compression with hotcam
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
Being an lt1 it will be able to get away with more.. I am running 12.4:1 scr in my 383 and running 91 octane. My cam is rather large at 245/253@.050 with .612/.612 on a 107lsa. I am not going to pretend like I am a professional like some people but I have seen 11.5:1 and a hotcam be fine. Its more a matter of attention to details then working around a number.
Last edited by pr0zac; May 31, 2011 at 03:29 PM.
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
Being an lt1 it will be able to get away with more.. I am running 12.4:1 scr in my 383 and running 91 octane. My cam is rather large at 245/253@.050 with .612/.612 on a 107lsa. I am not going to pretend like I am a professional like some people but I have seen 11.5:1 and a hotcam be fine. Its more a matter of attention to details then working around a number.
I understand you have been bashing others on MANY Other Forums for some time just you do with me on C4 Tech.
I have my inside sources to veify this.
Just to let you know,
I have bigger spec cams than you in my 1970 TA, My 1963 GP 455, My 410 ci sbc, And what my late friend built biggirl with.
I prefer cams with overlaps or 85 to 105 degrees.
Shake the ground down below.
If you are going to give out cam specs,
Give them out at .020" & .050" valvelift, Intake & Exhaust valve opening & closing points.
IVO EVO
IVC EVC
Just like on a cam card.
That way exact intake & exhaust centerlines can be determined from from those numbers, valve overlap, ect.
I can run a computer simulation in 30 seconds also from actual cam specs given to see what it will do theoretically too.
Valve lift is a secondary issue.
BR
Last edited by 87 vette 81 big girl; Jun 1, 2011 at 08:36 AM.
Race Director
Joined: Sep 2001
Posts: 14,668
Likes: 749
From: NEwhere Ohio
93 Ragtop,
you and I have messed around with similar setups (on our 93's) for many years.
2 years ago, I added a procharger p600b and water/meth injection and will never ever look back.
I urge you to strongly consider forced induction, at which point you would obviously want a LOWER compression ratio.
Amazing streetability (dont need to puke on idle fumes from as big a cam) and you'll make more power with boost than a 13:1 race motor.
Boost makes more power than compression.
you and I have messed around with similar setups (on our 93's) for many years.
2 years ago, I added a procharger p600b and water/meth injection and will never ever look back.
I urge you to strongly consider forced induction, at which point you would obviously want a LOWER compression ratio.
Amazing streetability (dont need to puke on idle fumes from as big a cam) and you'll make more power with boost than a 13:1 race motor.
Boost makes more power than compression.
Melting Slicks
Joined: Mar 2004
Posts: 2,141
Likes: 2
From: Pittsburgh Pa
Still bashing me I see.
I understand you have been bashing others on MANY Other Forums for some time just you do with me on C4 Tech.
I have my inside sources to veify this.
Just to let you know,
I have bigger spec cams than you in my 1970 TA, My 1963 GP 455, My 410 ci sbc, And what my late friend built biggirl with.
I prefer cams with overlaps or 85 to 105 degrees.
Shake the ground down below.
If you are going to give out cam specs,
Give them out at .020" & .050" valvelift, Intake & Exhaust valve opening & closing points.
IVO EVO
IVC EVC
Just like on a cam card.
That way exact intake & exhaust centerlines can be determined from from those numbers, valve overlap, ect.
I can run a computer simulation in 30 seconds also from actual cam specs given to see what it will do theoretically too.
Valve lift is a secondary issue.
BR
I understand you have been bashing others on MANY Other Forums for some time just you do with me on C4 Tech.
I have my inside sources to veify this.
Just to let you know,
I have bigger spec cams than you in my 1970 TA, My 1963 GP 455, My 410 ci sbc, And what my late friend built biggirl with.
I prefer cams with overlaps or 85 to 105 degrees.
Shake the ground down below.
If you are going to give out cam specs,
Give them out at .020" & .050" valvelift, Intake & Exhaust valve opening & closing points.
IVO EVO
IVC EVC
Just like on a cam card.
That way exact intake & exhaust centerlines can be determined from from those numbers, valve overlap, ect.
I can run a computer simulation in 30 seconds also from actual cam specs given to see what it will do theoretically too.
Valve lift is a secondary issue.
BR
Melting Slicks
Joined: Dec 2008
Posts: 2,772
Likes: 64
From: Mystic CT
Good point...
Mines at 10.5:1.
In order to run smoothly and yeild the max performance with the max advance, it needs 93oct min and has a max op temp of around 220 (to avoid knocking) Depending on ambient temp. Under these conditions it can rev to the redline under load and survive.
