Hey guys, I have an 86 Z28 with a 350, 300 hp, looking to convert the round air filler to the factory TPI style snorkel with carb hat and tubing. Has anyone done this? Is it a worthwhile mod? My car runs hot and thought this would be better. Looking for advice.

thanks

 

It is always a good thing to get outside air into the engine. I am not sure if the hats currently sold can support that power level.

 

Interesting, I’m not sure what to do.

 

These guys might have something you'd like.

www.ramairbox.com

 

I bought a proform carb hat to try someday for myself But honestly there is more to it than just ducting cold air. Pipe/duct material heatsoak, engine bay venting, tight turns. fuel temp & intake heatsoak. I'll leave the ducting to EFI or boosted apps for now.

 

i would put a stock type air filter assembly on it. think of the carb/tpi inlet like the drain in a sink where all the water draining goes into the hole from all directions. if you put up a wall around half of the drain, that is how it would flow through an elbow. -not as good.

 

I did this and a bunch of experimenting before settling on what finally worked. I found stock v6/TPI intake plastic components in a scrap yard but the hardest part was the "hat" portion on top of the carb. I spent a LOT of time figuring out how to make it work decent, and ultimately I cant say it made any difference over the old open filter element that drew hot air from around the carb. I recommend just sticking with an open element or buying a complete aftermarket intake designed for carbs. Here are a few notes that might help you though.

-I tried several aftermarket "hats" on top of the carb and even welded my own together. The issues had to do with hood clearance and adequate airflow. Most of the aftermarket stuff did not flow enough air and created so much air restriction that it choked my mostly stock 305. Some replies above allude to this and are 100% correct.
-I ended up using a large aluminum aftermarket carburetor air filter housing found on Wal-Mart website and shipped from 3rd party. This was the only way I could avoid an air restriction and allow for clearance. It was a two piece air intake hat and I had to insert a steel mesh support inside to make it sit right since it was designed to hold a traditional carb air filter inside (I used the TPI/v6 air filters in the plastic intake housing for filtration instead, mounted in the plastic TPI housing in front of the radiator).
-I bought a 3" flexible air intake duct to attach the carb hat to the TPI plastic outlet. Bought a rubber reducer since the aluminum carb hat had a 4" inlet.
-I already was using a radiator top bracket that I had made myself out of steel. I had to modify it slightly to allow the plastic TPI intake to lay flat over the radiator. Probably not an issue if you are using a simple factory plastic radiator bracket, but if you have an engine driven fan shroud it would probably be a problem.
-Engine did not seem to run any cooler, even though the end result drew cool air from the front of the car vs the open element drawing hot air off the engine. No surprise there though, because engine cooling is primarily a function of sufficient airflow over the radiator and not so much temperature of intake air or volume of water in the system.

I cant seem to find any pictures on my phone and I'm away from home this week. I dont recommend the modification though. I did it for the heck of it and found it was not worth the trouble.

 

why not run one of these with 2 ducts to wherever you want?

 

When I originally bought my car, it still had the OEM air filters mounted forward of the rad with the air intake going over the rad. Previous owner had swapped out the 5.7TPI engine for a carbed 383. He used an old carb air cleaner to fabricate it into a snorkel feed from the front air intake. Looked real nice but was also very restrictive. Since I bought the car to make it into a race car, all that junk got removed and a 14" open element air filter was installed on the carb. A low profile base allowed the filter to fit under the hood.

 

Didnt the later trucks / S/10 use that style? You could get the hat from those then connect it up to the TPI junction / boot

 

The TBI and MPFI throttle body installations had an air horn closer in size to a 2-barrel carb. A converted stock air cleaner housing is probably a good starting point, and non-metallic ducting for the inlet air will minimize heat transfer from the usually hot underhood air.

 

I’m going to give it a try, I know someone selling a carb hat setup. I’ll post back with the results in the spring. Thanks for all the advice!

 

I had a fairly low profile spectre with a 4" air duct on my Express van on top of a dual plane mpfi intake and 1000 cfm 4bbl throttle body. Even though it was low profile it breathed well enough to make ~550 hp. The stock extremely low profile Vortec van air hat with its 3.25" ID and 80mm throttle body was enough to make ~500 hp.

My old G20 with TBI made ~425 hp at the crank with a FWD Caddy intake hat.

A 300 hp 350 is only moving about 500 cfm of airflow. I have made 240 hp on the primaries of a Q-Jet which IIRC are about 275 cfm.

 

Looks like this has been covered pretty well. My idea for the piping has been to set it up with pvc pipe. Then wrap the whole thing in aluminum foil and remove. Then overmold carbon fiber on it and slip out the pvc. Now you have Carbon Fiber piping, can't get any lighter and won't heat soak. To make elbows you can carve a chunk of foam and use that as a mold.

The biggest issue for me is the carb hat. Because it comes down to the distance between your carb/throttle body and hood. That can disclude may of the good hats/elbows.

 

a flat base inlet will make more power n/a than an elbow.

 

Picture of upper radiator support



TPI/v6 intake



Air filter housing (no air filter inside)



Old open air element


Here are pics of the setup I put together. What you cannot see is the metal mesh I had to insert in the aluminum carb air filter housing to support the two pieces since there is no air filter inside. Again, I actually dont recommend this. The old open filter element (last picture) performed exactly the same and is much more simple. An open filter element or premade dual snorkel system would be a much easier way to go I think.

