Performing Honda K24a3/AST5 6spd Conversion

[kmead]

The plastic grille mesh I used is already buckling from the heat, and I've only driven it 3-4miles, maybe. I'm going to have to open up another slat on the right & add bracing that aligns with the top slats for the mesh.

I think moving, the flow up from below is decent - stationary, it's cooking the engine cover, but the fan wasn't running at all with the sensor where I had it.

Time for metal mesh

 

[Bjorn Nilson]

One wonders if a fan blowing upward from under the car would help much.

I have a sucking fan on the engine hood. It does a good job when standing still. And aluminium mesh

 

[lookforjoe]

Time for metal mesh

I have a sucking fan on the engine hood. It does a good job when standing still. And aluminium mesh

I had metal mesh before - I switched to this as it matches my grille

I'll add the bracing & see how it goes.

Ran the car today, and all is well with the two WBO2 readings - they both match nicely - the AEM LSU4.9 is slightly quicker to respond than the olde tech Denso WBO2 used by Honda in the mid 2000's

14.7 AFR at normal op temp, rad cooling fan just kicked in

Cover fan kicks on idling when sensor hits approx 160ºF

hottest area of cover (trailing edge over header) - temp once engine reaches normal operating temp of around 180ºF

trunk access cover temp

header temp after burnout/ romp

This is all with ambient temps around 40ºF. It's gonna be toasty in the summer.

 

[Bjorn Nilson]

M

Cover fan kicks on idling when sensor hits approx 160ºF

My fan kicks in at 185⁰F. At 160 it would probably run constantly during hot days. Fighting heat is challenging on these cars.

 

[NEG]

Could you wrap the header Hussein?

 

[lookforjoe]

Could you wrap the header Hussein?

I was going to ceramic coat it. Jet-Hot kept giving me bogus quotes, so I decided to leave it as is for now. When I pull the motor to replace the short block, I'll get the header coated.

 

[BrianM]

For keeping heat out of the engine bay nothing beats header wrap.

 

[lookforjoe]

For keeping heat out of the engine bay nothing beats header wrap.

However it's a bad idea for any setup that is going to get wet, even if mine is stainless. I used header wrap on my original ram headers on my Volvo T5 build , which had a hood vent over the rear of the engine - rotted out the welds of the header in less than 2 years.

 

[lookforjoe]

Worked on the door gap issue today. Jacked up the car at the rear & put it on jack stands, using the factory points at the rear of the rocker. Doing so opens the door gap about .060" on each side - which is fine on the passenger side - goes from .090" at the top to .15", but on the DS the gap is basically zero to begin with, so .060" isn't going to be enough gap to start boxing in an additional support, as I'm sure it will still close up when on the wheels

I found that there was in fact some rust in the PS inner sill - covered with a fiberglass patch. I cut it out. Repairing this made NO difference to the door gap.

added a "L" plate first

then a shaped section to replace the rust

welded first plate

then second

I'll add some body caulk to the seams once that's properly dry

also noted that two welds on the tunnel side cracked, presumably when the tunnel was damaged (where I scraped the paint to inspect). I'll stitch weld those somewhat , above the brake/clutch lines.

So now I need to get the body to open up some more before I make a box section, so that it will have room to close up when back on the wheels.

Any boxing cannot be very deep, or it will interfere with the seat mount on the left (washer on floor, right side in pic). I can make it fairly tall - rocker height is what I'm thinking

 

[GregS]

Would a triangular box be stiffer than a square box?

 

[lookforjoe]

Would a triangular box be stiffer than a square box?View attachment 56033

Thanks Greg, I will have to play with that concept. it would definitely be easier to construct.

I do think I want the widest footprint across the tunnel & inner rocker planes to minimize the twist that is happening forward of the bulkhead. A triangular section would tie the floor & bulkhead, but would have less contact area over the tunnel & inner rocker. I could be wrong, I'm not an engineer. I've just been going with box section in my sketches to mimic the existing members.

 

[Ron Avery]

Man talk about rebuilding your car. Section by section, it is a good thing. That they were over built structure wise from the factory for USA crash standards.

 

[lookforjoe]

Man talk about rebuilding your car. Section by section, it is a good thing. That they were over built structure wise from the factory for USA crash standards.

Indeed! I'm pretty sure my current woes stem from taking the car offload at high speed last year. At this point, I just want to beef it up as much as possible to avoid issues down the road with the flex potentially worsening.

cardboard sections to box the tunnel to the sill

under layer, formed to fit within the small flats

I have contemplated a tube cross brace over the under bracing. I have sections of DOM tubing I bought from Summit, originally intended for the crossmember over the header. I would have to weld it to the end plates before welding the end plates to the tunnel & sill

planned outer boxing

I had time to cut & spotweld the heavier gauge SS sheet for the left side corner bracing. I want to avoid welding along the floor/sill joints as the factory caulk makes really nasty fumes, plus it will be a major PITA to reseal, given the under bracing for the jack point.

shaped to fit around the existing reinforcement plate for the seatbelt reel. Added M8 rivnuts for the bulkhead and inner sill, the plan is to weld the outer perimeter. the floor bolt is where the Honda seat rail mounts.

vertical corner will be welded

I'll make the tunnel side plates next

 

[kmead]

I guess the thing you need to think about is what are you hoping to achieve.

