Choosing the right pistons
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Joined: Aug 2007
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Piston choice is determined by the desired compression ratio, which in turn depends on the goals and purpose of the build. All things being equal I prefer a flat top for flame travel, but the most important thing is to get the desired compression ratio. Domed pistons (rarely used on Oldsmobiles) can be a pain due to clearance issues with the valves.
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Joined: Feb 2013
Posts: 178
Piston choice is determined by the desired compression ratio, which in turn depends on the goals and purpose of the build. All things being equal I prefer a flat top for flame travel, but the most important thing is to get the desired compression ratio. Domed pistons (rarely used on Oldsmobiles) can be a pain due to clearance issues with the valves.
Out of Line, Everytime😉
Joined: Dec 2006
Posts: 9,971
From: Melville, Saskatchewan
Really only flat top, 1.4cc, 3cc and 6cc in forged pistons. Only two have modern ring packs, the CP and Probe. But they are limited to a hone clean up and .030 over bore. Then there is the sbc 400 and rod combos.
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Out of Line, Everytime😉
Joined: Dec 2006
Posts: 9,971
From: Melville, Saskatchewan
The Probe and CP are 2618 alloy and the Speed Pro are 4032, I believe. Some believe the 2618 is superior, softer but more forgiving for detonation. Either way forged are far superior to hyper or cast and only need slightly more clearance with modern designs. No hyper pistons are made for the 350, unless you go the 400 sbc piston and rod option.
Last edited by olds 307 and 403; Dec 29, 2013 at 05:12 AM.
Thread Starter
Registered User
Joined: Feb 2013
Posts: 178
The Probe and CP are 2618 alloy and the Speed Pro are 4032, I believe. Some believe the 2618 is superior, softer but more forgiving for detonation. Either way forged are far superior to hyper or cast and only need slightly more clearance with modern designs. No hyper pistons are made for the 350, unless you go the 400 sbc piston and rod option.
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Joined: Oct 2011
Posts: 390
From: Munich, Germany
The spark from your spark plug ignites the air fuel mixture in your combustion chamber and a flame front travelling through it builds up. A flat top piston allows the flame front to travel faster and disperse more even along the piston head, which means to put it briefly, more power.
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Joined: Nov 2008
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From: Central Fl
The spark from your spark plug ignites the air fuel mixture in your combustion chamber and a flame front travelling through it builds up. A flat top piston allows the flame front to travel faster and disperse more even along the piston head, which means to put it briefly, more power.
Ehhh kinda.
Combustion chamber shape, spark plug location, fuel, and compression ratio also contribute to flame travel. There's more to it than just the top of the piston.
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From: Munich, Germany
Connoisseur d'Junque
Joined: Sep 2010
Posts: 21,183
From: The Hudson Valley
At this juncture, I think it fair to say:
OldSkool84, you are asking much better questions now, but you are asking questions that can't or shouldn't be answered on an internet forum.
You now need to go out and get some books (or even on-line resources) about engine design and performance and read them in order to gain a basic understanding of piston design, piston materials, head flow and porting, compression ratios, flame front propagation, valve and ignition timing, and carburetion / fuel injection.
See the current thread on home porting, for instance.
Once you have absorbed a basic level of knowledge, you will be better able to fix your own engine, and to ask the sorts of questions that will allow you to properly plan the sorts of upgrades you would like.
- Eric
OldSkool84, you are asking much better questions now, but you are asking questions that can't or shouldn't be answered on an internet forum.
You now need to go out and get some books (or even on-line resources) about engine design and performance and read them in order to gain a basic understanding of piston design, piston materials, head flow and porting, compression ratios, flame front propagation, valve and ignition timing, and carburetion / fuel injection.
See the current thread on home porting, for instance.
Once you have absorbed a basic level of knowledge, you will be better able to fix your own engine, and to ask the sorts of questions that will allow you to properly plan the sorts of upgrades you would like.
- Eric
Thread Starter
Registered User
Joined: Feb 2013
Posts: 178
At this juncture, I think it fair to say:
OldSkool84, you are asking much better questions now, but you are asking questions that can't or shouldn't be answered on an internet forum.
You now need to go out and get some books (or even on-line resources) about engine design and performance and read them in order to gain a basic understanding of piston design, piston materials, head flow and porting, compression ratios, flame front propagation, valve and ignition timing, and carburetion / fuel injection.
See the current thread on home porting, for instance.
Once you have absorbed a basic level of knowledge, you will be better able to fix your own engine, and to ask the sorts of questions that will allow you to properly plan the sorts of upgrades you would like.
- Eric
OldSkool84, you are asking much better questions now, but you are asking questions that can't or shouldn't be answered on an internet forum.
You now need to go out and get some books (or even on-line resources) about engine design and performance and read them in order to gain a basic understanding of piston design, piston materials, head flow and porting, compression ratios, flame front propagation, valve and ignition timing, and carburetion / fuel injection.
