Hot Rod Forum banner

1 - 20 of 28 Posts

·
Registered
Joined
·
157 Posts
Discussion Starter · #1 ·
I got these impressions on the mating surface of my aluminum heads. It isn’t pitting. It’s almost like the composite gasket screenprinted itself onto the head surface. Cant get it off with a plastic putty knife and don’t want to put anything abrasive on it. Any ideas?
616776
616777
 

·
More for Less Racer
Joined
·
20,117 Posts
if you can't feel any discontinuity don't worry about it
What he said^^^

It's just gasket face coating pressed into the pores of the metal basically....the surface finish from any cutter finish is not smooth at the microscopic level. It has to be buffed reflective to actually be smooth.
Once you've scraped the surface down with a razor blade, all that is left is the shadow remains of coating down in the grain of the surface finish....much like stained wood finish.
 

·
Registered
Joined
·
119 Posts
Might try a FINE scotchbrite pad attached to a flat piece of wood and sprinkled liberally with diesel fuel. Go lightly and don't push unevenly or on hard to get spots. Just a light touch............
They also sell some Scotchbrite blocks that are thick but soft. You don't want a shiny finish, just clean.
 

·
Registered
Joined
·
14,207 Posts
Scotch bright has imbedded fine grit that gets into everything mechanical, your cleanup must be meticulous and then some or you get to kiss things like valve guides goodbye.

Bogie
 

·
Registered
Joined
·
119 Posts
Scotch bright has imbedded fine grit that gets into everything mechanical, your cleanup must be meticulous and then some or you get to kiss things like valve guides goodbye.

Bogie
Since he is working on a flat surface on the face of the head and using a liquid it should be very easy to flush/wash the surface clean. Any abrasive leaves residue which much be flushed away after the machining process. Abrasive is used for crank grinding, cylinder honing, and even resurfacing heads, so exercising a little care should alleviate any problems. It was good that you mentioned this point though, because cleanliness is something that needs to be taken into account.
 

·
Registered
Joined
·
14,207 Posts
It’s like a reminder, many people don’t realize that stuff like Scotch Brite is not just a coarse, stiff plastic but actually has an a powder abrasive imbedded that sluffs off.

Bogie
 

·
******* Professional
Joined
·
1,264 Posts
Might try a FINE scotchbrite pad attached to a flat piece of wood and sprinkled liberally with diesel fuel. Go lightly and don't push unevenly or on hard to get spots. Just a light touch............
They also sell some Scotchbrite blocks that are thick but soft. You don't want a shiny finish, just clean.
NO, just NO frickin scotch brite pads or rotary wire brushes on an engine!! Never!

Razor blades, rags, and carb cleaner are acceptable. I sharpen a 1" putty knife with a file to razor sharpness and use that.
 

·
Registered
Joined
·
119 Posts
NO, just NO frickin scotch brite pads or rotary wire brushes on an engine!! Never!

Razor blades, rags, and carb cleaner are acceptable. I sharpen a 1" putty knife with a file to razor sharpness and use that.
I built my own crankshaft polisher and it does beautiful work using a belt with abrasive media attached.........just like the professionals do. They also have abrasive grinding wheels for finishing head surfaces. If you prefer not to use proven practices, thats your choice..............but all engines and their componests have to be cleaned throughly before assembly so there should be no problem. One other thing.............people often lap the valves into their seats using abrasive lapping compounds. Vapor blasting with abrasives is routinely done to aluminum heads to close the cells of the aluminum and produce a nice sheen on older heads. Abrasives are quite simply a proven product in building engines.

 

·
Race it, Don't rice it!
Joined
·
8,069 Posts
Abrasives are well known to destroy engines. Care is needed. in this case an abrasive nets you nothing but hte risk of getting it somewhere you don't want it it higher than the need for it.
I'd send it as is and worry about whats for lunch.
 

·
******* Professional
Joined
·
1,264 Posts
I built my own crankshaft polisher and it does beautiful work using a belt with abrasive media attached.........just like the professionals do. They also have abrasive grinding wheels for finishing head surfaces. If you prefer not to use proven practices, thats your choice..............but all engines and their componests have to be cleaned throughly before assembly so there should be no problem. One other thing.............people often lap the valves into their seats using abrasive lapping compounds. Vapor blasting with abrasives is routinely done to aluminum heads to close the cells of the aluminum and produce a nice sheen on older heads. Abrasives are quite simply a proven product in building engines.

The OP's engine isn't completely disassembled. How should he clean up after sanding the block deck surface? How do you control the depth of your sanding of the aluminum head? Do you really advise sanding the surface of those AFR heads with a scotch brite pad??
 

·
Registered
Joined
·
5,077 Posts
engine machinists just love mechanics who take a roloc to aluminum heads; to save time and effort just take the heads to your machinist and have them decked before 'cleaning'.
 

