V8 head reconditioning

N

ngw01

New Member
G'day gents,
Some time back I was attempting to trace the cause of a coolant loss in my P6. After trying many things as suggested by members of the forum, I discovered that the head/gasket was the cause for the leaking coolant. When I removed the tappet covers there was a lot of cream oily sludge in the valve gear and rocker assembly. So out with the manual and remove the heads. I have just received them back after a full recondition including grinding, new valves and seats etc and pressure tested. Now I am getting ready to replace everything and get the car back on the road. I am hoping that some of you that have done the job might give me some tips. I have got new bolts for the heads and a full gasket kit. One question I have is, should the exhaust manifold be attached to each head before replacing on the block. Secondly, is it necessary to use a gasket compound between the gasket and the block/head. And, will a wipe of oil on the bolt threads be sufficient (torque tension as per factory manual) or should a thread-lock like Loctite be used? I just hope that I have not bolts left over! Any tips would be appreciated as this is a first for me and I am a little in awe of the job ahead.
regards Nick.
 

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Hello Nick,

When my P6 developed a head gasket leak back in 1997, I too had the heads reconditioned prior to fitting. I didn't replace the head bolts given that they are high tensile grade 8 items, but I did use an anti seize lubricant on the threads prior to fitment. It is made by Loctite, but has no thread locking properites. It is an excellent product so the when the heads were removed again in 2007 after the engine was removed for replacement, the bolts came out without any issues at all, still coated with the lubricant just as when they were fitted 10 years earlier. The head bolts that you have purchased, are they also high tensile or are they "torque to yield" or otherwise known as stretch bolts?

Are you fitting tin or composite gaskets? No gasket compound is advised especially if composite gaskets are used, although with tin gaskets I have heard of hylomar being applied.

You don't need to fit the manifolds prior to fitting the heads, although it does make it a tad easier. I didn't use any sealant between the manifold and head as there was none applied originally, and there were no leaks afterwards. You can apply a thin layer if you wish to, but be sure it doesn't enter the exhaust ports.

Ron.
 
On the manifold front I left them till afterwards as it makes for easier manouvering...

Don't forget to alter the bolt tensions for the outer row of bolts to 20 lbft (the 4 nearest the exhaust manifold.)

Rich
 
I would have thought you'd want the inlet manifold in place before tightening down the head bolts to make sure all the bolts line up
 
DaveHerns said:
I would have thought you'd want the inlet manifold in place before tightening down the head bolts to make sure all the bolts line up
Click to expand...

I've never had problems getting the inlet manifold bolts lined up and the only way I can see that you would is if too much had been skimmed off the heads without any coming off the manifold. I wouldn't advise doing what you suggest.
 
Thanks guys for your responses. The bolts are high tensile G8 and I have a composite head gasket. I did notice that when I removed the exhaust manifolds there was no gaskets, but the gasket kit has them - is this normal? Also can anyone recommend a brand of spark plugs?
Nick.
 
Hi Nick,

What is the compression ratio of your engine? This will influence the spark plug choice hence my question.

With composite head gaskets, don't use anything on them when you refit the heads. They will lower the compression ratio by 0.6 or so unless your heads have been machined so as to reduce the volume of the combustion chambers from a nominal 36cc to 28cc.

The gasket kit that you have, does it have a tin inlet manifold gasket or is that composite too? Head, inlet manifold and exhaust manifolds for all Rover V8 engines of all capacities are interchangeable as far as fit goes, so the exhaust manifolds on some of the Rover V8 engines as fitted into Range Rovers did have exhaust manifold gaskets as standard fitment, hence the reason they are included in the kit that you have.

You don't need to use them with the P6B manifolds, just bolt them back onto the heads as they came off.

Ron.
 
Hi Nick, I concur with the experienced chaps before me, nickel anti-sieze on the head bolts and hylomar on the tin gasket if fitting a new tin gasket, although you said you are fitting a composite gasket, did it originally have a tin gasket when you took the heads off?? I ask as you need to be aware that fitting the composite gasket will alter the preload values on the hydraulic lifters, obviously depending on how much was skimmed off your heads and the difference in thickness between the composite and tin gaskets. I speak as a novice at these things as i only found out after i had my heads refurbished including skimming and when refitting the heads with a composite gasket (in place of the original tin one) noticed that the pushrods were just touching the rocker arms when fully tightened and some could rotate. Having later found out about lifter preload, i ought to have fitted a new tin gasket and shimmed the rocker pedestals accordingly to achive factory lifter pre-load tolerance. As it happens I am running the V8 with too little pre-load, not knowing what the ill effects are it seems to run ok (the rover V8 must be very forgiving) and as i am refurbishing a spare engine I will run with it until I'm ready to do the engine swap. I found all my info from http://www.google.com.au/url?q=http...UQFjAA&usg=AFQjCNEtYXPR2M3TaHk1qDv38lBsVdHbrQ see part eight "rebuilding V8 heads", basically if fitting a tin gasket you need to shim the rocker shaft pedestals (all the same shim size) to compensate for amount of skim taken off the heads (if known how much was removed) and if upgrading to a composite gasket then remove metal from the rocker shaft pedestal equal to the (difference between composite gskt minus tin gskt) then whatever positive amount remaining after you minus amount skimmed off head (i think that sounds right, experts please correct me if not). But have a read of the web link and you'll read that a factory pre-load range is 20 to 60 thou, the rest of the article regarding rebuilding V8 heads is ineresting as are the other parts, I have printed this as good reference when rebuilding my spare motor. It was my first at V8 head rebuild but I know what to be wary of when i do my spare thanks to the web site info,
Regards,
Scott
 
