#21  
Old 01-18-2023, 11:20 AM
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What does the cam need to look like?
Brian,
Here are the specs for the Chevy 632 ci 1004 HP 12:1 CR crate engine. Recommended Fuel: Premium pump (93 octane or higher)

Stan
Attached Files
File Type: pdf 2022ChevyPerformanceCatalogweb41122_Page_192.pdf (259.6 KB, 65 views)

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  #22  
Old 01-18-2023, 04:20 PM
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Brian,
Here are the specs for the Chevy 632 ci 1004 HP 12:1 CR crate engine. Recommended Fuel: Premium pump (93 octane or higher)

Stan
Lobe separation and center line are listed though. Those are pretty important.

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Old 01-18-2023, 04:42 PM
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What does the cam need to look like?
Always questions, you were a pump gas guy so you know.

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Old 01-18-2023, 05:14 PM
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Always questions, you were a pump gas guy so you know.
Ya the cam I picked was based on the power and rpm I wanted. Had nothing to do with pump gas or compression. Just curious what a pump gas cam is??

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Old 01-18-2023, 05:45 PM
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Lobe separation and center line are listed though. Those are pretty important.
Yes they are, But looking at CI, RPM, CR and head flow I would not have picked the cam Chevy is using. Maybe someone can tell me why it needs so much exhaust duration?

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  #26  
Old 01-18-2023, 05:56 PM
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Yes they are, But looking at CI, RPM, CR and head flow I would not have picked the cam Chevy is using. Maybe someone can tell me why it needs so much exhaust duration?

Stan
It's a really big engine, and somewhat small valve

  #27  
Old 01-18-2023, 10:08 PM
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I'm all ears on cam recommendations.

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  #28  
Old 01-18-2023, 10:44 PM
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I didn't see any LSA or ICL any one know what it is?

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Old 01-19-2023, 12:42 AM
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This article says the LSA is 113
https://www.chevyhardcore.com/tech-s...ormance-zz632/

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  #30  
Old 01-19-2023, 01:06 AM
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This article says the LSA is 113
https://www.chevyhardcore.com/tech-s...ormance-zz632/

Stan
Sounds like the cam is pretty close to what I'll be running.

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Old 01-19-2023, 04:05 AM
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Ya the cam I picked was based on the power and rpm I wanted. Had nothing to do with pump gas or compression. Just curious what a pump gas cam is??
A high effort pump gas cam is not unlike a NO2 cam.
The cam used in the linked BBC crate engine is not all that different than one of my cams. Its on a 112 with a little bit less lift and duration.
Like the article says, the wide LSA helps bleed off cylinder pressure.
That helps avoid detonation.
In a NO2 engine-cam you need to hold back the cylinder pressure some because you are going to artificially add it when you hit the button and want to avoid detonation.
In a pump gas engine, well, you are on pump gas so the wide LSA cam is a crutch to help.
No free lunches. Valve timing is everything.

  #32  
Old 01-19-2023, 08:29 AM
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Quote:
Originally Posted by Dragncar View Post
A high effort pump gas cam is not unlike a NO2 cam.
The cam used in the linked BBC crate engine is not all that different than one of my cams. Its on a 112 with a little bit less lift and duration.
Like the article says, the wide LSA helps bleed off cylinder pressure.
That helps avoid detonation.
In a NO2 engine-cam you need to hold back the cylinder pressure some because you are going to artificially add it when you hit the button and want to avoid detonation.
In a pump gas engine, well, you are on pump gas so the wide LSA cam is a crutch to help.
No free lunches. Valve timing is everything.

Factory cams have 112-113 ls, OF from SD is 112, those pump cams? I just don't think labeling a cam a pump gas or nitrous cam is smart or means anything at all. A cam is cam no such thing as a pump gas cam imo. I do again valve timing is everything but that applies to any engine no matter the fuel used or the compression.

  #33  
Old 01-19-2023, 10:32 AM
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IMO first one needs to know why a certain LSA maybe spec'd to begin with. Then what effect of extending or shortening the exhaust duration is going to have. The intake duration needs to be matched to the rest of the parts in the combination along with the lift..... That would include cylinder head characteristics, bore, stroke, rod length, piston design, induction system, exhaust, transmission, gear ratio, tire size, users end goal, among others.

There is much more to it than a two input, on-line, free computer program. If you have the correct cam for a pump gas engine then one could accurately describe it as a pump gas cam. If one uses nitrous and has a cam spec'd optimumly for the combination, one could call that a "nitrous cam". If one has a fifteen second bracket car and only races the vehicle that could be called a full race cam.

I remember years ago, racing a guy with a 79 Z/28 that ran really well and took us by surprise. It ran so well we raced a second time just to make sure it wasn't a fluke. The guy was all proud if the way his car ran and any question I would ask him about the car, I would get a response that "it's the right combination". He really thought the he had something I wanted to know, even though I just beat him two times in a row.... We joked for many years later that he had "the right combination" camshaft.

At the end if the day you can name a cam whatever you would like, but once they're close to what you need they'll look identical on paper, only the numbers will be different.

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  #34  
Old 01-19-2023, 02:08 PM
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Factory cams have 112-113 ls, OF from SD is 112, those pump cams? I just don't think labeling a cam a pump gas or nitrous cam is smart or means anything at all. A cam is cam no such thing as a pump gas cam imo. I do again valve timing is everything but that applies to any engine no matter the fuel used or the compression.
OK Boomer.
You had problems at 11-1 right ?
Guys that make their livings designing cams just might tell you something different about this stuff. That is not to just say you can run this special pump gas cam and run 12-13 -1, It does not work like that.
I deal with a tech at Ross. He has a high effort Ford pump gas car. Its 13-1 running on CA pump pi$$. He gave me the name of a tech at Bullet who designed his cam. It can be done , but everything has to be right with no room for error.
Static compression is different that dynamic compression. It all matters.
There is a difference between a all nuts NA cam and a pump gas cam and a difference with a NO2 cam.
Its not just about a wide LSA.

