Machine shop must measure these what ever brand heads you Buy!!!!!

I am really curious how this works out for you. I have been debating leaving these 502s alone and upgrade my 454s with these heads. Those are gen vi mag 454 short blocks with 500EFI heads and cams. They do well, but if the stuff I am reading is accurate, those heads are probably good for another 100hp.

The straubtech trick rocker you speak of works great! Scott Foxwell is the guy behind the design of those rockers..

I used the same promaxx heads and was able to get good geometry on my 454 builds. I used the same crane rockers. I do think the Staub rockers design looks good. I just bought all my top end components from Teague and they use the cranes with a good track record.

Without Scott Foxwell designing those those rockers for those heads Straub would not be selling that rocker. So far I have not had any problems out mine for my 2 555's.

I believe they had Harland Sharpe make them.
Many used the Crower ones that worked well and they got the idea from.
ie: pushrod cup moved a tad. Something like .100” ? Don’t remember full details

Correct Harland Sharp does make them. Scott Foxwell used to work for Straub and designed the rocker. Long story short he does not work for him anymore.
Scott said he contacted Harland and had them start making them. this was X amount yrs ago. My 555's have a set of Promaxx's 317's on them that Scott built for me 2 yrs ago and did some minor bowl blending. they had 2.25 intake valves at that time. Now they have 2.30 intake valves And engines were freshened up last yr and were dynoed. 704.9 HP @6100 677.1 Tq @4900. Best I've seen with my old 92' 35' fountain on GPS was 86.5 MPH.

There is def some drama over this.

What rpm did you end up propping the engines?

I'm sure it really work for you ..and the Promaxx heads really perform.

I crunched the Cross Sectional Area...CSA for the 2.3" valves. At 90% thrpaut dia...you have a 3.59sqin throat (less valve stem dia). 2.25" valve is 3.44sqin.

Your 555 at 6100 rpm wants 3.11sqin CSA.

This would mostly reduce port velocity at your lower rpms for cruising.

The Promaxx heads are more focused on big inch high rpm. Nothing wrong with that...perf marine often gets the back seat.

Some great NA power numbers for sure.

Did I miss your cam specs?

Longer story short, many of us here knew him well before Foxwell did. Took forever for Foxwell to, well, see the light. Doh !