V8 inlet manifold refurbishment.

WarrenL

WarrenL

Active Member
Gents, with my carburettors currently away for their overhaul, today I removed the inlet manifold. At first glance I thought the rearmost cooling channels were blocked with gunk, but upon tapping and gently scraping it appears they are plugged with metal. On purpose, like.

DSC08475.jpg


This is new to me and I can't see why it would be. Can anybody explain the reasoning? Or has something really odd been done to my engine?

And I would also like to know the best product with which to have the inlet manifold recoated so it's back to its beautiful best when it goes back on the engine.
 
Hello Warren,

The manifold is actually designed that way. Because the Rover cylinder heads are not sided, that is to say that either head can be fitted to either side of the engine, coolant leaving the block enters each cylinder head at the rear. In order to ensure that the coolant then flows right through the head prior to exiting, the part on the inlet manifold that you highlighted is designed that way so as to ensure that this occurs.

Coolant flows through each cylinder head and exits at the front, entering the inlet manifold at this point. There is a coolant exit point at both ends of the cylinder head, but the design of the inlet manifold ensures that only the front one is used.

POR manufactures an engine enamel in grey, which I understand is truly excellent.

I hope that this helps,
Ron.
 
Aha! That makes perfect sense. I knew there had to be a simple explanation. A certain amount of gunk had built up in the cylinder head against this blanked off port so that when I removed the manifold, it appeared as if a gallery was blocked. It was only when I looked at the inlet manifold that I realised it wasn't a blockage, but just a build-up against a blanking.

For the most part, the coolant galleries look very clean. There is gunk build-up around the coolant sensor probe, the tubes you plug hoses onto, etc, but further inside the cylinder heads and the manifold it all looks quite clean for a 37 year old engine that at the moment is probably in a greater state of disassembly than it has ever been.
 
I go for powder coating. They have a standard grey that is a great match for the original and I feel that it lasts better than paint.

Colin

48063281a171556d986d8799fc1c74800077d3c0cca1884499bc85e9f35cc238e6e97521.jpg
 
That looks awesome, Colin. There's a powder coating firm not far from me. I might take the bits in and have a chat to them. Also, inbetween posts, I've been looking for POR15 paints and found the local distributor is also not far off my beaten track. So there's two options.
 
I'm about to order a new inlet manifold gasket, since the old one has a lot of surface rust and is looking a bit manky.

Is this one OK? I presume composite is a better option than the old tin plate version?

http://cgi.ebay.com/ROVER-V8-COMPOSITE- ... 1|294%3A50

Or this one?

http://cgi.ebay.com/ROVER-V8-COMPOSITE- ... 1|294%3A50

I can't see the difference but I'm not sure I understand what they mean by "This Will Fit All Varities Of V8 But Note Older 3.5 Engines Could Have The Previous Design Of Rubber Seal. We Can Supply You If Required With Later Style Clamp Plate To Bring Up To Latest Spec or If Required Older Style Rubber Seal." I thought it best to check here first!
 
Hello Warren,

If your engine is fitted with the original cylinder heads which have nominal 36cc combustion chambers designed to be used with pressed metal gaskets, and is fitted with those, then you must use a tin inlet manifold gasket.

If you fit composite head gaskets to your original cylinder heads, or indeed for that matter to any Rover V8 cylinder head manufactured up until 1994 (heads made up until this time have 14 drillings for head retention) this will lower the compression ratio as the heads now sit slightly higher on the block deck, and as such to compensate for the change a thicker composite inlet manifold gasket must be used so as to keep all parts and the distance between them within original specification.

Ron.
 
GF148 has never had the cylinder heads lifted, so the gaskets are original.

What would be the effect of the inlet manifold sitting slightly higher on a composite gasket? I figured the coated composite gasket wouldn't rust like the old one has - and look smarter!

However, if you forbid me from using a composite gasket, the consolation is that the tin plate one is considerably cheaper.

I'm certainly glad I asked the question though - without you guys I would have forged ahead and used a composite gasket without knowing any better, simply assuming the more modern material was a useful improvement on the original.
 
Hello Warren,

Given that your engine is indeed fitted with the original tin cylinder head gaskets, then in order for the inlet manifold to sit correctly in relation to the cylinder heads, the tin inlet manifold gasket, plus new rubber seals for the ends is the way to go.

I agree that the composite gaskets do indeed look very nice, but they are thicker for the reason I outlined above, so to use one on your engine as it currently stands may result in any number of potential problems.
Incorrect alignment between the inlet manifold ports (now sitting higher) and the cylinder heads resulting in possible head thread damage when torquing down the inlet manifold, not to mention problems with correct sealing to ensure no air or coolant leaks.

I have heard on more than one occassion when fitting the inlet manifold of the threads pulling out of the cylinder heads with less than the specified torque applied. A possible reason being the additional side loading applied to the bolts as a result of using a composite inlet maniold gasket when a tin gasket should have been used.

If at some stage you were to fit composite head gaskets to your original cylinder heads, or for that matter to any of the later large valve 14 bolt cylinder heads should you acquire a pair, then you would certainly use a composite inlet manifold gasket.

Ron.
 
Tin it is, then!

I think you've spelt that out very comprehensively Ron, so thanks. The local supplier of composite gaskets certainly had none of that sort of advice.

Next question - do I need to apply something to the new gasket, such as silicon grease, Hylomar, etc?
 