 

An observation and a question.
From one fellow in particular who has tested the TPI intake housing, the restriction is the 3" pipe. Flow tests have shown than when the case volume is increased by 1/2" or so and adapted to a 4" pipe (to a forward facing TB by the way), even with the two panel filters in place, CFM is more than enough to supply the testers HP targets of 500+/-.



Something like 1000 CFM at 28".

Now, the question is where did that blank aluminum filter case come from? If that's a 4" inlet, I'd say modifying the TPI housing as Chad has done in the picture above would net strong results.

 

The aluminum carb filter housing was found on Wal-Mart.com and shipped from whatever vendor was selling it in their website at the time. I tried to find it again there before I wrote this but no luck.

The restriction issues I had were all to do with the housing mounting on top of the carb, not the TPI intake itself. This aluminum housing solved that. Of course it is just a 305 and demand for air is relatively low..

 

I tried this years ago too. Had to use a Spectre low profile carb hat to clear the hood. Problem was it didnt leave much room between the choke horn and the top of the carb hat. Didnt take long to swap back to open element.

Also Engine Masters done an interesting test on a carbed motor with heating and cooling the intake and air charge. Had air inlet temp data at the carb entrance and in the runners. IIRC they found that the real power gain was just in keeping the fuel cold.

 

No, from a "my car runs hot" perspective, it's not worth while. The intake air temp will not affect the engine operating temp at all.

From a power perspective, it might help....depends if the current air filter is a restriction, and if you can get cool enough air, to exploit it with more timing. Might be good for a few hp, but not for engine cooling. Radiator cools the engine.

 

You are using a belt tensioner on the back side of a v-belt. Tell me more. How is this working out for you?

 

That was an experiment to reduce belt slop and chasing an a/c vibration issue. I determined the vibration was unrelated to that and fixed it. The belt slop itself didnt turn out to hurt anything either, but I just left the tensioner in place. Thousands of miles ago and no problems with it yet. The downside to its presence is another part with bearing inside to wear out and introduce a point of potential failure. Goes against my "simple is better" philosophy so I should probably take it out.

 

Thousands of miles ago and no problems with it yet.

 

Still very cool!

 

I think so too.
I'd like to see what the base of the closed "filter" case looks like. Is it dropped? Contoured?
Combining that with the modified (opened to 4") TPI inlet I think is probably the best available CAI these cars could have.
Speiers demonstrated some ram air effect as well as he went the step further with ducting in the fog light openings. His was a modernized version of the original tin ducting that was offered up years back.
CAI is on my to do list and I'd prefer this style above rather than incorporating my cowl hood with seals and a "cake pan". This way, the cowl may serve as an outlet for some of the hot air that accumulates.

 

For the OP, I finally found a link to the one I used.
https://www.spectreperformance.com/c...14-low-profile

 

The link above works but the product selection takes you to a dead end.
​​​​​​But some of what's shown looks very adaptable to the TPI filter assembly.

 

Just an update on my experiment with this.

I recently cleaned and made minor adjustments to my carburetor and afterwards noticed a slight hesitation when accelerating. It felt like the engine was short on air / restricted intake, but it was subtle. The dual TPI filters were still pretty clean so I tossed the open element assembly back on. Problem instantly solved, but I drove it multiple trips and a couple hundred miles with lots of hard acceleration just to confirm. Somewhere in that modified TPI system (probably the aluminum housing hat on top of carb) there is still some restriction. I'm done messing with it for now. Maybe I'll make a dual snorkel system later but I have no plans to retry the TPI snorkle.

Again, I don't recommend converting to TPI snorkle for carb.

 

What did you use on top of the carb again?
You mentioned "hat" although there's a picture of a closed filter "case" in one of your posts.
FTR, the hats, or 90° elbows do seem to present some restriction with the limited space for the air to turn.
For that matter, the air filter base has a lot to do with directing the air as well.
​​​​​​

 

I referred to it as a hat because a lot of people have started calling it that these days, but it is actually an aluminum carb filter housing with the TPI intake plumbing into the 4" opening. See pics above.

I'm actually surprised there was any noticeable restriction from it, especially since this is just a warmed over 305.

 

As posted above, from Chad Speier's testing (he's a cylinder head porter that had an IROC he experimented with) he found that the TPI housing was restrictive in stock form.
His approach was to split the housing along the seam and add a 1/2" of material in that "plenum" area. The outlet pipe was to increased to 4".
From what I can see of that blank filter case (with the 4" inlet), if you used a modified TPI intake with K&N filters, your restriction would disappear.

 

I'm guessing the desire was to keep a stock appearance/hood? Because if not then a 2" cowl induction hood works nicely with an open element, My 14x3 filter fits right up in the hood. But I understand the desire to make things look stock too.

 

There is something to the stock hood look. That's what Speier's managed to do.
I'm in the same boat as you with a cowl hood as I like that look. And even at only 1-1/2" tall, I've room for a 4" open element on top of an RPM Air Gap.
Ultimately though, the whole point of the cowl hood was to seal it with a pan to the filter case and build a functional cold air cowl hood intake system.
That said, if I could incorporate a modified TPI snorkel to an enclosed filter housing (with or without a filter depending on whether I use the TPI filters) I'd go that route and leave the open cowl to help remove some of the intense heat that builds up under there.