V8 head gaskets.

since I've got to lift the head on this bugger again, I'd value input on the matter of head gaskets:

Steel or composite? that is the question.

pro steel - thinner gasket, hence higher compression.

pro composite - better sealing (?)

any other opinions?

the word from some people is "if it had steel ones, fit steel ones", whereas the word from others is "fit composites anyway".

Reply to
Austin Shackles
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I wonder if anyone has ever calculated just how much.

Better sealing, yes, but if you've had the block / heads skimmed then you should get as good a seal with metal - then again, if you've had either or both skimmed, then fitting a composite will not really affect the compression - as it'll probably put it back to what it should be...

Fit composite :-)

Reply to
Mother

Austin, NO engine leaves here with steel gaskets! That's how much I think of them. Gimme composites every time. I did once work out their effect on c.r. but it varies according to the capacity and c.r. of your engine as std. If I remember right, they dropped a

9.75c.r. down to about 9.5c.r., on a 3.5 engine. Not a "major" difference, and well worth the extra sealing quality, in my opinion. About 85% of the engines with tin gaskets that I've stripped over the years have exhibited a leakage of combustion gases into the valley area, about 70% of those had the lower 4 bolts already at a lower torque than std, something I always check when an engine comes in, because of the known gasket failures. This extra blow-by into the valley is a prime cause of the carbon-like oily sludge which creates extra contaminants in the oil returning to the sump, which pours onto the cam and followers causing premature wear! Just my tuppence-worth, only you can decide what to do with your own engine.

Badger B.H.Engineering, Rover V8 engine builders. Landy 110 3.9V8 Auto, on gas. BMW 330dSE Sport Auto, on summit!

Reply to
Badger

Austin Shackles posted ...

All the following is _not_ based specifically on LR engines, but on a variety of various manufacturers .. and general engineering principles.

Composite ..

If you skim the heads, then a composite gasket will retain standard compression, or thereabouts .. If you skim the heads and use a steel gasket compression will rise, but this isn't always a 'good thing' ..

Much better sealing, longer life, can still retain a seal even when head bolts [1] are torqued incorrectly.

I fit Composites anyway, when available ..

[1] Some bolts are notoriously awkward to get to torque correctly, especially with an engine still in situ .. and many people don't use or know how to use a torque wrench correctly, including some garage monkeys. ;)
Reply to
Paul - xxx

I was advised to fit composites when I rebuilt the 3.5 in Tiggrr last year. The CR may be slightly lower (which may not be a bad thing - lower peak power but more tractable) but I reckon it will be in the order of a fraction of a percent.

No problems so far.

Reply to
Richard Brookman

On or around Fri, 7 May 2004 13:48:38 +0100, "Paul - xxx" enlightened us thusly:

'tis if you're running on LPG.

Reply to
Austin Shackles

On or around Fri, 7 May 2004 13:48:38 +0100, "Paul - xxx" enlightened us thusly:

but I do...

some slight investigation today. offed the rocker cover on the offending side of the engine, and fired 'er up with the cover off. Observed that some pushrods are spinning merrily, others are not but spin for a while if prodded to start 'em off - put this down to the cam getting on a bit, though it still has all its lobes :-). Significantly, #1 inlet pushrod doesn't turn, and is reluctant to turn even if you grab it and twist it.

This ties in with my theory about a dodgy cam follower - the only thing I can think of which would explain the fact that the dud #1 cylinder is affecting the running of the engine as a whole is for the low compression to be (partly) caused by the #1 inlet valve not closing properly, and allowing gas to blow back into the manifold, thus upsetting the vapouriser and causing the low-speed running problems. obviously, at higher speed/throttle opening, lots of air is rushing in, and a minor leak back through a valve will have little effect. I'm currently speculating that the follower might be stiff. hope it's not knackered it's hole, is all.

There's also a slight unscheduled squeak in the engine, and this, once the rocker cover is off, is apparently coming from the front of the crankcase somewhere inside - could be a dodgy follower, still.

will hunt gaskets and open 'er up next week, once the gaskets are to hand.

