Valve guides/Unleaded conversion

Date: Mon, 09 Nov 1998 18:45:44 +0000
From: Andy Greenshields
Subject: [imps] Valve guides/Unleaded conversion

Hello Impers

I have got some very nice chaps in Hanwell to convert a rather decent cylinder head I have to unleaded (It hasn't even been Skimmed). At the same time I have decided to completely overhaul the valves, guides, springs etc. However, I have obtained some new remanufactured guides from Mr Anderson and the quality of them seems to be somewhat poor. Out of the eight I bought, only three were deemed to be within tolerance by the machine shop. Could anyone recommend an alternative source for valve guides, either steel or alloy ones.

The very same machine shop has recommended that they only need to replace the exhaust seats. Is this information correct. I am sure that this is an old nutshell that has been discussed many times here, but any advice would be welcomed.

Many thanks
Andy Greenshields


From: TMo5018257@aol.com
Date: Mon, 9 Nov 1998 15:05:08 EST
Subject: [imps] Re: Valve guides/Unleaded conversion

Andy,

Regarding valve seats......

I am told that this is the correct information. The inlet seats should be replaced if they are in anything other than perfect condition - whilst they are doing the work, they might as well do the whole lot.

Regarding valve guides.....

Blind animal that lives in the woods (no eye dears) !!!!

Cheers,
Tim


Date: Mon, 16 Nov 1998 10:21:11 +0800 (WST)
From: Paul Greville
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi Andy,

I would suggest that you try K Line valve guide inserts. This system uses an insert inside the old valve guide which is reamed to size and thus produces an exact guide with no error whatsovever.

I have used this method successfully to redeem Imp and other heads and have been impressed with the results - The system may have some other name in the U/K.

Regards,
Paul Greville.
Western Australia.


Date: Sat, 21 Nov 1998 19:45:06 +1000
From: Darcy Maddock
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi,
seeing that all Rootes alloy headed engines used a very high quality valve and valve seat I am suprised that they would need changing for use with unleaded fuel.
I know that it is a must with iron heads and the lower quality foreign rubbish. I will check with my engine specialist and follow this up. I am having an alloy head rebuilt for my Rapier and he has already informed me that the seats are quite suitable for unleaded and the OE brand new Rootes valves I supplied him with are superior to any he can buy for the modern unleaded cars he repairs.
Darcy Maddock


From: Nickcleak@aol.com
Date: Sat, 21 Nov 1998 11:02:33 EST
Subject: [imps] Re: Valve guides/Unleaded conversion

> seeing that all Rootes alloy headed engines used a very high quality
> valve and valve seat I am suprised that they would need changing for
> use with unleaded fuel.

Yes i would agree with that , i have been using unleaded for 3000 miles now ,
no loss in power , in fact , it may even be better ,,
nick ..


From: TMo5018257@aol.com
Date: Sat, 21 Nov 1998 13:30:37 EST
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi Nick,

Regarding your unleaded 'conversion' - I have heard conflicting reports about Imps and their suitability for running on diet petrol. One Imp specialist (Dave Llewelyn) says he has been running his engines on unleaded for a while.......

However, I have seen a head where the exhaust valves have definately receded into the ports. I would be interested in anyone else's input about this as it is definately going to become a problem in the next few months. I am loath to start running the Husky on caffiene-free gas in case of the damage it may do.

Cheers,
Tim


From: Gary and Carol Henderson
Date: Sun, 22 Nov 1998 09:47:41 +-1300
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi Tim

> From NZ, where the 'change' happened some time ago... sorry, I just looked in the Imp logbook and find I didn't actually note when it first happened, but I think it was about April 1996.

I chose to just run it, without 'Valvemaster', based on the tiny Mk 1 valves, the low-mass valve-train, and on remembering that lapping-in Imp valves was extremely tedious compared to iron-heads. Also, I felt that it probably should have a head-off job sometime, as it was coming up to 30,000 miles since last time. It has only done about 4000 miles since, but on our regular hill run. A slightly noisy tappet is still slighly noisy, and it's still running pretty well.

I did think I would chicken out & dose it if I was doing a sustained highway run, but now I don't think so.

My son had an alloy-head Hunter which we still have acquaintance with - it hasn't started asking for regular tappet-setting activity since the changeover.
Kenneth, what have you been doing in yours?

A local engine-shop said Rootes alloy-heads were fine, but Valvemaster propaganda said they had to be dosed.

I did postpone filling with unleaded 96 for as long as possible, for another reason: The first round of the new stuff here had very high aromatics, which devoured rubber & plastic parts in fuel systems, causing lots of middle-aged Fords to catch fire. Now that the fuss has long since died down, I must recheck the ancient fuel pump again...

So unless you're cruising at over 5000 rpm all the time, I think don't worry. If you are going hard, keep in touch with Nick & reserve your judgement whilst keeping your wallet intact!

Good luck
GaryH


From: Nickcleak@aol.com
Date: Sat, 21 Nov 1998 16:20:00 EST
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi ,

> Dave Llewelyn says he has been running his engines on unleaded for a
> while.......

well mine is hardly a conversion , i ran my CLAN on unleaded for quite a while
, it has the big valve competition head , these valves are good quality anyway, as are the standard Imp vales ..

