Do hardened Exhaust seat lower head cfm?

[Joe C.]

Re: You will not beat the Vortec heads

You can do it yourself. More satisfaction that way.
When you send them out, be sure to have them flow test the same cylinder both before/after porting. They should add a stub pipe to the exhausts and a section to the intake to simulate manifolding both upstream and downstream. Both tests should be done at 25 or 28 inches water column, preferably 25 inches.

Joe

[Joe C.]

Re: You will not beat the Vortec heads

You can do it yourself. More satisfaction that way.
When you send them out, be sure to have them flow test the same cylinder both before/after porting. They should add a stub pipe to the exhausts and a section to the intake to simulate manifolding both upstream and downstream. Both tests should be done at 25 or 28 inches water column, preferably 25 inches.

Joe

[Werner M.]

Re: Do hardened Exhaust seat lower head cfm?

I'd like to echo Duke William's closing comments on installing hardened valve seats. They are not required on street engines unless operated under extreme conditions; specifically unless you plan to operate the engine at 80% throttle, above 3500rpm for extended periods (hours), you needn't be concerned with valve seat recession. To meet the above listed conditions, you'd have to tow your Airstream across the desert at speeds above 85 mph. Not likely use for a Corvette.

While there is usually no harm done when installing hardened seats (other than needlessly lightening ones wallet), we've encountered two situations where machining the pockes for the inserts exposed the water jacket (probably due to core shift and/or casting porosity). This occured on a '66 425hp and a'67 350hp engine. Overheating problems manifested themselves, that were eventually corrected by replacing the affected head casting.

[Werner M.]

Re: Do hardened Exhaust seat lower head cfm?

I'd like to echo Duke William's closing comments on installing hardened valve seats. They are not required on street engines unless operated under extreme conditions; specifically unless you plan to operate the engine at 80% throttle, above 3500rpm for extended periods (hours), you needn't be concerned with valve seat recession. To meet the above listed conditions, you'd have to tow your Airstream across the desert at speeds above 85 mph. Not likely use for a Corvette.

While there is usually no harm done when installing hardened seats (other than needlessly lightening ones wallet), we've encountered two situations where machining the pockes for the inserts exposed the water jacket (probably due to core shift and/or casting porosity). This occured on a '66 425hp and a'67 350hp engine. Overheating problems manifested themselves, that were eventually corrected by replacing the affected head casting.

[Duke W.]

Re: Do hardened Exhaust seat lower head cfm?

The protective effects of the slight lead oxide deposit buildup on exhaust valve seats from TEL occurs quickly and is fairly long lived.

Therefore, if you absolutely, positively believe you need the valve seat protection benefits of TEL, add some 100LL avgas or leaded racing gas once in a while, and it's not a bad idea to do the same on a fresh engine.

Duke

[Duke W.]

Re: Do hardened Exhaust seat lower head cfm?

The protective effects of the slight lead oxide deposit buildup on exhaust valve seats from TEL occurs quickly and is fairly long lived.

Therefore, if you absolutely, positively believe you need the valve seat protection benefits of TEL, add some 100LL avgas or leaded racing gas once in a while, and it's not a bad idea to do the same on a fresh engine.

Duke

[Duke W.]

Re: You will not beat the Vortec heads

I prefer seeing exhaust flow data without a pipe extension, since this most closely replicates the OE manifolds.

The most common depression used is 28", but it's easy to covert 25" data since flow is proportional to the square root of depression.

On the inlet side it is common to use clay to from a lip on the upstream boundary of the inlet port to eliminate the turbulence that is formed from the sharp edge, which is not the case when the manifold is installed, assuming the manifold and head ports have been matched at the interface.

Duke

[Duke W.]

Re: You will not beat the Vortec heads

I prefer seeing exhaust flow data without a pipe extension, since this most closely replicates the OE manifolds.

The most common depression used is 28", but it's easy to covert 25" data since flow is proportional to the square root of depression.

On the inlet side it is common to use clay to from a lip on the upstream boundary of the inlet port to eliminate the turbulence that is formed from the sharp edge, which is not the case when the manifold is installed, assuming the manifold and head ports have been matched at the interface.

Duke

[Dave Suesz]

To add to the comments about 3 angle...

I have never seen replacement inserts which were not already manufactured as "3-angle" seats. There may have been some, but I've never seen them. Last time I had work done on my "driver", which had over 300,000 miles at the time, I had the heads off, so I had them looked at. I was told they needed 5 inserts, so I had all 16 done. Now, I port-matched the exhaust before installing the heads, so I wonlt make any specific claims for the inserts, but the engine was a tiger when I hit the road, much smoother, and noticeably more power, even though the cam, intake, distributor, and exhaust system were undisturbed.

[Dave Suesz]

To add to the comments about 3 angle...

I have never seen replacement inserts which were not already manufactured as "3-angle" seats. There may have been some, but I've never seen them. Last time I had work done on my "driver", which had over 300,000 miles at the time, I had the heads off, so I had them looked at. I was told they needed 5 inserts, so I had all 16 done. Now, I port-matched the exhaust before installing the heads, so I wonlt make any specific claims for the inserts, but the engine was a tiger when I hit the road, much smoother, and noticeably more power, even though the cam, intake, distributor, and exhaust system were undisturbed.