Heat riser - necessary? 1994 TBI 350

[R422b]

The big question is how restrictive is the fender itself?

You know you have a problem when you go to pass a ford and your fender collapses from the suction. [emoji1787]

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[Mindtriped]

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I forgot to mention I live in S. Florida so no worries of cold starts. I also cut the air cleaner base for a salad bowl and have the k&n filter top.

 

[thinger2]

Hello friends,
I have always wanted to know, is the heat riser really necessary on these TBI motors? For example, you see lots of folks flip the lids on their air cleaner housings, which would completely negate the heat riser. I even drove my '95 TBI 305 GMC for a year with the lid flipped and it ran fine year round, which tells me the heat riser is perhaps nice...it helps a little on cold starts...but that's it?
Do folks ever delete them just to clean up the engine bay?
I'm getting ready to do some tune-up and clean up on my 1994 Z71 and I'd love to know prior to getting my hands dirty.
Thanks.

Odd, I thought 94s all had the "dryer vent" tube and no flapper.
Either way that system does some pretty important things for you.
When you start an engine the first thing that gets hot real fast is the exhaust side of the head.
Thats why any type of heat riser comes off of the exhaust.
So engineers use that otherwise lost heat to bring the carb/TBi/whatever
to a point where it can function.
This also helps to heat the intake faster through the high idle process on an obd 2
A TBI will freeze.
It just depends on where you live and the weather.
If you take a bunch of short trips,
Ten minutes here, 15 minutes there.
Then you go to do an oil change and the cap is full of crud?
Thats just water emulsion.
But its still water.
If you live in the Northwest,
Its pretty mild but wet as hell.
It is like driving in a dishwasher.
And sometimes it goes from 40 degrees to 20.
And as oil cools, it sucks in moisture
Chuck some ethyalted corn 10% water retaining gas into the mix
Keep that heat tube .
Carb iceing and intake iceing
And injection iceing
The dryer vent is a pretty cheap
They didnt put it on cuz it looked cool,
That little hose uses the heat off of the exhaust and that hot air rises as hot air will do and it heats the throttle body and the air as is passes through the intake.
And yes, in the right circumstance it does de-ice the throttle body.
Just like the old door flaps would de-ice a carb.
keep it.
Just cuz its cheap and a pain doesnt mean you dont need it.
Keep it

 

[LVJJJ]

Hi thinger2, I'm not in Lawrence Kansas, that's where I was born. I actually live in Blaine, somewhat north of you in Tacoma. (I've tried to change the location but haven't been able to figure it out). Been here since 1962. I have removed every heat tube on every truck I've had. Never had any problems. Did that on my 1988 3/4 ton Suburban with a 454. Also had dual air intakes. It just seems to me when you are towing up a 6% mountain pass you need as much cold air as you can get.

 

[CrustyJunker]

I know there's plenty of contributors, but here's my real world TBI experience:

Summarized - I did almost everything you're "not supposed to do," and have yet to have throttle body icing that was harmful or problematic. I haven't actually pulled my lid off and proven or seen said "icing." I've driven quite a few days/nights below 0°F, coldest cold start to date being -17°F. No ill effects! If anyone wants details, I'll share.

 

[Pinger]

How does doubling the surface area exposed to engine bay heat, doubling the hot contact area of the incoming air and slowing to half the incoming air speed (through the ducts) provide 'cooler' air?

If the aim was to maximise transmission of engine bay heat to incoming air, that's how you'd go about it.

 

[R422b]

How does doubling the surface area exposed to engine bay heat, doubling the hot contact area of the incoming air and slowing to half the incoming air speed (through the ducts) provide 'cooler' air?

If the aim was to maximise transmission of engine bay heat to incoming air, that's how you'd go about it.

Yeah. I was thinking something that insulates better than aluminum would probably be a good idea too.

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[badco]

I had to write a letter to GM about flipping the lid over when I was in high school and shop teacher seen it.

They answered with a yes on performance increase and even mpg but it would not pass a emission test and could have issues in real cold weather was their answer. Ive never had a issue on mine but I've only been in real cold once in my 90 but still had no issue. As far as air flow you can put a 8" stove pipe out your hood and it shouldn't affect it negatively at all. Now the spacer under air cleaner is a necessary evil. If it is removed to use a normal type carb air cleaner the fuel spray from injector is disrupted and doesn't run to good and always have fuel smell.

 

[Southwest ORV]

I had to write a letter to GM about flipping the lid over when I was in high school and shop teacher seen it.

They answered with a yes on performance increase and even mpg but it would not pass a emission test and could have issues in real cold weather was their answer. Ive never had a issue on mine but I've only been in real cold once in my 90 but still had no issue. As far as air flow you can put a 8" stove pipe out your hood and it shouldn't affect it negatively at all. Now the spacer under air cleaner is a necessary evil. If it is removed to use a normal type carb air cleaner the fuel spray from injector is disrupted and doesn't run to good and always have fuel smell.

That's interesting! Do you still have that letter? I'm sure we'd love to see a copy of it.