Milling the block or head

[Thomas]

I have a perfectly good block, OK almost pefectly good block except for some scratches on the top of the block when we took the head off.
My question is how much milling can be done to clean up some of these scratches without upsetting the overall timing of the motor?
Am also going to the British higher compression pistons vs. the American 8 to 1 compression pistons.
Thanks in advance.
Tom

[john 215]

Hi Tom,

Not a lot at a guess, the factory certainly as far as I have ever seen never gave any specs. If you go this route make sure you bolt the front cover on and get that machined as well as the block. Otherwise it will sit proud of the block and will never allow the head to sit level and seal.

Thicker head gaskets are available incidentally and would certainly rec. that to help with cam timing.

Cheers John




LIVE LIFE A QUARTER OF A MILE AT A TIME!

1976 Speke FHC Beauty Now with an overdrive conversion

1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6, BUILT NOT BROUGHT !!!!

[jclay (RIP 2018)]

You will have to ream out the STUD holes in the head when you remove metal from the mating surfaces. Remember that the stud holes are at an angle to the block surface, so the holes will not line up properly if metal is removed from the mating surfaces.

Clay

[url="http://www.jclay.me/"]My Triumph Site[/url], [url="http://www.triumphtechnical.me"]Technical Stuff[/url], [url="https://docs.google.com/folder/d/0B8MWEvqOpX3udEF4SmFQUW9RS09hbU5uNW5Wd0xrUQ/edit"]My Public Folder[/url],

[Thomas]

Thanks, guys. After reviewing previous posts and your recent info it is probably better to start with new (used) block and head. Glad I asked, thanks for responding.
Thomas

[nick]

There is a spec on the minimum head thickness and it is contained somewhere in this forum. I suggest a search. The measurement is from the top of the moon shaped cutout to the top of the head. If I could only remember the number....

[img][IMG]http://i615.photobucket.com/albums/tt234/nickmi/TR7%201975/Yellow.jpg[/img]
nick
'79 TR7 DHC
'76 TR7 FHC

[Stag76]

It's 4.427 inches or 112.45mm.

TR7 Convertible
Sprint Motor
MegaSquirt EFI

[trsforever]

Hi Tom, You might be surprised at how little will have to come off to clean up the surface, but only you know if they are scratches or groves. Normally a face will clean up with 0.005-0.008 thous of an inch this will not affect the valve timing, the most important thing is the bump clearance which is the top of piston to top of block which should not be less than 0.020 thou, you might gain a bit using the thicker gasket but that will lower the comp ratio which you are trying to raise. My personal preference is to have blocks ground not milled much better for removing the minimum amount of material.
I would suggest a piece of 80 grit emery tape on a flat sanding block about 8" long and give it a clean up first and then access the damage. And as John suggests machine the block with front cover fitted, and if you buy another block make sure it has "its" front cover! Good luck.

Regards Scott

[Hasbeen]

My old 7 engine must have had a serious decking or head shaving at some time in it's life.

It had a 0.12" thick solid sheet of brass machined up, like a head gasket, to match the top of the block. It was a very neat job, & must have suited the prepose well, as it did over 60,000 kilometres in my ownership, & it was the head that cracked, not it or the gasket that failed.

I left it with our local Triumph bloke, when it was easier to buy an engine to overhaul, to replace the cracked cylinder head, than buy a cylinder head.

Any competent machine shop could knock such a spacer up, using the block, [particularly if they were machining it, or a head gasket as a template.

Hasbeen

[Cobber]

Hearing of Hasbeen's brass head shim reminds me of an ancient diesel engine that I had in a boat, I couldn't get a head gasket for it so I made one out of copper sheet.
I'd cut, drilled, filed and annealed the copper sheet, fitted it on the engine and it lasted for many years, in fact long after the engine was scrapped the copper gasket was hanging on the wall of the shed.

"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"

80'Triumph TR7, 73'Land Rover (Ford 351. V8),
'89 Ford Fairlane
'98 MG-F, 69'Ford F250.

[Thomas]

As usual you guys (generic term) are great!
Thomas

[john 215]

Hi,

The steel shim repair is still used, I have fitted several over the years to Rover K series engines that have had to there ' banana ' shaped heads skimmed flat again.



Going back to your car, a good used block is the right repair IMHO, it not it cant be done as far as refacing your old one but why would you if you can get a replacement.


Cheers John


LIVE LIFE A QUARTER OF A MILE AT A TIME!

1976 Speke FHC Beauty Now with an overdrive conversion

1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6, BUILT NOT BROUGHT !!!!

[dursleyman]

Funny this thread has just come up because I just got my black back after having a liner fitted due to water damage in no.4, my fault I left it on the garage floor for a year or so! They had to face the top about 10-12thou and I realised yesterday when I was doing a bit of test fitting that I will need the timing cover doing to match.



Russ

1981 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

[john 215]

Hi Russ,

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><font size="3"><font color="red">I realised yesterday when I was doing a bit of test fitting that I will need the timing cover doing to match.</font id="red"></font id="size3"><hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">


You are not the first, neither will you be the last, that why I mentioned it, very easy thing to over look.

Cheers John


LIVE LIFE A QUARTER OF A MILE AT A TIME!

1976 Speke FHC Beauty Now with an overdrive conversion

1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6, BUILT NOT BROUGHT !!!!