1. Less oct 89-91 requires one OR both lower op-temp or less ign advance or ambient temp.
2. Cheap gas (87) means stock advance, op temps of less than 200 and no stress driving habits.
3. All gasoline is created equally. Its all the same product with a different name on the bottle...exxon, shell, whoever. The difference in the grades is in the addmixture to increase Octane, which is just a measure of time. How long does the explosion last? The longer it does, the higher the Octane.
Basically, hi-oct fuel burns slower, providing more consistant pressure on the piston dome, and pressure that last longer to hold the tension on the piston longer so that it is not free to flop around in the cylinder. Its not more pressure, its longer lasting pressure that increases as the volume of the cylinder is increasing with the piston moving downwards.
4. Knocking is poor or incomplete combustion thats happens quick, so the bang is over before the piston has moved thru its entire stroke. This is where the cam timing comes into play. As long as that ex valve is closed, that explosion should be ongoing. This calculation is well beyond my ability, but you get the idea.
5. Lower compression engines are designed to utilize the low oct fuels in order to maintain that precious 14.7:1 air to fuel ratio. Less thermal efficiency from the fuel, less air required to maintain that ratio.
Mines at 10.5:1.
In order to run smoothly and yeild the max performance with the max advance, it needs 93oct min and has a max op temp of around 220 (to avoid knocking) Depending on ambient temp. Under these conditions it can rev to the redline under load and survive.
1. Less oct 89-91 requires one OR both lower op-temp or less ign advance or ambient temp.
2. Cheap gas (87) means stock advance, op temps of less than 200 and no stress driving habits.
3. All gasoline is created equally. Its all the same product with a different name on the bottle...exxon, shell, whoever. The difference in the grades is in the addmixture to increase Octane, which is just a measure of time. How long does the explosion last? The longer it does, the higher the Octane.
Basically, hi-oct fuel burns slower, providing more consistant pressure on the piston dome, and pressure that last longer to hold the tension on the piston longer so that it is not free to flop around in the cylinder. Its not more pressure, its longer lasting pressure that increases as the volume of the cylinder is increasing with the piston moving downwards.
4. Knocking is poor or incomplete combustion thats happens quick, so the bang is over before the piston has moved thru its entire stroke. This is where the cam timing comes into play. As long as that ex valve is closed, that explosion should be ongoing. This calculation is well beyond my ability, but you get the idea.
5. Lower compression engines are designed to utilize the low oct fuels in order to maintain that precious 14.7:1 air to fuel ratio. Less thermal efficiency from the fuel, less air required to maintain that ratio.
1.Huh??? octane and engine temperature are not even related in any way only cylinder temp and more cylinder pressure related.
2. My 2002 Pontiac runs 87 octane 210 degress and I beat it to an inch of it's life and it loves it so myth discounted.....
3. Gasoline is not all the same it is a hydro carbon soup and there are many ways to get to the same or similar place with much different burn characteristics. You are leaving out just to begin vapor pressure specific gravity aromatic hydrocarbon percentage distilation curve and oxygenated or not if so with what additive package.
Octane has nothing to do with burn speed only resistance to pressure and temperature. You need to read and possibly learn some chemistry.
4. Knocking is uncontrolled combustion it can be from low octane glowing parts that cause preignition or it can be from end gas combustion from thinking too rich is always safe.
5. With E10 that we all buy stioc is 14.3 octane has nothing to do with the air required thermal effeciency has nothing to do with the fuel at all and have no idea where that thought comes from. typically higher octane fuel has fewer btu per pound. deisel engines are the most effecient and running what amounts to #2 fuel oil the octane so low off the chart they use cetane numbers on a whole different lower scale.
You can crystal ball respout all ya need to do from hot rod mags. I made 640 ft lbs and 720 hp at 7k rpm out of a 6 liter Aston Martin GTP engine what did you do?
Melting Slicks
Joined: Nov 2008
Posts: 2,765
Likes: 5
[QUOTE=ddahlgren;1577769315]I added numbers to make the answers easier to follow without repeating what you wrote.
1.Huh??? octane and engine temperature are not even related in any way only cylinder temp and more cylinder pressure related.
2. My 2002 Pontiac runs 87 octane 210 degress and I beat it to an inch of it's life and it loves it so myth discounted.....
3. Gasoline is not all the same it is a hydro carbon soup and there are many ways to get to the same or similar place with much different burn characteristics. You are leaving out just to begin vapor pressure specific gravity aromatic hydrocarbon percentage distilation curve and oxygenated or not if so with what additive package.
Octane has nothing to do with burn speed only resistance to pressure and temperature. You need to read and possibly learn some chemistry.
4. Knocking is uncontrolled combustion it can be from low octane glowing parts that cause preignition or it can be from end gas combustion from thinking too rich is always safe.
