way would I call that streetable and I bet most people with these kind of Chevy’s are spending most of their time below 3000-3500rpm (where most dyno pulls start). The 128 rule of thumb also only works for symmetrical valve lift profiles. It’s not going to work with Harold’s lobes, some of Mike’s, and a handful of Comp’s lobe families.

Also, I need to caution about lobe profiles when you simulate. You really need the actual lobe / valve lift profiles you want to test. I have bought cams specifically to have CamDr’ed for simulation work (and sold them). You can kind of rough in one, but it’s not the same and you will be missing a bunch.

i agree for best WOT power in the 2500-3500RPM the best LSA will be something like 70 degrees with moderate lobe duration ~230@0.050 but wouldn't want that at part throttle

i measure the valve lift curve on the head (measurements of the cam are useless with a sliding rocker) and compare to the generated ones and vary parameters to get the best fit so i can make a family of lobes.

[digger]

I think this is also fundamental to the rule.
Although, peak torque may be more of an emphasis. The average would fall into place. Of course, there are exceptions.

I think the first thing people need to do is to create a histogram rpm plot on how they drive. We use 104-106 LSA (104/104 centerlines, or around 102/106 centerlines) on road race engines. Work great, make a lot of power for something that redlines around 7200rpm, but no way would I call that streetable and I bet most people with these kind of Chevy’s are spending most of their time below 3000-3500rpm (where most dyno pulls start). The 128 rule of thumb also only works for symmetrical valve lift profiles. It’s not going to work with Harold’s lobes, some of Mike’s, and a handful of Comp’s lobe families.

Also, I need to caution about lobe profiles when you simulate. You really need the actual lobe / valve lift profiles you want to test. I have bought cams specifically to have CamDr’ed for simulation work (and sold them). You can kind of rough in one, but it’s not the same and you will be missing a bunch.

Most of my stuff is 11-12:1 pump gas and I haven’t used over a 108 LSA on any of them. My own engine is on a 105 in at 105. None of them are bad or hard to drive on the street. They idle clean and will idle down to 700 if I let them.

That’s GM, Ford and Chrysler small and big block. My engine will go on the pump late this winter or early spring. I’ll test it with some other cam if someone wants to pay for the cam and lifters. I’ll do the dyno for free and post the results here.

what are the typical durations? obviously 106LSA with a 210@0.050 cam is going to idle better than a 110LSA and 260@0.050 cam

[Tom68]

I only mention 128 because that's the OP's thread title.
Obviously, everyone has their own approach to specifying their cam specs.
128 is just one example. And a very narrow one at that so much as it's only offering up an LSA.

I thought 128 was for LCA, which I assumed would be for intake, then you would have a formula for exhaust area to bore size. If not and they're both the same cl, ie. now LSA, where does the ever successful 4 degrees advance fit in, makes my 1.72'' 4'' example 101 inl cl. It would be a monster off idle, great heavy truck motor but probably with poor fuel economy.

[ClassAct]

I think the first thing people need to do is to create a histogram rpm plot on how they drive. We use 104-106 LSA (104/104 centerlines, or around 102/106 centerlines) on road race engines. Work great, make a lot of power for something that redlines around 7200rpm, but no way would I call that streetable and I bet most people with these kind of Chevy’s are spending most of their time below 3000-3500rpm (where most dyno pulls start). The 128 rule of thumb also only works for symmetrical valve lift profiles. It’s not going to work with Harold’s lobes, some of Mike’s, and a handful of Comp’s lobe families.

Also, I need to caution about lobe profiles when you simulate. You really need the actual lobe / valve lift profiles you want to test. I have bought cams specifically to have CamDr’ed for simulation work (and sold them). You can kind of rough in one, but it’s not the same and you will be missing a bunch.

Most of my stuff is 11-12:1 pump gas and I haven’t used over a 108 LSA on any of them. My own engine is on a 105 in at 105. None of them are bad or hard to drive on the street. They idle clean and will idle down to 700 if I let them.

That’s GM, Ford and Chrysler small and big block. My engine will go on the pump late this winter or early spring. I’ll test it with some other cam if someone wants to pay for the cam and lifters. I’ll do the dyno for free and post the results here.

what are the typical durations? obviously 106LSA with a 210@0.050 cam is going to idle better than a 110LSA and 260@0.050 cam

I’m 255 at .050 on 340 inches. My wife drives the car.

[skinny z]

I only mention 128 because that's the OP's thread title.
Obviously, everyone has their own approach to specifying their cam specs.
128 is just one example. And a very narrow one at that so much as it's only offering up an LSA.

I thought 128 was for LCA, which I assumed would be for intake, then you would have a formula for exhaust area to bore size. If not and they're both the same cl, ie. now LSA, where does the ever successful 4 degrees advance fit in, makes my 1.72'' 4'' example 101 inl cl. It would be a monster off idle, great heavy truck motor but probably with poor fuel economy.

128 is to define the lobe separation angle. If we follow the originator of the 128 rule and continue on to the same author's TM program, you'll find that 4 degrees tends to be built into the cam specs.
What did 128 determine for an LSA with a 1.72" valve, your CID and CR?

[Stan Weiss]

I only mention 128 because that's the OP's thread title.
Obviously, everyone has their own approach to specifying their cam specs.
128 is just one example. And a very narrow one at that so much as it's only offering up an LSA.

I thought 128 was for LCA, which I assumed would be for intake, then you would have a formula for exhaust area to bore size. If not and they're both the same cl, ie. now LSA, where does the ever successful 4 degrees advance fit in, makes my 1.72'' 4'' example 101 inl cl. It would be a monster off idle, great heavy truck motor but probably with poor fuel economy.

128 is to define the lobe separation angle. If we follow the originator of the 128 rule and continue on to the same author's TM program, you'll find that 4 degrees tends to be built into the cam specs.
What did 128 determine for an LSA with a 1.72" valve, your CID and CR?

In TMC the Min intake valve for a SBC is 1.8"

Stan

[Tom68]

128 is to define the lobe separation angle. If we follow the originator of the 128 rule and continue on to the same author's TM program, you'll find that 4 degrees tends to be built into the cam specs.
What did 128 determine for an LSA with a 1.72" valve, your CID and CR?

This is all I've seen of 128.

128.jpg

[Geoff2]

Not all cam companies grind 4* of adv into their cams. Crane used to use 5* with some of their grinds.

If you want to know how much advance the cam needs for best hp, you would need to do what DV does: put the engine on a dyno.

[Geoff2]

106 LSA.
Did I hear someone 'tight'?
How about 98 LSA & 92 ICL?
Jon Kaase used this in his EMC entry & won. And none of the predicted catastrophies happened. HP didn't go over a cliff after peak hp because of the tight LSA. Didn't need long rods, used short rods. Cam was reverse pattern, had less exh duration, & not that big either.

[Geoff2]

This obsession with wider LSA on US made factory engines is not worldwide. The LSA of the production cams in the humble Morris Mini were on 107.5. Factory performance cams were on 102.5.

[Tom68]

This obsession with wider LSA on US made factory engines is not worldwide. The LSA of the production cams in the humble Morris Mini were on 107.5. Factory performance cams were on 102.5.

There's been some tight LCA little SBC's to. 104 degrees.