Valve seats

[datty240Z]

When I restored my 240 about 10 years ago I took the precaution of having hsrdened valve seats fitted. Now the cars has only done a few thousand miles since. In the past couple of weeks it develpoed a tapping noise in number 5 cylinder. Yesterday it turned into a loud knock and went off a cylinder. I took the head off last night. The exhaust valve seat has dropped out and the valve is jammed and looks bent. There are contact marks on the piston but jts looks ok.

Do you thjnk I should have any come back with the company that did the valves given the low miles even though it was 10 years ago?

 

[Rob Gaskin]

10 years ago is far too long ago IMO. Talk to them though, they need to know and you might get a discount on a new seat?.

 

[Stockdale]

I have always understood that the very early 240z's had a compression ratio to suit the normal fuel of the time (at around 9.13:1 but that it was dropped (8.76:1) during their production in '72 to accommodate unleaded. If this is the case then mods to later (72-73 240z's don't actually need any valve seat change. All 260z's should be quite safe on unleaded?

 

[Rob Gaskin]

I have always understood that the very early 240z's had a compression ratio to suit the normal fuel of the time (at around 9.13:1 but that it was dropped (8.76:1) during their production in '72 to accommodate unleaded. If this is the case then mods to later (72-73 240z's don't actually need any valve seat change. All 260z's should be quite safe on unleaded?

Valve seats wear due to the removal of lead not compression ratio.

 

[Joe NI]

Andrew, I have a valve spring compressor here and spare valves. don't know if they are the right ones thou as they came out of an N42 head. I assume the repair is a machine shop job though.

 

[Stockdale]

Valve seats wear due to the removal of lead not compression ratio.

Yes of course. The point I was making though that the engines were originally designed for the higher octane fuel of the time (which was leaded) and was intended for a relatively high compression ratio. There is a correlation between compression ratio and octane and the ratio was lowered in 72 (I thought) to compensate for the reduced octane number in unleaded fuel. Given that unleaded fuel requires hardened valve seats that the change at that time would have necessitated their inclusion and so from that point the engine valve seating required no further work

 

[SKiddell]

Do you thjnk I should have any come back with the company that did the valves given the low miles even though it was 10 years ago?

You are kidding right.

 

[kev64]

You are kidding right.

Nice one Steve:lol::lol:!!!

 

[Alphabettispaghetti]

Yes of course. The point I was making though that the engines were originally designed for the higher octane fuel of the time (which was leaded) and was intended for a relatively high compression ratio. There is a correlation between compression ratio and octane and the ratio was lowered in 72 (I thought) to compensate for the reduced octane number in unleaded fuel. Given that unleaded fuel requires hardened valve seats that the change at that time would have necessitated their inclusion and so from that point the engine valve seating required no further work

The reduction in compression ratio was for emissions, nothing else. Even when it was lowered they were still running leaded fuel.

The compression ratio was actually lowered in 71(I think) when the cars stopped using the E31 head.

I hope I'm right as it might mean I've got a good s30 fact

 

[mattbibbey]

I did 20k+ miles on unleaded fuel and when I took the head off it was fine. That was on the original seats. The old, old head, when I removed it, I plonked it down on the work bench and two valve seats were dislodged! Haha. I think it's just (un) luck of the draw!

P.S. If you're after a fairly priced place to have valves cut etc, have a look at Rob Walker. Last I checked he was very cheap and his experience speaks for itself.

 

[datty240Z]

You are kidding right.

Why would I be kidding? I went back to the engineering shop today. He remembered me soon as I went in. He was pretty apologetic and said he'd fix it and replace the valve and head set. Nice one!

 

[datty240Z]

P.S. If you're after a fairly priced place to have valves cut etc, have a look at Rob Walker. Last I checked he was very cheap and his experience speaks for itself.

I think it might be a bit too far for me to travel from N.I. Ha ha!

 

[Rob Gaskin]

10 years ago is far too long ago IMO. Talk to them though, they need to know and you might get a discount on a new seat?.

.......... I went back to the engineering shop today. He remembered me soon as I went in. He was pretty apologetic and said he'd fix it and replace the valve and head set. Nice one!

Decent customer service then, nice to hear these days.

 

[datty240Z]

Andrew, I have a valve spring compressor here and spare valves. don't know if they are the right ones thou as they came out of an N42 head. I assume the repair is a machine shop job though.

Thanks Joe but hopefully I won't need them. I'll let you know if I do.