Does opening up the top of the cylinder help performance?
February 4th, 2013, 08:42 PM
#1
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Does opening up the top of the cylinder help performance?
I have seen some build threads were the builder opened up the top of the cylinder to help breathing of the 455.
Dose this work?
Pros and cons of this modification?
When I mean open up its like a large chamfer at the top of the cylinder on the intake side of the cylinder wall.
Dose this work?
Pros and cons of this modification?
When I mean open up its like a large chamfer at the top of the cylinder on the intake side of the cylinder wall.
Last edited by Bernhard; February 4th, 2013 at 10:17 PM.
February 5th, 2013, 07:06 AM
#2
Gasket matching is a easy way to make sure there is no restrictions to your gas/air mixture making it to the combustion chamber......I have always gasket matched intake to head,Thats one of the things a novice can do to add a few free HP........If its all ready on the car that would make it alot more difficult but not impossible.......
February 5th, 2013, 07:38 AM
#3
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I think he's referring to the to the very top of the cylinder just above the top ring. I've seen this done on BBC to unshroud the intake valve but you need to have a corresponding chamfer in the head to make it work. I'm not sure if it's a good mod for the Olds because of the differences in an Olds vs a closed chamber Chevy head. It's my belief the BBC benefit more because of the larger valves and the closed chamber design.
Since the Olds combustion chamber is basically the same diameter as the cylinder I doubt it makes much difference and you also run the risk of interfering with the head gasket sealing ring depending on what head gaskets you use.
I'd put your effort more into the heads (porting, gasket match, etc.) for a worthwhile benefit.
Since the Olds combustion chamber is basically the same diameter as the cylinder I doubt it makes much difference and you also run the risk of interfering with the head gasket sealing ring depending on what head gaskets you use.
I'd put your effort more into the heads (porting, gasket match, etc.) for a worthwhile benefit.
February 5th, 2013, 08:11 AM
#4
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I think he's referring to the to the very top of the cylinder just above the top ring. I've seen this done on BBC to unshroud the intake valve but you need to have a corresponding chamfer in the head to make it work. I'm not sure if it's a good mod for the Olds because of the differences in an Olds vs a closed chamber Chevy head. It's my belief the BBC benefit more because of the larger valves and the closed chamber design. Plus remember on BBC and Pontiacs, they radiused the top of the bore because some engine sizes had a smaller bore, i.e. 326 Pontiacs and 366/396 BBC, and valve to block interference was an issue.
Since the Olds combustion chamber is basically the same diameter as the cylinder I doubt it makes much difference and you also run the risk of interfering with the head gasket sealing ring depending on what head gaskets you use.
I'd put your effort more into the heads (porting, gasket match, etc.) for a worthwhile benefit.
Since the Olds combustion chamber is basically the same diameter as the cylinder I doubt it makes much difference and you also run the risk of interfering with the head gasket sealing ring depending on what head gaskets you use.
I'd put your effort more into the heads (porting, gasket match, etc.) for a worthwhile benefit.
February 5th, 2013, 08:49 AM
#5
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Can you elaborate a bit more on the best bang for the buck procedures for head porting?
February 5th, 2013, 09:02 AM
#6
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I think he's referring to the to the very top of the cylinder just above the top ring. I've seen this done on BBC to unshroud the intake valve but you need to have a corresponding chamfer in the head to make it work. I'm not sure if it's a good mod for the Olds because of the differences in an Olds vs a closed chamber Chevy head. It's my belief the BBC benefit more because of the larger valves and the closed chamber design.
Since the Olds combustion chamber is basically the same diameter as the cylinder I doubt it makes much difference and you also run the risk of interfering with the head gasket sealing ring depending on what head gaskets you use.
I'd put your effort more into the heads (porting, gasket match, etc.) for a worthwhile benefit.
Since the Olds combustion chamber is basically the same diameter as the cylinder I doubt it makes much difference and you also run the risk of interfering with the head gasket sealing ring depending on what head gaskets you use.
I'd put your effort more into the heads (porting, gasket match, etc.) for a worthwhile benefit.
Yes I was referring to the top of the cylinder just above the top ring. I was looking at this more for a 400 G block. I would like to know if there was any benifit or negative result with this mod.
Last edited by Bernhard; February 5th, 2013 at 09:09 AM.
February 5th, 2013, 10:31 AM
#7
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Location: Rogues Island, USA
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Other than the sealing ring on the head gasket I don't know of any downside but I still think the upside will be minimal at best if even noticeable. Like Cutlassefi said gasket matching the ports is least likely to produce noticeable results either. There is an article I used to have showing in percentages what head mods produced the most results. Unfortunately I can't find it but you should be able to Google it. As stated, bowl blending and short side radius are at the top of the list.
Found one article:
http://www.popularhotrodding.com/eng...s/viewall.html
Found one article:
http://www.popularhotrodding.com/eng...s/viewall.html
Last edited by TripDeuces; February 5th, 2013 at 10:38 AM.
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