Quote:
Originally Posted by funkykar My brains still havent understood the 'correct way(whatever is feasible in market and based on availability of parts)' of a head job. What is the correct solution for the below queries:
1) If the spark plug threading is worn out on the head (if even the adaptor is not sitting properly), whats the correct way to fix it?
2) If the triangular holes on the head where the water circulates is worn out (normal wearing out over a period of years), what is the correct way to fix it?
3) Are new heads of good quality available in market? If so, what make and what price are they.
4) Heard Senator heads are not of very good quality. Is a repaired PA head better or replacing with a new Senator better.
Replies would be highly appreciated. The answers to these queries should benefit a lot of other Fiatians also. |
In my personal opinion, I would not do any work on the cylinder head except valve polishing and resurfacing. Sparkplug threads can re-threaded by using a M14x1.25 size tap.
Please understand that a cylinder head is an integral part of the engine. If the head which is removed from the engine shows discrepancy due to routine wear and tear, all the other parts like pistons, block, etc,etc will also be in a similar situation except in very rare cases. The same will apply to damage caused due to overheating. Attending to just one part when an engine is opened isn't the correct way to do things according to me. Opening up the engine (which included the cylinder head) is the very last option. Any jobs except those listed in the first paragraphs cannot be done to precision by local workshops.
Arun, an identical problem was faced by our friend Ravi on his SuperSelect. Due to a loose sparkplug, there was total compression loss on one cylinder. The engine used to sound like a steam engine. The whole issue was solved WITHOUT opening up the head. I am sure Ravi would explain the whole series of episodes in detail.
So what would be the solution ? Actually there would be two correct solutions. One, with a lot of patience, find a good original PAL cylinder head from the scrapyard. The valves should be tan brown in colour without any oil on them. Please do not even look at heads which are pre-cleaned. Take the cylinder head to a good turner and tell him to just resurface it (usually they shave about 0.25 to 0.5mm), check the threads on all groves including the ones for manifold stud and water-pump. Re-thread if necessary. Do not touch the valve seats in any case. Mostly nothing much happens to them. Just get the valves polished. The intake valve is 30mm diameter and the exhaust valve is 32mm diameter. The sequence is E-I-I-E-E-I-I-E. The valves are numbered by small engraved dots to the corresponding cylinder. (Valves on cylinder no 1 will have one dot and the ones on no.4 will have 4 dots). Ensure that the valves are fitted as per their corresponding cylinder only. There is also a torquing sequence of the cylinder head bolts which I will post some other time. No body follows the torquing sequence and uses a torque wrench and all but the cars of people who do (I know of only 3 people in Mumbai) run 'differently'.
The second solution would be to stock a engine from a good running car which has come for scrapping. You may even get a test ride of the car before it is scrapped. When a problem is faced, simply replace the whole thing without breaking ones head on anything. The whole job will not take more that 3 hours at a stretch. But one never knows when this 'new' engine will start giving trouble.
Personally, I would still prefer solution number one.
Waiting for your replies,
Regards,
Adheesh Parelkar |