Loose valve guide :-(

[bigvalvehead]

Hi Pete
If the guide has been moving around a bit in the head you may need to go for the +2 thou guides. As well as heating the head put the guides in the freezer then dip lightly in oil before tapping in. They should not need much to get them in.

[elansprint71]

Hi Pete
If the guide has been moving around a bit in the head you may need to go for the +2 thou guides. As well as heating the head put the guides in the freezer then dip lightly in oil before tapping in. They should not need much to get them in.

Thanks again Dave. Could I use garlic-butter instead of oil?

The old guides are now out; here are my collected thoughts on using a domestic oven:

1. Car designers are mainly not too bright, how many of them actually measured up a domestic oven before drawing up their blocks and heads?
2. Even a wet towel can start to burn.
3. Before starting this job ensure that you have oily fish (mackerel is ideal), strong aromatic coffee and bread in the house.
4. 150 degrees is extremely hot, don't plan on carrying the head too far.
5. Glass oven doors can be quite brittle.
6. If the phone rings, ignore it.
7. A two-pound engineers hammer is very effective for knocking out, a one-pound one will be sufficient for knocking in.
8. Electrical tape over the oven-door micro-switch can leave a sticky and smelly mess.
9. Smoke alarms can be really annoying.
10. In case you are wondering about #3, the answer is they all make lots of strong smells when over-heated, which may be required before your wife gets home and jumps to any conclusions.

Having got a feel for how much force was required to get the old ones out I'm now going to measure up the old guides and decide which size to order.

[ppnelan]

The guides seem to have been fitted by QED about 20k miles ago.
I'm thinking that this guide might have taken to wandering up and down the stem, sometimes sticking in the right place, sometimes dropping down and allowing bad stuff to happen.

I had a similar thing with a QED-rebuilt head some years ago. I saw the signs but had no idea there was a serious problem - repeated fouling of 1 plug only, and occasional metallic tapping noise when hot (guide rattling around). It finally came to light when a chunk burnt off the valve! I was about 100 miles from home, but managed to get back at under 50mph, sounding like a rally Subaru...

Matthew

[CBUEB1771]

If the guide has been moving around a bit in the head you may need to go for the +2 thou guides.

My apologies if this has been covered, but the bore in the cylinder head needs to be very carefully inspected and measured before you buy replacement guides. The guide must have excellent heat transfer to the head in order to control the valve temperature. Therefore you need complete contact between the guide and head. If there is much variation in the bore diameter, either an out-of-round condition or variation along the axis you will want to ream the bore first and then specify what you need for outer diameter of the guide.

[GrUmPyBoDgEr]

Hi Pete
If the guide has been moving around a bit in the head you may need to go for the +2 thou guides. As well as heating the head put the guides in the freezer then dip lightly in oil before tapping in. They should not need much to get them in.

Thanks again Dave. Could I use garlic-butter instead of oil?

The old guides are now out; here are my collected thoughts on using a domestic oven:

1. Car designers are mainly not too bright, how many of them actually measured up a domestic oven before drawing up their blocks and heads?
2. Even a wet towel can start to burn.
3. Before starting this job ensure that you have oily fish (mackerel is ideal), strong aromatic coffee and bread in the house.
4. 150 degrees is extremely hot, don't plan on carrying the head too far.
5. Glass oven doors can be quite brittle.
6. If the phone rings, ignore it.
7. A two-pound engineers hammer is very effective for knocking out, a one-pound one will be sufficient for knocking in.
8. Electrical tape over the oven-door micro-switch can leave a sticky and smelly mess.
9. Smoke alarms can be really annoying.
10. In case you are wondering about #3, the answer is they all make lots of strong smells when over-heated, which may be required before your wife gets home and jumps to any conclusions.

Having got a feel for how much force was required to get the old ones out I'm now going to measure up the old guides and decide which size to order.

I guess your wife's name could be Betty?
Some mothers do 'ave 'em

[elansprint71]

If the guide has been moving around a bit in the head you may need to go for the +2 thou guides.

My apologies if this has been covered, but the bore in the cylinder head needs to be very carefully inspected and measured before you buy replacement guides. The guide must have excellent heat transfer to the head in order to control the valve temperature. Therefore you need complete contact between the guide and head. If there is much variation in the bore diameter, either an out-of-round condition or variation along the axis you will want to ream the bore first and then specify what you need for outer diameter of the guide.

Not the easiest place to measure without an inside micrometer so I searched out a washer with nominal diameter same as the bore, made a handle for it (wooden pencil screwed thro the washer hole). Shining an LED torch from below, I lowered the "gauge" down and observed both the shape and size of the bore as the washer was passed through the bore.
It looks near enough round and pretty much the same diameter all the way through until getting near the lower end, as one might expect.
I have ordered seven guides at the standard diameter (judging by the force required to get the old ones out there still seems to be a good interference fit) and one at each of the oversizes available.

With a damaged head I would be very nervous of trying to ream out the bores in the head without a very accurate head-mounting gauge to ensure that the angle is correct and even then it would be necessary to get a bespoke diameter guide turned up. Reaming by hand would be a risky process.

Believe it, or not, I actually am (or was) a time-served precision tool-maker although I've probably not displayed much of that talent on this forum; reading some of my previous posts.