Hello Warren,

I am very pleased that I have been able to assist, and that you found my posts helpful... :D

On the subject of using a sealant,....with the rubber seals which locate at each end of the lifter gallery, you can if you wish to....just apply some silicon grease to both sides. That is all that was originally recommended by Rover. Personally I prefer an application of Hylosil Type 101 or 106 as this will provide a far better seal and a significantly better chance of preventing oil leaks.

Hylomar Universal Blue (or another equally good silicone sealant of your choice) should be applied to the corners of each cylinder head, the manifold gasket and the manifold itself, providing a nice even coverage around the coolant channels. For added security and peace of mind, although technically it is not necessary, an application around the inlet passages will ensure that no air leaks,..ie loss of vacuum from the inlet manifold occurs.

A coating of an anti seize lubricant such as the one manufactured by Loctite to all the inlet manifold bolts prior to installation will prevent any corrosion occuring between the steel bolts and the aluminium alloy cylinder head threads, not to mention making subsequent removal at a later date trouble free. When you refit the bolts, start in the centre and gradually tighten each in turn, alternating back and forth from one cylinder head to the other, gradually working your way out to the ends of the manifold. Then repeat starting at the centre again until finally all bolts are torqued, mimimum setting is 25lbs/ft, maximum setting 30lbs/ft.

Ron.
 
Thanks Ron, the help is hugely appreciated. As I said before, I would have blindly bought a composite gasket, believing it to be a better modern alternative, without your help.

I have both Hylomar Universal Blue and a good quality anti-seize thread compound, so I will apply both where relevant. I quite like the idea of coating around the inlet passages just for additional security of seal, as you mention. And I'll follow your torquing instructions to the letter.

All the best,
Warren
 
Right guys, next question. This is really Car Maintenance 101 but once again I thought I'd sound you all out. I've removed all the hoses and pipes related to the inlet manifold and rocker covers and while none are on their last legs some are getting marginal. My problem is not having any reference items nearby with which to compare mine.

Take the engine breather pipes:

DSC08482.jpg


They aren't cracked or perished but both pairs are as hard as stone. Shouldn't they be at least a little pliable?

Then there are the heater hoses:

DSC08484.jpg


Both are in generally good condition, but as seen in the following shot the ends are getting a bit flared and squishy. Should I replace these while I'm on the job?

DSC08483.jpg


The reason I'm checking with you is that I'm about to order all the stuff I need for this job and don't want to order unnecessary items; or not order necessary ones! And my knowledge of this stuff is barely enough to get me by - I bow to your collective superiority and wisdom in these matters.
 
Hello Warren,

The flame trap hoses do indeed become as hard as stone, but fortunately they are in the main quite resistant to cracking. When new, the hoses are quite soft and flexible, and as you can see they are specific in their design. Normal constant internal diameter hoses, even if they could be made to fit would be incorrect in that they would not function as the genuine items are designed to. The gradual reduction in internal diameter assists in drawing the fumes out of the engine,...a suction effect. A large portion of the residue and other bits being retained by the flame traps. Spraying degreaser into the hoses along with using a drill bit by hand to remove the hard baked on bits usually has them pretty clean.

New flame traps are the way to go if the old ones are getting blocked. I remove and degrease mine every 2 to 3000 miles, so they tend to last a little longer that way, but eventually the flow rate will be compromised so new ones are then fitted.

New heater hoses too will provide peace of mind and a job well done. The outlet on the rear of the inlet manifold which directs coolant via the hose to the heater comes in two different diameters, with hoses to match.

Ron.
 
Thanks Ron. On closer inspection I have found lots of tiny cracks on the bends of the breather hoses, so I think I will include new ones in my order. JRW sells them all at quite reasonable prices so I might as well go the whole hog. That's as long as Mr Wadham processes his internet orders more assiduously than he answers his emails.

Does anybody have any reason why I shouldn't order from Wadhams?
 
Hello Warren,

I have purchased a number of items over the last few years from JRW and have found the items to be excellent. While it is true that returning emails is not a strength of JRW, I am not privy to the number of people working there, so I cannot really comment as to why that might be the case. Having said that though, on one occassion the postage quoted was more than it should have been, and of course I paid what was quoted. A few weeks later I received a letter from JRW advising that I had been overcharged, and with the letter a cheque for $50.00 (about 20 Pounds at the time).

That was an extremely honest thing to do, for until then I was none the wiser. I mentioned this to a friend and fellow P6 owner, who also has purchased on a regular basis from JRW, and he too said that he had recieved a refund for a postage overcharge on one occassion.

I will continue without reservation in purchasing from JRW when I need to, and I have no hesitation in recommending them.

Ron.
 
Thanks Ron. JRW seems to have by far the best online list of parts. I've looked at www.p6spares.co.uk but their website is pretty crappy, and their online ordering (via the contact form) abysmal. I used to deal with Ray Weekley back in pre-Internet days but I gather he's no longer with us.
 
Renewing flame trap hoses? :oops: I just decided that all those "dirty little fumes" wern't going back into my clean (2 or 3 hundred thousand Kmh)never rebored or reringed engine :? I just elected the two into one pipe and down to the road with all those fumes solution :wink:
As for the heater hoses, it is a false economy not to replace them which I learned to my cost when on the top of the Rai Saddle the rear heater hose decided that it had had enough and all I had was blunt knife as a tool :mrgreen:

Graeme
 
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