Good small block heads on a 455
February 26th, 2010, 03:04 PM
#1
Good small block heads on a 455
This is probably a dumb question but I ask it anyhow. Can a good set of ported 5, big valve heads make any improvement on a stout 455 with, for example stock E heads with the small valves?
The compression rise is nice to get, but will the flow inprovement bee enough. Is it wise to test? I´m sure some of you have tried. Please informe me? If the quesation already been asked , I´apologise.
Regards
Stanley
The compression rise is nice to get, but will the flow inprovement bee enough. Is it wise to test? I´m sure some of you have tried. Please informe me? If the quesation already been asked , I´apologise.
Regards
Stanley
February 26th, 2010, 05:58 PM
#2
Registered User
Join Date: Sep 2009
Location: KY
Posts: 1,489
You would be better off putting a higher compression piston in your engine and having your bbo heads machined.
The sbo heads are going to be restrictive on a big block. Not flowing enough for the bbo to be worth the swap.
The smaller chambers might raise cr a little but without the air in. I just don't seeing it working well.
The sbo heads are going to be restrictive on a big block. Not flowing enough for the bbo to be worth the swap.
The smaller chambers might raise cr a little but without the air in. I just don't seeing it working well.
February 26th, 2010, 06:02 PM
#3
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Join Date: Nov 2008
Location: Central Fl
Posts: 7,973
You would be better off putting a higher compression piston in your engine and having your bbo heads machined.
The sbo heads are going to be restrictive on a big block. Not flowing enough for the bbo to be worth the swap.
The smaller chambers might raise cr a little but without the air in. I just don't seeing it working well.
The sbo heads are going to be restrictive on a big block. Not flowing enough for the bbo to be worth the swap.
The smaller chambers might raise cr a little but without the air in. I just don't seeing it working well.
February 28th, 2010, 07:50 AM
#5
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Join Date: Mar 2008
Location: Phx, AZ
Posts: 1,012
Port volume is NOT the concern, here. Port obstruction is. He did say ported.
You will have to raise the intake port .300" (at the manifold entry point) for this to be a viable swap. This is an awful lot of material to remove by hand, although very possible. Even still, the intake port will usually be around 10-15cc smaller due to the lack of arch in the roof (unless you can port that in equally also). The casting can take it, we have done it.
Both heads are from the same design with a few differences. SBO castings have been ported to flow in excess of 270 cfm on the intake side, ours ended up being around 240/250 cfm-bad port/good port. Enough to feed a BBO, even our 430" engine. Small valve BBO heads usually flow 205 cfm, at .500 lift, stock.
Valve sizes (intake, and exhaust) must be increased from stock size (obviously you know that).
We have done this in the past with excellent results,although we had started the process by having my brother remove most of the intake port material out on a large mill. The intake port roof (in the MIDDLE of the port, not the entry) was still a slight bit shorter than a std big block cylinder head, but the heads flowed well enough, and we ran it successfully on our car years ago.
You will get a 1 point boost on compression.
You can still use factory valve train parts (as long as you do not use any 78 and up rocker arms).
You will have to open up one of the alignment pin holes in the head, to bolt it on the other engine. Why does everyone forget this part?
It will cost some money for porting the head, correctly. Do the bowls too, plug the crossover, big valves. Your gonna be around 1000-1100 U.S. dollars (complete set of heads with new springs, retainers, valves, etc.) to do this right, unless you are able to do NICE port work.
The point of compression is nice, but it is easier to get a set of pistons, than to do this. If you do not have a set of BBO heads available, it is by FAR less expensive to get the correct heads. If you are redoing old heads with new parts, want to bump compression on an older build, and have access to a machine shop (i.e. mill, AND hand grinding equipment), then you MIGHT consider it.
My opinion.
Jim
You will have to raise the intake port .300" (at the manifold entry point) for this to be a viable swap. This is an awful lot of material to remove by hand, although very possible. Even still, the intake port will usually be around 10-15cc smaller due to the lack of arch in the roof (unless you can port that in equally also). The casting can take it, we have done it.
Both heads are from the same design with a few differences. SBO castings have been ported to flow in excess of 270 cfm on the intake side, ours ended up being around 240/250 cfm-bad port/good port. Enough to feed a BBO, even our 430" engine. Small valve BBO heads usually flow 205 cfm, at .500 lift, stock.
Valve sizes (intake, and exhaust) must be increased from stock size (obviously you know that).
We have done this in the past with excellent results,although we had started the process by having my brother remove most of the intake port material out on a large mill. The intake port roof (in the MIDDLE of the port, not the entry) was still a slight bit shorter than a std big block cylinder head, but the heads flowed well enough, and we ran it successfully on our car years ago.
You will get a 1 point boost on compression.
You can still use factory valve train parts (as long as you do not use any 78 and up rocker arms).
You will have to open up one of the alignment pin holes in the head, to bolt it on the other engine. Why does everyone forget this part?
It will cost some money for porting the head, correctly. Do the bowls too, plug the crossover, big valves. Your gonna be around 1000-1100 U.S. dollars (complete set of heads with new springs, retainers, valves, etc.) to do this right, unless you are able to do NICE port work.
