ironhead88

I'm wondering what other guys have discovered to be true with the effect of blocking or restricting the heat riser and crossover passage on the intake manifold.
I've tried it both ways, but I've never done a controlled experiment where the crossover passage is the only variable that was changed. So I'll have to admit that I really don't know.
This would be for a Performer intake application, With a carb BTW
I have read various articles on the subject, and read some online discussion, but there aren't any articles where they actually did a side by side comparison on the same engine. So it still seems unresolved
What I read though, is that just as everything else, there's a trade-off.
Wtih the heat riser / crossover, we get better atomization particularly during warm-up ...at the expense of charge density.
If an automatic choke is used the choke stays on longer and fuel consumption is supposedly greater without the riser

Fast355

iTrader: (2)

I swapped a performer rpm onto my old G-van years ago with the heat riser passage way blocked off. My 83 Q-Jet had an electric choke which does not rely on the heat from the crossover at all. By the time the choke came off about 90 seconds after startup the engine was already running smoothly. I had headers so no EFE valve. I did have a TBI preheated air cleaner and a piece of pipe welded to one of the header primaries for heat to the air cleaner. My carb was jetted slightly richer than factory but my mileage was actually better. The factory carbs on those trucks were jetted lean and EGR was used to compensate which caused mileage to tank​​​​​​.

ironhead88

Good information
So your fuel consumption was good too.
I have a Q-Jet as well
I'm trying to build something that will be fun but still burns 87 pump gas and gets good economy at cruise