Preparing For Honda K24a3/AST5 6spd Conversion

lookforjoe

True Classic
A tight package indeed.

Getting the plenum under and back seems like the best way towards keeping the TB out of the space for the fuel tank and not having it removed to the side as others have had to do.

Not a lot of choices, Midwest certainly did a good job with getting that monster in there in the first place.

Personally I wouldn’t want to get too many things made and resolved until actually start to fit the beast into the engine bay.

Sorry for all my dumbass distractions. Thanks for suffering them.

Wish I lived closer, you on the other hand are likely thankful that I do not.
"Personally I wouldn’t want to get too many things made and resolved until actually start to fit the beast into the engine bay."

Now, where's the fun in that :D?

I think there are enough pics to gauge the available space, I just have to pay attention. I know I will have to wait for some things, like the exhaust. I'm going to make as much as I can. If I end up having to rework what I have it will still be less work than starting for scratch, IMO. This sort of challenge is engaging.

I would have no problem with you as a neighbor - I appreciate your ideas and input. Defintitely helps keep me on my toes :)
 
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TonyK

True Classic
A tight package indeed.

Getting the plenum under and back seems like the best way towards keeping the TB out of the space for the fuel tank and not having it removed to the side as others have had to do.

Not a lot of choices, Midwest certainly did a good job with getting that monster in there in the first place.

Personally I wouldn’t want to get too many things made and resolved until actually start to fit the beast into the engine bay.

Sorry for all my dumbass distractions. Thanks for suffering them.

Wish I lived closer, you on the other hand are likely thankful that I do not.

Not to highjack this thread but similar problems arose when I was installing the Abarth engine in my test body that needed to be resolved. Use of the spare tire compartment is often a solution for more room in the engine bay in engine swaps. The approach though between the K20 and the Abarth swap is basically the same but differs in that the K20 has an extension tube that is welded to the enlarged hole into the passenger compartment and a bolted cover. The Abarth swap rather than using a tube with a cover uses only a formed removable cover. Due to the size of the turbo Exhaust and CAT some space was also required into the gas tank area and that is where casting a hammer form to accomplish the complex shaping of the section around the turbo charger exhaust pipe was required. Some shaping of the gas tank was also required. Rather than get into a long description I think it is better to share some picture with you
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of the solution.

TonyK

Grimsby Ontario Canada.
 

lookforjoe

True Classic
Not to highjack this thread but similar problems arose when I was installing the Abarth engine in my test body that needed to be resolved. Use of the spare tire compartment is often a solution for more room in the engine bay in engine swaps. The approach though between the K20 and the Abarth swap is basically the same but differs in that the K20 has an extension tube that is welded to the enlarged hole into the passenger compartment and a bolted cover. The Abarth swap rather than using a tube with a cover uses only a formed removable cover. Due to the size of the turbo Exhaust and CAT some space was also required into the gas tank area and that is where casting a hammer form to accomplish the complex shaping of the section around the turbo charger exhaust pipe was required. Some shaping of the gas tank was also required. Rather than get into a long description I think it is better to share some picture with you View attachment 15377 View attachment 15378 View attachment 15379 View attachment 15380 View attachment 15382 of the solution.

TonyK

Grimsby Ontario Canada.
Many thanks for sharing that Tony. Good to note that need be, It's not the end of the world if the tank has to be modded also. I definitely am not moving it to the front :D Your pics also make me think I should chop the back off my parts car & set it up the garage so I can work on it over the winter. Not sure I have room, actually, but it's a nice idea :D

What did you use to chop it off?
 

lookforjoe

True Classic
Had about an hour to work on the plenum today. Realized it will be much easier to repurpose the stock plenum entry/flange & pie cut pieces to fill the void vs. building a new extension. Welded it along the base after I test fit to check TB clearance.



Depth looks good - not much over 5" off the head



Rad hose neck will be redone after intake


Should fit like this though



Stock TB flange will be ported to match adaptor ID

 

Rodger

True Classic
That 80 mm TB looks huge compared to the stock 62 mm one. Is there enough beef in your intake tube/flange to hog it out to 80 mm? Sure doesn't look like it.
 

lookforjoe

True Classic
That 80 mm TB looks huge compared to the stock 62 mm one. Is there enough beef in your intake tube/flange to hog it out to 80 mm? Sure doesn't look like it.
Hey Rodger, yes there is plenty of meat in the flange to accommodate the removal of about 5-6mm all around the ID. I’ll take a few pics when I actually get to that part.

EDIT: To clarify, the bore is tapered from the flange going inward, so it's not 80mm straight back into the plenum neck.
 
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lookforjoe

True Classic
Got the Plenum > TB Flange junction squared away. Not pretty, but functional. Have to do the hogging out of the internal weld overlaps & TB porting next. 2.25" cast 90º elbows should be here in a week or so, then I can play around with the runner layout. They are gonna be a PITA to weld.





Cut a wedge of thick wall 4" aluminum tube , tacked it at one end, and beat it into submission as I went around the other side. Not a uniform shape, so it got a tad messy (hence all the bash marks). Top has to indent to allow for passage under runner #4 (above pic)




Found I already have a nice 2.5" SS rigid liner flex coupler & 3" SS V-band, so those will be put into service when the time comes. Braided mesh liners are very bad - the liner will swell & choke the passage. Ordered the same magnaflow 11236 muffler as Rodger has, a cat and some 2.5" SS U-Y piping. I’ll use standard pin type hangers with Volvo mounts.

