Head warped through to cam bearings

[scoobydo123]

Hi again. Machine shop said they had fettled the cam bearings after machining head and block but exhaust is still binding :-( IMO machine shop should have straightened head prior to machining flat. I am mow left with a flat head and block but have rocking exhaust cam that is binding a bit:-( does anyone know of any machine shops who can deal with this in the UK.

[GreenV8S]

scoobydo123 said:

IMO machine shop should have straightened head prior to machining flat.

Straighten how? The usually technique is to claim a flat surface and machine everything else relative to that. If that leaves the cam bearings out of true then they'd need to be line bored again then new shells fitted. I'd have thought any engine machine shop would be able to do that for you.

[E-bmw]

^^^^ Wot 'e said.

Should be bread & butter for a decent machine shop.

[InitialDave]

Yes, as above.

First stop is what did they do, including what sequence they did it in.

[Megaflow]

GreenV8S said:

scoobydo123 said:

IMO machine shop should have straightened head prior to machining flat.

Straighten how? The usually technique is to claim a flat surface and machine everything else relative to that. If that leaves the cam bearings out of true then they'd need to be line bored again then new shells fitted. I'd have thought any engine machine shop would be able to do that for you.

Very unusual for a head to have cam bearings these days, they normally just run in parent metal, so if the head is warped enough knock them out of alignment then it is scrap I'm afraid.

[scoobydo123]

As what megaflow has put this head does not have bearing shells it is just line bored caps against the ally head. I have researched and I think best practice is check cam carrier for rock and if it rocks then straighten via a press and shimstock and oven bake to take stress out so that when it is unbolted it stays put. Then and only then machine the head to block face flat. I have seen videos where instead of baking you use the block and shims and use oxy acetylene to relieve the stress in the side of the head by getting just to melting point and the moving along the head. This seems feasible to me and do-able if you have access to oxy acetylene. Cannot get a replacement head so am up a creak without a paddle ;-( I appear to be in a dire situation :-(

Order of play thus far is head and block was given to the machine shop with the cams and cam caps. Block was machined and head machined. On assembly I found the exhaust cam was binding despite the machine shop saying that they had fettled the cam as it was bent. When I put the exhaust cam onto the inlet I get no rock so the issie is with the head in my world. Also confirmed with engineers straight edge I get rock on the exhaust side and also the rocker cover face is also showing signs as I can get a 4 thou feeler gauge under that between cylinders 3 and 4 ;-(

Edited by scoobydo123 on Friday 21st November 17:05

[stevieturbo]

Sure the wrong caps haven't been put in the wrong location ?

Have you tightened the caps one at a time to see if one, or more are binding ?

A little hone might clear it up.

[scoobydo123]

Yes caps are in the correct places. I have identified that it is cylinder 3 and 4 on the exhaust that is causing the binding. Have also plastigauged 3 and 4 and that also confirms as they are out of spec 1 and 2 are bang on.

This seems reasonable to get me back in the ballpark appreciate will need another skim. I can turn the cams by strong thumb pressure so is not a total bind but certainly takes quite a bit of pressure. Only other thing I thought of is using shim stock under the cap mounting surface to create space!

Edit cylinder 3 also was where the combustion gasses were leaking to the water jacket before I tore it down.

https://youtu.be/VMMj2OrUMxs?si=JM6LrTg6TT5h1VXR

Edited by scoobydo123 on Friday 21st November 19:57

[Hawkshaw]

Surely the head and cams should go back to the machine shop and let them sort it out?

Don't know what head this is, but if I have followed the description, it has already been skimmed so the underside is flat.

If your alignment error is 4 thou, then it should be possible to machine say 5 thou from the top face of the cam bearings and 5 thou from the mating face of the bearing caps. This will leave the bearings undersize, and not truly circular. They can then be line bored, to restore the correct diameter and alignment. This of course leaves the cam sitting slightly lower in the head, but should still be within tolerances as long as only the minimum of metal is removed to correct the error.

[scoobydo123]

Yes agree should go back. However starting to question how they didn't spot the problem and I personally think that the head should have been baked flat or use the above method which seems more than reasonable to get the camshaft alignment back to where it should be with perhaps just a hone required of the journals if anything.

Yes block has been machined flat and head has been machined flat. It is a ka24de head.

https://drive.google.com/file/d/1VylCKqUdpRP_ETTGo...

Edited by scoobydo123 on Friday 21st November 21:21

Edited by scoobydo123 on Friday 21st November 21:34

[Megaflow]

Hawkshaw said:

Surely the head and cams should go back to the machine shop and let them sort it out?

Don't know what head this is, but if I have followed the description, it has already been skimmed so the underside is flat.

If your alignment error is 4 thou, then it should be possible to machine say 5 thou from the top face of the cam bearings and 5 thou from the mating face of the bearing caps. This will leave the bearings undersize, and not truly circular. They can then be line bored, to restore the correct diameter and alignment. This of course leaves the cam sitting slightly lower in the head, but should still be within tolerances as long as only the minimum of metal is removed to correct the error.

In theory that is possible to do, ignoring concerns around if removing 5 thou from the bottom of the cam caps and then re machining leaves enough material to retain their strength, the biggest problem with that is going to be finding a machine shop with a boring bar long enough to line bore all the cam bearings in one hit.

[stevieturbo]

Why did you leave head to a machine shop in the first place ?

What specifically did you ask them to do ?

