Anyone ever compare a single plane manifold with a 4bbl TB and a carb hat on it against the same manifold with either a standard EFI TB on it?

I have the manifold converted for injectors, a 4bbl accel TB but no hat and a few choices of stock EFI style TB's (TPI/LT1 2 bore style as well as LSx single bore style) but no elbow putting me in a 6 half dozen situation WRT to which to use, one way I need a carb hat, the other I need an elbow, so I might as well go with whichever will work better/run faster. I suppose that the 4bbl + carb hat might be easier to mount/route the ducting to it (not as fussy WRT to location and angles, more room for a thermostat housing), but the elbow+stock TB probably looks better and gives more places to mount stuff, no winner there.

 

I've seen several big name builders say that the 4bl TBs have better distribution than single blade TBs and an elbow under them.

 

I am with slow, I have read about the 4bbl TB and a hat being better for a carb intake since that's how they were designed to flow. If I was building something EFI it would either be an EFI long runner intake or a carb intake with a 4bbl TB and hat, not a single with an elbow.

 

The 4bbrl throttle body and hat for sure has better even air distribution over the single blade and elbow. The problem isn't the single blade but the elbow. Air flow through the elbow doesn't turn on the short side very well so most of the air will go towards the long end. There are ways to take care of this. Air diversion plates or a 4 hole spacer will do the same thing as the 4bbrl throttle body does.

The downside to the hat is the gasket or oring. You are trying to seal boost with one stud in the center and fight air leaks around the hat. Take your pick they both have issues.

 

Good point on both ends... which is also one of the reasons why I don't understand why "elbows" are made like elbows are... I'd probably be tempted to make something more plenum shape that extends past the flange in front and behind, to get rid of the smooth bend at the back dumping all the airflow to the back of the manifold, maybe a little lip inside the back of it over the flange.

Going as far as diversion plates to fix this seems like you're just asking for a tuning problem- you'd need to do a lot of testing and then finally only really tune it for a specific range where it would work well... doesn't seem like the best approach for a "street car"

 

A 4 hole spacer would net you the same straight air flow as the 4bbl throttle body. Run a spacer that has the tear drop style bottom upside down and it will look like the top of the 4bbl throttle body.

 

That's a good idea flipping it upside down, I went with a 4 barrel style throttle body though, supposed to transition better and operate at part throttle smoother for the street. I want to go fast but realistically ill be on the street %99 of the time.

 

You can thank me later.

 

I'm not sure I get it... I still don't think that it will work unless you have some sort of plenum chamber up above it, if you just bolt it between the manifold and elbow it might make things better but you'll still likely get more flow towards the outside of the bend in the elbow.

Sickspeed- hey Bernie, when did you start hanging out here, and better question, why?

 

The vortex swirl action is where its at!!

About a year ago I joined and not much has been happening since then except for me dreaming.

And then I just picked up an 010 block 355, 4 bolt main that has been bored/honed, align honed, decked, and has cam bearings and freeze plugs installed. I also have a balanced rotating assembly... 4340 eagle crank, eagle h beams, and speed pro forged aluminum pistons. It came with a roller comp cam, springs, pushrods, retainers/locks, and the wrong lifters for the old style block... so I need new lifters. And finally, I have some Dart Pro1 215cc heads with 76cc chambers (I think thats the chamber size... I bought it all from a friend and he said it's set up for 8.5:1, got a good deal and couldn't pass it up).

So I guess next on the adgenda is to start collecting fuel system parts, get the HSR, get and build the MS2, and get her running on fuel injection. Probably going to set it all up on the current cast 8.5:1 GMPP 260hp engine, maybe even the turbos too, just so I don't risk burning up the expensive stuff while I learn the ropes.

 

We have addressed this problem two different ways and both worked great. The first was to bend a flat plate that fit inside the elbow and basically divided the airflow into a front and back. Worked very well but was a bit of work to make fit then weld inside so it stayed put. The other solution was the carb spacer with the teardrop flipped up side down. The added benefit of the carb spacer was improved drive ability off boost. Either one will work. The plate inside the Elbow is the cheap way but takes time. The carb spacer is the expensive way but it's fast and easy. What do you have more of... time or money?

 

I generally act like I have more time which I usually have almost none of, I probably have more money, but usually when I spend the money on the "right" part I end up pissed off or putting as much time into it making it exactly right as I would have doing it from scratch.

On that note, anyone have a spacer they recommend? How about an elbow (I'm sure I'll get a few of the edelbrock elbow, and I'm betting I'll end up making something anyway)

 

I hear you on that, I wrote with a sharpie on my welding shield "bolt on" cause it seems I have to mod everything I buy anyways. Tell you a spacer NOT to get, I have one of the cheap 2in jegs tapered spacers and after the heat and possibly gas on it it for a few months the thinnest parts of it are distorting and you can bend them back and forth easily.