 
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lookforjoe

True Classic
That 80 mm TB looks huge compared to the stock 62 mm one. Is there enough beef in your intake tube/flange to hog it out to 80 mm? Sure doesn't look like it.
So, I did the TB flange work today. In fact, only about 6mm additional material is removed,

PRB TB flange approx 64mm




as the flange adaptor is just over 70mm ID



flaring out to 80mm on the TB side



Mine, after enlarging. Need to remove approx another 1mm around



Rough work with a barrel grinder, working into marker line (RBB flange)



then finer carbide grinder, coarse file, fine file & a little sandpaper





flange fit



TB

 
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fiatmonkey

Tim Hoover
Many thanks for sharing that Tony. Good to note that need be, It's not the end of the world if the tank has to be modded also. I definitely am not moving it to the front :D Your pics also make me think I should chop the back off my parts car & set it up the garage so I can work on it over the winter. Not sure I have room, actually, but it's a nice idea :D

What did you use to chop it off?
I did the same thing - I can't find my post, maybe its on FB, but I used a plasma cutter to saw X in 1/2. Saved the engine bay for fitting engine. REALLY helped me when I decided to reverse mount the intake manifold. It saved me from having to modify the fuel tank side of the engine bay (for the most part).
 

Rodger

True Classic
So, I did the TB flange work today. In fact, only about 6mm additional material is removed,
Ok, I am going to ask a dumb question here. Why start with an 80 mm TB if you are confined to the original inner diameter of the stock intake? I realize that you tapered the flange to transition from 80 mm down the the 64 of the original intake, but isn't airflow volume dictated by the cross section of the narrowest place in the intake?
This is a quote from Hybrid Racing. This is from the description of their 70 mm throttle body that I had purchased, but have passed on to Tim for one of his projects. "A note about boring your intake manifold: It should be noted that a big bore throttle body should never be used on an intake manifold that has not had the inlet bored out to match the bore of the throttle body. A setup using a big bore throttle body mated to an OEM sized inlet port will yield lower performance than the OEM throttle body. That said, when boring the inlet on an intake manifold, it’s best to overbore slightly (about .25-.5mm is sufficient), to prevent the chance of a lip that could create turbulence."
 

lookforjoe

True Classic
Ok, I am going to ask a dumb question here. Why start with an 80 mm TB if you are confined to the original inner diameter of the stock intake? I realize that you tapered the flange to transition from 80 mm down the the 64 of the original intake, but isn't airflow volume dictated by the cross section of the narrowest place in the intake?
This is a quote from Hybrid Racing. This is from the description of their 70 mm throttle body that I had purchased, but have passed on to Tim for one of his projects. "A note about boring your intake manifold: It should be noted that a big bore throttle body should never be used on an intake manifold that has not had the inlet bored out to match the bore of the throttle body. A setup using a big bore throttle body mated to an OEM sized inlet port will yield lower performance than the OEM throttle body. That said, when boring the inlet on an intake manifold, it’s best to overbore slightly (about .25-.5mm is sufficient), to prevent the chance of a lip that could create turbulence."
Hey Rodger the intake is “bored”. What they are referring to is the TB flange/neck area. That has to match the ID of the backside of the TB housing. The inside of any manifold is much larger than the reduced neck/flange area, varying by design of course.

What I meant was using the adaptor flanges that KTuned provides, the increase in ID is only about 6mm (64 up to 70ish).

I admit I was surprised that they taper the flange ID down from 80 to 72, that would seem counter productive. What I may do is weld their 1st flange to the intake, as that is a straight 80 ID.

I’m going to leave it as is until I’ve put it all together & driven it. If the Butterfly is too large for the build, you end up with a very twitchy throttle. The plan here was to allow for further mods DTR, so the reduction to 72mm may be fine with the current overall setup.
 

Rodger

True Classic
I understand that the plenum is larger than 80 mm. What is the inner diameter of the pipe that you made to go from the flange to the plenum?
 

lookforjoe

True Classic
I understand that the plenum is larger than 80 mm. What is the inner diameter of the pipe that you made to go from the flange to the plenum?
That section is the original RBB plenum neck, rotated & expanded/tapered to meet the plenum orifice - it is 4" or greater once you go past the flange area, it expands off to the right (in terms of the pics I took)

Neck/Throat opens to this:



You can pretty much see the increase off the flange here:

 
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lookforjoe

True Classic
After Rodger's observations, I went back in & removed a fair amount more out of the entire throat. Got the bore as straight-walled as I can. I realized that although the RBB adapter is only 72mm ID there is that lower 1.25” area to be factored into the ID. I don’t have math skills to figure out what that does to the overall ID.

EDIT: Looking at these, I still need to take little more out on the right (in pic)



 
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lookforjoe

True Classic
That says it an RBC, but the RBC is not a two part manifold. Different ones identified & tested here:

http://www.superstreetonline.com/how-to/engine/sstp-1002-k-series-intake-manifold-shootout/

That looks like the RBB intake I have. Could also be RAA which is also two-part. The TB flange position is identical. It is quite possible the stock RBB manifold would fit in the available space better than the K20 manifolds, simply because the flange is offset differently.
 
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