Hi Scott,

When I fitted composite head gaskets (and a tin inlet manifold gasket) in 1997, no mention was ever made concerning lifter pre load, especially when I purchased them. The company that refurbished the heads also made no mention to me. I didn't look on the internet as I wasn't aware at that time that there was such a thing. I just used the Rover workshop manual. In fact the first time I became aware of lifter pre load was from RPI in 2007 while investigating a possible engine replacement.

So I just fitted the composite gaskets, popped on the heads and torqued all 14 bolts following the procedure as outlined in the manual to original spec...once again no mention of setting the outer four at a reduced torque (that also I became aware of in 2007). I also fitted new rocker shafts although I retained all the original rockers and pedastals. If doing it now though I would have fitted complete new rocker assemblies.
N.B The reduction in torque on the outer 4 bolts on 14 bolt heads was introduced by Land Rover for all Rover V8 engines so fitted in circa 1994, prior to that all would have been torqued as per the original spec.

So likely my lifter pre load was well above the 60 thou recommended max, but with a slight reduction in compression and being thus able to advance the initial timing by a couple of degrees, the engine ran with improved performance. It was a little more 'ticky' I thought at the time, but that was about all and it didn't bother me.

The engine would continue to run like this for another 10 years, only just on 44,000 miles added during that time, and it was only during 2007 from the notes that I had made that performace had really started to drop off. Acceleration was still fine as was the ability to cruise at highway speeds, but climbing was where the reduction in torque was really evident.

Ron.
 
Well lads, you have thoroughly confused me. Does this now mean a reasonable difficult job is turning into an extremely difficult job? As a layman, I would have thought that whatever was taken off to level the heads would be compensated by the thickness of the composite gasket - within reason? I was not advised anything to the contrary by the head specialist that did the job - who also supplied me with the gasket kit. In answer to your question Ron, the valley manifold is tin as it was originally.As far as I am aware the compression ratio it is 9.25:1.

On a side issue I have attached a couple of pics of the head and block and am wondering where the oil comes into the head, I have marked two holes with arrows in red that I thought but there is only one on the block. The coolant has a large aperture at the rear of the block but not at the front, only a small holes (black arrow)? The manual does not go into these specifics.
 

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Hi Nick,

You could take it on face value and just fit them with the composite gaskets as supplied which is what I did back in 1997 as nothing was said to me about mine either. The engine worked perfectly fine as I mentioned above. That is certainly the easiest approach and the composite gaskets do form a better seal when compared to tin gaskets. Having said that though if you decided that you wished to use tins instead, then dare I say they would likely be fine for at least another 25 years if not a lot more.

For a 9.25:1 CR engine, NGK BP5HS seem to work better than the champion L92Y equivalent.

The heads are not sided so either head can go on either side. Coolant flows up through the block and enters the rear of each head, travelling through before exiting at the front into the inlet manifold. The small hole at the front of the block is a coolant bleed hole, and is there to prevent air locks. Oil travels up through the block at the front and enters each head via from memory a 3/16" gallery. The oil passes up through the front pedastal that supports the rocker assembly and is then distributed through the rocker shaft and out through the bleed holes on the underside. The hole marked with the red arrow is the oil gallery, but only the front one is used once the heads are fitted. The rocker shafts must be fitted the right way around in order for the galleries to align, and this is achieved by ensuring that the identification groove is uppermost and towards the front of the engine on the o/s (RH side) and towards the rear on the n/s (LH side).

