I'm trying to find info on the maximum head resurface / machining specs for a 2015 Accord 2.4L Earth Dreams K24W1 cylinder head. Bought the car with 75K miles, knowing it had been in an accident with previous owner.

I drove the car for another 6k with no problems - never overheated and ran fine all around, until I got a #2 misfire code and found a small coolant leak looking into cylinder 2. I'm not sure of the exact cause, but I think the previous accident may have hit the radiator or caused it to run without coolant for a period after the accident.

Regardless, I took off the head, found a small area in the head gasket by the #2 cylinder that likely caused the leak, and then took the head to be pressure tested and resurfaced. The machine shop found it was warped and had to be machined ten thousandths (0.010), but found no cracks and it held pressure fine.

I'm trying to find if 0.010 is within, or very far out of, spec for resurfacing. I haven't been able to find any info on the max "allowed" by Honda for this head. I've found a few instances of K20 engines saying 8 thousandths max, but nothing for the K24 (K24W1 Earth Dreams).

Wondering if I should just go for it, or if there is anything I should be concerned about in doing so. Also, I'm wondering if there are any adjustments I should accord for with any difference in tolerances.

Any assistance is much appreciated!

(I also posted in the engine machining forum - I'll remove if that's against the rules)

 

Do you not trust the machine shop? They know how much can be removed and usually have reference material for such.

Measure the head height. If it exceeds these specifications, it has to be replaced:

111.95－112.05 mm (4.4075－4.4114 in)

 

I do trust the machine shop, and they stated that the head was warped 0.010" and that it may be out of spec. The spec states 0.0039" is all that is allowed to be removed, which matches with the heights you provided.

I suppose my question is more along the lines of whether being 0.0061" shorter than the "official" minimum spec will really be a killer. Can it be accommodated by a thicker gasket, or are there any other issues I may have to deal with such as retarded timing, etc.? People modify cars all the time to get more power (obviously with certain risks), and I'd hate to just pitch this head in the bin if it's something that will simply "void the warranty", as opposed to being a major reliability issue. On the other hand, I don't want to put good money after bad and go down with a sinking ship if it's just plain toast. I also haven't checked how planar the surface of the block is yet, but I didn't think the block was as prone to warp as the head.

If the engine has such tight tolerances that 0.0061" will cause a big bang, or if a thicker gasket or other options are not viable, I'm also considering just doing a full engine swap. There are quite a few options on the auction sites for less than 1K with similar miles. If I have a warped block, I'd think that would be the way to go.

 

Tolerances are pretty tight these days, with most engines.

A thicker head gasket will absolutely work,if you can find one that will fit your needs.

The problems would be timing issues or piston to valve clearance. Thermal expansion and contraction during operation would play a role as to determining if the specifications are warranted or not.

You can assemble the engine and check for proper timing and P2V clearance before running the engine,but those clearances may change during operation.

 

Is there a drawback to running with a thicker head gasket? I've already talked to a local gasket manufacturer that can make a custom thickness head gasket, and they said it would be somewhere around $100. I've already paid $150 for the head machining. If there is little downside to putting in a thicker gasket and the block is straight, that seems like the way to go. However, considering what a pain it was to get this far just to take off the head, I don't want to re-assemble and then find out in 2k or 20k miles that I have to do it all over again, and only THEN go through and swap engines.

I also know that genuine Honda gaskets are typically recommended, but in my case, I don't think that's an option. I'd hope the custom one might be on par with the genuine Honda quality - at least I'd know it's not made in some sweatshop in China.

 

Honestly Id talk to the machine shop about it. I dont know how thick is too thick.

Off the top of my head I wanna say you shouldn't have an issue, but I do not have experience with this.

 

Head Warpage 0.05 mm (0.002 in) max.

no service limits given for surfacing

 

The service limit given is to not exceed the deck height specs:

Check the cylinder head for warpage. Measure along the edges, and three ways across the center:
If warpage is less than 0.05 mm (0.002 in) cylinder head resurfacing is not required.
Maximum resurface limited to the cylinder head height standard as shown.


Cylinder Head Warpage Standard (New): 0.05 mm (0.002 in) max.



Cylinder Head Height Standard (New): 111.95－112.05 mm (4.4075－4.4114 in)

 

So to follow up on progress: I had a 0.010 shim made to account for the resurfacing of the head, and I'll install the shim with an OEM gasket. I was told to remove the rivets from the OEM gasket and place the shim gasket as the second layer from the bottom.

However, now I'm wondering if I have another issue that I didn't originally think of...

The surface that was machined took off 0.010", but that also means the top of the head is also off by that much. So, the locations where the camshafts are mounted to the head are also off. I put a straight edge across the length of the head at the mounting holes for the camshaft holders, and it appears that the center of the head is about 0.005-0.006" higher than the ends. (I measure approximately 0.010" warp if I hold one end of the straight edge flat to one end of the head and measure the gap on the other end, so the head is crowned upward in the middle.)

After machining, the surface that mates to the block is flat, and the block itself is flat, so that surface should be good. But, the top of the head is still off, which I suppose is to be expected, since it wasn't machined. Will this variation from end to end cause problems with the camshafts or bearing surfaces, leading to excessive wear or some other issue? I can't find any info as to what the tolerances should be for those bearing surfaces.

Am I overthinking this? I have almost all the parts to put this back together and now I'm wondering if I'm screwing myself.