Performing Honda K24a3/AST5 6spd Conversion

So, I'm trying to understand what about the t/stat is causing the flow restriction.
I'm scanning through your post here and saw this comment. I might have something to add here.

One battle I fought on the X1/9 K20 conversions was that the bypass circuit had less resistance than it ought to compared to the radiator circuit. The bypass circuit was basically normal for a K20, but the radiator circuit had an additional 15' or so of tubing to push the coolant through. Only on one of the cars that I built did I have the luxury of using the Acura thermostat. On Pete's car, I had to use the crappy K-tuned single-acting unit, and on all subsequent cars I used a Lancia Beta thermostat because it was a discrete self-contained unit that I could package well into the cramped space between the engine and firewall under the intake manifold. In some cases, I placed a restrictor in the bypass circuit, reasoning that even reduced flow through the bypass circuit was sufficient to clear any air bubbles and allow the engine to reach operating temperature safely before the thermostat began to open.

Were you observing temperature fluctuations before your head gasket failure?
 
On Pete's car, I had to use the crappy K-tuned single-acting unit, and on all subsequent cars I used a Lancia Beta thermostat because it was a discrete self-contained unit that I could package well into the cramped space between the engine and firewall under the intake manifold.

Yeah, the K-tuned unit caused a problem with the car slowly overheating anytime the revs were below about 3200. So at idle, stuck in traffic, loping along in 6th on a slower freeway, etc. I quickly switched to the Beta dual-action unit, and my temps have been rock solid ever since.
 
I'm scanning through your post here and saw this comment. I might have something to add here.

One battle I fought on the X1/9 K20 conversions was that the bypass circuit had less resistance than it ought to compared to the radiator circuit. The bypass circuit was basically normal for a K20, but the radiator circuit had an additional 15' or so of tubing to push the coolant through. Only on one of the cars that I built did I have the luxury of using the Acura thermostat. On Pete's car, I had to use the crappy K-tuned single-acting unit, and on all subsequent cars I used a Lancia Beta thermostat because it was a discrete self-contained unit that I could package well into the cramped space between the engine and firewall under the intake manifold. In some cases, I placed a restrictor in the bypass circuit, reasoning that even reduced flow through the bypass circuit was sufficient to clear any air bubbles and allow the engine to reach operating temperature safely before the thermostat began to open.

Were you observing temperature fluctuations before your head gasket failure?

Hi - thank you for the input - no, the temp became an issue once I developed the HG leak. I also used a Volvo t/stat housing of similar design to the stock Honda unit & mounted it to the water housing in the stock configuration for all I/O at the water housing.

I never did compare the stock t/stat itself to the Volvo one in terms of aperture dimensions, just that the operating temp value was the same.

I also modded the VW pressure cap to open at 4-5psi instead of 15+, that helped - but I have taken the precaution of bleeding the rad after every day of driving to relieve the combustion pressure being added to the system. I also run Evans Waterless, not standard coolant/water mix.
 
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Yeah, the K-tuned unit caused a problem with the car slowly overheating anytime the revs were below about 3200. So at idle, stuck in traffic, loping along in 6th on a slower freeway, etc. I quickly switched to the Beta dual-action unit, and my temps have been rock solid ever since.

Being frank here: the car shouldn't have left the shop with that cruddy tstat on it. It was bad news from day one. I hear that K-Tuned has since fixed their housing and have gone to a dual acting thermostat. If true, that's great--and I also hope that they fixed their housing's tendency to leak constantly. I think I took to putting a shmear of pipe dope between the articulating parts of that housing to try to help it not leak.
 
Hi - thank you for the input - no, the temp became an issue once I developed the HG leak. I also used a Volvo t/stat housing of similar design to the stock Honda unit & mounted it to the water housing in the stock configuration for all I/O at the water housing.

I understand. Maybe I missed something. Why are you thinking that the current tstat is a problem/restriction?

I also modded the VW pressure cap to open at 4-5psi instead of 15+, that helped - but I have taken the precaution of bleeding the rad after every day of driving to relieve the combustion pressure being added to the system. I also run Evans Waterless, not standard coolant/water mix.

That seems permissible since the coolant can operate without pressure, but it also seems that the low pressure would make bleeding the system more difficult. I remember occasionally having to use every trick I could think of to bleed an X's cooling system and needing full operating pressure to push the air out.
 
I understand. Maybe I missed something. Why are you thinking that the current tstat is a problem/restriction?



That seems permissible since the coolant can operate without pressure, but it also seems that the low pressure would make bleeding the system more difficult. I remember occasionally having to use every trick I could think of to bleed an X's cooling system and needing full operating pressure to push the air out.

The t/stat restriction is purely an issue (it would seem) with my current engine situation - with blowby into the cooling system, it must be creating air pockets at the t/stat, as the coolant temps went to 210-220 whilst driving, esp if I didn't baby the shifts & keep rpm's down. With no t/stat, I have temps that sit around 185/190 once fully warmed, and drop from there when moving.

When I put it all back together with the new head/head gasket, etc., I just want to make sure I have covered every aspect that could impede sufficient coolant flow - pretty much I've had cooling (overheating) issues of one sort or another with every iteration of engine/mod since I got the car 🤪 - I'd like to be done with that.

Yes, the reduced pressure cap would make bleeding more difficult in normal circumstances, but I have increased pressures right now from the HG blowby - so I have to keep bleeding the rad if I continue to drive it at this point.
 
