Type 4 2 litre CU heads (dropped intake valves)

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marcw
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Type 4 2 litre CU heads (dropped intake valves)

Post by marcw »

Hello, (type 4 2 litre intake valves loose - related to post - viewtopic.php?f=4&t=37241)

I noticed the intake gap on my tappets decreasing rapidly after a 25K service, after a long trip to the Kruger park. She ran very lean for about 500 kms after the air screw rattled out of the primary carb (the third carb attached to the 3/4 cylinder head). My assumption was that the seats were loose. I have stripped the motor this weekend and have the heads out.

1 - Do I have both the heads seats replaced? (is this an OK procedure to have done for longevity - will the heads last this time?)

2- Do I get new heads from some very expensive place overseas (if so from who? California import parts etc etc)

3- Do I need to get, new sears, new valves, guides replaced, rockers, etc etc etc? I.e. rebuild the heads completely

4- If I get new heads I fear that I should then get new cylinders as well, but that means new pistons at the same time)

My focus is longevity not cost. Obviously I do not want to spend R100K on my motor, but I want to do this right at a reasonable price. The main point is now to have a daily runner that will last at the very least 80k kms with out me having to take the engine out again. BUT if it is too costly I will chuck the aircooled engine and put in a nice 2 litre VW water cooled engine.

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Re: Type 4 2 litre CU heads (dropped intake valves)

Post by retrovan »

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Re: Type 4 2 litre CU heads (dropped intake valves)

Post by Terry Phillips »

People seem to forget how old these heads are and how many times they have been machined each time more and more metal is removed and oversize seats fitted. Best is try and get a good set of heads to start with then you will get good service out of them.They are also known to have cheaper materials used so who does the heads has a lot to do with reliability.
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Re: Type 4 2 litre CU heads (dropped intake valves)

Post by marcw »

So that begs the question. Who to send the heads to?

I would need the seats replaced.

Marc
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Re: Type 4 2 litre CU heads (dropped intake valves)

Post by Dawie »

As Terry mentioned, people sometimes forgot how hard these engines have worked the past 40+ years of their life.

Most rebuilders would only have seats re-cut, sometimes re-used old valves, and replace valve guides if too far beyond wear limits. Seats were seldom replaced, only when really necessary.

Loose seats happen from severe thermal cycling over time. Different materials, different expansion rates.
The good aircooled machining specialists have each, over the years, out of experience, found their procedure which works for them. (Interference fit, preheat temperature, etc). Too little interference and seat falls out, too much causes head to crack.) They know to pre-heat head to max operating temp, (which is much higher than that of a watercooled head), before measuring hole diameter where seat must live.

In the old days, Mac Donald Engineering in JHB were aircooled specialists. Porsche also used them to do their heads. The locals may have a better opinion on their quality of wormanship nowadays.
Staying Aircooled is so much nicer.
Do'nt assume anything- (While doing fault-finding).
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