Performing Honda K24a3/AST5 6spd Conversion

Couple small updates to keep track of things - 2850K miles when I left for MWB open house.

Oil temps are better with the duct I added - never went up to 220 (mostly around 200, I'd gauge) even with hours of driving @ highway speeds in very high ambient temps Thursday & Friday on the way to Carlisle PA & then Columbus Ohio

Switched to conventional 5W30 motor oil - makes no difference to oil consumption - used a quart over the course of the past 3 days. No visible oil smoke on deceleration with the VTA breather setup though. Definitely have oil smoke when idling hot & then accelerating from a standstill.

The AC hoses have held up for over 700 miles of driving the past 3 days, with numerous spirited pulls that would stress the fittings, so the revisions with brackets seem to be doing the trick. I noticed on the drive that the AC seems to drop out under higher load/acceleration - however on Friday morning I was driving for hours with no AC - and I observed that the heat was coming on (I have a bay-mounted vacuum controlled heater valve with an ancillary reservoir) - so, I need to revise the system to maintain vacuum to the valve under those conditions.

I really would like to have cruise control for these long drives also :rolleyes:

View attachment 50762

Friday - following Brian in his wife's 500 Cabriolet - it was great to have company & enjoy their tremendous hospitality :)

View attachment 50763
The round trip was 2800 miles? I’m reading that wrong, right?
 
The round trip was 2800 miles? I’m reading that wrong, right?

2850 was the starting mileage - 4047 was the mileage when I got home, so 1200 miles all told. I don't know how to use the trip meter aspect of the Marshall GPS speedo, so I don't touch it. Mileage displayed is total on Honda engine / K-swap.

PXL_20210816_171344610.jpg


Based on fuel purchased, and miles travelled I averaged 28.6mpg, driving mostly 70-80mph or doing 3-4-5 pulls to wind out the motor & listen to it's awesome note 😁
 
Last edited:
So, this is the header I will mod to fit, or mod the chassis to fit, whichever way it ends up going 😁

PXL_20210816_203157927.jpg


PXL_20210816_203209754.jpg



probably going to have to remove much of the cross brace & revise that. At the very least, I can cut back the top - the early cars don't have that - I saw this one (75?) @ MWB:

PXL_20210814_175832814.jpg
 
Last edited:
Revised the low side AC line (again) - the last one worked well, however it still came loose on the way home due to the 'spirited' driving sessions over the course of the past 4 days

PXL_20210816_215300506.jpg


revision is similar to earlier version with 180º loop, but heavier gauge tubing, and longer flexible section. I also retain the line clamp to secure the loop section to the compressor mount. See how this one goes.

PXL_20210816_220839694.jpg


PXL_20210816_220851922.jpg


got the vent temps to around 55ºF idling, with about 24oz of R134a. I'll have to drive it & check again, pretty sure I had more in there last time, but maybe not.

PXL_20210817_002405891.jpg
 
Last edited:
May have to stop in NY on my way to Vermont to try this thing out on roads more appropriate to its capability… :)

Only two more weeks to go.
 
Swapped out the injectors for the brand new Honda-packaged Denso 410cc (RDX) injectors to see if it makes any difference to the top end rich condition.
PXL_20210817_141543354.jpg


PXL_20210817_134801629.jpg


Just a little fiddly to get the injectors in - had to put them in the runner first, then finagle the rail back in, then get the retainer clips in place without dropping them down behind the intake...

PXL_20210817_141553502.jpg


there was oil spray from the cam cover vent on the heater feed below it - found out why today - the cap of the breather blew out

PXL_20210817_145328326.jpg


put on the new one I bought a couple years ago

PXL_20210817_145334870.jpg


AC still below 60 - I think I still need to add some more freon though, even the old 740 gets to 50 on a day like to today

PXL_20210817_170546734.jpg
 
probably going to have to remove much of the cross brace & revise that. At the very least, I can cut back the top - the early cars don't have that - I saw this one (75?) @ MWB:

View attachment 50935
Yes they put the bump over the top of the struts apron sometimes in the 1979 model production year (but I have seen some early 1979 without it). I'm sure they added it for a reason, probably to get more strength. I had to cut mine on my 1980 when I fit a set of universal Carrera camber plates. If you don't already have plate doublers underneath, I would consider them if you remove that bump, especially if you have the intention of doing some off-road anymore!
1629250144463.png


Nice exhaust snake. I hope you will find a way to keep it visible when you pop the hood!
 

Attachments

  • 20200602_154232.jpg
    20200602_154232.jpg
    219.7 KB · Views: 87
Swapped out the injectors for the brand new Honda-packaged Denso 410cc (RDX) injectors to see if it makes any difference to the top end rich condition
I doubt smaller injectors will affect the rich condition at heavy load. The ECU should adjust for that. I have 440cc injectors in my UT with much smaller displacement and they are big enough to run E85 I think. The only issue I have is to get idling adjusted to 850rpm. My engine idles at 1000rpm but I can live with that.
 
I doubt smaller injectors will affect the rich condition at heavy load. The ECU should adjust for that. I have 440cc injectors in my UT with much smaller displacement and they are big enough to run E85 I think. The only issue I have is to get idling adjusted to 850rpm. My engine idles at 1000rpm but I can live with that.

Same size - just brand new vs. reman units. There was a concern that the remans might be dumping fuel at high duty cycle. In initial driving tests, I don't think there is a difference.
 
May have to stop in NY on my way to Vermont to try this thing out on roads more appropriate to its capability… :)

Only two more weeks to go.

You should text me with possible dates - we will be up in Saratoga & Lake Placid next week, then home for a couple of days, then 'camping' for 2 days after that.
 
You should text me with possible dates - we will be up in Saratoga & Lake Placid next week, then home for a couple of days, then 'camping' for 2 days after that.
Sounds like fun.

We will be out there the first two weeks of September, I unfortunately don’t really expect I will be able to get down to where you are given the activities my wife has planned. I am also my Mom’s chaffeur to see her friends as I am picking her up on our way out to VT on 9/4. It’s been three years since I was back there.

We will be looking at places around Lake Champlain for places to live when we leave Michigan when that needs to transpire so that will likely eat up a bunch of my time.

Thank you.
 
Getting 4 of the 80a BMW-based poly mounts recommended by MWB where there is excessive engine movement under heavy load. I think that is the only way I am going to keep my AC lines intact 😁

Screen Shot 2021-08-18 at 7.37.22 PM.png


Also added a check valve for the heater valve, that resolved the issue of the heater coming on under high rpm / load situations.

I've decided I'm going to go with one of the Vintage Air electronic heater valves - with my setup, I cannot regulate heat flow, it's on or off - which is fine in local use, but not so good for the longer distance drives I want to use the car for.

Have to figure out how to mount the dial discreetly - not going to use the mount provided, that's for certain.

Screen Shot 2021-08-18 at 7.39.01 PM.png
 
Back
Top