Cylinder Head conundrum

[europeanme]

having suspected my valve guides and oil seals have seen better days i have decided to source a 7A head, refurb the head and swap the rods (as it makes sense to do this now!!...) i have come up against a bit of a dilemma.
Having read Mr. Nugents posting about his head rebuild and the replacement parts costing over 2k i have decided to ask the forum's opinion/advice....shall I...

1. transfer all my old bits from my ABY head to the 7A?....
2. source some good 2nd hand bits and rebuild??...
3. cannot think of any other options....

are there any parts i should change as a matter of course...oil pump will be replaced when this rebuild takes place...

the main issue is that the avant is my daily driver and cannot live without it for too long....

all help very appreciated...

Mike

[JP]

£2k for replacement parts!!!! damn.

Long and short of it the springs in the 7A head are fine to use, lifters and cams can be swapped straight over. Clean the exhaust valves up and lap em in and they are fine to swap over to.

So you can have the head skimmed and ready with intakes installed. then when old head comes of remove cams and lifters. Remove exhaust valves and fit to new head after cleaning and lapping. Bolt new head to block, fit cam position sensor, fit lifters, fit cams, fit rear timing cover shield, fit cam pulley, fit timing belt and of you go. What's the conundrum?

If not doing the rods the whole job is a long day. If doing the rods it's engine out as it will need a re balance as the crank is percentage balanced to the rod/piston assembly.

[mcandmar]

I dont see your logic in replacing the head, replacing the guides and oil seals isnt that big a deal. If it were me i would remove/strip the head, then get a machine shop to change the guides and skim it for you, they should be able to turn it around in a few hours. All you have to do it lap the valves and reassemble. Far less hassle and a lot cheaper IMO.

If you use a 7A head you need to find somebody to modify it for use on an ABY = time, money and more hassle.

[Jamo]

2k for replacement parts? VRS had a race head fully ported and prepped available for 1k!

[Rocco]

2k for replacement parts? VRS had a race head fully ported and prepped available for 1k!

who is VRS??

[bernsaudi]

What difference would a head like that make in comparison to a stock head?

[pixsaudisex2]

Sorely you could get your aby head redone in like a week tops new guides etc cost me about 400 i think then about 100 odd for the tappets. job done..

[JP]

What difference would a head like that make in comparison to a stock head?

Depends who's done the work and what it was spec'd for. At the moment I just taken the ported head of mine for some further r&d prior to swapping to a stroker and temporarily fitted a stock head.

So far peak boost is around 500-700rpm later depending on the gear I'm in. I can no longer make over 1.9bar of boost on the same duty cycle as the ported head that saw 2.2bar of boost. Midrange torque is lacking on the stock head so much more of a kick when the power comes in despite it being less. EGT's are around 50celsius higher than before resulting in a melted EGT probe that now no longer works. Takes longer to make it's way up the rev range and is a lot less throttle responsive on the stock head.

Will be putting the car on a dyno later this month just to see the difference in the power curves. All in all want the ported head back on but will have to make the sacrifice for the time being until all the bits are ready to put a stroker together as don't fancy having to spend money unnecessarily twice for the same thing.

[europeanme]

thanks for the info folks....my guides appear to have seen better days...the engine has done 173k and having been focused on other parts of the car the engine has just been treated to oil and fuel...
my avant is my daily so once the head is off i am stuck....the cost of bits came from a head 'sticky' on this page...
as mentioned before, who is VRS?....

another question...if the rods are swapped for a forged set why would i need to balance??....

@Pixaudisex2....who was this??..

i don't want the head to have much work i am just trying to safeguard myself from further problems down the line by eliminating any possible weaknesses with certin parts....

i intend to get the head flowed...

Mike

[AndyP]

as mentioned before, who is VRS?....
Mike

http://stores.ebay.co.uk/VRS-Northampton

[Jamo]

read my post though where it said "had" it's now earmarked for his white Avant afaik

[GazzaG60]

what rwd19t says is best practice.

my engine is smoother now than when on stock rods. i took it apart sent pistons for skimming. i think this is one reason it feels better. the pistions are lighter.

i send rods in to be matched and set with pistons.

i then bolted it back together.

no engine out. i left it in. its easy that way i found. sump off. head off. rod end caps off. piston and rod out. fanny with new spring locks and pistons on rods. use ARP ring compressor to reinstall. ensure rings are aligned properly.

what JP says is the correct route but a lot more costly unless your build um like he does.

i send my head to impulse for a clean up, new seals and its been fine since. id like a nice ported one now though. its an excuse to get dirty.

[europeanme]

i have time against me....this car is my daily drive and cannot afford for it to be off the road for too long....i suspect this will take longer than a week..

@gazza - did you only have the rods and pistons balanced but not the crank??... was it to make each piston/rod the same weight??....

looks like my valve guides are getting worse...smoking like a good 'un!!...

[JP]

Lets just confirm what type of smoking you have, these are the most common causes but not necessarily the only ones or necessarily the correct ones just the most common.

Smoke on start up

1) White smoke light rises evaporates quickly, small amounts, raining overnight? Moisture in exhaust system
2) White smoke, sweet smelling, lies a bit heavier? Potential waterway crack or headgasket
3) Grey white'ish smoke, catalytic converter fitted, smells acrid fuelly? bad watertemp sensor or lambda probe causing overfueling on startup
4) Light blue grey smoke lies heavy to the ground? Stemseals

Smoke under Load

1) Grey/Black smoke under heavy acceleration? Overfueling
2) Blue smoke under load? Worn rings/bores
3) plumes of grey smoke under load? Turbo seals

Smoke on over run/idle

Pretty much always a light blue/grey smoke

1) Worn guides
2) Damaged turbo bearing/seals due to contaminated oil
3) poor turbo oil return - kinked hose?
4) clocked up breather system pipes - or air leak in breather system aprticularly around the one way check valve under the intake


If you have headgasket failure other tell tale signs are as follows

Pressurised water hoses, If you go for a proper drive under load there will be water deposits under the bonnet above the header tank filler cap where it has vented excess pressure. Blown radiator core, blown heater matrix core. Whilst engine is running at full temp after a good run take of header tank filler cap and smell if it smells fuelly you have blown headgasket. Crystalisation in header tank is usually an indication of some sort of radweld/block seal compound that crystalises on cool down, indicating potentially a previous problem that has been temporarily resolved. As the rad weld starts to break down the headgasket problem gets worse again. Check spark plugs see if any have burned white with pink/red spots on them indicating burning of coolant.

hth JP

[GazzaG60]

yes what i did was as follows.

took engine apart in car.
removed pistons and rod assembly
had skimmed and scats weight matched.
refitted with new bearings.
left crank 100% as is. not even checked bearings.

the reduction in weight and the matched rod and piston helps for sure. im always a little sceptical about factory balance. that big dual mass and that big crank damper.

its over 2 yeasr on now.