Twin cam Valve Guides.

[Grizzly]

Hi all.

I've finally got sick of my Elan blowing blue smoke out.

There is a bit of history with this engine when i bought the car it was a none runner, it had a Cam chain fail on it and the previous owner had it repaired but couldn't get it running (ignition was 180deg out) so when i got it running it appeared fine but i was told it blew a bit out on overrun (but i have never seen it myself) and it smokes for a minute or so when first kicked up from cold, so at the moment i have a Shinny new Galvanized chassis for it so it makes sense to look into it while the engine is out.

So i have dug the receipts out for the engine work and if they are accurate it didn't have any guides even though it had all 8 valves, so i'm thinking that they may have been damaged at the same time and no one noticed or maybe just wear/old age?

Before i took the engine out of the chassis i compression tested it (quite evenly 140psi a pot and as its not been run for two years i think thats not bad), so at this moment in time i have made a bit of a shopping list of things i have wanted to replace but the Guides have to be my main priority.

Right, so i have done some reading up and ordered a full set of bronze inlet / exhaust Guides from Burton and its coming up to the big day. So i have a few questions for those who have done this bit of a job before, if you dont mind....

Well the first thing is whats the best way to remove them, i have read they should just tap out cold but i want to air on the side of caution so would it help if i warmed the head up first?

Then there is the Guides them selves, I was planning on reaming them on the lathe before fitting then running the reamer through by hand just to clean up after there in but i read most people fit the guides before doing any machining? thing is with the head warmed up i suspect they will go in quite easy and thus save myself lots of time setting the machine up to ream them out properly. While i'm on the subject of reamers, my lotus manual says it should be .3113-.3123 or 7.90-7.932 tolerance. So am i correct in saying if i run a 7.90mm reamer through that should give me the desired effect?

The last thing i wanted to ask was if there any man traps i should be aware of before setting off, i understand the head surface is easily marked/damaged as is any alloy head but i don't want to scrap my cylinder head because of some i missed of did Dumb.

Cheers.
Chris.

[elansprint71]

Have you tried the valves in the new Burton guides to see if they fit before putting a reamer anywhere near them?

You should heat the head in the oven to remove the old guides.

[Grizzly]

No, the guides haven't arrived yet.

What sort of Temp would you say would be ideal?

[StressCraxx]

Grizzly,

First off, the twink head has no valve guide seals, so a little blue smoke on startup and a little on overrun is normal. The valve stems and guides are bathed in oil and it wicks down between them to provide the bloke behind the little puff of blue.

Do you have a copy of the Elan shop manual? There is a procedure for removal and installation of the valve guides in the manual. I would recommend this is one of those areas where reading the book is highly recommended to prevent a costly mistake.

If your guides are worn, so likely are your valve stems. Guides should be matched to each valve stem and reamed if necessary after installation. Its also possible to find the new valve guides are on the loose end of the tolerance.

The clearances in the elan shop manual are fairly loose. Dave Bean's Elan book has recommendations for closer clearances and reduced oil consumption. Additional benefit is the valves and guides last longer.

Think of the entire valve train as a mechanical system. That means from the cams, bearings, thrust washers, buckets, bucket liners(in the head), shims, springs, keepers, guides and valves all need to be within the tolerances. If one clearance is too loose(most likely) all the rest is at risk for premature wear or even failure. These engines are not too sophisticated, but they have to refurbished properly.

When you tested compression, was the engine warm and the throttles wide open? 160 PSIG is the minimum with all cylinders within 20PSIG of each other. A leakdown test may be in order. You may be able to discern if your rings are worn too.

Best regards to you. Sounds like you will have a really nice Elan when you are done.

Regards,
Dan Wise

[Grizzly]

The main reason i'm not going to mad with the rebuild is the engine has done 32,000 miles and the bottom end is sound (now have the head off and can still see the original hone marks in the bores and it only made 5-8psi difference to the compression when i put oil in the bores) i think the situation with the oil/blue smoke has allot to do with the cam chain failing (btw all the valves where replaced less than 500 miles ago). As for the general condition of the head, the valves are quite badly gunged up (technical term for a mix of oil and carbon deposits) and i also took the cams/Buckets/shims out turned it over and put some paraffin in the combustion chambers (with the plugs in of course) and it ran out of the exhaust valves very quickly. I understand Paraffin is a little thin to be doing this test with but the exhaust valves are not properly seated. I was shocked at the build up for the amount of miles it had done since the head was last off but also happy there is little to no water way corrosion.

