V8 head reconditioning

westOz74P6B wrote,...
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??
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Hi Scott,

Yes. Do it this way means that all valve gear can be bolted on and all will fall within factory spec as per lifter pre load.

Scott also wrote,...
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.
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Using tin gaskets with 10 bolt heads will indeed raise the compression ratio and the lifter pre load will need checking and adjustments with the valve gear will need to be made. In my case as you say and as I wanted, and as no one told me differently at the time, I went ahead and fitted composite gaskets with my 14 bolt reconditioned P6B small valve heads. Remember this was back in 1997, I saw nothing on the internet concerning lifter pre load and nothing in Rover's manuals made mention of it. The current engine overhaul manuals which I didn't have at the time also make no mention of lifter pre load, hence the reason they stipulate on using the correct gasket with the appropriate head. The reface limit for all cylinder heads is 0.50mm (0.02") which will keep everything within spec. As it was the engine as mentioned still ran fine, and at no time until replacement did it give me cause for concern, and I am a very fussy person!

I don't have any head gaskets in either form to measure, but when compressed the composites will make up the difference in the missing 4cc from the 10 bolt head combustion chambers. With a known diameter the compressed height is an easy calculation.

Ron.
 
chrisyork wrote,...
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.
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Sorry Chris, but that is not correct. All 14 bolt heads, those on the P6B, SD1, all the later heads up until 1994 have nominal 36cc combustion chambers. Those on the P6B have smaller valves, all the others have (except for the very early SD1 engines) the larger valves.

During 1994, Land Rover introduced an all new cylinder head which was to be the final casting, and this head featured 10 bolt retention with nominal 28cc combustion chambers. The valves were the same size as those fitted to the later SD1 and all those cylinder heads that followed.

Ron.
 
SydneyRoverP6B said:
Those on the P6B have smaller valves, all the others have (except for the very early SD1 engines) the larger valves.
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All SD1's had the larger valves and single valve springs.
 
So as I see it, a decent upgrade would be SD1 heads and tin gaskets or 10 bolt later heads with the composite one - both of those retaining the original comp ratio but gaining in bigger valves and better port angles.
 
I think If you have a 9.25 engine then tin gaskets ... 10.5 composite.... ( assuming you check the preload)

Sd1 heads yes!

Rich
 
rockdemon said:
I think If you have a 9.25 engine then tin gaskets ... 10.5 composite.... ( assuming you check the preload)

Sd1 heads yes!

Rich
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How do you propose altering the preload if it's out once you've fitted the composite gaskets? (In the event you haven't skimmed the heads to compensate, in which case you won't see any reduction in the cr.) Another thing that never seems to get mentioned is that recutting the valve seats also causes problems if you cut them in to far. Easily rectified by shortening the top of the stem. ISTR there's a set distance from the valve spring seat to the top of the valve.
All of this only becomes a problem once you start deviating from standard, or mixing and matching parts without knowing what you're doing.
 
Yes enough to make my head spin. Adjustable push rods is my best guess. Couldn't afford than when pae got sd1 heads.. so running a tin gasket currently...
 
rockdemon wrote

Yes enough to make my head spin
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Ah!, head spin, that is a completely different thing altogether, that is caused by excessive alcohol intake while reading this thread!! and can be rectified by substituting alcohol for a nice cup of tea!! :LOL:

harveyP6 wrote

How do you propose altering the preload if it's out once you've fitted the composite gaskets? (In the event you haven't skimmed the heads
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What we need to do is once the heads have been fitted with a composite gasket in place of a tin one and if the heads did not require skimming (even the Haynes manual I have only mentions cleaning up the heads before refitting with no mention of checking for warpage or getting them skimmed or checking lifter preload) then after we refit the pushrods and rocker assembly and tighten them up, you have to check the gap between the spring retaining clip on the lifters and the cup which butts up to this spring clip to see if you still have preload value to measure. If you have a value within the 20 - 60 thou then all is OK, if you have between zero and 20 thou then your lifters will still open the valves and the engine will in all probability still run ok, but if your pushrods are loose a bit and you can feel play in them, then you need to compensate by machining an equal amount off each pedestal untill you get back into the 20 - 60 thou range. In the opposite direction if you find you have more than 60 thou gap (say 70 0r 80 thou) at the retaining spring then you will have to fit pedestal spacers to bring the gap back into tolerance (the likes of Real Steel sell both pedestal shims and adjustable pushrods, but the adjustable pushrods at considerable expense of course)

I have never done the above checking but reading up on it you have to use different thicknesses of wire bent at 90 degrees to determine and measure with a micrometer (imperial micrometer of course, not these new fandangled confusing metric ones!!) what gap you have between the spring and cup on your hydraulic lifters.