> I have seen a head where the exhaust valves have definitely
> receded into the ports.

I have seen this sometimes on very standard engines , but the engine was not running on unleaded ...
Perhaps valves were sourced from a motor factor ???

> I am loath to
> start running the Husky on caffeine-free gas in case of the damage it may do.

As i see it there are two issues with unleaded :

1 , compression ratio and pinking ...

Some Imp engines seem rather tollerant of a high compression ratio and don't pink at all , others may be sensitive to it .
The answer would be to retard the advance curve slightly only at the point of pinking , not where it runs fine , this may not be easy to achieve , but it must be possible ....
also perhaps the compression ratio can be lowed slightly on problem engines ,
i wouldn't recommend it , but some manufacturers answer is to use two Cylinder head gaskets ...

2 Valve seat and guide wear ..

I don't see this as a problem , as Imp guides seem to wear anyway!
The seats and valves are good quality anyway , my Turbo never had any valve trouble and they got rather hot i would think on occasions !

If you don't drive hard for long distances , then i don't think it will be a problem ....
If you do drive hard for long periods , then i believe the valves will still last quite a while ...

I am not too worried although i shall remain on 4 star whilst it is available..

Nick ...


Date: Sun, 22 Nov 1998 11:42:00 -0800
From: Kenneth Barlow
Subject: [imps] Re: Valve guides/Unleaded conversion

>>From NZ, where the 'change' happened some time ago...
> Kenneth, what have you been doing in yours?

I have been running straight 96, no lead, and no valve master. I have done approx 7000 miles, and I have not noticed any extra noises or where. I have been told to try 91 also, (this has no lead either). My flat mate tried it in his Imp and says there is an improvement in power. I am wanting to pull the head off to see if there is any where in there due to Unleaded fuel, but at the moment I am not about to sacrifice a head gasget and the time for tapets or re torquing just for a check. Will let you know when I do pull it off.

Kenneth

> So unless you're cruising at over 5000 rpm all the time, I think don't worry.

My car is doing high revs most of the time, but not always this high


From: Paul Williams
Date: Sat, 21 Nov 1998 23:41:35 -0000
Subject: [imps] Re: Valve guides/Unleaded conversion

> The very same machine shop has recommended that they only need to
> replace the exhaust seats. Is this information correct.

I seem to remember hearing somewhere that standard Imps will run perfectly well on unleaded for at least 50,000 miles. I know that Jill White (Somerset ACO) has been running her car on it for about 18 months with no problems to speak of, unless anything's happened since I last spoke to her!!

Paul


From: Gary and Carol Henderson
Date: Sun, 22 Nov 1998 21:49:12 +-1300
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi Kenneth & all

On reflection, the change happened during Feb-March 1996.

If the valves recede into the seats, the tappets will go quieter, then the engine will start to run rough & then burn valves, because they no longer get to close.

Back in the days of CNG-conversion mania (late 1970s) the BMC B engine was by far the worst for valve-seat recession when run on gas, except for trucks with valve-rotation gear.

So if you're worried, check the clearances every so often...

Re the aromatics problem: Suggest you make the changeover gradual (i.e. first fill of unleaded when still a good half-tank of the 'good' stuff; keep this routine at least a couple more times, so the rubberware can re-acclimatise.)

Re use of 91: I intend to try this cautiously sometime, in case of supply problems. The London-Sydney Hunter could be run quite happily on low-octane (much lower?) by setting ignition timing to 10 deg AFTER TDC. An Imp behaves far better with respect to pinking, running on etc and has more precise timing due to distributor drive direct off crankshaft. Carol's Mirage runs 9.6:1 and is meant for 91 octane.

A sidelight on leaded vs unleaded: Our old L300 van used to run happily on leaded 91, but started pinking at mid-revs once unleaded 91 came along. It was only curable by retarding to a point where its performance became unacceptable to us hill-dwellers.

Best regards
GaryH


Date: Mon, 23 Nov 1998 00:59:24 -0500
From: Gary Harding
Subject: [imps] Re: Valve guides/Unleaded conversion

All,
It's true, I'm afraid. All non Sport (I have no information, to date, on Sport cylinder heads) Imp cylinder heads must have hardened exhaust valve seats and harder exhaust valves fitted before they can be run 'normally' on unleaded. Yes, the existing valve seats are steel but are of a very low grade meaning that they still require protection by lead or a suitable substitute.
In mainland Europe and New Zealand where leaded fuel has not been available for some time and there a variety of fuel additives have been around to provide the necessary exhaust valve seat protection. Can any of you NZ Impers give us details of the best lead substitute - I've been told that the Phosphorous based products are good.
Of course there are those that claim to run their Imp on unleaded for years with no problems. Next time you speak to one of these people ask them about their driving style as damage to the exhaust valve seats occurs mainly at 'normal' and above engine temperatures and at higher speeds. So if you potter around at below 'normal' engine temperature and at low RPM then yes your Imp will run for years on unleaded - this is not the solution.
The solution is either to convert to harder exhaust valve seats and valves or use a fuel additive, that is if you wish to continue to drive your Imp to it's full potential.