5. With E10 that we all buy stioc is 14.3 octane has nothing to do with the air required thermal effeciency has nothing to do with the fuel at all and have no idea where that thought comes from. typically higher octane fuel has fewer btu per pound. deisel engines are the most effecient and running what amounts to #2 fuel oil the octane so low off the chart they use cetane numbers on a whole different lower scale.
You can crystal ball respout all ya need to do from hot rod mags. I made 640 ft lbs and 720 hp at 7k rpm out of a 6 liter Aston Martin GTP engine what did you do?[/QUOTE
Dave,
I don't think my 410 will run like your 6.0 L Astin Matin GTP.
But it should run pretty good for an old dinosaur tech pushrod V8 engine.
What do you think of "Swain Tech coatings" ?
Is the technology race & street proven in your eyes ?
Thermal barrier enhancing coatings for the Cylinder head combustion chambers, piston tops/ domes, Intake manifolds, ect ?
I have been told its one of the greatest secrets in Professional Racing Motorsports.
Many of the "JEGS" Engine Masters Series yearly competition engine builders have used them to win the $100,000 prize.
John Kasse has won it several times.
Once competed with a traditional Pontiac V8.
I think he won that year too.
He is Ford guy usually.
Brian R.
1.Huh??? octane and engine temperature are not even related in any way only cylinder temp and more cylinder pressure related.
2. My 2002 Pontiac runs 87 octane 210 degress and I beat it to an inch of it's life and it loves it so myth discounted.....
3. Gasoline is not all the same it is a hydro carbon soup and there are many ways to get to the same or similar place with much different burn characteristics. You are leaving out just to begin vapor pressure specific gravity aromatic hydrocarbon percentage distilation curve and oxygenated or not if so with what additive package.
Octane has nothing to do with burn speed only resistance to pressure and temperature. You need to read and possibly learn some chemistry.
4. Knocking is uncontrolled combustion it can be from low octane glowing parts that cause preignition or it can be from end gas combustion from thinking too rich is always safe.
5. With E10 that we all buy stioc is 14.3 octane has nothing to do with the air required thermal effeciency has nothing to do with the fuel at all and have no idea where that thought comes from. typically higher octane fuel has fewer btu per pound. deisel engines are the most effecient and running what amounts to #2 fuel oil the octane so low off the chart they use cetane numbers on a whole different lower scale.
You can crystal ball respout all ya need to do from hot rod mags. I made 640 ft lbs and 720 hp at 7k rpm out of a 6 liter Aston Martin GTP engine what did you do?[/QUOTE
Dave,
I don't think my 410 will run like your 6.0 L Astin Matin GTP.
But it should run pretty good for an old dinosaur tech pushrod V8 engine.
What do you think of "Swain Tech coatings" ?
Is the technology race & street proven in your eyes ?
Thermal barrier enhancing coatings for the Cylinder head combustion chambers, piston tops/ domes, Intake manifolds, ect ?
I have been told its one of the greatest secrets in Professional Racing Motorsports.
Many of the "JEGS" Engine Masters Series yearly competition engine builders have used them to win the $100,000 prize.
John Kasse has won it several times.
Once competed with a traditional Pontiac V8.
I think he won that year too.
He is Ford guy usually.
Brian R.
Last edited by 87 vette 81 big girl; Jun 2, 2011 at 07:55 AM.
Melting Slicks
Joined: Dec 2009
Posts: 2,749
Likes: 50
From: Westmont Il.
Amateur here, but I have 11:1 and Hotcam (advanced 4*) in my '91.
Everything is good. Attention to details, like Prozac said.
Here is a article by David Vizard that helped me with those details.
http://www.popularhotrodding.com/tec...eze/index.html
Everything is good. Attention to details, like Prozac said.
Here is a article by David Vizard that helped me with those details.
http://www.popularhotrodding.com/tec...eze/index.html
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019
Amateur here, but I have 11:1 and Hotcam (advanced 4*) in my '91.
Everything is good. Attention to details, like Prozac said.
Here is a article by David Vizard that helped me with those details.
http://www.popularhotrodding.com/tec...eze/index.html
Everything is good. Attention to details, like Prozac said.
Here is a article by David Vizard that helped me with those details.
http://www.popularhotrodding.com/tec...eze/index.html
http://www.popularhotrodding.com/tec.../photo_18.html
A lot of times when people talk about max SCR, compression, or DCR (as related to a particular cam choice), they don't talk about where coolant temps need to be. I haven't seen a better chart than Vizzard's.
Notice too,,,his emphasis on quench!
Last edited by GREGGPENN; Jun 2, 2011 at 12:44 AM.
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