Second hand head

[William2]

I am being offered a bare Weber type cylinder head. Apart from measuring the height to check skimming tolerance can anyone give me tips on what to look for? I realize that ultimately it would need a pressure test. Also can anyone recommend any companies in the SE of England that have experience with twin cam heads (repairs, valve seats, etc)

[rgh0]

Things I look for in a head when buying

1. What type is it ( 4 major variations of Weber heads) and approximate age, engine number or code numbers on bottom face, back face of head and code letter on boss at front of spark plug well. Has it been ported or had bigger valves and valve seats fitted, any other modifications

2. Hardness - a soft head is a killer. Look for recession of head bolts and marks from fire rings in the face of head. If any signs of softness ( or recent machining to remove signs) get a hardness test done.

3. Corrosion - Look for corrosion in the water passages. if too much they can encroach on the head gasket fire rings. Generally easily repairable with welding but a risk of more corrosion elsewhere that will be harder to repair.

4. Cracking - Look for cracking between the spark plug holes and valve seats usually some small cracks present and not a problem. Check around the head bolts also. Do a pressure test

5. Threads - check out the threads for all the studs and spark plugs. All can usually easily be repaired with thread inserts.

6. Guides - check for wear - need a small diameter bore gauge to do accurately and check along the full length as the wear hour glass shape.

7. Seats - check for damage and excessive recession through being recut to many times

8. Thickness - The heads can be skimmed well beyond the Lotus recommended maximum amount without problems but if the lettering on the bottom face of the head has started to be cut then it is starting to get near its limit.

9. Straightness - check the cam tunnel bores are straight by checking a cam turns freely in them and that the top and bottom faces are flat with a steel straight edge and feeler gauges.

cheers
Rohan

[promotor]

In addition to Rohans' comprehensive list things to look out for are :

Check that the timing quadrant pivot pin hole isn't damaged and that the threads are good.

Are bucket sleeves present (early heads had either none and the bucket ran in the aluminium, or just the exhaust valve bucket pockets had steel sleeves in with the inlets running in aluminium)? If they are present have they "risen/sunk"? suggesting a seizure of a bucket or boiling of the head.

Check that the front cam retaining groove (the part that dictates endfloat) isn't excessively worn on both inlet and exhaust side.

Have the valve pockets been machined excessively resulting in a hole through into (normally) the inlet port?

Plenty to go at and always easy to forget something - focus on the important stuff like corrosion and head bolt sinkage etc as generally this is a terminal issue - most others can be solved with welding and machine work.

[RichardHawkins]

William,

I eventually took my head to Serdi UK in Uxbridge (01895 232215). After spending a lot of time on internet searches, writing to companies and visiting premises I settled for Coventry Boring and Metalling as they had the facilities to do what I requested. Unfortunately they did not do what I had asked for, there seemed to be a management/quality assurance problem, as my written requirements did not reach the man doing the work.

I had bought valves from G&S, and seats from Serdi recommended by G&S. I did not realise that Serdi offered a machining service, I thought they were a component and machine tool supplier. After my difficulties with Coventry Boring and Metalling I asked G&S if they could suggest/recommend a machine shop, and that is how I came to use Serdi. John Dorma is the proprietor.

I still think that Coventry boring have the capability, but something went wrong in the application. Coventry Boring and Metalling did reimburse me for the errors, so I would not dismiss them out of hand. The work done by Serdi was better and quicker, not cheap but good. My car is still in pieces, but I don't expect any problems with the work done by Serdi.

Don't limit yourself to a company who happen to be convenient as the time and effort and money spent sorting out errors will soon dwarf time taken travelling to someone competent. Remember it has to be technically correct or will soon turn into another problem.

Richard Hawkins