Thanks again for all the advice support and good humour on the forum, there really is no place like this.

Now, I'm off to grease, or oil, my trunnions and decide which tires (sic) might be best for my car, after I've studied the paint codes for British Racing Yellow.

[alexblack13]

Believe it, or not, I actually am (or was) a time-served precision tool-maker although I've probably not displayed much of that talent on this forum; reading some of my previous posts.

Thanks again for all the advice support and good humour on the forum, there really is no place like this.



You sure kept that quiet Pete! Talk about teaching one's Granny etc!!!


I can send you a loan of a small internal bore gauge if you want one to check the head. But for WIW.. I would have it sorted by a pro' outfit.. Esp' if needing machined!

Let me know and I will post it down to you asap..

Alex...

[elansprint71]

Believe it, or not, I actually am (or was) a time-served precision tool-maker although I've probably not displayed much of that talent on this forum; reading some of my previous posts.

Thanks again for all the advice support and good humour on the forum, there really is no place like this.



You sure kept that quiet Pete! Talk about teaching one's Granny etc!!!


I can send you a loan of a small internal bore gauge if you want one to check the head. But for WIW.. I would have it sorted by a pro' outfit.. Esp' if needing machined!

Let me know and I will post it down to you asap..

Alex...

Alex,
I could weep when I think of the tools that I sold/gave away when I decided to take the Rotring route rather than the Hardinge road. Swapped the slip gauge for the slide-rule, etc.

Thanks for the offer but I think that the head job is self do-able; fortunately I did not do many trips in the car after the smoke first appeared; the trip to LM was the only big one and, as you know, it did not smoke all the time, so presumably the guide spent a fair bit of its time in the correct location.

As for giving work to the "pros", I really do view most of these folks as a very last resort. If I can fix it myself, I will. Many of them are just blokes with the kit an' full o' shit.

Despite what you might have read in the papers about my (hopefully) forthcoming redundancy package, I am a man of limited means so, having done the sums, worst case is I sell off the remaining Lotus bits and build a couple of 26/R Zetec Shapecraft +2 convertibles and retire to the Riviera.

[alexblack13]

Ok.. All the best with it.

Al' .......

[elansprint71]

New valve guides are in, head is cooling as I write; Mackerel for lunch, to disguise the smell in the kitchen!

I chilled the guides and knocked in a standard one first to judge the "feel", tried the +.002 one in the "worn" bore and it was just a tiny bit tighter, as a precaution I put a drop of Loctite 620 (look it up before commenting ) on the guide, the rest had a smear of oil. If this guide had gone in easier than the first, I had a +.005 in reserve but that is quite a step up.

So; next job reaming the guides, Brian has kindly supplied adjustable reamers, so it's softly, softly with this job; the 2lb hammer can go back in the drawer for a while.

[rgh0]

I presume you have fitted bronze guides. When reaming the guides aim for the tight end of the lotus spec clearance range for the inlets to minimise oil leakage down the guides. Aim for mid range on the exhausts as oil leakage less critical and you want to avoid binding due to the greater valve stem expansion on the exhaust. If using the original style cast iron guides aim for midrange on both.

cheers
Rohan

[john.p.clegg]

Pete

Just a thought,what I did after fitting new guides was to taper the top of the guides with a lathe tool welded to a bit of 5/16" rod so as to eliminate oil sitting on top of the guides....no problems since....

John

[elansprint71]

Two good tips; thanks guys.

[elansprint71]

Well, engine runs and (as far as I can tell) does not seem to smoke. The problem with having a car on SORN is that you can only drive it to the MoT station to get it tested, so there is no possibility of checking things out on the road and all the running and revving on your driveway does not represent the real world of under-load driving.

Test passed with flying colours, now got to sort out some new electrical problems which have surfaced.

[AHM]

Hi Pete

The old guides are now out; here are my collected thoughts on using a domestic oven:

1. Car designers are mainly not too bright, how many of them actually measured up a domestic oven before drawing up their blocks and heads?
2. Even a wet towel can start to burn.
3. Before starting this job ensure that you have oily fish (mackerel is ideal), strong aromatic coffee and bread in the house.
4. 150 degrees is extremely hot, don't plan on carrying the head too far.
5. Glass oven doors can be quite brittle.
6. If the phone rings, ignore it.
7. A two-pound engineers hammer is very effective for knocking out, a one-pound one will be sufficient for knocking in.
8. Electrical tape over the oven-door micro-switch can leave a sticky and smelly mess.
9. Smoke alarms can be really annoying.
10. In case you are wondering about #3, the answer is they all make lots of strong smells when over-heated, which may be required before your wife gets home and jumps to any conclusions.

Having got a feel for how much force was required to get the old ones out I'm now going to measure up the old guides and decide which size to order.

Having just done the job I would add the following to this useful thread
Point 1 above - the head went into my standard oven width ways on the diagonal.
If the old guides were difficult to get out, the new ones are going to be difficult to get in.
Oil on the new parts makes a big difference - oil before putting in deepfreeze. I did the exhaust guides without oil and the heads are not pretty - once you are half way you have to keep hitting! A good job they need to be reamed.
The ally is easily marred by the drift when it is at 200c - watch the edge of the drift.
Smoke - lots of smoke
skin doesn't blister at 200c - it comes straight off