Hello technically wise people, here are some questions about cylinder heads. I've had a manifold blow on my car since the middle of last year, one of the studs snapped and in drilling it out i buggered the thread, i retapped it M8 but the blow returned pretty soon after and I think it might be time to bin it and fit another one. (I imagine it's eroded the head by now anyway) Instead of my usual trick of just finding the nearest head and slapping it on, I thought I'd take a pair and give them a bit of a going over.

My car feels like it has bugger all compression anyway (it's quite gutless and I've played with the timing and stuff but it's never been much cop since I fitted the engine. I'll do a comp test before I take it apart and see what it's like.

Now, what should I be ordering from ECAS? I assume a gasket set including valve stem oil seals and pushrod tube seals for starters.

When I lap in the valves, is it essential that they all go back where they came from and I don't mix them up side to side, or as I'm lapping them in, does it not matter?

Lapping them in by hand, seems ok, but, why can't I stick them in an electric drill and speed things up a bit?

Is it worth matching the exhaust port to the manifold?

Is it worth me taking a spare barrel to work, cutting the fins off and using that to lap the mating face? I've read this in a 2cv tuning book I bought once, but wondered if it was worth doing.

If I take this a step further, I only have 8.5:1 pistons and barrels, how much material can I remove from the barrel to increase the compression ratio? I assume this is done on the engine end and not the head end? Is it purely a case of slapping it in a lathe and taking a bit off the end?


Sorry if this all sounds amateurish and dumb, but then, look who's asking...




Oh yeah, and why for the love of God didn't Citroen put a removable panel on the inner wings?

Russell,
the standard gasket set sometimes has a set of valve stem seals included, but Roy's advice is these aren't brilliant quality, so best to buy some good ones separately.

For lapping valves, an oscillating movement is best and attachments for that purpose are available which will fit onto a drill.

One tuning book I read ages ago advised making a 'step up' from the head into the manifold, suggesting that would produce a reflected wave in the system. Never tried it myself...

Always worth giving the seating surface inn the heads a bit of a tickle with a scrap barrel, but be extra careful to wash out every last trace of grinding compound. There's an undercut part of the recess in the head where it can lodge, with scored barrels the result.

I've always removed material from the top of the barrel, on the basis that removal at the lower end will give the rings a rough ride if there's any wear ridge in the barrels.
I can dig out the calculations if you want, but 'around' 20 thou rings a bell, to take the CR up from 8.5 to 9.0:1.

hf, ken

edit. Hadn't noticed the last bit. Didn't someone cut access hatches in the inner wings of their Ami, once upon a time in the South.
Where's Ami Matt?

Great, thanks Ken.

I guess if I take the top off the barrel on the lathe I need to take the machining marks off of it with grinding paste and a flat sheet of glass?

Russ,

You've pretty much asked all the questions that I think I was about to ask Off to the garage in 10 mins to start stripping down an engine to work out if I completely broke it, or there's just a whole load of coke blocking the piston's smooth passage.

Ben

Yep,
that or oiled 120 grit paper, followed by 180 grit?

Done the maths again as I can't find anything following the recent VAT plus income tax turmoil...

2.5 ccs less means 0.58mm/23 thou off the barrels, maybe stick at 20 thou if you don't want to whack an exhaust valve with a piston?

ken.

I seem to recall seeing that in 2cvgb mag a while ago. I've still got to take them off to cut holes in them, but hopefully next time it'll be easier...

Surely it's easier to take the wing off than it is to stick your head between the wheel and wing and work through a hole in the inner?

It's just a pain Joolz, it'd be impossible to get the head off with the inner wing in place (it's almost impossible to remove a rocker cover). To take the inner wing off means removing the outer wing and the front panel. All you'd have to do under the wing is simply pass the head through it once it was off.

What engine are we talking about? My advice is to find buy this kit
http://www.2cviking.eu/catalog/product_ ... cts_id=568
or just find the pistons you need. Unless you know, I would ship off the heads to an engine rebuilder for total reconditioning. When all back together, you'll know that the job is done correctly and no more opening the engine for a while.
Valves may be old and worn (out) exhaust stems are no good after years of heating and cooling. The metal is weak and changes, you can adjust the valves every 10.000 click
No don't bother, you can fiddle all the time and may regret that you didn't
Cheers
Viking bastard

PS. Sometimes we need to except that parts do not last forever and some can not be reconditioned.

Full gasket set but the valve stems seals aint the best and can split or un seat

before going at the head with the spring compressor sit the head on a wheel chock so the valves cant move then using a socket as a drift give the top spring seat a smart tap to free the collets othewise youll give yourself a hernia trying to un stick them against the spring pressure

if your manifold isnt seating take the stud out and countersink the hole in the head as the bolt and the tapping can pull up a high spot, re face it with a flat file, some roughness is desirable you dont want a mirror finish.

lapping valves isnt a big chore putting it in a drill wont work as it willl be too fast. little wooden dowel and sucker/paste sets are cheap

HOWEVER ( top tip) keep the drill handy as its the best way to de coke a valve ....stick the drill in the vice, put the valve stem in the chuck and fire it up, an old hack saw blade can be used to remove all the crap quickly, then the valve can be polished with some emmery. DONT touch the stem or the seat... hey presto polished valves.

( and before anyone gets all "health and safety" about putting fingers near 2000rpm machinery and lead particles... if you cant work it out for yourself stay in front of Big Brother telly eating buckets of chicken you muppets )

valve paste on the top of the barrel and wiggle it back and forth.

you can give the ports a bit of a tickle with 120 grit paper too but dont try to open out inlet port, just smooth out any steps and edges, again a rough finish to encourage "laminar flow"

wash heads off in a bucket to get all the grinding paste from the valves and head work out

on assembly-
a smear of coppaslip on the barrel to head joint helps( it is actually a high temp sealant) and some on the gaskets for the manifold

dont go nuts with the torque wrench on the oil feed unions

anneal all the new copper washers too


and your last question-
well serves you right for getting a fancy pants "i want to be a real car" ami

chop the inner wings a la racer?

Sean