I left the heat riser functioning when I did the last rebuild, I live in Colorado and do drive in the cold. I was thinking about it last night and I don't think the heat riser is necessary with EFI, and i should block it to slow the heat soak what say you forum?

 

Bump

 

Can I ask why you think it's not needed? My thoughts are that's it's doing the same job as a carb, but possibly with less atomization. Port injection I would say no, but with this I'd like to hear what others had to say as well.

 

In a carb app it's there to keep the carb from freezing on cold days, which i don't know if it applies to the high pressure efi or not. Also the turbo is pushing warm air most of the time, i really don't know. That's why i'm asking. Most performance builds run a block or restrictor plate.

Also i wonder if i can run a restrictor plate with a smaller orifice, since the exhaust is a lot more restricted than a normal performance build.

 

Good points. Do factory tbi setups run one?

 

I have no idea

 

Early tbi used it. There's a few stock Camaro's with tbi 305's and 350's that still have the heat riser pipe. I think the trucks used it too. Probably more to help emissions than anything else.

 

The GM throttle body trucks had the tube from the manifold to the snorkel on the breather, but I don't think they had the flap in the manifold. I can't remember ever seeing one with the flap.

That being said, even the stuff with port injection used coolant through the throttle body to warm the incoming air. Albeit most likely for emissions as mentioned above.

My junk with Holley EFI on E85 will start with temps in the teens with no problems. It runs a little rough when it first fires, but if I were a better tuner I could fix that. I personally wouldn't worry about a heat riser.

 

Alright, I'll try a full delete and see if it acts ok. It will still have coolant running through and if it drives poorly in the cold i will drill the delete.