Performing Honda K24a3/AST5 6spd Conversion

[jimmyx]

Would a weak tensioner cause 'chatter' that stresses the chain?

For the limited info I've seen, it looks like the answer is yes and no. It seems chatter is a "thing", even to the point of be audible at times, but the actual cause most cited is momentary low oil pressure. The spring in the tensioner is supposed to compensate under those conditions, but if the spring is weak they say it can all go off the tracks quickly. I haven't read back through your entire build thread, but I think I remember that you had to use a K20 pump and sump on the K24 to complete the swap? If that's the case, was swapping the pump just a straightforward bolt-in, or were some other mods required? I know nothing of what's involved so that's why I'm asking. Also curious if the broken links were next to each other or in random spots along the chain? It would not be out of the ordinary for several links (all at the point of impact) to be damaged. Random would be a little odd, but can still result depending on how the broken chain was whipped around before coming to rest. I agree that the cause may never be definitively known, but my hope is you will exhaust everything you can in the process because the only thing worse than repairing a major failure is ever having to do it again.

 

[lookforjoe]

Given the way the guides are set up, supporting a long length of the chain, I doubt there is any way to blame the tensioner short of the tensioner somehow overtensioning the chain--and that is a stretch, so to speak. I certainly don't see the tensioner allowing any harmonics to build up in the chain. You probably just got super unlucky with the chain you got. Are you planning on one of those upgraded tensioners when it all goes back together?

No, just an OEM Honda unit for chains and tensioner. I don't rape the motor in use, nor is it over stock output to any meaningful degree, so I don't see the need for it.

took pics of the chain details- multiple single link fractures. I have emailed the vendor, not that they will do anything, however they should know there is a QC issue.

arranged the chain so the visible exterior fractures are mostly grouped in the center of pics

other side

 

[kmead]

No, just an OEM Honda unit for chains and tensioner. I don't rape the motor in use, nor is it over stock output to any meaningful degree, so I don't see the need for it.

took pics of the chain details- multiple single link fractures. I have emailed the vendor, not that they will do anything, however they should know there is a QC issue.

arranged the chain so the visible exterior fractures are mostly grouped in the center of pics

View attachment 63708

View attachment 63709

There are a lot of cracked or stress risered links there when you start looking at them

 

[lookforjoe]

Good news for the replacement K24 short block at least - the crank & mains are good, the pistons & bores are good. So, just a hone, new rings (apparently different for JDM vs. USM pistons) and new rod bearings. Should be ready mid week, so I have some incentive to get going on removing the drivetrain.

I will probably have to use my original RBB head ( was decked & valve seats checked), as the shop will likely not be able to do anything about the (expected) bent valves on my K20Z3 head before he has to close up shop.

 

[lookforjoe]

For the limited info I've seen, it looks like the answer is yes and no. It seems chatter is a "thing", even to the point of be audible at times, but the actual cause most cited is momentary low oil pressure. The spring in the tensioner is supposed to compensate under those conditions, but if the spring is weak they say it can all go off the tracks quickly. I haven't read back through your entire build thread, but I think I remember that you had to use a K20 pump and sump on the K24 to complete the swap? If that's the case, was swapping the pump just a straightforward bolt-in, or were some other mods required? I know nothing of what's involved so that's why I'm asking. Also curious if the broken links were next to each other or in random spots along the chain? It would not be out of the ordinary for several links (all at the point of impact) to be damaged. Random would be a little odd, but can still result depending on how the broken chain was whipped around before coming to rest. I agree that the cause may never be definitively known, but my hope is you will exhaust everything you can in the process because the only thing worse than repairing a major failure is ever having to do it again.

Using the K20 pump is bolt on, besides modding the base to clear the block. You just have to use the K20 chain & guide, those I bought from Honda. The links are randomly spread throughout the chain. The Honda guy I trust on K20a has built high output versions & never seen a chain fail. Stretch, yes, but not snapped links.

 

[jimmyx]

never seen a chain fail

Not specifically Honda, but I have seen a fair number of chains fail over the past 50 years. Never have I run into an early failure due to a defect. Most chain failures are ductile and lead to separation at the intersection of the link end and pin after a a good number of miles. Sometimes a failure will show up at the pin but the cause is a brittle fracture; yours appears to have multiple brittle fractures in the center of some random links. I've never seen a chain actually break directly in the center of a link. I wish I had paid more attention during my metallurgy class, but if there is anyone on the board that knows how this condition came about I'd love to know!

 

[Jonohhh]

Holy crap, that chain has been through some serious **** . That is a LOT of steel to simply crack or fatigue in such a short time.


