If I am understanding the problem correctly the lt1 intake drops off on the top end due to lack of plenum volume? So just like a engine with a carb a spacer between the TB and manifold will help bring the horsepower peak up. But, what stops you from mounting the throttle body where the maf typically is and building an aluminum elbow to connect the two you would add significant plenum volume?

 

Or instead of trying to reinvent the wheel you could just use a 58mm TB which is an effective compromise, allows the motor to more easily tap into the intake tract.

 

I'm not sure I buy into a 58MM TB being large enough to change the intake tract into plenum space. Plenum is there at idle all the way to WOT the intake tract is only seen the same as plenum at WOT in the case of a 58MM TB.

 

i think the geometry for the throttle linkage would be a huge set back

 

I run such a spacer between the front of my Hogan manifold and the stock throttle body. The linkage geometry was not a problem after I made a new bracket that mounts the linkange on the Hogan. It increased the available plenum capacity.

c

 

How did you deal with idle air and how did you port out the intake manifold? did you just open the two ports up bigger, merge them into one? or what?

 

Since my car is not street driven I dispensed with the IAC. It is not a factor. The front of the Hogan manifold is an open cavity so porting the inlet area isn't a factor either. When I originally built the motor I needed to space the throttle body forward to clear the linkage arm but I wasn't sure what the effect would be. We machined four spacers of varying thicknesses, indexed them to eliminate misalignments and moved the throttle bodyforward about 2 3/4". I could remove one or more of them but things seem to be working fine. Going farther forward probably wouldnt work too well because I'm running out of room with hood clearance. I have pictures if you're interested.

c

 

I would definately ike to see pics. The idea to add a spacer just seems to simple when you consider that people are making custom manifolds for thousands of dollars whithout even trying any type of spacer first.

 

What I am interested in is if anyone has tested this on a stock intake and dynoed to measure the results.

 

Someone has probably tried it although it would necessarily be a more complex task on a stock manifold. Additionally, I question the ultimate benefit on a stock manifold. I believe that the primary advantage is the increase of volume within the plenum. If you're not completely sucking all the air out of the plenum under WOT conditions, the additional volume wouldn't be a particular advantage.

 

The plenum volume thing is a WOT issue not a part throttle issue which is why this is an effective compromise. Is it the ultimate solution, maybe not but what it is is cost and results effective. By the time you would add enough volume to have any real impact I would think thermostat housing clearance will be an issue.

 

If ya have a TB large enough to replace the air the engine uses then plentum volume is not such a big issue.
If ya have a 1300CFM TB it is sort of like having a dominator carb that flows 1300CFM,which is enough for most builds at or under 7500RPM's.

 

True, and if you have a stock throttle body and the engine needs to pull up to 8500, you need a LOT of plenum.

 

Agreed. I hope you did not take my comments as saying you went the wrong way. I had noticed the Hogan and stock TB so I figured your combo was WAY outside the norm.

 

Don't worry about anything you wrote. It's all part of the discussion. Most of the things on my car aren't really aligned with the cars most people choose to discuss on this forum but once in a while some of my experiences are germane to the conversation.

The car is an NHRA Super Stocker and it is required to meet certain rules limitations that don't apply to all. I've occasionally wondered what would happen if I bolted on a bigger TB. Since I don't have one, I've never tried it.

c