·
Registered
Joined
·
119 Posts
The OP's engine isn't completely disassembled. How should he clean up after sanding the block deck surface? How do you control the depth of your sanding of the aluminum head? Do you really advise sanding the surface of those AFR heads with a scotch brite pad??
He was not asking about the block deck surface. If he needs to freshen the block deck, then he needs to take the appropriate steps to be able to insure he gets any grit out. If the surface of the deck isn't satisfactory, are you suggesting that he do nothing ?

Some problems can be fixed with scraping but some need different methods. So it depends on what the problem is before deciding what needs to be done. A block can be tilted so that abrasive tends to fall away from rather than into the engine. Cylinders and crevices can be stuffed with rags and/or masked Ultimately if the problem can't be fixed that way, then the engine would need disassembly. Doing absoulutely nothing and hoping it works is a recipe for failure later.

As for controling the depth............metal removal is going to be minimal at best. Probably won't even be able to measure it with conventional shop available tools.I'd be surprised if it took .001 off.
Milling should only be done when you want to remove a sizeable amount of metal to correct warping or to raise compression. Milling will remove more material than grinding. If there isn't a warpage problem, then minimal removal of surface metal will restore a head. By a "sizeable amount", I'm meaning .005 or more.

And the last question......Yes. Look at the heads closly and you will see machining marks. Microscopic inspection would show peaks and valleys. That surface roughness helps seal. A fine scotchbrite pad supported by a flat backing plate will remove the problem areas and still keep a good sealing surface.

Something to consider for the guys that advocate milling as being the only way to correct the surface. Do you believe that people who race for a living and are constantly disassembling their engines remill the surface every time? Also, when engines are decked and heads resurfaced, you can create problems for the engines valvetrain if its a non-adjustable valve train.

Don't know why there is so much paranoia over a little grit, because the whole engine machining process consists of operations that use abrasives and often coolant containing other impurities. Its a fact of life that machining is a dirty process.......you just need to clean the parts well when done.
 

·
******* Professional
Joined
·
1,264 Posts
I really don't think that AutoGear was advocating surfacing the heads to clean them. He was saying that a machinist will likely need to surface the heads if you sand on them, so might as well just surface them in the first place! I thought it was very strange to tell someone to sand the surface of an expensive head. Not exactly an offshore casting!

I can tell you that a little grit goes a long ways! I once primed my oil pump on a V6 rebuild with an old drill that shed some brush particles into my lifter valley because I had the intake off at the time. Primed that oil pump really good for a few minutes, turned the engine over 1 rev and did it again! Took the bearings out of the engine over the next 4000 miles. Sent the bearings into Mahle and they analyzed/sent me microscopic images and logic supporting the "strange debris in the oil" - so tore it down completely, back to the machine shop, resized two rods, line hone again, replaced the crankshaft, bearings, cam bearings, rings, radiator (has oil cooler) and started over from scratch - even took lifters apart and valves out of the heads to clean. This time when I primed the oil pump I had the intake on and I found had a nice collection of grit on top of the intake underneath the drill. It was at that point that I realized what I had done the first time. A real blonde moment!

So you can give me all your excuses for how your use of abrasives will be fine if you do some rudimentary cleaning and try to not take off too much and I will ignore it. My personal experience cost me a lot of money, time, and effort. Nuff said.
 

·
Registered
Joined
·
14,207 Posts
Well you het the key issue which is cleaning, in this particular case I, as I think others did, got the feeling that the head was going to be attacked without benefit of complete disassembly and cleaning.

I expect that the issue with excessive valve guide wear that pops up on the forum fairly frequently is the result of cleaning failure in the guide, often be the manufacturer.

So those of us that build engines with some frequency freak out when we see the garage hobbiest doing a partial disassembly and going at cleaning with abrasives, probably not even knowing that these things contain micro abrasives that need careful follow up to be sure the residues are removed and that process cannot be trusted to be sufficient without complete disassembly and cleaning of all parts that could be exposed.

Since I expect this is a street engine that doesn’t see disassembly unless there is a failure to be fixed what I saw as fretting around the fire ring would prompt me to set ‘em up and put enough mill cut to clear that area.

As for surface finish when new I like it just short of polished to where it is just becoming reflective. This being the new or fully refurbished starting point, not a goal at every service.

Bogie
 

·
Registered
Joined
·
5,077 Posts
I really don't think that AutoGear was advocating surfacing the heads to clean them. He was saying that a machinist will likely need to surface the heads if you sand on them, so might as well just surface them in the first place! I thought it was very strange to tell someone to sand the surface of an expensive head. Not exactly an offshore casting!
My personal and professional experience is that a whizz wheel on a flat, machined surface with a specific RA (measurement of how smooth a surface is); the aftermath will often a. not seal well and b. require excess steps and products to restore a leak-free seal. This often culminates with aluminum pieces needing a buzzcut.