This is a job i have been putting off for some time so i have quite a lot of literature on the subject collected over the last few years (but typically not the book you mention, do you know the books full name as i'm just struggling to find a copy of it) , i have been going more of the Lotus manual but there seems to be a few different idea's as to what size the guides should be with stock size valves, i did think about measuring the valve stem and then making my own decision on the reamer size but as i haven't got the Guides in my hand yet and only just tonight got the head on a bench so i'm not quite at that point in the game, but this is one of those things i wanted to run past you guys before spending all that time doing the job then find Lotus made the guides too loose and it still smokes or worse the valves start sticking in the guides if its too tight.

I do understand that the design of the head will cause some cold start smoke but i think this is excessive, Dense blue smoke so thick you can't see through it on cold start for 60 seconds then tails off after the next 4-5 mins, it does smoke when driving too but i have three different accounts of when it happens and i don't trust anyone enough to drive it for me plus i found a split link in the Timing chain which made me very paranoid about running it (hate split links) which is the main reason its been off the road for a bit. (its getting a decent quality endless chain)

[StressCraxx]

The main reason i'm not going to mad with the rebuild is the engine has done 32,000 miles and the bottom end is sound (now have the head off and can still see the original hone marks in the bores and it only made 5-8psi difference to the compression when i put oil in the bores) i think the situation with the oil/blue smoke has allot to do with the cam chain failing (btw all the valves where replaced less than 500 miles ago). As for the general condition of the head, the valves are quite badly gunged up (technical term for a mix of oil and carbon deposits) and i also took the cams/Buckets/shims out turned it over and put some paraffin in the combustion chambers (with the plugs in of course) and it ran out of the exhaust valves very quickly. I understand Paraffin is a little thin to be doing this test with but the exhaust valves are not properly seated. I was shocked at the build up for the amount of miles it had done since the head was last off but also happy there is little to no water way corrosion.

This is a job i have been putting off for some time so i have quite a lot of literature on the subject collected over the last few years (but typically not the book you mention, do you know the books full name as i'm just struggling to find a copy of it) , i have been going more of the Lotus manual but there seems to be a few different idea's as to what size the guides should be with stock size valves, i did think about measuring the valve stem and then making my own decision on the reamer size but as i haven't got the Guides in my hand yet and only just tonight got the head on a bench so i'm not quite at that point in the game, but this is one of those things i wanted to run past you guys before spending all that time doing the job then find Lotus made the guides too loose and it still smokes or worse the valves start sticking in the guides if its too tight.

I do understand that the design of the head will cause some cold start smoke but i think this is excessive, Dense blue smoke so thick you can't see through it on cold start for 60 seconds then tails off after the next 4-5 mins, it does smoke when driving too but i have three different accounts of when it happens and i don't trust anyone enough to drive it for me plus i found a split link in the Timing chain which made me very paranoid about running it (hate split links) which is the main reason its been off the road for a bit. (its getting a decent quality endless chain)

Grizzly,

Understood, 60 seconds of smoke is far excessive. Sounds like you have done your homework, agree about the split link too. My first teardown for rebuild 30 years ago, the valves could wiggle easily in the guides!

The book is available from Dave Bean Engineering, http://www.davebean.com/. Click on the tab "Catalog" Its the Elan/+2 Catalog that is organized like the manual, and has excellent background, maintenance and reliability information. Dave is a BSME from California State Polytechnic University, so he knows the math and theory too. Best of luck to you!

[Grizzly]

Cheers for that, i love getting as many different approaches to a job as possible as you often find the specialists know best (often they have much better ways and techniques than Lotus them selves)

Just a bit of an update, today i took both valves out of no1 cylinder and had a good look at the valves and guides, i checked the valves with a micrometer and sure enough no wear on the inlet or exhaust (good start) i put the valve back into the guide and slowly drew it out whilst wiggling it to see if there was any play, sure enough there was quite a bit of movement (mainly in the Inlet guides) so i have been collecting reamers for a while too and i have a .3132 reamer which i understand is outside the large lotus tolerance and just pushed it into the guide as an idea of the size/wear in it. I was surprised to find it would go 1/3rd of the way from the bucket side and about the same amount in the valve side with no effort but was not having it at all when it got near the center of the guide. So with that and the fact the inlet valves are very oil stained i'm now feeling more happy i'm doing the right thing replacing them all.

