Cylinder head overhaul

[mazfg]

So, carrying on from my blue smoke issue....I'm going to remove the head over winter and overhaul it.

Just wondered about any pointers?

New valve guides, valve seats, valves valve springs, pushrods.  Check rocker gear for wear too.
Do the pushrods have guides and if so change?

Was going to find a local engineering company and get them to do the neccessary for the valve seats, guides and valve grinding... What also might need doing to the head itself..?

Hardened valve seats and exhaust valves are all that's required to run unleaded right?

Thanks in advance....am a first timer for doing this.

[JohnD]

maz,
BLUE smoke is usually oil burning, which implies that the oil is getting into the chambers either down the valve guides or up from the crankcase.   In the second case, a head overhaul is unlikley to help, so you should plane to pull the sump bring the pistons up, to see if the piston rings are worn or sticking in the grooves, and if the bores are in good condition.  Simple inspection will show the last.

On head work.  New valve guides will be necessary if you find any slackness at all in 'wiggling' a valve in the guide.  It should be firmly held.  There has been some correspondence on the Sideways site about bad, new guides so beware.  Only exhaust valve seats need steel inserts - the valves are steel - and new pushrods are rarely needed, unless you skim the head a lot and need shorter ones.  Valve springs?  I you want it for a road car, I'd keep the old ones.
You local machinist will need to cut seats in the new steel inserts for you, but you should then grind them in, with valve grinding paste and a 'posser' or 'lapping tool', a wooden rod with a suction cup on each end. See eBay and many descriptions of the hand technique/
http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p5197.m570.l1313&_nkw=valve+grinding+tool&_sacat=See-All-Categories

JOhn

[mazfg]

Thnaks John....I'm hoping it is the valves.....my vacuum gauge drop every now and again whilst idling...seems to point towards a valve type problem...http://www.classiccarhub.co.uk/articles/tuning-and-fault-finding-using-a-vacuum-gauge.html

Still, once the head is off I can check the pistons and bores too....

Not sure what you mean re: valve springs.....just thought I'd renew these whilst I'm at it..?

[Mark Hammond]

Before you remove the head, compression test the engine dry and wet to determine worn rings.  Whereas John says blue smoke is usually oil burning, it isn't always a symptom of knackered bores/rings.  Does the car use a lot of oil? or is it smoking on overun (usually a sign of worn valve guides)?

M.

[thebrookster]

Personally I would go for 3 angle seats for the valve seats, I don't think it costs much more than a simple 45 degree seat, but does count for an "improvement" without losing originality on the engine.

You MAY need to think about a contingency budget for things like head skim, if you are not leaking out the head gasket I reckon you should get away with it, but don't spend your entire budget elsewhere and then discover it needs doing!! Again, not hugely expensive IIRC.

[mazfg]

So as this is reserved for Autumn/ Winter....what's the damage to the engine with it as it is...ie: blowing smoke re: drawing in oil via the valves guides?

I really want to enjoy the car now and drive it about, especially with the Summer on our doorstep. I spent most of last weekend driving and it was great....blue smoke only seems prevalent during idle...

[mazfg]

thebrookster wrote:

Personally I would go for 3 angle seats for the valve seats, I don't think it costs much more than a simple 45 degree seat, but does count for an "improvement" without losing originality on the engine.

When you say 3 angle seats....is this what the engineering cut them to, as oppose to 45 degree cuts?

[Mark Hammond]

It really does sound like worn valve guides to me.  If you keep your eye on the oil level I doubt that there will be any long-term damage.

M.

[thebrookster]

It is to do with the air flow past the seat. I'll start from basics, so bear with me :)

Your valve insert is simply a ring like a washer, only much thicker. The valve seats itself against the inside radius. If it was to be left as a right-angle the valve only seats against a very small surface, and wear easily occurs, plus if the edge is damaged you lose the seal needed for compression. By cutting a seat here, and having the back of the valve at the same angle allows a much bigger seating area, which gives a superior seal.

If you have the one 45 degree cut, you go from vertical  to 45 degrees to horizontal, which if you draw on a piece of paper you can see creates two "sharp" edges so to speak. This disrupts the air flow past it, which is not ideal, but a darn sight better than the right-angle :)

Now if instead of one angle cut here we put three in, drawn as follows: Take horizontal as 0 degrees and draw a line, then draw a line at 30 degrees, then 45, then 60 and finally at 90 degrees, As you can see, this basically rounds the corner more, allowing the air/fuel mixture to flow past it easier.

It may sound like a lot of work, however for an engine shop this is pretty much standard practice these days, modern cars have this 3-angle cut as standard, whilst our cars were built before things like this were really thought about hence the 45 degree single seat. It will enable your engine to produce a touch more power than it otherwise would, but is not a modification that will concern the insurance companies. Throttle response will improve slightly as well.

As you may guess, you can play around with this, add more angles in, change angles around etc etc, this is what racers etc play with when trying to get every last drop from their engines, however standard angles are as I gave above, 30-45-60. In fact, if you were to say to your engine builder 3 angle seats this is likely what he would put in.

Make more sense now :) (and I apologise if I have made this too simple, I was trying not to bog the post down with un-needed info, which I regularly do otherwise  8) :X 8) )

Cheers,

Phil

[mazfg]

Mark, thanks, I'm hoping that's the case. Will do the wet/ dry compression test this weekend.

Phil, wonderful explanation, very enlightening and helpful!

cheers guys  :)

[Pete Lewis]

before you jump just make sure this is not just down to  a rich mixture washing the bores
  whats on the boot lid,, black soot, oily deposits , whats the actual oil consumption ,

pete

[mazfg]

peterhlewis wrote:

before you jump just make sure this is not just down to  a rich mixture washing the bores
  whats on the boot lid,, black soot, oily deposits , whats the actual oil consumption ,

pete

Mixture setting seems optimal....although it does smell petrolly...but leaning off the  carbs just makes it run lumpy. I've set them up using colour tune in the past and now monitoring a vacuum gauge too..... They seem adjusted correctly...but maybe the engine needs a richer running mixture.......?

The blue smoke is more apparent when fully warmed up..which I'#d suggest means more the valve guides than rich mixture...? Not so much when first started....when mixture tends to be even richer?

[mazfg]

Found a nice local engineering company that I think I'll use: http://www.fjpayne.com/

As I want it unleaded ready afterwards, I have these questions:

1. Do I just need hardened valve seats for the exhaust section?
2. Is it worth replacing the inlet valve seats too?
3. Do the valves neeed to be hardened types for unleaded, or are all valves just standard
4. Are the valve guides standard or are they required to be hardened too?


Thanks

[Nick Jones]

Hardened seats needed for exhaust valves only.
Inlet seats just need re-cutting as lightly as possible to clean them up.
Exhaust valves might need upgrading for unleaded but probably ok as are.
Standard guides are fine.

Nick