Basically you have a strong horizontal platform linking two multi box structures (the rear body with engine and the front with the frunk etc). The two box structures have multiple bulkheads and horizontal structures with notable vertical sections.

The center platform has few of these things. It is basically two outer beams linking the two boxes at the bottom and a center beam with a little more section but many openings which compromise its integrity. Between these beams is the floor which really is along or the ride relative to the beam strength of the center of the car which is why one can cut the floor out with relative impunity. The floor does have torsional value and due some of its structuring, load transfer across the center of the car in side impact.

OK so ultimately to get the ultimate in structure you should weld the doors shut. This would join the front and rear boxes most efficiently. Clearly that is not what you would want but it does demonstrate that you want to get the bracketry added to be as tall as possible and reach along the horizontal beams as far as possible.

As the side beams are attaching to the two boxes at the bottom, the best thing to do to is to improve the connection of the beam to the box. The taller that connection can be, the better. You have already done some of that. I would posit that you might consider making L shaped braces that run further along the horizontal beam and then up the B pillar further. The thickness of the L can only be as tall as from the floor where the seat mounts to the top of the beam and preferable across the top of the beam. It would connect to both the floor, the vertical face of the beam and the top of the beam. On the vertical leg going up the B pillar it could be deeper than the existing structure because your seat is always going to be in the door opening anyway, if there was some steel alongside it there really woudn’t be an issue in terms of entry or egress. This would want to be boxed as much as possible so for example it could be as deep as the mount for the seat belt reel and run over and be welded to the weather strip rib or have a flat with plug welds to weld on the flat alongside the seal rib. There is a limit to what you will gain by just adding more material following an existing section versus adding more vertical section meaning making the structure taller. A thick walled tube is very little weaker than a solid bar of the same diameter due to the dimiinsisting I value as you get closer and closer to the.

Honestly making a super stiff connection from the flexible flat floor to the flexible back bulkhead in front of the gas tank is not going to achieve too much. The action of the structure is happening out by the doors not inside the floor pan. What you are showing for the structure in your hand drawn pictures won’t help much to achieve what you need.

One thing I didn’t mention is adding more section by going downward but I don’t think that is possible due to your external body work.

My apologies for being a downer.

 

[jimmyx]

I'm with Karl on this one. It's a long shot that bracing to relatively flexible panels will eliminate the problem. This is a common issue on restorations where door gaps need to be perfect. If the underlying chassis structure is sound and the hinges are not compromised most shops turn their attention to the door itself. I've seen weld added to a door edge to correct to wide a gap, and the use of a flap disc to open up too tight a gap. If it takes significant metal removal to alleviate a very tight gap, the door edge will need to have a bead of weld to close the gap between the door structure and the skin, and ground smooth to finish. It's not the only means to an end, but it's one way of attacking it.

 

[lookforjoe]

I guess the thing you need to think about is what are you hoping to achieve.

Basically you have a strong horizontal platform linking two multi box structures (the rear body with engine and the front with the frunk etc). The two box structures have multiple bulkheads and horizontal structures with notable vertical sections.

The center platform has few of these things. It is basically two outer beams linking the two boxes at the bottom and a center beam with a little more section but many openings which compromise its integrity. Between these beams is the floor which really is along or the ride relative to the beam strength of the center of the car which is why one can cut the floor out with relative impunity. The floor does have torsional value and due some of its structuring, load transfer across the center of the car in side impact.

OK so ultimately to get the ultimate in structure you should weld the doors shut. This would join the front and rear boxes most efficiently. Clearly that is not what you would want but it does demonstrate that you want to get the bracketry added to be as tall as possible and reach along the horizontal beams as far as possible.

As the side beams are attaching to the two boxes at the bottom, the best thing to do to is to improve the connection of the beam to the box. The taller that connection can be, the better. You have already done some of that. I would posit that you might consider making L shaped braces that run further along the horizontal beam and then up the B pillar further. The thickness of the L can only be as tall as from the floor where the seat mounts to the top of the beam and preferable across the top of the beam. It would connect to both the floor, the vertical face of the beam and the top of the beam. On the vertical leg going up the B pillar it could be deeper than the existing structure because your seat is always going to be in the door opening anyway, if there was some steel alongside it there really woudn’t be an issue in terms of entry or egress. This would want to be boxed as much as possible so for example it could be as deep as the mount for the seat belt reel and run over and be welded to the weather strip rib or have a flat with plug welds to weld on the flat alongside the seal rib. There is a limit to what you will gain by just adding more material following an existing section versus adding more vertical section meaning making the structure taller. A thick walled tube is very little weaker than a solid bar of the same diameter due to the dimiinsisting I value as you get closer and closer to the.