And yes Im a NY'er (closer to Canada than NYC) and my sense of humor can be difficult to get across. Sorry :)
 

·
Registered
Joined
·
119 Posts
I really don't think that AutoGear was advocating surfacing the heads to clean them. He was saying that a machinist will likely need to surface the heads if you sand on them, so might as well just surface them in the first place! I thought it was very strange to tell someone to sand the surface of an expensive head. Not exactly an offshore casting!

I can tell you that a little grit goes a long ways! I once primed my oil pump on a V6 rebuild with an old drill that shed some brush particles into my lifter valley because I had the intake off at the time. Primed that oil pump really good for a few minutes, turned the engine over 1 rev and did it again! Took the bearings out of the engine over the next 4000 miles. Sent the bearings into Mahle and they analyzed/sent me microscopic images and logic supporting the "strange debris in the oil" - so tore it down completely, back to the machine shop, resized two rods, line hone again, replaced the crankshaft, bearings, cam bearings, rings, radiator (has oil cooler) and started over from scratch - even took lifters apart and valves out of the heads to clean. This time when I primed the oil pump I had the intake on and I found had a nice collection of grit on top of the intake underneath the drill. It was at that point that I realized what I had done the first time. A real blonde moment!

So you can give me all your excuses for how your use of abrasives will be fine if you do some rudimentary cleaning and try to not take off too much and I will ignore it. My personal experience cost me a lot of money, time, and effort. Nuff said.

First let me say that I once made my living as Machinist at a government weapons manufacturing facility.......after completing their 4 year apprenticeship which included not only shop work, but technical schooling and time in the assembly shops. Then I moved up to an Inspector position where I inspected quality gears, used co-ordinate measuring machines, and trained other inspectors. Surface finishes were part of our responsibility. I can tell you that virtually all of the finest finishes on parts are produced with abrasives. They go into precision assemblies that would fail quickly with a simple mill or lathe finish. We used to make ball valves for nuclear submarines and the final finsh was accomplished by lapping their surface with abrasives. Abrasives are not something to fear, they are a friend. One thing all those parts have in common is that someone cleans them properly before assembly. Thats imperitive.

In an awful lot of engine rebuilds, the hobbiest does not do a thorough job of cleaning . They may send it to a shop for various types of cleaning but they don't follow through with cleaning the oil gallies and getting into the small crevices. They let the block set and develop internal rust. The rebuild you mentioned employed abrasives to resize your rods, line hone your block, and likely rehone your cylinders. You were happy with that and apparently any and all abrasive residue ( inside a maze of internal passages) was easily and completely removed.

Now you have a simple head sitting on a workbench and for some reason you feel that it would be virtually impossible to get it clean after abrasive surfacing. Doesn't make much sense to me.


The basic question here is not whether abrasive will damage an engine, but whether using a scotchbrite pad will ruin the surface finish of the aluminum head. My opinion is that a head surface should have a little "tooth " to it rather than being high gloss smooth. With the scotchbrite if the finish looks too smooth, just use a coarser grit. Yep we all hate to do anything to something shiny that makes it look less desirable, but if its flat and has some tooth to it, it will work fine.
 

·
******* Professional
Joined
·
1,264 Posts
Now you have a simple head sitting on a workbench and for some reason you feel that it would be virtually impossible to get it clean after abrasive surfacing. Doesn't make much sense to me.
Where did you get that? Sanding with a scotchbrite pad simply destroys the flatness.

The basic question here is not whether abrasive will damage an engine, but whether using a scotchbrite pad will ruin the surface finish of the aluminum head. My opinion is that a head surface should have a little "tooth " to it rather than being high gloss smooth. With the scotchbrite if the finish looks too smooth, just use a coarser grit. Yep we all hate to do anything to something shiny that makes it look less desirable, but if its flat and has some tooth to it, it will work fine.
Unbelievable!! Where did you get that? I personally don't give a hoot about the surface finish of the head or the imprint of a gasket on it. Scrape it and the surface of a block deck with a razor blade and carb cleaner (remember when I said this).

But by telling someone to use a scotchbrite pad, you not only take a chance on his destroying the flatness of his aluminum head - you imply that is a good way to clean off gaskets. Since the bottom end of his engine is still assembled I could imagine him taking the scotchbrite pad to his deck and sanding the heck out of it. So how is he then to clean up all the abrasive now in his cylinders, pistons, rings, and lifter valley? It was just bad advice and I stated so.

The rebuild you mentioned employed abrasives to resize your rods, line hone your block, and likely rehone your cylinders. You were happy with that and apparently any and all abrasive residue ( inside a maze of internal passages) was easily and completely removed.
Yes, and my engine was completely disassembled and washed by the machine shop to remove all abrasives and residual bearing material. The point was that running an engine with abrasives inside is bad and that the OP did not have the luxury of complete disassembly to clean.

Just let it go.
 
1 - 20 of 28 Posts
Top