My new Pponk engine build will have venture intake seats. Should I expect much performance diff from the straight seats?

You're kidding, right?

Call P-Ponk and tell them you want straight seats.... and see what they say

I dont have much luck reaching Steve by phone or e-mail, just relying on the advice of one of his approved engine builders. What's your 2 cents?

The science behind Venturi valve seats is good and in theory it *should* provide some bang for the buck. I believe ECI is the only choice for a certified bird to get Venturi valve seats, and they did not invent the technology, they borrowed it from the auto and motorcycle world.

I suspect that like many engine mods, on it's own you will no notice a marked improvement, in fact if the change was significant than ECI would have had to document that change and it would have been subject to FAA testing and approval. But combine it with better port work, and more meticulous balancing of the reciprocating mass, and now you start to notice things... I chose that route because of the port shape of the ECI's vs the competition. Their ports are better flowed right out of the box, and if you are not having any port work then that is a bonus. BTW, Port and polish work by someone without a flow bench and years of experience is a good way to burn a boat load of cash...

Now beyond all my opinion stuff... You are getting this directly from the one guy who knows Pponk engines better than anyone else... He has built and tested them in more configurations, and continues to do so. I can't imagine in assembling an engine for a customer he gets a significant enough profit difference in your cylinder choice to blatantly make up horse power differences, and yet he shows a difference between the Venturi and straight seats.

Have fun with your new engine, it is going take you smile