Overheated Head

[satanherself]

How hard is it to fix a overheated Twin Cam head?? How much can be decked?

[types26/36]

How hard is it to fix a overheated Twin Cam head?? How much can be decked?

Lotus specs:
Small valve .......... 40 thou
Big valve................10 thou
but in practice I have skimmed more off then that.

[satanherself]

Is it a common repair ?

[types26/36]

Only if it is necessary, take off as little as possible as many heads have been destroyed by over skimming. A competent motor engineers should be capable of checking if the head requires surface grinding.
If the engine overheated it may have damaged the pistons so there can be more problems then just a distorted head.

[satanherself]

Thank You

[rgh0]

Overheating of the head can cause a range of problems

1. Warping of the head itself - The head can be straightened in a press and then milled to produce a flat final sealing surface. The cam tunnel bore needs to be checked also and line bored if necessary along with the cam cover gasket surface flatness. You can mill the head face down until the cast lettering at the side of the face dissappears at least from what I have seen in practice but given the cost of heads you want to always take off the minimum you can get away with. If you have a heavily milled head You will need to do some work on the combustion chamber or pistons to restore the compression ratio unless you deliberately want a racing comp ratio.

2. Softening of the head - The head alloy material was marginal in the first place and can soften further with overheating resulting in the head bolts sinking into the head and loosing tension and the head gasket fire rings sinking into the sealing face. This leads to continual blowing head gaskets. The head hardness can be checked. Theorectically you can re-heat treat the head to restore the hardness but I don t know of anyone who has actually done. I have a friend with a soft head and one day I may try it.

3. Loosening of valve seats and bucket sleeve. Look for signs of movement or rotation. If you can see any movement you need to remove and replace with the correct interference the seats or sleeves.

For all of this work ensure you use a machine shop familiar with working on a Twin Cam head as a ruined head due to a machining or other error is a very expensive problem that lots of shops dont understand.

regards
Rohan

[denicholls2]

If you're thinking about the one on eBay, it's a Federal Europa head, meaning it's a big valve and allows less skimming.

I suspect the seller knows its reclamation prospects.

Note the price has stayed around the scrap value. A useable core would be an excellent candidate for John McCoy's conversion, so my guess is that the community puts little stake in its usability.

Not a bidder myself, no bottom end to fit with it. If it is salvageable, you've got a real deal here. If not, you've got a lump of scrap aluminum or a good way to auction off your duff Twincam while keeping the Weber head for a brighter day.

-- Doug Nicholls, 54/1822 Ma~

[satanherself]

Yes I was looking at that ,but the fellow selling it has not answered any of by questions so ,I'm going to pass on it

[PA]

Doug,
What is John McCoy's conversion? Is it a conversion of a Stromberg head to allow the fitting of Webber/Dellorto carbs?

Thanks

Paul