Ron.
 
sorry to have confused you Nick, but as in Ron's case, he has no problems after his head recon and as i don't either, you will in all probability be ok with using composite gaskets on your rebuild. The reason we don't get this info from our head reconditioners (as i didn't either) is because they want our business and as we are suppling our heads to them, all they do is overhaul them and skim as neccessary and give them back to us and they have completed their part of the bargain. Unless the chap is concerned to ask us about preload (which would be nice) all they do is just what we have asked them to do even supplying a gasket kit which we have specified or what they deem appropriate (most gasket kits are good quality) just depends on wether we ask for tin or composite gasket, the rest is up to us to finish the job to the best or our ability and with the best info we can obtain (usually a reputable workshop manual or this forum or website links as mentined in my last post). I suppose if an engine reconditioner has the job to do the complete engine then they would check for preload so as to give a warranty with the finished article. But in saying that the factory tolerance of 20 to 60 thou would give allowance for any future head skimming of say, for example; if the factory setting had a 30 thou preload and you had 15 thou skimmed off the head (to clean up any warpage/corrosion etc) and fitted a new tin gasket, you would have the factory preload +15thou to give you 45thou preload which is still within the tolerance, you could then have another head skim down the track of 10 thou and still be within tolerance if using tin gaskets. I only opted for the composite gasket myself because like yourself I heard on this and other sites that they were a better sealing gasket with (then) no knowledge of lifter preload. Even now i dont know what the difference in thickness is between the tin and composite gaskets is so as to determine what preload i may be gaining or losing, but after reading up on it, it becomes a factor to be aware of if thicker gaskets are used which will have the effect of decreasing lifter preload, and so you have to compensate by taking (machining) off metal from the rocker shaft pedestals, (or use adjustable pushrods, at extra expense of course)
I hope i haven't scared you away from V8 rovers now, otherwise i might get banned from this forum!!!,
Actually the reason I sold my first 85 rover sd1 was because I didn't know much about the V8 engine and was worried about rebuild costs, but once you've had a rover V8 I longed for another, and they are pretty straighforward once you swat up on them, have you read the link i gave earlier?? its quite good,
Regards,
Scott
 
I guess most heads are skimmed by a machine shop that deals with all engine marques so wouldn't necessarily have knowledge specific to the rv8 especially considering the now outmoded push rod design...

Rich.
 
Presumably, if there's no skimming, then standard P6 heads and tin gaskets should result in the same rocker pre-load and comp ratio as the later heads and the composite gasket?
 
yep. They're all compensated for as standard....

of course at 43 years old most v8 heads will have been skimmed at some point!

Rich
 
1396midget wrote,...
Presumably, if there's no skimming, then standard P6 heads and tin gaskets should result in the same rocker pre-load and comp ratio as the later heads and the composite gasket?
Click to expand...

Yes, all 14 bolt heads were designed to run with tin gaskets, and the 10 bolt heads which came into being in 1994 were designed to run with composite gaskets. All 14 bolt heads have 36cc combustion chambers, the 10 bolt have 28cc combustion chambers.

By rights, the safest option in terms of pre load if using 14 bolt heads would be to use tin gaskets, even if the heads have been skimmed. The Land Rover engine overhaul manual of 1997 for all Rover V8 engines from 3.5 to 4.6 makes that very clear. In my case back in 1997, I wanted to lower the compression ratio so composite gaskets would allow me to achieve that outcome.

Ron.
 
Ron wrote
All 14 bolt heads have 36cc combustion chambers, the 10 bolt have 28cc combustion chambers.
Click to expand...

So then, If you agree Ron, we can take it that Rover machined a bit more off the face of the later 10 bolt heads (which is why they have less cc in the head chambers) to compensate for the thicker (better sealing) composite gasket and all other valve gear such as rockers, pedestals and pushrods would remain standard and interchangeable?? and if you used a later head with tin gaskets on your earlier engined car then you would effectivly be increasing the comp ratio without realising it.

I know the topic is getting a bit pedantic but we need to be aware of what changes we are making so as not to loose out on efficiency, reliability and performance as would be the case for any other pushrod V8 (or pushrod V6, V4 for that matter) and certainly if we are rebuilding our V8's for optimum performance we need to take all of the above info discussed so far into consideration.

It would be nice to know the difference in thickness between the tin and composite gaskets (I've thrown all my old ones out, can any one oblige with measurements in thou??) so if we fit a composite in place of a tin, then to know how much preload we are actually losing would help us determine how to compensate when required. As you wanted a lower compression ratio Ron, it would still be nice to know how much preload you would be losing by fitting a composite gasket as I noticed that my pushrods at TDC on #1 cylinder had just a little bit of nip on them so I could be getting close to being out of tolerance or hardly any preload on my lifters but with the engine still seems to be running ok

Ron also wrote
By rights, the safest option in terms of pre load if using 14 bolt heads would be to use tin gaskets, even if the heads have been skimmed
Click to expand...

As you say Ron i may opt for tin gaskets when rebuilding my spare engine (is the later engine with oil seals) as I am intending to use the recently reconned heads I am running on my daily.

Scott
 
Also, there are two varieties of 28cc heads, with the P6/P5 type heads having smaller valves than the later SD1 type. The 36cc heads are a different valve size again.

Chris
 
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