big block heads on small block
January 31st, 2010, 08:33 PM
#42
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Join Date: Jan 2010
Posts: 33
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i did. Typical ROP people, no wonder they have the rep they do all over the Olds community. But no worries My dad and I have been told for years BBO heads don't fit on a SBO and with all the other BS people have said it is just the norm anymore.
i did. Typical ROP people, no wonder they have the rep they do all over the Olds community. But no worries My dad and I have been told for years BBO heads don't fit on a SBO and with all the other BS people have said it is just the norm anymore.
February 1st, 2010, 05:41 PM
#43
Registered User
Join Date: Mar 2008
Location: Phx, AZ
Posts: 1,012
Don't bother-here is a pic.
Gasket is a Mr Gasket BBO part #404.
It is set on the manifold correctly, same direction as manifold face.
If you zoom in you can see how close to the runner opening is to the top lip of the manifold surface.
Manifold may be an old used Holley 300-16 unit, but port openings are untouched by any grinders and old gasket residue gives a sobering visual as to where things really are.
Most of the people on ROP are decent,
Do not let a few bad apples spoil your lunch.
Let's try to keep things on a positive note.
Jim
Gasket is a Mr Gasket BBO part #404.
It is set on the manifold correctly, same direction as manifold face.
If you zoom in you can see how close to the runner opening is to the top lip of the manifold surface.
Manifold may be an old used Holley 300-16 unit, but port openings are untouched by any grinders and old gasket residue gives a sobering visual as to where things really are.
Most of the people on ROP are decent,
Do not let a few bad apples spoil your lunch.
Let's try to keep things on a positive note.
Jim
Last edited by Warhead; February 1st, 2010 at 05:59 PM.
February 1st, 2010, 08:28 PM
#44
Registered User
Join Date: Dec 2008
Location: Somerset Wisconsin
Posts: 1,167
Oldsman71, Cool cars, awesome engine compartment. I'm glad you came back.
Warhead, Stupid question time. As long as the head ports are larger why wouldn't a guy leave a little extra intake material on the manifold to keep the integrity of the manifold? In actual HP numbers wouldn't it be a very small loss only at very high rpm? Is there a chance that Oldsman71's engine builder did just that?
Warhead, Stupid question time. As long as the head ports are larger why wouldn't a guy leave a little extra intake material on the manifold to keep the integrity of the manifold? In actual HP numbers wouldn't it be a very small loss only at very high rpm? Is there a chance that Oldsman71's engine builder did just that?
February 2nd, 2010, 01:56 PM
#45
Registered User
Join Date: Mar 2008
Location: Phx, AZ
Posts: 1,012
Not a stupid question, a very good one.
Yes you can do that, with only a small loss in power.
Notice that even Holley made the ports smaller than the port opening to the standard small block Oldsmobile cylinder head, as do most manufacturers. In fact many people (including Dale-GMrocket on his beeter 403 project a few years ago) use the RPM Performer on BB heads without enlarging to the BB port size, on their small blocks.
The real issue is with using this manifold (and most others) is that even without porting, there is still not enough material above the runner, to keep the gasket in place. The top of the manifold surface is only about 60-80 thousandths above the cylinder head port opening.
Most of the time, it will squeeze some when torqued down, causing a major vacuum leak.
I am glad that oldsman71 has not had issues here, but if I were building this for someone, I would use a manifold with more material at the top of the runner, or modify one to support the top part of the gasket opening better than this, so they would not come back pissed when the gasket does let go.
I have done this both ways, just trying to help others to not go through- what I had to learn the hard way.
My opinion,
Jim
Yes you can do that, with only a small loss in power.
Notice that even Holley made the ports smaller than the port opening to the standard small block Oldsmobile cylinder head, as do most manufacturers. In fact many people (including Dale-GMrocket on his beeter 403 project a few years ago) use the RPM Performer on BB heads without enlarging to the BB port size, on their small blocks.
The real issue is with using this manifold (and most others) is that even without porting, there is still not enough material above the runner, to keep the gasket in place. The top of the manifold surface is only about 60-80 thousandths above the cylinder head port opening.
Most of the time, it will squeeze some when torqued down, causing a major vacuum leak.
I am glad that oldsman71 has not had issues here, but if I were building this for someone, I would use a manifold with more material at the top of the runner, or modify one to support the top part of the gasket opening better than this, so they would not come back pissed when the gasket does let go.
I have done this both ways, just trying to help others to not go through- what I had to learn the hard way.
My opinion,
Jim
Last edited by Warhead; February 2nd, 2010 at 02:02 PM.
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