Reply to
Austin Shackles

Austin Shackles posted ...

Ho yuss ..

Reply to
Paul - xxx

Austin Shackles posted ...

I don't doubt it, and didn't mean to imply you didn't .. ;)

Hmmm .. It'd be preferable to have 'em all doing the same thing I guess ..

Along with the rest of the description you give, I'd agree. I'd suggest also having a close look at the outlet .. If there's a problem on inlet there may well be a corresponding problem here .. ;)

Yeah .. been there got the tee .. no gaskets available for miles around, and on an engine where a Kellogs cardboard box just won't do .. ;)

Reply to
Paul - xxx

On or around Sat, 8 May 2004 08:32:26 +0100, "Paul - xxx" enlightened us thusly:

as I understand it, the followers are meant to turn, hence I assume the pushrods may do. A pushrod which doesn't spin is not a major issue provided it's not stiff, but one that declines to turn at all even when provoked is definitely suspicious.

Reply to
Austin Shackles

On or around Sat, 8 May 2004 08:32:26 +0100, "Paul - xxx" enlightened us thusly:

Real Steel seem to be the guys to help there.

annoyingly, I think I'll have to postpone changing the cam. I've some good-ish second-hand followers I can swap in for now, if one's dodgy. I'll not have the time for more than a quick look-and-fix session next week, and I don't want to run it longer than I have to without looking at it.

changing the cam adds another hour or so to the plot if it all goes smoothly, and I've yet to get a socket that'll fit the centre pulley bolt.

Reply to
Austin Shackles

You wimp, Austin! Get a socket and do it all in a one-er. You know you want to, really. Box arrived yet? Badger.

Reply to
Badger

On or around Sat, 8 May 2004 14:37:27 +0100, "Badger" enlightened us thusly:

heh. nah, just a quick head-off-looksee and hopefully quick fix I can do in between the 2 school runs. no prizes for not having it back running by about 2:45, and I'll not start on it 'til about 10, probably. Besides, the cam that's in it isn't bad, from previous observation. will hopefully get the manifold swapped at the same time though, since it's got to come off anyway.

yep. meant to email you to this effect yesterday. will arrange the financial aspect.

now to have fun working out what pipes go where. what's the bit just under the throttle butterfly, with 2 small pipes? heater? ...doesn't look as if it's essential, anyway :-) I don't see that any sort of manifold heating is advantageous on an LPG-only motor.

I reckon all I really need is an inlet and a throttle valve. and maybe an idle bypass, if it has such. The K-jet on the Ford has. I assume that's the big screw down a hole beside the throttle body. Mind, 's got that idle control doofrit, I suppose that does automagical idle adjustment on an EFI system.

Reply to
Austin Shackles

Hahaha, wimp!

No probs.

One pipe (still on the plenum, I think) goes to the stub pipe sticking up from the inlet manifold, next to the 2 holes that are for a couple of EFI sensors. The other is the bleed to the top of the radiator, currently attached to the front of the pentroof on your carby manifold. 2 bigger pipes, one goes from the stub pipe to the rear of the throttle housing, to the pipe bolted to the trumpet plate that runs under the throttle body. should be a pipe from that metal one at the front to the fast idle valve, and one from the fast idle valve to the plenum ("U" shaped one).

Prevents throttle body icing in cold, damp weather. I'd fit it.

That's the idle speed screw.

Only raises cold idle speed, it's got a bimetallic strip inside that senses water temp via direct conduction from the mounting flange on the manifold, and an electric heating element inside that wires up to the ign live. It's normally connected via the efi harness, but I'm sure you can find a 12v feed for it. (Coil?). I'd wire it up anyway, or the engine will hang at too high an rpm as it's warming up. BTW, if you ever fit a 3.9 engine, use the idle speed valve from a series 3 4.2 XJ6, bolts straight on and gives the correct cold idle speed!!

Have fun. Badger.

Reply to
Badger

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