Cylinder head rebuild

[Howard81]

Just had the head gasket blow on my 1970 MKIV so may as well get the head skimmed, rebuilt and converted to unleaded while it's off!  Any recommendations?  I'm in London.

[nang]

Put a straightedge on the block to be sure that it's flat. A bit hard to see but clean it off and try a thin feeler gauge between straightedge and the block.
Tony.

[Velocita Rosso]

nang wrote:

Put a straightedge on the block to be sure that it's flat. A bit hard to see but clean it off and try a thin feeler gauge between straightedge and the block.
Tony.

Correct. Just had mine gone, done the same check ,no grinding required, straight replacement
London?....talk to Dale(Moordale)

[JohnD]

The thinnest feeler gauge will be wider than the English Channel to a photon.
Put a bright light behind the straight edge.

John

[Mark Hammond]

Sutton Rebore in Sutton.

Mark

[Nick Moore]

You're on the right track. A cylinder head shop may want to give it a skim anyway to be sure it's flat. More of a skim will increase the compression ratio, but they should measure the chamber capacities to be sure how much to skim off. A 9.5:1 CR is fine for a road car.

Hardened valve seats are a good idea. Check the valve guides for wear. If the guides are worn, they can be reamed and fitted with inserts (eg K Lines) rather than replaced. There are aftermarket valves available that are said (mostly by the sellers) to improve flow, but unless you're going to have the ports smoothed out, the standard valves will be fine. Larger valves make it harder to fit hardened seats, and anyway, the larger a valve is, the nearer it is to the wall of the combustion chamber, which impedes flow.

As for 'porting and polishing', it's a black art. Some gurus proclaim they know how to vastly improve flow, but the more you read, the more confused you will get. My impression is that road engines don't need anything more than matching the ports to the manifolds, and cleaning up any rough casting ridges.

Get the shop to check the valve springs. If they're all similar rates then chances are that none have softened, and they can be reused. 'Uprated' springs are generally stiffer and will increase strain and wear on the lifters, camshaft lobes and the block journals that the camshaft runs in, for no performance benefit.

Also check your rocker shaft and rockers for wear while they're off. If they're worn, they can be replaced.

[BiTurbo228]

1218 wrote:

Sutton Rebore in Sutton.

Mark

I'd recommend these people too :)

[Tim Bancroft]

Keep hearing nothing but good things about Gosnays of Essex:

http://www.gosnays.co.uk/acatalog/index.html

[Velocita Rosso]

Nick_Moore wrote:

You're on the right track. A cylinder head shop may want to give it a skim anyway to be sure it's flat. More of a skim will increase the compression ratio, but they should measure the chamber capacities to be sure how much to skim off. A 9.5:1 CR is fine for a road car.

Hardened valve seats are a good idea. Check the valve guides for wear. If the guides are worn, they can be reamed and fitted with inserts (eg K Lines) rather than replaced. There are aftermarket valves available that are said (mostly by the sellers) to improve flow, but unless you're going to have the ports smoothed out, the standard valves will be fine. Larger valves make it harder to fit hardened seats, and anyway, the larger a valve is, the nearer it is to the wall of the combustion chamber, which impedes flow.

As for 'porting and polishing', it's a black art. Some gurus proclaim they know how to vastly improve flow, but the more you read, the more confused you will get. My impression is that road engines don't need anything more than matching the ports to the manifolds, and cleaning up any rough casting ridges.

Get the shop to check the valve springs. If they're all similar rates then chances are that none have softened, and they can be reused. 'Uprated' springs are generally stiffer and will increase strain and wear on the lifters, camshaft lobes and the block journals that the camshaft runs in, for no performance benefit.

Also check your rocker shaft and rockers for wear while they're off. If they're worn, they can be replaced.

...and new ARP head studs and nuts.....the old may have stretched

[don cook1]

Had mine done at Gosnays a few years ago...pricey!

[HMaze]

Hi Howard,
does your cylinder bores have a recess on top of the bore?
The early MkIV engines up to engine# FH25.000 had no recess.
The head gasket you show looks like one for recessed bore.

Harry

[RobPearce]

2250 wrote:

The head gasket you show looks like one for recessed bore.

I disagree - to me it looks like the non-recessed Mk4 type (which is a definite improvement on the copper/asbestos thing on Mk1 Vitesses!)

[Richard B]

2250 wrote:

Hi Howard,
does your cylinder bores have a recess on top of the bore?
The early MkIV engines up to engine# FH25.000 had no recess.
The head gasket you show looks like one for recessed bore.

Harry

Agreed, do check the block for machined rings at the top of each bore. That gasket looks like a late style (with rings).

[That Man]

Yes that does look like a flat block and a recessed head gasket.

[Dogsbody47uk]

The gasket has a tab at the back so it is for a recessed block. Can't tell from the picture whether the block is recessed or not.

[Howard81]

There is no engine number as the engine was a rebuilt replacement (Gold Seal maybe?) from years ago.  Here's the block:

[Dogsbody47uk]

Looks like a recessed block.

[don cook1]

I think a couple more photos of the top of the bores/block are required for a definitive answer: much closer and one at  bit of an angle. Not that I'd know!

[Howard81]

Here's the photos of the block:

[don cook1]

Recessed block, then the head gasket was correct!

[Howard81]

I'm just wondering if the head gasket failure could be down to me using a cheap head gasket of unknown age..  It came in an old Unipart gasket set.  It's probably done 500 miles since replaced.  I have a new Payen gasket to go back on.

[RobPearce]

Only 500 miles? Wow! That makes my Vitesse look decidedly good.

The failure mode you suffered is the same one Tessa does. Likely contributory factors are:
- extreme overheating (Tessa showed signs of this just before blowing the gasket on most occasions)
- bad pinking (knock), possibly related to above
- defective or worn-out head studs or nuts
- damage to block or head face (though your photos don't look bad on that front)
- defective or damaged gasket used

[Howard81]

Well it blew during a blast up the M3, I didn't experience any noticable overheating and the temperature gauge didn't rise above half way.  The car did start running rough in a 45-minute traffic jam in the New Forest but sorted itself out again once the traffic got moving again.

The engine is a bog-standard 1300 with 1300 exhaust, although I am running the HS4 carbs off a 1500.

[don cook1]

On No1 pot do you have a water-way that has breached into the recess on the cylinder? Might need a dab of weld on there and perhaps at the other end as well?