I'd inspect the timing sprockets very, very, very closely for any signs of abnormal forces on the profile.

It is possible for a near total lack of tension to cause the chain to not seat properly on the oncoming/approaching sprocket teeth, which can put extreme forces between individual links on the chain ( potentially far greater than overall chain tension or force needed to drive the valvetrain). This is especially true as the chain wears and slack develops in the pins, but that shouldn't be a factor in your case.


You also don't want to reuse a damaged sprocket of course, so best to check anyway.

Oh and ofc, don't forget to pre oil the guides and soak the chain before the first run! I've seen people omit that step...which isn't particularly good for the chain or nylon guides.

 

[lookforjoe]

Holy crap, that chain has been through some serious **** . That is a LOT of steel to simply crack or fatigue in such a short time.
I'd inspect the timing sprockets very, very, very closely for any signs of abnormal forces on the profile.

You also don't want to reuse a damaged sprocket of course, so best to check anyway.

Oh and ofc, don't forget to pre oil the guides and soak the chain before the first run! I've seen people omit that step...which isn't particularly good for the chain or nylon guides.

I won't be re-using the crank sprocket for the replacement, since I have a complete other short block (to resolve the oil consumption issue with the current block)

I did not think to soak the chain & guides when I assembled that block, I just doused them with assembly lube... I really doubt that caused the chain failure though. There is no play in the links themselves. I will inspect & post pics of the old guides etc., when I take it apart.

 

[dcioccarelli]

No, just an OEM Honda unit for chains and tensioner. I don't rape the motor in use, nor is it over stock output to any meaningful degree, so I don't see the need for it.

took pics of the chain details- multiple single link fractures. I have emailed the vendor, not that they will do anything, however they should know there is a QC issue.

arranged the chain so the visible exterior fractures are mostly grouped in the center of pics

View attachment 63708

other side

View attachment 63709

I'd be surprised if the chain itself was the root cause of the problem given that a number of links failed (what is the probability of this happening simultaneously?). Isn't it more likely that something became blocked causing the sprockets to pull the chain apart?

 

[lookforjoe]

I'd be surprised if the chain itself was the root cause of the problem given that a number of links failed (what is the probability of this happening simultaneously?). Isn't it more likely that something became blocked causing the sprockets to pull the chain apart?

I can't conceive of what would create that scenario. Especially since the motor just stopped - under light load, no uneven running, jerkiness or anything that would indicate binding/restriction/blockage of moving parts.

 

[Jonohhh]

I won't be re-using the crank sprocket for the replacement, since I have a complete other short block (to resolve the oil consumption issue with the current block)

Ahh okay

I did not think to soak the chain & guides when I assembled that block, I just doused them with assembly lube... I really doubt that caused the chain failure though. There is no play in the links themselves. I will inspect & post pics of the old guides etc., when I take it apart.

That's totally adequate then...it only needs a slight amount of oil for full protection. Definitely not the cause of chain failure, it's more for the guides sake.

 

[lookforjoe]

Started stripping the back of the car to prep for engine removal

EMS out

trunk panels out, exhaust out

That was a few days ago - it's been way to hot to work in my driveway, so I've been taking care of the yard work/landscaping that needed attention.

Today I started putting the replacement block together. Hone, new rings, new rod bearings. $525 for the machine work/rings/ ring gapping/bearing clearance checks, etc.

Block on the stand

removed the galley plug for the RSX oil pump block off

nice clean crank

Pistons assembled on rods, ready to go in block. He marked each per cylinder he fitted them for to make my life easier

pistons & rods installed (drop of oil on rings to help install), assembly lube on bearings & crank in, lube on rod cap bearings, caps torqued (2 stages, 25ft/lb then 120º)

hondabond for carrier plate, mains bolts oiled & torqued in sequence; two stages (22ft/lb, then 56º). 14 M8 bolts torqued in sequence to 16 ft/lbs

 

[lookforjoe]

High 90's today, so I only worked (slowly) for a few hours, setting up the car for drivetrain removal, disconnecting the top harnesses, fuel lines, removing slave cylinder, disconnecting shift cables, separating the AC compressor from the engine, removed the alternator & disconnected wiring harnesses from the motor to the spare well junctions. Drained the fluids, and that was all I could manage. Went for a dip in the town pool after that with the Mrs.

noting AC wiring routing

compressor tie wrapped to the right engine cover hinge, works perfectly in that supporting role

also noted the exhaust manifold gasket that came with the header doesn't look great - certainly looks like it was either leaking off #3 or getting ready to. They shipped that loose in the box & I recall it had a slight kink in it - I'm going to assume that was the cause. Either way, I think I'll go back to the graphite gasket.

