Compression

[filthyrich]

G'day awwl,

Im currently looking to buy a GQ 93 petrol 4.2 from a good friend. The twist is, that the "head" apparently needs a recon. The theory for this is its running on gas (HOT) and the compression is down from the cylinders when measured... But! the compression is equal across all six pots. No water in the oil. Advise from back yard mechanic is that the valve seats drop into the boiling hot cylinder head thus not giving a good seal with the valve. ?? Or maybe the bore's have worn....but equally?? across all 6??
Thought i'd throw it out thier, see if anyone else has seen or experienced this.
Thanks for reading

[Parksy]

Sounds to me that the engine is just tired and in need of a freshen up. Rings, head and what ever else is worn. The story you were told sounds like bs.

[happygu]

Gas does run hotter, and does wear out the valves themselves and their valve seats, especially if they aren't made for it.

The valve seats don't drop as such, but it may just need a reconditioned / new head to be on it's way again.

It would want to be fairly cheap, or in otherwise fantastic condition to take it as is, as it will normally cost you a little more than you think to get it up to spec....

Mic

[Cuppa]

Others with more recent experience or better memory than me might confirm, but I seem to recall that the way to tell of compression is down due to ring/bore wear or valves is to squirt a little oil into the cylinder & then test compression. If it improves with the oil it indicates ring/bore wear. if no different - indicates valve leak.

Cuppa

[Clunk]

I know nothing on such matters but I do know I'm not a fan of duel fuel. Fro. What I've read and heard, it seems to be more trouble than its worth. If you get the car cheap enough, if it were me I'd fix it up and rip out the gas system, stick to petrol. Yes they're thirsty beasts but we didn't buy them because they were frugal.

[Bob]

I know nothing on such matters but I do know I'm not a fan of duel fuel. Fro. What I've read and heard, it seems to be more trouble than its worth. If you get the car cheap enough, if it were me I'd fix it up and rip out the gas system, stick to petrol. Yes they're thirsty beasts but we didn't buy them because they were frugal.

Beg to differ mate as my Dual Fuel performs great on both Petrol & Gas with very little difference in Performance across both Fuels.
Always kept well tuned and a Tank of ULP through every 4 tanks on Gas
I have had about 4 Patrols on Dual Fuel over the years and I am still a Fan

Have heard some horror stories though.

My Son in Law has a 4.2 which has 580,000 on the Clock and has been run on Gas since new

Regards
Bob

[filthyrich]

Thankyou very much for your replies guys. Yes from what i can see the cat has done very little off road use if any. The valves if just need lapping etc head skim/gasket should be cheap enough. ill give it a whirl myself. The cars is priced at $3500 au but thinking $3000. i have tried to look for "what to look for when buying a GQ" on here but failed. tried for some time too. Anybody see anything like that on here?
Once again guys thanks for your input

[GQ TANK]

If you need to do the head - bank on $1200 - $1500

Look for rust - rear quarter panels, radiator support, fire wall.
Check body mounts - they fail / crack the floor
Take for a drive any wobbles ( you could also jack the front wheels and see if there is any movement - 12 / 6 o'clock push backwards and forwards = swivel & wheel bearing - 3 & 9 o'clock are wheel bearing
What are the tyre like if you have a spare it must be road worthy, have a jack etc
If the seats have holes put a cover over
Does the steering wheel rubber have any movement - vehailes have been failed road worthy for this

[filthyrich]

Thanks for the heads up Tank. I bought the car yesterday. went over all items mentioned above and the car came up top marks. thanks for your advise.