The V8 Owners Forum -

hi ,first message hope in right place,ive only ever had rv8,s since left school,still a young 44...
anyway point being ,ive been suffering back pressure in my water system,its a 3.5,so i decided to whip the heads off incase gasket gone...ive had them skimmed down 35.thou(bh enginnering) what head gasket composite or tin....engine no.27gooo21b??
the tappets are as quiet as a mouse,and wanted to keep that way....
even though ive always had v8,s,ive never had on go wrong till now!!!

You will get a lot of people that state that tins are OK, equally a lot of people state that they have failed.

I pulled the heads of a 3.5 that had only done 5k miles since being rebuilt, the gaskets where starting to show signs of blowing. (Brown marks heading towards the valley area).

Rover ditched the tins on the bigger RV8's so that must say something!

Personally I would fit composites and also NOT fit the outer head bolts. (The ones that are not under the rocker covers). Or fit them and only torque them to 10-15 ftlbs if you want to fill the holes with something.

The comps are generally 20 thou thicker than the tins so you have still upped the CR due to the 15 thou extra that has come off. 8 thou is worth 1cc off the chambers so yours will be about 2cc less. (Standard being about 36cc for old 3.5 heads). Your lifter pre-load will also have been effected.

Pete

Go with composites.

Check the tappet preload though to make sure it's all in spec.

Chris.

mcgill, as I explained to you on the phone before you sent me your heads, use composite head gaskets (and preferably a composite inlet manifold gasket as well).
Use a light smear of blue hylomar jointing compound on the face of the block around the water jackets either end, same on the head face also, and repeat the process for the inlet manifold gasket around the 4 water passages as well.
Your heads actually had 0.030" skimmed, not 0.035". Your rocker geometry ought to be as near as makes no odds to what it was originally, but it's worth checking the rocker preload and it's cheap to fit shims if required.

sidecar is absolutely correct with his comments re. head bolts - either leave the outer rows out completely or fit them to about 15 to 20 lbft only. From my personal experience, and this may change according to supplier, the difference in compressed thickness is 0.028". I source my gaskets from Real Steel as I find the quality excellent.

Also, I meant to say to you on the phone, your head gaskets were showing signs of compression gas leakage into the water passageways on 3 out of 4 cylinders.

thanks for that,the gaskets i have ordered from real steel mddx...just having a panic up as was reading in my p5b owners room about tappet noise after,comp fitting.(I CANT STAND A TAPPY LUMP).Im off to google /search this forum and whip out the haynes re prelift etc.my mech knowledge goes to just swapping v8s.
thanks for the info......

McGill,

With the comp gaskets your heads will be sitting approx 8 thou lower, so you will not have a problem of not enough preload and as that figure has to be multiplied by 1.6 which is the rocker ratio giving an additional 13 thou. of preload you may as suggested above, need to shim the rocker pillars to reduce the preload a bit.

From memory the shim kits have 8, 16 and 32 thou shims so you may only need the thinnest one to get the preload back in the right area, as again you multiply the thickness of the shim by the rocker ratio.

Kevin

CastleMGBV8, you may well be absolutely spot-on, but I have found from experience that the composite head gaskets are not all the same, depends on who made them.
I've found that the compressed thickness can vary by almost 0.010" depending on source, and I wont buy the cheapo ones from fleabay any more as I once got 2 pairs that gave me 3 different uncompressed thicknesses!!

Out of interest (and I'll re-post this in the engines section) anyone that's ever experienced head gasket failure with composites, what head bolts were you using? Early, stretch or studs?

"opened up a can of worms here?"there was me going just to put the head on and away i went!
i fully understand the tappet preload (after the write up in rpi) and have just ordered up a shim kit.head gaskets on there way from real steel..
however i do not own a micrometre,and was going to adjust by sound.or rather fit ALL SHIMS,if its tappy,adjust a little bit at a time...i will be using all the old bolts that came out cleaned up.....
cAN ANYONE SEE A DOWNSIDE TO THIS????
apparently the gaskets im getting are... Bore diameter: 92.96mm/3.660" Comp. thkness: 1.0mm/.040"

mcgill wrote:"opened up a can of worms here?"there was me going just to put the head on and away i went!
i fully understand the tappet preload (after the write up in rpi) and have just ordered up a shim kit.head gaskets on there way from real steel..
however i do not own a micrometre,and was going to adjust by sound.or rather fit ALL SHIMS,if its tappy,adjust a little bit at a time...i will be using all the old bolts that came out cleaned up.....
cAN ANYONE SEE A DOWNSIDE TO THIS????

I can see a downside to this.....basically it's not a good idea!