Gary


From: Kristian Jonsson
Date: Mon, 23 Nov 1998 08:31:22 +0100
Subject: [imps] Re: Valve guides/Unleaded conversion

> Re use of 91: The London-Sydney Hunter could be run quite happily on
> low-octane (much lower?) by setting ignition timing to 10 deg AFTER TDC.

No. not 10 deg. after TDC. That is going to far ? Can that be right ? Ex .valves will be burnt in a very near future ??
Kristian Jonsson


Date: Mon, 23 Nov 1998 09:52:06 +0100
From: Bert Clewits
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi Impers,

I have been running several Imps on unleaded super since it was introduced and I have had no problems up till now.
My dad uses his Imp daily and uses a lead replacement which seems to work fine as well, (you can see the white lead deposits on the plugs)
(We have done about 50.000 km each with Imps so far since with sport and std engines)
(Also we had a head converted to unleaded for a very resonable price.)
This doesn't mean that there will be no accessive wear in the valve mechanism though !
As Gary said I'm running with a very cool engine.
The Stiletto's just out of the white region on the dial, using a four row rad, 74dgr thermostat etc.
The Chamois is completely standard (temp gauge in the middle), 78 degr stat.
Both cars run 110km/h on motoways continuously, besides the valve setting is on the max side.
But why bother as when the engine wears out on unleaded, you have to upgrade it with new seats and valves anyway.
I have this converted head ready just in case as I don't have any modern car to drive.

Hope this helps
Bert

P.S. Also there seems to be more then one sort of unleaded around !


From: Gary and Carol Henderson
Date: Mon, 23 Nov 1998 21:30:28 +-1300
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi Gary

The product on the NZ market is phosphorus-based 'Valvemaster'. It seems to keep iron-head BMCs, Fords, golden Holdens etc alive OK.

I would expect more troubles with the likes of a Hunter, with its heavy push-rod valve train, biggish valves, beefy springs and medium-high compression. Certainly a good item to experiment on, as checking/resetting clearances is free and fairly painless. The one that I know of for sure has been doing mixed running since early 1996 without being dosed. By comparison, a BMC B-series would have clearances go negative in weeks.

The ordinary Rootes seat-inserts are definitely a lot harder than the cast-iron of a head.

The Imp valve-train is tiny, lightweight and free of side-loadings. So wear due to abrasion of the seats could be expected to be less than a larger pushrod ohv. Mine hasn't had daylight inside for several years & 32,000 miles, so I'm prepared to give it a try, although as mentioned I'd consider dosing it for long hot running.

We hear about grades of material - is hard data available?

Cheers
GaryH


From: Gary and Carol Henderson
Date: Mon, 23 Nov 1998 21:34:29 +-1300
Subject: [imps] Re: Valve guides/Unleaded conversion

Hi Kristian

It's a while since I read Andrew Cowan's book, but I'm sure that's what he said they used.
Pinking is because the main explosion is propagating too quickly & so occurring too soon; lighting the fire a little later is one way to fix this!

The two cars drove into history - as winner and a high placing in Sydney.

Cheers
GaryH


From: Nickcleak@aol.com
Date: Mon, 23 Nov 1998 15:40:23 EST
Subject: [imps] Re: Valve guides/Unleaded conversion

> It's true, I'm afraid. All non Sport (I have no information, to
> date, on Sport cylinder heads) Imp cylinder heads must have hardened
> exhaust valve seats and harder exhaust valves fitted before they can be run
> 'normally' on unleaded. Yes, the existing valve seats are steel but are of
> a very low grade meaning that they still require protection by lead or a
> suitable substitute.

Apparantly , the oversize vales and inserts are suitable for unleaded according to the late Ian Carter ..
nick


From: Nickcleak@aol.com
Date: Mon, 23 Nov 1998 15:40:26 EST
Subject: [imps] Re: Valve guides/Unleaded conversion

> No, not 10 deg. after TDC. Ex. valves will be burnt

indeed , the exhaust gas temperature will be greatly above normal ...

nick


From: Smith, Neil
Date: Mon, 23 Nov 1998 10:25:18 -0000
Subject: [imps] Re: Valve guides/Unleaded conversion

I don't know if this would be of any use, but the last time I got my car MOT'd the garage had some adverts for a thing that you attach on the fuel pipe and it puts tin into the petrol.

This was claimed to give better power, better fuel economy, allows old engines to run with unleaded fuel, and increases engine life. I asked about this and the mechanic said that they had seen some results of their own independent tests which showed that it apparently did work.
Has anyone tried something like this, or have any idea what tin might do in an Imp engine?


From: Nickcleak@aol.com
Date: Thu, 26 Nov 1998 13:43:21 EST
Subject: [imps] Re: Valve guides/Unleaded conversion

> Has anyone tried something like this, or have any idea what tin might do
> in an Imp engine?

Not a lot, in fact nothing at all !

Nick ...