presumably this is the function of fitting hydraulic lifters (and the internal spring and valving within the lifters so they pump up with oil) to absorb any differences in the tolerance variation you may get on the engine assembly production line within the heads and valvetrain and also to allow for one or two head skims during the engines servicable lifetime before we have to start fitting pedestal shims (if using tin gaskets every time) as opposed to the Austin /Morris "A Series" engine with overhead valves operated by pushrods which rely on the setting of tappet clearance to achieve what the hydraulic lifters do automatically and quietly!, if only the rover had this adjustment at the rockers then we could set our preload quite easily rather than go to the expense of buying adjustable pushrods, or the USA made roller rockers which have this rocker adjustment I saw in another thread (i think it was the for sale section) again at considerable cost, I can't remember where, but one forum mentioned that volvo rockers have this adjustment and can be machined to fit the rover rocker shafts or re bushed, I'll search again for this info and post if I find it.

but as 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?
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then yes if we keep to the gaskets originally fitted and no or minimal skimming as required then we can be assured our preload will fall within tolerance for at least a couple of head refurbishments until we have to start physically measuring just to be sure.

now my head is spinning, where did those empty cans of Fosters come from????!!!! :wink:

Scott
 
just for clarity (as if we need MORE clarity I hear you say!!) here are pics to show where on the lifters we check for preload, obviously with the lifters fitted in the engine and with pushrods in place and rocker gear tightened it will make it a bit fiddly to get a wire guage in to measure the gap but it gives you an idea where we measure the preload value. this has to be done for each cylinder with the piston at TDC for the lifters you are measuring and of couse the lifters will be on the back face of the cam lobe. so shims the same thickness (to achieve an average preload for each bank of lifters) will have to go under each pedestal so as not to bend the rocker shaft,

[img]http://i884.photobucket.com/albums/ac42/westoz74p6b/IMG_9860.jpg[/img]

and a standard rover hydraulic lifter dismantled which shows the cup the pushros sits in and it is between this cup and the retaining clip we measure preload.

[img]http://i884.photobucket.com/albums/ac42/westoz74p6b/IMG_9864.jpg[/img]

and i reassembled the lifter and measured the full depression of the inner piston against the spring and got a reading of 190 thou but this inner piston has a one way valving arraingment which holds oil behind it to hydraulically transfer the push of the cam lobe to operate the pushrod, rockers and valves (hence the term hydraulic lifters) as opposed to the "A Series" engine which has direct mechanical acting lifters with tappet clearance set at the rocker arms individually for each rocker.

Scott
 
OK... One more question as you're on form... Do the hydraulic lifters offer any advantage over solid lifters as sold be real steel? The solid lifters are obviously considered an upgrade. Are they more prone to problems or more noisy or something of that nature?

Rich
 
My word! I can see why not many people get round to doing that!

The advantage of hydraulic lifters is that they lead to quieter valve gear and less maintenance. Quieter valve gear, because there is always some sort of a gap in a mechanical system. Even if you gt it absolutely spot on at one engine temperature, there would still be a change in clearance as soon as you moved away from that temperature. The disadvantage is that they tend to "pump up" so don't cope with high revs very well. So if you want to put a wild cam in a Rover, you're pretty well committed to solid lifters as well.

Chris
 
Ah well you've caught me out now Rich, I'm not really a Professor in lifterology!!

I've got the Real Steel rover parts list beside me (handy to print off for reference) and they say you have to use adjustable pushrods with the solid lifters which are designed for high performance and racing cams, the other web link I posted earlier goes into why solid lifters have an edge over hydraulic. Its a good read, Read all the parts and print off for handy reference if thinking of building a performance Rover V8, its got me thinking of what to look out for (in my case look to be able to afford it in the first place!!)

To quote from the article
"Many high lift cams do not work with hydraulic lifters and will need to use solid lifters and adjustable pushrods or adjustable rockers...so the ramps can be optimised for controlling the valve opening and closing rather than looking after the hydraulic lifter"

But later it says that engine outputs approaching 300BHP can be had with hydraulic lifters of a suitable design (ie a better quality than standard) so you are basically converting from a hydraulic lifter set up to that of the A series engine and setting tappet clearance at the valve/rocker gap same as a mini, 1100, 1800 etc and those engines are pretty reliable

Scott
 
Although I am now completely bewildered, I think I can help, I kept the old tin gaskets. The tin gaskets measure .016" and the composite gasket measures .050" and that would be a difference of .034"
regards Nick.
 
ngw01 wrote,...
Although I am now completely bewildered
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There is no need to be Nick... :wink:

Based on the measurements that you provided and knowing that the composite gasket once compressed will be slightly less in height, the initial thickness gives 5.36cc which is based on a diameter of 88.90mm.

The easiest option with the least amount of possible variation is to buy a pair of tin gaskets and fit those.

Ron.
 
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