See the current thread on home porting, for instance.
Once you have absorbed a basic level of knowledge, you will be better able to fix your own engine, and to ask the sorts of questions that will allow you to properly plan the sorts of upgrades you would like.
- Eric
Connoisseur d'Junque
Joined: Sep 2010
Posts: 21,183
From: The Hudson Valley
I agree with the recommendations made above for books.
The Chassis Service Manual is essential for everybody, and you should have the Fisher Body Manual as well. Mondello's and Trovato's books are definitely helpful if you're considering modifying your engine.
The Chassis Service Manual contains clear simple descriptions of how every part and system works, including the carburetor and ignition.
"Timing and Vacuum Advance 101" by John Hinckley is helpful, as is "Distributor Vacuum Advance Control units
Specs and facts" by Lars Grimsrud
The Rochester Carburetor Manual is good to read if you are going to use a QuadraJet, but most of what's in it is also in the Chassis Service Manual.
I also liked Cliff Ruggles's book on QuadraJets.
CarburetorManuals.com also has a number of different carburetor manuals.
Once you've looked through some of this stuff, you'll be in a much better position to ask questions that don't require several pages to explain, and don't lead to threads where people are arguing about the correct answers, and half of them are wrong.
- Eric
The Chassis Service Manual is essential for everybody, and you should have the Fisher Body Manual as well. Mondello's and Trovato's books are definitely helpful if you're considering modifying your engine.
The Chassis Service Manual contains clear simple descriptions of how every part and system works, including the carburetor and ignition.
"Timing and Vacuum Advance 101" by John Hinckley is helpful, as is "Distributor Vacuum Advance Control units
Specs and facts" by Lars Grimsrud
The Rochester Carburetor Manual is good to read if you are going to use a QuadraJet, but most of what's in it is also in the Chassis Service Manual.
I also liked Cliff Ruggles's book on QuadraJets.
CarburetorManuals.com also has a number of different carburetor manuals.
Once you've looked through some of this stuff, you'll be in a much better position to ask questions that don't require several pages to explain, and don't lead to threads where people are arguing about the correct answers, and half of them are wrong.
- Eric
Thread Starter
Registered User
Joined: Feb 2013
Posts: 178
I agree with the recommendations made above for books.
The Chassis Service Manual is essential for everybody, and you should have the Fisher Body Manual as well. Mondello's and Trovato's books are definitely helpful if you're considering modifying your engine.
The Chassis Service Manual contains clear simple descriptions of how every part and system works, including the carburetor and ignition.
"Timing and Vacuum Advance 101" by John Hinckley is helpful, as is "Distributor Vacuum Advance Control units
Specs and facts" by Lars Grimsrud
The Rochester Carburetor Manual is good to read if you are going to use a QuadraJet, but most of what's in it is also in the Chassis Service Manual.
I also liked Cliff Ruggles's book on QuadraJets.
CarburetorManuals.com also has a number of different carburetor manuals.
Once you've looked through some of this stuff, you'll be in a much better position to ask questions that don't require several pages to explain, and don't lead to threads where people are arguing about the correct answers, and half of them are wrong.
- Eric
The Chassis Service Manual is essential for everybody, and you should have the Fisher Body Manual as well. Mondello's and Trovato's books are definitely helpful if you're considering modifying your engine.
The Chassis Service Manual contains clear simple descriptions of how every part and system works, including the carburetor and ignition.
"Timing and Vacuum Advance 101" by John Hinckley is helpful, as is "Distributor Vacuum Advance Control units
Specs and facts" by Lars Grimsrud
The Rochester Carburetor Manual is good to read if you are going to use a QuadraJet, but most of what's in it is also in the Chassis Service Manual.
I also liked Cliff Ruggles's book on QuadraJets.
CarburetorManuals.com also has a number of different carburetor manuals.
Once you've looked through some of this stuff, you'll be in a much better position to ask questions that don't require several pages to explain, and don't lead to threads where people are arguing about the correct answers, and half of them are wrong.
- Eric
Registered User
Joined: Jul 2012
Posts: 370
Oldskool84, much info can just be gotten free off the internet. Just google a topic of interest and you can find tons of good info. Keep in mind of course not every shread on info will be 100% true and some info can be debated, but at least you can learn the basics and that will be very helpfull to you.
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Joined: Oct 2010
Posts: 1,275
From: Boise ID
Most important thing is to realistically decide what you are going to use your engine for and what compression ratio you are aiming for. Next is what set of heads you are using, the combustion chamber size will dictate which set of pistons you have to use to get the desired compression ratio and which material you have to have. Don't over complicate it.
Thread Starter
Registered User
Joined: Feb 2013
Posts: 178
Most important thing is to realistically decide what you are going to use your engine for and what compression ratio you are aiming for. Next is what set of heads you are using, the combustion chamber size will dictate which set of pistons you have to use to get the desired compression ratio and which material you have to have. Don't over complicate it.
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