Obviously you cannot try these "DIY" heating methods to "straighten" a head, after already machining one surface flat.

Plastigauge is not really a means of determining if a head is straight or not etc.

Get a ball hone and give those two journals a bit of a clean up, in lieu of a more suitable line boring arrangement. Or there are many videos online with different methods with either drill and flap wheel type setup, wet and dry, scotch brite etc etc.

etc etc https://www.youtube.com/watch?v=kGvg4fkyRAQ

[Hawkshaw]

Megaflow said:

In theory that is possible to do, ignoring concerns around if removing 5 thou from the bottom of the cam caps and then re machining leaves enough material to retain their strength, the biggest problem with that is going to be finding a machine shop with a boring bar long enough to line bore all the cam bearings in one hit.

I entirely agree. It may or may not be practical in this case, but I thought it worth explaining the basic process.

OPs point seems to be that the machine shop should have straightened the head with heat and press to start with. Maybe, but it's a bit late for that now. Even if they had done that, it would need finish machining.

Looking at the video, it is odd that the warp is all on one side, and there seems to be a bit more than 5 thou involved. If so, it is quite possibly scrap, in real terms.

How would you tackle it?

[scoobydo123]

It went to the machine shop as the engine was pressurising the water system on cylinder 3. Instructions were to ensure head and block was finish is suitable for MLS gasket and check and measure clearances. Thanks for the link will have a look at that. I used plastiguge prior to sending it out as I suspected it was binding. At the time I didnt not have a valve spring compressor to take the valves out. This was also mentioned when it was dropped off and was told it had been addressed. When I got it back due to delay on ordering I thought I would regrind any valves and this was when I found it was binding still :-(

Edited by scoobydo123 on Saturday 22 November 10:31

[Megaflow]

Hawkshaw said:

Megaflow said:

In theory that is possible to do, ignoring concerns around if removing 5 thou from the bottom of the cam caps and then re machining leaves enough material to retain their strength, the biggest problem with that is going to be finding a machine shop with a boring bar long enough to line bore all the cam bearings in one hit.

I entirely agree. It may or may not be practical in this case, but I thought it worth explaining the basic process.

OPs point seems to be that the machine shop should have straightened the head with heat and press to start with. Maybe, but it's a bit late for that now. Even if they had done that, it would need finish machining.

Looking at the video, it is odd that the warp is all on one side, and there seems to be a bit more than 5 thou involved. If so, it is quite possibly scrap, in real terms.

How would you tackle it?

We need some more information on how the head got warped to that extent first, because I fear it is scrap.

Was there any over heating?

I ask because I suspect there was and that is the cause of the head to warp. The concern here is if the head has got hot enough to warp that much then it has almost certainly got too hot to actually now be usable as a head and is likely scrap. You will need an expert in this head to know what the hardness should be and what it is now and is that a problem.

Some context for that statement, one of the concerns/issues with the K-Series (Rover not Honda) is the design of the water jacket in the head and if you get them too hot you can anneal the aluminium around the exhaust ports, Dave Andrews will confirm this, because that is where I got it from, and once that happens, the head is junk.

When my S1 Elise head went to Dave he checked it for hardness and it was almost at the factory hardness after 55k.

Edit: Apologies, I had not seen the OP's video in the Google drive link, I have now seen it. All of the above still stands, to an extent, however it is very strange that it is only on one side of the head...

Edited by Megaflow on Saturday 22 November 10:56

[scoobydo123]

Thanks Megaflow for your input. Car was running fine and producing decent power. It has in the past suffered in the ownership of the previous owner who ignored that it was consuming water. I thought I had fixed with a composite gasket as opposed to MLS as the deck surface was more like a file. During a journey the coolant got to 100c and I got fuel cut. When I checked 1L of coolant had been pushed to the reservoir. I this time decided to bite the bullet and get the deck resurfaced. Can only guess that the warp is concentrated on the exhaust side as that generates the most heat. The arp washers are not digging into the head when torqued. Really need to try and save the head if I can as almost impossible to source a replacement

Edited by scoobydo123 on Saturday 22 November 11:32

[DVandrews]

I would first ensure the cam is straight as the bind might be due to some distortion, then I would check to see whether the bind is on the bearing cap or in the head, this will determine what , if anything can/should be done. I have remedied this situation on a number of occasions on K series VVC heads which often (for reasons I wont go into) have the bearing housings out of line from front to back of the head. It isn't that difficult to remedy given the right approach and a lot of patience.

[scoobydo123]

Hi I have confirmed with engineers straight edge that the warp is in the head side of cam carrier. Cylinder 1 2 has no rock as soon as I extend to cylinder 3 I start to get rock and I feel cylinder 4 is even lower. I used 1 thou shim stock as a spacer under the cam caps and still it was binding I then tried 2 thou and still binding. I have moved the exhaust to the inlet and no difference so camshaft is ok. I definitely can afford patience with the head as I have no other choice as cannot source a replacement. Thanks

[Hawkshaw]

Nissan KA24DE heads are still available new.

Several listings on Ebay. The most expensive is around £900 from a UK source, and you can get down to around £600 if you don't mind a Chinese one.

Not worth wasting time trying to repair it. Just buy a new one, job jobbed.

[scoobydo123]

These are not available unfortunately this is a unique casting with the dizzy on the back of the head. part number 11040-5C001

Edited by scoobydo123 on Sunday 23 November 11:45