Cylinder heads

L

lewis2392

Member
Hi there,
Iv got a 1972 3500s and i need to change the cylinder head as one of the spark plug holes has been cross threaded and bodged by someone using the incorrect spark plug.
I have 2 cylinder heads off a 1975 3500 auto, are the heads going to be the same? as i seem to remember reading the engines compression ratio changed on later engines?
Also do you have to use new cylinder head bolts? or are they not the stretch type bolt?
Many thanks in advance.
Lewis
 
welcome :) those heads will be fine. you can use the original bolts no problem. when you do the bolts up leave outer row on each bank at about 25 lb/ft^2. composite gaskets will lower your compression ratio a little too which helps :)
 
The heads will be the same as yours. The cr is changed by different pistons, not heads. You can re-use the head bolts. Why not upgrade to SD1 heads while you're there?
 
Thankyou very much for the replies. What are the benefits of changing to sd1 heads? And as for composite gaskets are they costly? And wheres the best place to get them. Finally if i use composite gaskets do i have to change anything else?
Many thanks.
 
lewis2392 said:
Thankyou very much for the replies. What are the benefits of changing to sd1 heads? And as for composite gaskets are they costly? And wheres the best place to get them. Finally if i use composite gaskets do i have to change anything else?
Many thanks.
Click to expand...

SD1 heads have bigger valves so give a (small) performance increase. Composite gaskets will lower the cr from 10.5 to about 9.9:1.
 
Thanks. Can i use V8 heads from any sd1? like single plenum, twin plenum, carbed, injected etc?
Where can i get these composite gaskets?
Cheers for your help
 
lewis2392 said:
Thanks. Can i use V8 heads from any sd1? like single plenum, twin plenum, carbed, injected etc?
Click to expand...

Yes, and from any later (single valve spring, 3/4" reach plugs) Land/Range Rover with 14 bolt heads.
 
any rover v8 engine supplier will have composite gaskets. Rimmerbros, realsteel, ebay, rpi, v8tuner, along with all the landrover/rangerover suppliers. (paddock, john craddock and others...). Any of the p6 suppliers will probably also have them. That's jrwadhams, wins, mark gray...

They're a little more money wise but give better sealing and help with the high compression ratio.
 
According to the 1997 Land Rover engine overhaul manual, 14 bolt cylinder heads with steel gaskets retained by high tensile bolts, for 3.5 litre engines the procedure is...lightly oil threads of cylinder head bolts, progressively tighten bolts to :

Outer row 44lbs/ft
Centre row 66lbs/ft
Inner row 66lbs/ft.

Ron.
 
bt don't forget that the manual is wrong!!! The outer row should not be torqued beyond 20lbft - ie just nipped up to retain the ironmongery in place. If you use the factory 44lbft setting you increase the risk of head gasket failure. Rover subsequently dispensed with them altogether.

Chris
 
harveyp6 said:
rockdemon said:
when you do the bolts up leave outer row on each bank at about 25 lb/ft^2.
Click to expand...

I wouldn't do that with shim gaskets.
Click to expand...

chrisyork said:
bt don't forget that the manual is wrong!!! The outer row should not be torqued beyond 20lbft - ie just nipped up to retain the ironmongery in place. If you use the factory 44lbft setting you increase the risk of head gasket failure. Rover subsequently dispensed with them altogether.

Chris
Click to expand...

Having just acquired a set of SD1 heads for my V8, and given the above comments, what should the outer row of bolts be torqued to if I use shim gaskets?

Dave
 
good question. When using shim gaskets previously i did exactly that. Could be why the vitesse heads gave me so much trouble?
 
Dave3066 wrote,...
Having just acquired a set of SD1 heads for my V8, and given the above comments, what should the outer row of bolts be torqued to if I use shim gaskets?
Click to expand...

and rockdemon wrote,...
good question. When using shim gaskets previously i did exactly that. Could be why the vitesse heads gave me so much trouble?
Click to expand...

Hi Dave and Rich,

It is my understanding that tightening the outer row of bolts to the equivalent torque of the remaining ten can allow combustion gases to leak into the lifter gallery. That would explain all the dry dirt and grit that accumulates inside the rocker covers, over the rocker assemblies and inside the flame traps that you can see. Hence the reason why regular oil and filter changes is advised. Even so, the engine should still run for over 200,000 Miles (320,000km) before needing a major rebuild.

The original tin gaskets in my Rover ran for 23 years before one of them failed, while a friend of mine with his Rover still has the originals, 39 years after the engine was built, so they don't fail in a hurry.

John Eales has a reputation for building some very fine Rover v8 racing engines, so you could send him and email of give him a call and see what he advises.
http://www.johnealesroverv8.co.uk/

Ron.
 
I concur with Ron. I have fitted my skimmed heads last weekend on my 3.9, which are the 14-bolt type. I have used the standard-tin gaskets, I didn't feel like lowering the compression ratio by having composite gaskets in. If properly tightened, the tin ones should work just as well as composite ones. I have spoke to Chris from Rpi and he advised me to torque the outer 4 bolts to half of the torque figure of the other 10 bolts, due to the same reason that Ron is pointing out. Engine is not yet running so I don't have any results yet.

Having said that, I used Blue Hylomar instead of Minnesota Mining Company thread sealant (as per manual) and used new headbolt because during removal one sheared off completely. I didn't want to risk shearing one while refitting.

Kind regards,
Andries
 
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