Can You Surface IDI Cylinder Heads with Sandpaper?

[bulletpruf]

So, I surfaced some cylinder heads this weekend in the garage quickly and accurately with some 60 and 80 grit ceramic sandpaper (Don't use box store sandpaper! Get Hercules ceramic sandpaper from Harbor Freight), a feeler gauge, an OEM Tools 2' machinist straightedge, and an inexpensive granite surface plate. Curious whether this will work on IDI heads with the pre-cups, because some machine shops won't surface these heads because of the pre-cups.

Anyway, I used a 12 x 9 x 2 granite surface plate that was about $80 from Amazon, and after I cleaned the machined surface on both heads, I found that one was .0025" warped and the other was .003" warped. Both were within spec of .001" per cylinder (max of .004" per head) but I've been wanting to try this process for a while and I also wanted to give the mating surface a bit more texture to grip the gasket (not using MLS gaskets).

I used 3M's 77 spray adhesive to secure the sandpaper to the block and I used the surface block like a sanding block. I used my straightedge and a black sharpie to draw a grid of diagonal lines to give me a better idea of where I was removing material.

I started with 60 grit, and after a few minutes, when I checked my progress, and I had already taken it down about .001". At that point, I switched to 80 grit to finish it up. I was able to get both heads straight within .0015"; that's the thinnest feeler gauge that I have and it wouldn't go under the straightedge anywhere.

I realize 99% of the folks get this done at the machine shop, but if your machine shop is an hour away, you don't have time to wait in the queue, and/or you just want an excuse to buy more tools and learn a new process, this is worth trying. I was surprised at how easy it was.

I shot a video of the process in case anyone is interested. Mods - please feel free to delete the link if not allowed.

xc_hide_links_from_guests_guests_error_hide_media

You must be registered for see images attach

 

[scsmith42]

That's an interesting technique, what I'd call an "old school" method. If I were to do something like that I'd probably try to find a wider surface plate so that the entire head was on the plate at all times. Otherwise I find the method to be valid.

Those look like angle plug small block chevy heads, but I confess that it's been close to 40 years since I last did machine work on some.

Thanks for sharing.

 

[bulletpruf]

That's an interesting technique, what I'd call an "old school" method. If I were to do something like that I'd probably try to find a wider surface plate so that the entire head was on the plate at all times. Otherwise I find the method to be valid.

Those look like angle plug small block chevy heads, but I confess that it's been close to 40 years since I last did machine work on some.

Thanks for sharing.

I was worried about the smaller size, too, but I couldn't find a large enough surface plate at a reasonable price.

These are AMC V-8 heads for my 24 Hours of Lemons road race project. I'm building a low-buck 350'ish hp engine for it.

You must be registered for see images attach

 

[Clb]

Sheet of glass and a towel on top of the granite,? Maybe?
Did you mike the granite first?
I've seen some less than stellar treatments in commercial sourced slabs.
But I have glass matched stuff that then stayed sealed...
Reason being glass (iirc) is poured onto a liquid surface to cool...

 

[bulletpruf]

Sheet of glass and a towel on top of the granite,? Maybe?
Did you mike the granite first?
I've seen some less than stellar treatments in commercial sourced slabs.
But I have glass matched stuff that then stayed sealed...
Reason being glass (iirc) is poured onto a liquid surface to cool...

It's a granite surface plate. Precision ground to .0001". Much flatter than glass or store bought granite. I tried to use thick plate glass in the past, but it wasn't super flat; maybe .004" variation if I recall correctly.

 

[Clb]

Oooh really, sweet I like it.
Do they give you storage instructions?
Iv seen countertops stored against a wall bow.
I can't see why that wouldn't work, shy of the size / length of the heads vs stone.
Do you flow a lubricant/surfactant
( water soluble ( sp) cutting oil/ dawn dish soap) like wet sanding paint...

 

[bulletpruf]

Oooh really, sweet I like it.
Do they give you storage instructions?
Iv seen countertops stored against a wall bow.
I can't see why that wouldn't work, shy of the size / length of the heads vs stone.
Do you flow a lubricant/surfactant
( water soluble ( sp) cutting oil/ dawn dish soap) like wet sanding paint...

No storage instructions, but it just sits on my stainless steel toolbox top.

I did it dry.

thanks

 

[WrenchWhore]

I'm always intrigued in these do it yourself at home methods. Just need to figure out a home brew magnaflux and you're in business.

 

[bulletpruf]

I'm always intrigued in these do it yourself at home methods. Just need to figure out a home brew magnaflux and you're in business.

Buy a lightly used yoke and some powder. I get a fair amount of use out of mine; used it last week to mag a block and heads.

You must be registered for see images attach

Speaking of DYI, I'm also a fan of the shoestring and sandpaper on a crankshaft; works quite well. Used it on my IDI crank.

xc_hide_links_from_guests_guests_error_hide_media

 

[FrozenMerc]

You can just pop the pre-cups out. Hell, most of the time, the darn things fall out as you pull the head away from the gasket....

 

[bulletpruf]

You can just pop the pre-cups out. Hell, most of the time, the darn things fall out as you pull the head away from the gasket....

I've never had any luck popping out pre-cups.

 

[IDIoit]

I'm always intrigued in these do it yourself at home methods. Just need to figure out a home brew magnaflux and you're in business.

Magnaflux comes in cans, i use this stuff to check cracks on my products

You must be registered for see images attach

 

[bulletpruf]

Magnaflux comes in cans, i use this stuff to check cracks on my products

Just to clarify, Magnaflux is the manufacturer of the well known electric yoke used to magnetize metal parts that have been coated in iron powder, known as magnetic particle testing.

Zyglo is used for dye penetrant testing. Dye penetrant testing typically involves 2 - 4 cans of aerosol spray, and it's fairly expensive.

Both are good methods for detecting cracks, but they're different processes.

 

[IDIoit]

Just to clarify, Magnaflux is the manufacturer of the well known electric yoke used to magnetize metal parts that have been coated in iron powder, known as magnetic particle testing.

Zyglo is used for dye penetrant testing. Dye penetrant testing typically involves 2 - 4 cans of aerosol spray, and it's fairly expensive.

Both are good methods for detecting cracks, but they're different processes.

ive also made plates to block off coolant passages to check the block for coolant leaks, and cavitation pin holes.

my first IDI i built had a issue, which turned out to be a spider webbed block from a lower stud install

 

[Indadesert]

Can You Surface IDI Cylinder Heads with Sandpaper?​

No! No you can’t and you should not.