So i have now got the 2 guides of no1 out, i had a quick go cold but they where having none of it so after two hours in the oven i had another go and they came out ok (wouldn't say easily but there out). Am i correct in saying the stock guides are cast iron? as i was tapping one out it shattered, it saved me a bit of time but i always thought they where made from Bronze?

[elansprint71]

Wilkins suggests that 150 degrees C is the best cooking temperature for removing valve guides. After your oven is up to temp it should only be ten minutes before the head is uniformly heated, assuming that you put the head in as it warms up. I could not quite shut the oven door, so wet towels were stuffed in the gap. Same temperature when you knock the new ones in.

The reason I asked about trying the valves in the Burton guides- my valve stems were not worn and they all fitted straight into the Burton guides. I did not use the Burton guides but that's another story, see here: http://www.lotuselan.net/forums/elan-f15/loose-valve-guide-t22263.html

You will find suggestions in that thread on how to disguise the smell of burning oil in the kitchen from anyone of the female persuasion who may be in your household.

[Grizzly]

Out of interest, how easy did the new Guides go in at 150deg? i am fortunate to have access to a large engineering oven but when i was playing today they where running it at 100deg so even though it was hot the guides where still aquard to get out, i put that down to tight fit but maybe a bit more heat is the key. I know what you mean about house hold ovens too, when i was planning the job i was caught measuring the oven up and when i told the better half what i was doing she was not best pleased, lets just say other options where looked into

MMMM with a bit of luck my guides will be hear tomorrow (Wednesday) so i can check them out but i don't like the idea they are already machined to size, i really wanted to ream them once in so i know there is no damage or off round shape caused by the fitting (plus a bit of an anticlimax after all the reading up and collecting reamers ). But i'm hoping they go in a sight easier than they are coming out.

[Grizzly]

The reason I asked about trying the valves in the Burton guides- my valve stems were not worn and they all fitted straight into the Burton guides. I did not use the Burton guides but that's another story, see here: http://www.lotuselan.net/forums/elan-f15/loose-valve-guide-t22263.html

Thats scary, out of interest did you try a standard size guide in the oversized hole? (was it noticeably loose?) i'm going all paranoid now after seeing that and QED fitted it too

[elansprint71]

Quote from the other thread:
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.

It was done by feel really, after fitting the standard one I knew how much "bash" to apply with the 1lb hammer, the +002 felt thereabouts, so that was it.
That reminds me; I have a set of Burton valve-guides and "circlips" to go on e-bay!

[Grizzly]

I think todays task is to make a better drift, i did make one out to a bolt that was turned down to fit nicely in the guide but i think its not hard enough as it's looking a bit sorry for its self after the first two, i'm also thinking of putting a matching taper on the tool so it sits a little better on the old guides so i can give them a bit more stick without bits of cast iron smashing off at a great rate of knots.

I would make a drift for the putting in of the guides too but still no sign of my new ones (always the same when parts are holding the job up)

[Grizzly]

we have a box


Unfortunately jammed full of fine shredded paper which has now made the kitchen floor look like its snowed in doors but looking at the bottom its well worth the ear ache....



Think we'll keep that box out of the way of the kids.....

[Elan45]

I made my guide drift of brass rod, just a few thou small than the guide OD. While I had it in the lathe, I bored a nominal 5/16 hole in the end and then pressed a pilot into the hole which then locates the drift exactly centered on the guide. My tool has been used for a couple of twin cam heads, at least one Coventry Climax and a Ford 105E head that I had bored out to fit 1/2" OD bronze guides.

Roger

[Grizzly]

I was planning on doing some thing along those lines myself but i've made one quickly out of an old head bolt with the end taken down to fit inside the guide and where the guide meets the shoulder i've shaped it so it sits round the taper so there is a better contact area and its quite a bit smaller then the guide OD in case it starts to spread at the end (if that makes sense) this will be my knocking out bruiser.

I'm now about to have a go at the refitting drift, i'm going to do some thing similar so the contact area is the same shape and have a locating peg but i'm not sure what i have about i can make it from, i really want it softer than the guide so my first thought was copper or one of the harder alloys? but i think it may be too soft so i need to have a trip up to my local Steel chap and see what they have but as you say Brass may be a good option if he has some thing suitable in stock.