Honestly making a super stiff connection from the flexible flat floor to the flexible back bulkhead in front of the gas tank is not going to achieve too much. The action of the structure is happening out by the doors not inside the floor pan. What you are showing for the structure in your hand drawn pictures won’t help much to achieve what you need.

One thing I didn’t mention is adding more section by going downward but I don’t think that is possible due to your external body work.

My apologies for being a downer.

I'm with Karl on this one. It's a long shot that bracing to relatively flexible panels will eliminate the problem. This is a common issue on restorations where door gaps need to be perfect. If the underlying chassis structure is sound and the hinges are not compromised most shops turn their attention to the door itself. I've seen weld added to a door edge to correct to wide a gap, and the use of a flap disc to open up too tight a gap. If it takes significant metal removal to alleviate a very tight gap, the door edge will need to have a bead of weld to close the gap between the door structure and the skin, and ground smooth to finish. It's not the only means to an end, but it's one way of attacking it.

I was hoping that tying the tunnel & sill together with that boxing would reduce the flex at least enough to reduce the deflection by .060", which would give me the gap I need. Both sides actually deflect the same amount (.060") at the door gap, but my DS was obviously tweaked going off road, as I didn't have such a close (basically non-existant) gap prior to April 2020 - you can see the paint chip in this pic, next to the door handle

Reworking the door edge would require removing the folded edge & rewelding the door afterwards, to get that minimum .060" gap. I really, really don't want to mess with the door, since it's tweaked top to bottom at the rear anyway. I may be better off getting another door if it comes to that.

I could potentially add a diagonal brace something like this - the issue then is access to the seat rail mounts becomes really awkward. If I recall, Brayden had something like that & it didn't make any difference to his flex issue, however his lower plate sits over the rear sill plate junction.

 

[jimmyx]

I just did a door that was too tight (not a Fiat), but the problem was in a bottom corner by the rocker. I had to do some welding and smoothing but the job was relatively easy. The difference is that on mine is it was prior to paint work so I didn't have to deal with that issue. Would have been great if you had another door to try, but most off road excursions screw up the opening rather than the door itself. I'm not sure the brace will get you where you need to go? If you can find a shop that has some good skills with a frame machine, they should be able to tweak the door aperture with a relatively minor pull. The problem is most shops hate small jobs like that and tend to price it high enough hoping you'll just go away.

 

[lookforjoe]

I just did a door that was too tight (not a Fiat), but the problem was in a bottom corner by the rocker. I had to do some welding and smoothing but the job was relatively easy. The difference is that on mine is it was prior to paint work so I didn't have to deal with that issue. Would have been great if you had another door to try, but most off road excursions screw up the opening rather than the door itself. I'm not sure the brace will get you where you need to go? If you can find a shop that has some good skills with a frame machine, they should be able to tweak the door aperture with a relatively minor pull. The problem is most shops hate small jobs like that and tend to price it high enough hoping you'll just go away.

I can force the opening to expand by jacking the left side at the support plate used for jack stands. I suppose I could weld support plates to B pillar & sill, then wedge a DOM tube section & see if that works to limit the flex/return when dropped...

I was just looking on MWB's website for a bare door...

 

[jimmyx]

I can force the opening to expand by jacking the left side at the support plate used for jack stands. I suppose I could weld support plates to B pillar & sill, then wedge a DOM tube section & see if that works to limit the flex/return when dropped...

I was just looking on MWB's website for a bare door...

I would think that the tube would have to be mounted very high up on the B pillar to have a shot at working? If jacking up the support opens the gap, that's why I was thinking a frame pull. They would put the machine blocks under the plate, tie down the front sill area and put a minor pull behind the plate to reverse the tweak. If you know a body guy locally and can show him what you have, I'd ask him if it was his car what would he do. This is common on unibody cars and they see it all the time so they may have something up their sleeve we haven't thought about. For us non-body guys these things are like groundhog's day, for them it's just another day at the office.

 

[kmead]

I agree around having the body pulled on a frame machine, a minor tweak of the unibody could resolve this in one swell foop.

You could alternatively do what has been done in the vintage car business for decades and that is cut the door edge back and weld it to give the reveal you want.

Nearly every pre 1990 ‘super car’ has had the door edges tweaked front and rear to match the opening in the body. I have seen built up weld along the edges of the doors on more old Merc’s, Ferarri’s and Lambos than I care to count. This was also done at the old body plants in Italy as the cars were never the same left side to right side either (this would have been in the 60s for all the old Abarths etc, basically anything that was hand formed out of aluminum or steel and then assembled progressively).

If the car is structurally stable in its current configuration this could be a solution, like so many things, less than ideal. Paint would of course be required.