 

[Longitudinal]

It hasn't been long enough since you had this view of things. But don't worry. You can rebuild it--better, stronger, faster than before.

 

[kmead]

It hasn't been long enough since you had this view of things. But don't worry. You can rebuild it--better, stronger, faster than before.

The six million dollar X…

 

[Longitudinal]

The six million dollar X…

They all eventually get there.

 

[Dan Sarandrea (Phila)]

also noted the exhaust manifold gasket that came with the header doesn't look great - certainly looks like it was either leaking off #3 or getting ready to. They shipped that loose in the box & I recall it had a slight kink in it - I'm going to assume that was the cause. Either way, I think I'll go back to the graphite gasket.

View attachment 64116

View attachment 64117

Remflex gaskets are Da Bomb.


On a side note......
I'm not trying to rub anything in, not trying to disparage anyone's efforts, not trying to make a point at the expense of anyone.

I hope people in the "Doing a/an XXXXX engine swap will make my X more reliable" camp are paying attention. Nothing is perfect, nothing lasts forever, 90% of everything is crap (© George Carlin), and **** happens.

 

[lookforjoe]

Worked on removing the drivetrain today, much more tolerable temps.

steps (following process used in 2020):
Disconnected heater hose from tube, disconnect heater valve hose, removed torque mount & bracket. Installed engine support.
Removed brakes, coilovers, hang calipers from towers. Disconnect axles from outer CV's (note - 2 CV bolts stretched), remove axles from transaxle.
Remove left & right control arms (18mm bolt heads, 21mm nuts) - (support arm on stool while removing bolts, swing arm downward to lever out of mount ears).
Remove nuts & washers for subframe mounts, remove 2 bolts each for forward & rear center attachment. Remove subframe.
Disconnect radiator hoses from tubes. move shifter cables out the way of drivetrain removal.
Raise body, remove jack stands, lower body until drivetrain sits on dolly. Reposition drivetrain during the lowering process to clear water pump
Remove engine support
Raise body, reinstall jack stands. Gradually raise body & reset jack stands until drivetrain clears wheel arch. Pull drivetrain out pass side

DS hook in place

RS hook plate

cables out the way

lowering

reposition to clear water pump (note AC bracket needs additional bracing to reduce vibration/load on manifold support)

almost down - had to remove the AC/ idler mount plate to avoid having to lift the body too high.

set on dolly

and out

 

[lookforjoe]

Remflex gaskets are Da Bomb.
On a side note......
I'm not trying to rub anything in, not trying to disparage anyone's efforts, not trying to make a point at the expense of anyone.
I hope people in the "Doing a/an XXXXX engine swap will make my X more reliable" camp are paying attention. Nothing is perfect, nothing lasts forever, 90% of everything is crap (© George Carlin), and **** happens.

It does. To me, with the car, it's been that way regardless of drivetrain origin

 

[kmead]

Worked on removing the drivetrain today, much more tolerable temps.

steps (following process used in 2020):
Disconnected heater hose from tube, disconnect heater valve hose, removed torque mount & bracket. Installed engine support.
Removed brakes, coilovers, hang calipers from towers. Disconnect axles from outer CV's (note - 2 CV bolts stretched), remove axles from transaxle.
Remove left & right control arms (18mm bolt heads, 21mm nuts) - (support arm on stool while removing bolts, swing arm downward to lever out of mount ears).
Remove nuts & washers for subframe mounts, remove 2 bolts each for forward & rear center attachment. Remove subframe.
Disconnect radiator hoses from tubes. move shifter cables out the way of drivetrain removal.
Raise body, remove jack stands, lower body until drivetrain sits on dolly. Reposition drivetrain during the lowering process to clear water pump
Remove engine support
Raise body, reinstall jack stands. Gradually raise body & reset jack stands until drivetrain clears wheel arch. Pull drivetrain out pass side

DS hook in place
View attachment 64230

RS hook plate
View attachment 64231

cables out the way
View attachment 64228


lowering
View attachment 64227
View attachment 64229

reposition to clear water pump
View attachment 64232

almost down - had to remove the AC/ idler mount plate to avoid having to lift the body too high.
View attachment 64233

set on dolly
View attachment 64234

and out
View attachment 64235

View attachment 64236

You forgot the picture of the long IKEA shoehorn to guide it out…

Painful.

Definitely looks like soot up the back of the valve cover or at least a lot of heat.