heatriser blockoff plate

has anyone noticed a difference with this blockoff plate?

And by "this" block-off plate, you mean? (Did you mean to attach a picture?) I'm curious about this thread because I've been thinking of blocking-off the heat-riser... I'm assuming people do such things..

i can't attach a pic but its the metal plate in between intake n exhaust manifold

I think a simple plate would work pretty good to block most of the heat (assuming you don't drive your slant when it is cold outside). But imagine the exhaust manifold flow is uglier than need-be. I used to have a /6 exhaust manifold where someone chopped off the heat-riser and welded it shut. The nice thing about that is the flow of the exhaust was probably much smoother than would be obtained by just using a plate. But... hey, I imagine the plate is better than no plate (assuming you never run cold).

... that said... I'm just hoping to eat pop-corn and listen to what other people think... I don't know much --just enough to make foolish speculations.