The point of compression is nice, but it is easier to get a set of pistons, than to do this. If you do not have a set of BBO heads available, it is by FAR less expensive to get the correct heads. If you are redoing old heads with new parts, want to bump compression on an older build, and have access to a machine shop (i.e. mill, AND hand grinding equipment), then you MIGHT consider it.
My opinion.
Jim
Last edited by Warhead; February 28th, 2010 at 08:47 AM.
February 28th, 2010, 11:21 AM
#6
Port volume is NOT the concern, here. Port obstruction is. He did say ported.
You will have to raise the intake port .300" (at the manifold entry point) for this to be a viable swap. This is an awful lot of material to remove by hand, although very possible. Even still, the intake port will usually be around 10-15cc smaller due to the lack of arch in the roof (unless you can port that in equally also). The casting can take it, we have done it.
Both heads are from the same design with a few differences. SBO castings have been ported to flow in excess of 270 cfm on the intake side, ours ended up being around 240/250 cfm-bad port/good port. Enough to feed a BBO, even our 430" engine. Small valve BBO heads usually flow 205 cfm, at .500 lift, stock.
Valve sizes (intake, and exhaust) must be increased from stock size (obviously you know that).
We have done this in the past with excellent results,although we had started the process by having my brother remove most of the intake port material out on a large mill. The intake port roof (in the MIDDLE of the port, not the entry) was still a slight bit shorter than a std big block cylinder head, but the heads flowed well enough, and we ran it successfully on our car years ago.
You will get a 1 point boost on compression.
You can still use factory valve train parts (as long as you do not use any 78 and up rocker arms).
You will have to open up one of the alignment pin holes in the head, to bolt it on the other engine. Why does everyone forget this part?
It will cost some money for porting the head, correctly. Do the bowls too, plug the crossover, big valves. Your gonna be around 1000-1100 U.S. dollars (complete set of heads with new springs, retainers, valves, etc.) to do this right, unless you are able to do NICE port work.
The point of compression is nice, but it is easier to get a set of pistons, than to do this. If you do not have a set of BBO heads available, it is by FAR less expensive to get the correct heads. If you are redoing old heads with new parts, want to bump compression on an older build, and have access to a machine shop (i.e. mill, AND hand grinding equipment), then you MIGHT consider it.
My opinion.
Jim
You will have to raise the intake port .300" (at the manifold entry point) for this to be a viable swap. This is an awful lot of material to remove by hand, although very possible. Even still, the intake port will usually be around 10-15cc smaller due to the lack of arch in the roof (unless you can port that in equally also). The casting can take it, we have done it.
Both heads are from the same design with a few differences. SBO castings have been ported to flow in excess of 270 cfm on the intake side, ours ended up being around 240/250 cfm-bad port/good port. Enough to feed a BBO, even our 430" engine. Small valve BBO heads usually flow 205 cfm, at .500 lift, stock.
Valve sizes (intake, and exhaust) must be increased from stock size (obviously you know that).
We have done this in the past with excellent results,although we had started the process by having my brother remove most of the intake port material out on a large mill. The intake port roof (in the MIDDLE of the port, not the entry) was still a slight bit shorter than a std big block cylinder head, but the heads flowed well enough, and we ran it successfully on our car years ago.
You will get a 1 point boost on compression.
You can still use factory valve train parts (as long as you do not use any 78 and up rocker arms).
You will have to open up one of the alignment pin holes in the head, to bolt it on the other engine. Why does everyone forget this part?
It will cost some money for porting the head, correctly. Do the bowls too, plug the crossover, big valves. Your gonna be around 1000-1100 U.S. dollars (complete set of heads with new springs, retainers, valves, etc.) to do this right, unless you are able to do NICE port work.
The point of compression is nice, but it is easier to get a set of pistons, than to do this. If you do not have a set of BBO heads available, it is by FAR less expensive to get the correct heads. If you are redoing old heads with new parts, want to bump compression on an older build, and have access to a machine shop (i.e. mill, AND hand grinding equipment), then you MIGHT consider it.
My opinion.
Jim
I have a 442 with a 455, forged small dish TRW:s and E heads and a set of really nice, ported 5 heads with 62 cc:s for a stout 350 engine beside.
Best regards, and thank you for the best technical car forum I have ever joined.
Stanley
February 28th, 2010, 05:07 PM
#7
Registered User
Join Date: Nov 2008
Location: Central Fl
Posts: 7,973
Thank you for your answer. I was only curious if somebody had tried this for real. I don´t have a plan to do this swap but its interesting´to know because the most of the readily (for example TRW:s) available flat top pistons for a 455 can only an manage a 10.5 static compression (probably less) with stock big block heads. It´s a tempting idea to put a pair of good 5 heads flowtested with big valves for 236cfm at .600, with small 62 cc compression chambers to rise the compression to maybee 11:5. This opens up a lot of interesting opportunities.
I have a 442 with a 455, forged small dish TRW:s and E heads and a set of really nice, ported 5 heads with 62 cc:s for a stout 350 engine beside.
Best regards, and thank you for the best technical car forum I have ever joined.
Stanley
I have a 442 with a 455, forged small dish TRW:s and E heads and a set of really nice, ported 5 heads with 62 cc:s for a stout 350 engine beside.
Best regards, and thank you for the best technical car forum I have ever joined.
Stanley
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