head machining marks

[oxford]

Hi everyone
As per my earlier post, I have started the engine on my BN4 but had some leaking on the r/h side of the head/block mating surface. I have now pulled the head and although I can't find any specific issue I have noticed some marks left after machining. They are deep enough to be felt with a fingernail, but not rough. I'm wondering if this may affect the integrity of the mating surfaces or if the head gasket should seal over them. My feeling is that they are a bit too deep. I've attached a couple of pics. It's a bit difficult to see, but you get an idea. Any help here would be appreciated.
Cheers Matthew

 

[tahoe healey]

Unfortunately, that is exactly what I found 12 years ago as the cause of a leak between the head and block. I took it to a machine shop and presto, no more leak.
TH

 

[blueskies]

That seems extreme. Didn't you just have the head and block resurfaced? At least you are lucky that the marks are on the head and not on the block. Or does the block have similar marks? Some head gaskets, probably especially the cheaper ones like it seems that you used, require very smooth surfaces.

You could take it back to the machine shop that did the work and ask for their opinion. Or take it to another machine shop and see what they say. If you don't want to have it resurfaced again, one of the copper based head gasket coatings may help.

 

[Randy Forbes]

Unfortunately, that is exactly what I found 12 years ago as the cause of a leak between the head and block. I took it to a machine shop and presto, no more leak.
TH

I concur; a light skim-cut (usually .003" - .004") should clean that up.

Make sure the machinist knows what type of head-gskt you'll be using, because one size (surface RA) no longer fits all.

 

[oxford]

Thanks for the advice everyone.
Yes, Blueskies. I did have the head and block resurfaced. I didn't notice the marks before hand. I'm not that pleased! The block does have some marks but they're not as deep. I might try some wet sanding with a 600 or so paper on the block, but I'll get the head redone. I have some copper based head gasket coating so I'll use that also; and I'll replace the studs and use a better (read more expensive) gasket. Don't want it to happen again.
Cheers
Matthew

 

[pan]

I had big problems with an engine reconditioner several years ago. Machining like this was one of the issues. Threats of legal action finally sorted out the mess!

 

[Bob_Spidell]

Off topic, I suppose, but it looks to me that there's an awful lot of rust in the coolant passages of that head. Don't know if heads can/should be hot-tanked, but I'd try to clean that rust out somehow.

 

[Randy Forbes]

Thanks for the advice everyone.
Yes, Blueskies. I did have the head and block resurfaced. I didn't notice the marks before hand. I'm not that pleased! The block does have some marks but they're not as deep. I might try some wet sanding with a 600 or so paper on the block, but I'll get the head redone. I have some copper based head gasket coating so I'll use that also; and I'll replace the studs and use a better (read more expensive) gasket. Don't want it to happen again.
Cheers
Matthew

If you want to attempt that, may I recommend a method I've used successfully on BMW I-6 cylinder blocks; when our house was built a few years ago, I asked the granite guy if he would cut me a couple of small blocks. This they routinely do, making chopping-blocks to match the rest of the counter tops. He cut me two (2) 11" x 15" x 1-1/2" blocks (one for the kitchen, one for the shop...).

First step was a light coat of machinist's blue dye on the top deck of the block. For a project like this, a thin coat from an aerosol application works best; any build up of dye (or worse, paint) will clog the sandpaper quicker.

Using the flattest side, I wetted (grammar?) a full sheet of 600 sandpaper, the granite and the top of the block, and began drawing the granite back and forth over the longest length of the block (front to back). There was enough overhang that I could keep the sandpaper in place with my fingers during the process, though the suction of the water does most of that work. Liberally applying water from a spray-mist bottle will minimize the sandpaper clogging up (even though, you'll still need to lift it off occasionally to rinse it down good).

The flatness of the granite will keep your efforts even, and its weight will insure uniform pressure from one end to the other. I was pulling the sheet of sandpaper halfway past each end of the cylinder block (when reversing is when you need to take care, or you'll catch and tear the paper).

Just a suggestion, of course, but you wouldn't want to make things any worse than when you started...

I expect just about every town these days has a granite place, I'm sure they'd square off one of their drops for a minimal charge (ours were free, but when you're already buying some four slabs, they'll do that for you!)

Off topic, I suppose, but it looks to me that there's an awful lot of rust in the coolant passages of that head. Don't know if heads can/should be hot-tanked, but I'd try to clean that rust out somehow.

Cast-iron lends itself very well for hot-tanking (in a caustic solution) and while you wouldn't want it left in there indefinitely, it can soak a couple-few days until the water-jackets are pristine clean.

Cam bearings in the block would be ruined, and they were hard to come by quite a few years ago__pretty sure they're readily available once again__so you want to have them already in hand before the cylinder block goes in.

With more and more aluminum engines in use today, hot-tanking may become a thing of the past__not exactly at the top of any green-lists__and heated (water-based) spray-cleaning machines are already very popular in machine shops; load it up at the end of the day, turn it on and unload the parts the next morning!

 

[oxford]

Thanks for the detailed reply Randy. We just had bench tops replaced so I might contact the company and see if they can help. It looks like a good way to flat the block. I have had the head and block hot tanked. I think the rust you can see is just from running water on the initial start up instead of coolant. I wanted to use water initially so I could drain it out with any rubbish left from the hot tanking. The block isn't as bad as the head and I think with a little rubbing, that it should be ok. I'll use some copper gasket sealer also.
Cheers
Matthew

 

[Brinkerhoff]

If you can feel those grooves with a fingernail , I doubt 600 grit will be aggressive enough for you to cut them down by hand sanding with a block ( given time , effort etc.) ! That head will need to be re surfaced. Before final assembly fit the head to the block without a head gasket and without , then with studs. The head should lay perfectly flat on the block flat with just its own weight. Try sliding a .002" feeler guage around the perimeter between the block and the head. Its not that unheard of that the head is surfaced at an angle other than 90 degrees to the studs ( seen this more than once).
Also the stud holes in the block should all be dressed with a countersunk bit to remove the very top of the thread which raises up when the stud is tightened. This can prevent the head from laying flat to the block ( seen this a lot)
So in the end the question of what head gasket to use or to use a dressing on the gasket or not , depends on the quality of the mating surfaces you have.

 

[blueskies]

You probably want to look for a machine shop with a top quality machine to resurface the head. Not sure how the British did it back in the day, but at least some American manufacturers used linear block (and head?) surfacing machines instead of rotary machines. The original GM blocks from the 60's, for example, had visible straight lines left front to back instead of the swirl patterns left by the machines used in many machine shops today. Apparently someone still has linear machines, as those who most expertly remove the original VIN numbers and then fake the stamped VIN markings on the front of GM blocks manage to recreate those linear patterns.