1FZ-FE rebuild question

[Judgey]

Hi Guys

My 1993 LC 1FZ-FE (has LPG injection as well) has started it run ruff as guts and has a ticking noise so I did a compression test with the following results:

1 0
2 135
3 125
4 145
5 140
6 140

No compression on No 1 cylinder and the other cylinders are below spec (171 psi) or more is standard I think
(Motor has 383000km on the clock)

So I thought it be best to get a new head and VRS kit and replace the old head

Gear bought to date so far:

1 x Brand New After Market Cylinder Head (suit gas/lpg) (includes 12x new intake valves, 12x new exhaust
valves, comes complete assembled with camshafts/ buckets and valve clearances set) $1500.00 incl shipping
1 x Permaseal VRS gasket kit $383.00
1 x head bolt set $75.00

Now a thought just struck me that I'm going to all this trouble to replace the head but what about the block?
I'm assuming No 1 Cylinder has a burnt out valve as there is no compression and the other cylinders are on the way out hence the head

What if the rings are gone on No1 ?
The bottom end is also worn hence a new head old bottom does not make sense?
Should I have just pulled out the motor had got an exchange reco one?
Can I now get a short block exchange or just get my bottom end done?

Now I have not yet completed pulling off my old head just yet, maybe by this weekend I will have it done

Hence my dilemma......what to do with the block?

Any suggestions would be appreciated

Thanks

 

[frank rabbets]

It's guess work really. If the engine was not using oil then you could assume that the bores and rings do not need attention. Close inspection of the bores should be done though. The definitive test however would be to put the exchange head on and then test the compressions. You could reinforce your good opinion of the block by looking at the valves whilst the head is off. If the camshaft is on you can rest the head on it's side and turn the camshaft to examine the valve faces and seats. If Nu 1 valves are damage the likelihood is that the others are damaged as well.

If you have an undiagnosed ticking though you could change the big end bearings just in case one lets go. The journals should be measured for true roundness and diameter al the way round. The crankshaft is very hard so may well not be worn even if the ticking is from a bearing.

So hopefully with the crank measured and reshelled and the valves looking burnt your bottom end should last a long time.

 

[StarCruiser]

Why did the valves burn? LPG or oil past rings? If the former, updating the LPG system to one that looks after valves may be a good idea, otherwise it's possibly a ring so you would most likely see oil fouling to the plugs and evidence of it in the cylinder.

 

[frank rabbets]

I've never heard of oil burning valves out and I've had quite a few engines with terrible oil consumption and perfectly good valves, and compression results. Compression test does not test for vacuum results in the cylinder. I've heard of problems with LPG but as there is no makers official way to convert a petrol engine to run on LPG I've never been tempted. The only time I've seen zero compression is when there was a hole in a piston but possibly really badly burnt valves could result in zero but it would be a gradual process.

 

[Judgey]

Why did the valves burn? LPG or oil past rings? If the former, updating the LPG system to one that looks after valves may be a good idea, otherwise it's possibly a ring so you would most likely see oil fouling to the plugs and evidence of it in the cylinder.

Thanks Star for the advise

Its also been suggested I do a leak down test to possibly confirm the vales are gone but also put pressure on the rings to see if I can hear a leak through the sump
This of course before I remove the head

Cheers

 

[Judgey]

I've never heard of oil burning valves out and I've had quite a few engines with terrible oil consumption and perfectly good valves, and compression results. Compression test does not test for vacuum results in the cylinder. I've heard of problems with LPG but as there is no makers official way to convert a petrol engine to run on LPG I've never been tempted. The only time I've seen zero compression is when there was a hole in a piston but possibly really badly burnt valves could result in zero but it would be a gradual process.

Well Frank,

I hope its not a hole in the cylinder but either way I need to do some tests and get on with this head job
Hmm..doesn’t sound right coming from a bloke now does it.....

Cheers

 

[frank rabbets]

Don't panic I said hole in a piston. lol.

 

[clivehorridge]

IMO zero compression would usually indicate a chipped, cracked or distorted valve, or as Frank suggested a holed piston, but the latter is a bit dramatic and not so common.

Broken compression rings usually return a compression after a few revolutions, which can build up to something less than normal values, but for broken rings to return zero compression, they must be in quite a bad way.

My money would be on a chipped or cracked valve caused by overheated burn from the LPG, hopefully the bores won't show scoring and the rings may be OK.

Bottom end may need BEBs, but I don't know this engine well enough to comment too much.

 

[Judgey]

Thanks guys

Appreciate your wisdom on this matter

 

[Gary820]

AFAIK lpg can burn the valves out on the 1fzfe and the valve seats.
A couple of pumps from an oil can into the cylinders then re check the compression is a good quick way to see if the rings are blowing past (seals the rings to bores crudely) lot of crankcase pressure would be present too if rings were that bad or a holed piston.
Leakage test is a good idea to see where it's losing its compression

Also if a fuel injector was stuck open and just pouring fuel in (more then a 1fzfe normally pours in) it can cause bore wash and lose compression that way.

If you can get your hands on a bore scope, have a look in though the spark plug hole at the pistons.
Likely the head is coming off.

 

[StarCruiser]

I have heard of holed Pistons on an Alfa Romeo through fitting the wrong plugs. They were supposed to be four earth plugs and the cheapskate owner put in standard plugs. Burned completely through one ally piston and almost through the next.

The smarts are well known for valve burning issues and it is reckoned to be due to oil getting past the rings. The cheap cure is new valves, the proper cure is a bottom end rebuild and new valves.

 

[frank rabbets]

I've seen 2 holed pistons in the last 2 years. One an E type inlet valve and the other a Renault Alpine A110. The Renault driver did 500 miles before bringing it to the garage.

That's a strange thing with the Smart. Years ago cars always used to start smoking and regularly had to be rebuilt but it was not a cause of valve problems. These modern engines are so highly stressed all sorts of weird things can happen I guess. Perhaps the oil actually caught fire and was still burning with the exhaust valves open. During normal combustion they are closed and loose heat through their seats

 

[Aspire]

lPG does burn valves but usually on high mileage ones I had a ford explorer that had done 190k miles that burnt the valves out and put 2 recon heads on it and the truck is still going strong. My 4.5 24 va
ve is converted did it last year and has a flash lube system on it so hope it won't burn the valves out.

Again if the compression is zero I would suggest bore and valves are the problem.