cracked head

[killer_garden_gnome]

my TB42 has cracked the head, so can anyone tell me if theres a better casting that the tb42s standard head or is that all i can get?

[BowTieGQ]

I think only the later efi casting is available which is the one to get anyway. Thicker around where it cracks. When I went looking for one, the Nissan parts guy said the old part number is obsolete and therefore refers to the new one which is the efi one.

[killer_garden_gnome]

o ok cheers for that how much are they worth if anyone knows

[BowTieGQ]

$1000-$1100. Don't pay more. That's bare though.

[killer_garden_gnome]

yeh thats what i was thinkin, is there a different valve set for LPG that i should be using since im doin it? i got LPG about 2 weeks before it shit. someone also said somethin about harder valve springs and shaving the head before i stick it on

[BowTieGQ]

Yep. Hardened inserts. Some say exhaust only, but do inlet as well. You prob will need new exhaust valves as well. Put old inlets back in. Use old springs. Lap it all. Fit the rocker gear and put it back on. Don't stress about the specs saying that the head bolts are torque to yeald. They are the sort that are meant to be replaced. Don't bother. Engine guys I know said don't bother on anything except very high performance applications. I wanted a second opinion and rang local Nissan. They said same. They don't have any new head bolts in stock and he couldn't even remember the last time they got some in. They always reuse the old ones too.
You could also get some port work done while you're at it. Needs some relieving around the bowl area. Works wonders.

[killer_garden_gnome]

1. did u get a head place to put ur seats in?
2. did u get the port work done by someone?

i can do all the othe stuff myself but have to talk to a head specialist on monday i guess

3. are valve guides hard too put in?

[mattsluxtruck]

Dont the efi heads come with valve seats already fitted?
Is the efu head a sure fire way to stop the bastards cracking? How do I tell what head is fitted to mine at the moment? It is a 4.2 carby

[BowTieGQ]

I got the guys to do all machining and porting on mine and reassemble it so I could simply bolt it back on. Yes, the new efi head will be ready to use out of the box. As with any ally head, it will already have been treated around the valve seat to harden it. Inserts are better again. In theory, any head that was destined to run unleaded should be fine to use with lpg as neither lubricate the seat. But lpg still eats them up eventually. I wouldn't say if the efi head is a definate fix, but the guy at Nissan, and others, have said that it is a thicker casting along the top of the chambers where they very often crack, from one vavle to the next, to the next..... Unsure when the newer efi head casting started, would simply assume with efi.
But I assume everyone reading this thread is reading the other about the TB42 head issues. It sounds like Nissan stuffed up the design in a big way and made up the gaskets to band aid the problem. The "steam pipe" setup that some have seems to work around this fault.