  #35  
Old 01-19-2023, 02:11 PM
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Originally Posted by PAUL K View Post
IMO first one needs to know why a certain LSA maybe spec'd to begin with. Then what effect of extending or shortening the exhaust duration is going to have. The intake duration needs to be matched to the rest of the parts in the combination along with the lift..... That would include cylinder head characteristics, bore, stroke, rod length, piston design, induction system, exhaust, transmission, gear ratio, tire size, users end goal, among others.

There is much more to it than a two input, on-line, free computer program. If you have the correct cam for a pump gas engine then one could accurately describe it as a pump gas cam. If one uses nitrous and has a cam spec'd optimumly for the combination, one could call that a "nitrous cam". If one has a fifteen second bracket car and only races the vehicle that could be called a full race cam.

I remember years ago, racing a guy with a 79 Z/28 that ran really well and took us by surprise. It ran so well we raced a second time just to make sure it wasn't a fluke. The guy was all proud if the way his car ran and any question I would ask him about the car, I would get a response that "it's the right combination". He really thought the he had something I wanted to know, even though I just beat him two times in a row.... We joked for many years later that he had "the right combination" camshaft.

At the end if the day you can name a cam whatever you would like, but once they're close to what you need they'll look identical on paper, only the numbers will be different.
I can not say I disagree with any of that. But no free internet program was used picking my cam. It was a hard to get and expensive program and the cam was a proven one.
You have built a lot more engines than me, so I do listen.

  #36  
Old 01-19-2023, 02:27 PM
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I can not say I disagree with any of that. But no free internet program was used picking my cam. It was a hard to get and expensive program and the cam was a proven one.
You have built a lot more engines than me, so I do listen.
I never implied anything in regards to your cam or cam choice or how you came about selecting one. I haven't used any type of cam program in years. But sometimes they are nice for a second opinion. I gave up interest once I realized they are fancy calculators and just add and subtract. If you ever play with one do something stupid like add a four inch exhaust valve and the program will tell you how much power you will gain with one or how the cam needs to be adjusted.

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Old 01-19-2023, 02:38 PM
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Quote:
Originally Posted by Dragncar View Post
OK Boomer.
You had problems at 11-1 right ?
Guys that make their livings designing cams just might tell you something different about this stuff. That is not to just say you can run this special pump gas cam and run 12-13 -1, It does not work like that.
I deal with a tech at Ross. He has a high effort Ford pump gas car. Its 13-1 running on CA pump pi$$. He gave me the name of a tech at Bullet who designed his cam. It can be done , but everything has to be right with no room for error.
Static compression is different that dynamic compression. It all matters.
There is a difference between a all nuts NA cam and a pump gas cam and a difference with a NO2 cam.
Its not just about a wide LSA.
I think I did just find with my cam. Ask your buddy if he races with that CA gas and 13:1 or if he spikes it with race gas. Big difference between cruising and racing.
By the way issues did I have????


Last edited by slowbird; 01-19-2023 at 02:48 PM.
  #38  
Old 01-19-2023, 03:07 PM
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Quote:
Originally Posted by PAUL K View Post
IMO first one needs to know why a certain LSA maybe spec'd to begin with. Then what effect of extending or shortening the exhaust duration is going to have. The intake duration needs to be matched to the rest of the parts in the combination along with the lift..... That would include cylinder head characteristics, bore, stroke, rod length, piston design, induction system, exhaust, transmission, gear ratio, tire size, users end goal, among others.

There is much more to it than a two input, on-line, free computer program. If you have the correct cam for a pump gas engine then one could accurately describe it as a pump gas cam. If one uses nitrous and has a cam spec'd optimumly for the combination, one could call that a "nitrous cam". If one has a fifteen second bracket car and only races the vehicle that could be called a full race cam.

I remember years ago, racing a guy with a 79 Z/28 that ran really well and took us by surprise. It ran so well we raced a second time just to make sure it wasn't a fluke. The guy was all proud if the way his car ran and any question I would ask him about the car, I would get a response that "it's the right combination". He really thought the he had something I wanted to know, even though I just beat him two times in a row.... We joked for many years later that he had "the right combination" camshaft.

At the end if the day you can name a cam whatever you would like, but once they're close to what you need they'll look identical on paper, only the numbers will be different.
Paul,
Let me add one more thing and that is rocker arm ratio. The Chevy has 1.8:1 What really matters is the valve lift curve. So if one was running 1.65:1 rocker arm ratio they would in fact need a different cam lobe than if running 1.8:1 rocker arm ratio.

Stan

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  #39  
Old 01-19-2023, 03:17 PM
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Paul,
Let me add one more thing and that is rocker arm ratio. The Chevy has 1.8:1 What really matters is the valve lift curve. So if one was running 1.65:1 rocker arm ratio they would in fact need a different cam lobe than if running 1.8:1 rocker arm ratio.

Stan
Hi Stan, yes that is absolutely correct. I recall plotting that out many years ago on a project. Definetly an area that would be helped with a computer program. Going from memory, I want to say we picked up four or five degrees of duration comparing a 1.6 to a 1.7 rocker arm at .050. Lifter diameter will have a small affect also.

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  #40  
Old 01-19-2023, 06:15 PM
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Originally Posted by Dragncar View Post
I can not say I disagree with any of that. But no free internet program was used picking my cam. It was a hard to get and expensive program and the cam was a proven one.
You have built a lot more engines than me, so I do listen.
Care to share what software / program you used?

Stan

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