Does opening up the top of the cylinder help performance?
Thread Starter
Registered User
Joined: Jul 2012
Posts: 2,990
From: Vancouver BC
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; Feb 4, 2013 at 10:17 PM.
I bleed Oldsmobile
Joined: Dec 2007
Posts: 1,390
From: Iowa
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.......
Registered User
Joined: Jun 2010
Posts: 3,613
From: Rogues Island, USA
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.
Registered User
Joined: Nov 2008
Posts: 8,477
From: Central Fl
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.
Registered User
Joined: Apr 2012
Posts: 2,972
From: New Mexico
Can you elaborate a bit more on the best bang for the buck procedures for head porting?
Thread Starter
Registered User
Joined: Jul 2012
Posts: 2,990
From: Vancouver BC
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; Feb 5, 2013 at 09:09 AM.
Registered User
Joined: Jun 2010
Posts: 3,613
From: Rogues Island, USA
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; Feb 5, 2013 at 10:38 AM.
Thread
Thread Starter
Forum
Replies
Last Post
costpenn
General Questions
69
Aug 29, 2018 11:42 AM
GoBigRed
Brakes/Hydraulic Systems
15
Oct 5, 2015 01:00 PM
rootney
Racing and High Performance
12
Nov 20, 2014 12:39 AM
wmachine
General Discussion
11
Dec 30, 2009 05:55 AM