For starters you will end up pulling off the valve gear several times, in the long run you would be better off just doing it right the first time. Also if you wanted to actually measure the pre-load at some point in the future you will have to drain the coolant and take the manifold off.

You can buy a micrometer for a few quid, then get some bits of wire of various thicknesses. I even used a bit of coat hanger that I straightened out and stuck in my pillar drill so that 8mm was sticking out of the chuck. I then spun the wire and held a fine tooth file against it to turn it down to the right size then bent the last 4mm over to 90 degrees. Basically you need two bits of wire, one at 20 thou and one at 60. (One at 40 is nice to have).

If the 20 thou wire does NOT go in then the preload is too small, if the 60 DOES go in then the preload is too big. This is the crudest way that is acceptable in my opinion. It was not acceptable for my engine so I went a lot further. My engine runs adjustable pushrods with each and every pre-load set to exactly 20 thou. Personally I hate shims and found the whole job to be a total PITA on my 3.5 lump, thats why I went to adjustables on my 4.6 lump.

Each lifter must be on the base circle of its cam when you are checking the preload.

You really need to drain all the lifters of oil, this is easy to do by dismantling them. If they are not brand new make sure that they all go back in the same lifter bore that they cam out of! (If they are brand new then they won't have any oil in them so that saves you a job)

At the end of the day it's your engine so its up to you how much effort you want to put in when rebuilding it.

Pete

i can see what ya saying,and it all makes sense...
im just going a little stir crazy....
im a bit on the rural side and this is the only motor ive got(apart from the p5b restoration),it went rear shaped new years day and i havent been anywhere since,thus the need to rush...i had to buy all new tools from flebay,as all my proper tools are with the other car in a garage 35 miles away.new year also brought job loss and without motor cant find another.......this.ll teach me to move to a nice quiet rural area,all friends family 200+miles away............off to ebay for a micrometer......
thanks all for ya help.........

mcgill wrote:i can see what ya saying,and it all makes sense...
im just going a little stir crazy....
im a bit on the rural side and this is the only motor ive got(apart from the p5b restoration),it went rear shaped new years day and i havent been anywhere since,thus the need to rush...i had to buy all new tools from flebay,as all my proper tools are with the other car in a garage 35 miles away.new year also brought job loss and without motor cant find another.......this.ll teach me to move to a nice quiet rural area,all friends family 200+miles away............off to ebay for a micrometer......
thanks all for ya help.........

No worries mate!

It will be just as quick to do it the 'normal' way and you will have a nice new micrometer to play with when you've finished the job!

Pete

Macgill,

Whilst a lot of the guys on here are building or have built performance engines and strive to obtain the best preload setting, for an everyday standard spec engine, the preload is not that critical and basically anywhere between the min. of 20 thou and max. of 60 thou will be ok.

The two bits of wire Pete suggested will do fine, so as long as a 20 thou. wire will fit beween the piston in the lifter and the wire retainer and a 60 thou wire wont your basically ok.

Kevin.

You beat me to it Kev.
For a road engine just make sure you have the preloads between the min and max as Kev says M.

I have a set of pre load check wires. They are the springy bits that held a set of Allen keys onto a key ring thing. I think I bought them from Halfords or B&Q. I just measured the wire thickness and tweaked the ones I wanted into handy little tools.

THANKS ALL FOR YOUR OBVIOUSLY NEEDED ADVICE!!!
well after ages fiddling about checking preload,my fingers far too fat,it averaged out at 35thou,so it all went back together,apart from one bolt,but thats another story......
i spun it over a few times without ht lead on ,refitted and fired up first time as always,quiet as a mouse.very happy..........UNTIL....IT STARTED RUNNING LUMPY.
so checked on here in search mode.
Checked it wasnt arcing anywhere,spark test ,well theyre all sparking,but bought ,new,plugs /leads/dissy rotor(checked it was same place as previous rotor arm,it needed packing .)/air filter.....still exactly the same.
this is a 87 rr lump with flapper efi......
so today i pulled off bits and pieces just nosing around and found quiet a bit of oil in my plenum(spark plugs are clear though),it seems(as the entrance to plenum and butterflyis a bit oily).it may be comming through from the fire trap pipe.????or is it back through the trumpets?????
maybe connected but checking anyway,vacum pipes!
all the big pipes are where they should be,but just to check,dissy vac to top of plenum,trumpet base to the vacum ball thingy??vac pipe rear plenum .going nowhere about 6 inches long....
im pretty sure thats right.
but something is blowing oil in .
Any pointers ideas to try ??????
thanks all

Check that you haven't connected the breather on the rocker cover to the plenum.