Being frank here: the car shouldn't have left the shop with that cruddy tstat on it. It was bad news from day one. I hear that K-Tuned has since fixed their housing and have gone to a dual acting thermostat. If true, that's great--and I also hope that they fixed their housing's tendency to leak constantly. I think I took to putting a shmear of pipe dope between the articulating parts of that housing to try to help it not leak.
I used the newer K-Tuned dual action thermostat with my build but I did tap in another port for the heater circuit. I have had no overheating and no leaks with mine. Granted, I do not have a ton of miles yet but it did not have any cooling issues during my dyno session.
 
I used the newer K-Tuned dual action thermostat with my build but I did tap in another port for the heater circuit. I have had no overheating and no leaks with mine. Granted, I do not have a ton of miles yet but it did not have any cooling issues during my dyno session.

Good to know! I really don't know what Canadian variety of dope they were smoking to think a single acting thermostat would be a good idea on a modern car with a dual circuit cooling system.
 
Yes, the reduced pressure cap would make bleeding more difficult in normal circumstances, but I have increased pressures right now from the HG blowby - so I have to keep bleeding the rad if I continue to drive it at this point.

So every dark cloud really does have a silver lining. "I got this blown head gasket, but it really helps pressurize the system for bleeding."
 
JDM. US is a little lower, but still (EDIT) 4.7:1 (!), I believe. 4.10:1 or 3.98:1 would be preferable. I mean, it's not the end of the world since I have no reason to be driving well over 100 anyway. 100 is still ok in terms of rpm's in 6th :D

Could be worse! Integra Type R transmissions have a 5:1 ring and pinion.

Pete is right; those JDM cars are geared purely for acceleration. Shorter tires make K swapped Xs a little worse, but not a lot.
 
Hussein, you are so close to the answer it will hit you in the face when I tell you the solution. Abarth swap has the same issue, solution, install the X1/9 idle up AC air valve. The ECU will see the change in MAP value and adjust the injectors accordingly. Feed the solenoid valve from the clutch wire of the AC compressor. On the Abarth it works so fast that you really have to pay attention to a very small hiccup in the idle.

TonyK.

Grimsby Ontario Canada.

I know I'm late to this party, but have you played with the duty cycle on the Honda idle air control? I turned down the duty cycle on the K swaps I did that had Hondata. It smoothed out the idle considerably.
 
I know I'm late to this party, but have you played with the duty cycle on the Honda idle air control? I turned down the duty cycle on the K swaps I did that had Hondata. It smoothed out the idle considerably.

In the end, I had to put a smaller TB on it, and a Honda-packaged IACV. The 80mm was just too large.

Could be worse! Integra Type R transmissions have a 5:1 ring and pinion.

Pete is right; those JDM cars are geared purely for acceleration. Shorter tires make K swapped Xs a little worse, but not a lot.

I bought the mFactory 4.00:1 R&P - looking forward to more sane gearing with that - I don't drive pedal to the metal in every gear so much these days :D
 
Going to rework the shifter while I have it apart. I don't care for the lever offset, so I going to use a modified Volvo shifter :D

Stock TSX shifter on left, Volvo C30 on the right
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The Volvo knob matches the Honda shift pattern

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Cut the Volvo lever at the base, heated & doglegged it. I'll cut the existing rod off, counter drill the base, insert the new one & then weld

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this will put the lever about a knob's width to the left - which should center it in the gate.

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Had to make a new high side fitting off the compressor - the one I previously made suffered from pinhole leaks as with my old high side hard line

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Started prepping for drivetrain removal. Took out the trunk panels, dropped the exhaust, and removed the AC compressor.

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Flange is not flat - gasket has leaked at either end. P2R makes a thicker (1.6mm) graphite gasket to replace the stock metal one. The flange isn't that warped - but enough for this to have happened

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The damage back here from the accident does not extent beyond the cracked weld from the tube I added - so that's good news

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Also got thicker hub-centric wheel spacers from MWB - so I can switch to the other wheels if I so desire - they didn't clear the calipers with the 1/2" ones

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Started prepping for drivetrain removal. Took out the trunk panels, dropped the exhaust, and removed the AC compressor.

PXL-20201105-205331584.jpg


PXL-20201105-210252627.jpg


Flange is not flat - gasket has leaked at either end. P2R makes a thicker (1.6mm) graphite gasket to replace the stock metal one. The flange isn't that warped - but enough for this to have happened

PXL-20201105-205342260.jpg

Did you notice the cracks in the header primaries? Do you purge your stainless welds? Without purging, that black chromium oxide that forms on the inside of the tube will lead to premature failure.
 
Flange is not flat - gasket has leaked at either end. P2R makes a thicker (1.6mm) graphite gasket to replace the stock metal one. The flange isn't that warped - but enough for this to have happened
After I got done with my header mods, my flange was significantly not flat. I was able to find a general machine shop that could mill it back to flat. The automotive shops couldn’t do it.
 
Did you notice the cracks in the header primaries? Do you purge your stainless welds? Without purging, that black chromium oxide that forms on the inside of the tube will lead to premature failure.

EDIT - No, no yes cracks in the primaries, none at the collector. Only the flange is warped from all the welding - I had read that even aftermarket headers suffer from this, and often the flange will pull flat when torqued correctly, mine has about 1/16- 3/32" deviation from center to extremities

After I got done with my header mods, my flange was significantly not flat. I was able to find a general machine shop that could mill it back to flat. The automotive shops couldn’t do it.

My local speed shop has a nice wide table belt sander , but it's broken at the moment, so I went with the thicker gasket.
 
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