ProComp/Speedmaster aluminum heads

As Ive said previously about these heads.......
The set of SBM assembled SM heads I had in the shop this spring had no problems with the guide clearance or seat runout.
The dual springs that they can with wouldn’t have been suitable for a solid cam imo, but they were fine for the hyd cam that was used with the heads.
2 springs tested low, and those got shimmed up to make the loads equal to the others.
The valve seals fit the guides very poorly....... and had they not been replaced, the motor would have def had an oil consumption issue.

One of my customers uses quite a few Chinese SBC heads. He buys them bare along with a parts kit, brings everything over...... i check everything over, correct any issues I find, and put them together.
In the last several years, I have had very few guide clearance or seat runout issues for these heads.

On a pump gas 406 with an off the shelf solid cam, rpm type intake....... those SBC heads make right at about 500hp.
Easy peasy.