Outer Limits 4x4 Board

PhilipA is the man who was talking about 35 thou... However, I was under the impression that 3.9s already used composite gaskets? In which case, shaving 35 thou wouldn't be neccesary to keep it at the standard 8.23 compression of a lowcomp. However, PhilipA is the expert in that field.

I would suggest you may want to cc a cylinder also, with a piston at TDC, for good accurate calculations.

With my motor (and all of this was calculated on a 4.0, so use only as a guide!), I shaved 110 thou off the heads. This included 35 thou (approx) for the composite gaskets, as my heads were tin gasket 3.5 ones. I then shimmed the rocker pedestals up by about 68 thou. I would have preferred to have gone a little more, but I had easily workable metal in that thickness. The reason for this was - if you subtract the 35 thou for the different gaskets off 110, you get 75 thou. This is the change in height relative to the cam (in the block) of the rocker assembly compared to standard, as the head is now 75 thou lower. Which means, at the end of the day, I have about 7-8 thou more preload on my lifters than standard. Seems fine, as I can use my thumb and forefinger to rotate any pushrod not being acted on by the cam, and the valvetrain isn't noisy, so I'm happy that they aren't loaded up too much.

I also had to shave quite a lot off my intake manifold, it ended up being something like 70 thou a side, which was much more than I was led to believe it should be by an older post on this forum.

The end result of which, in calculations, should have given me about 9.3:1 compression. I never cc'ed the heads on their return, so I don't know what it is exactly, nor do I particularly care. I know its comfortably over 9:1, and thats good enough for me. The reason I'm not sure exactly what the compression is, is due to the shape of the chamber in the head - it gets smaller in diameter the more you shave, and also kidney shaped. So in calculating how much volume would be lost, I used a smaller diameter than the actual measured diameter of the chamber, and erred on the safe side. I would however comfortably say that the compression in the end lies between 9.2 and 9.5.

Earlier 3.9s with the old style oil pump and 5 head studs up to say 1993 have tin gaskets.

To measure combustion chamber volume , get a sheet of perspex, and seal around the chamber with grease. then fill the combustion chamber with kero, while measuring the volume. a syringe is suitable or if you want to be pukka a burette.
I shaved my head 50 thou to start with a bit more compression, then I relieved around the inlet valve until I had about 28CC volume, ie the same as a composite gasket head.
I do not know what CR you want but a reiterate what I said in the earlier post, anything over about 8.8 :1 requires PULP.
Regards Philip A

G`day Luke

I`ll be interested to read what you come up with .




Cheers

Peter

okay the heads have been cc'd at 34cc. My plan is to remove the thickness of a compressed composite gasket and then cc the heads again to see what im left with. If there too low i'l do as Peter R suggested and clean up the comp chamber until i get my 28cc's. That way my heads should be in a similar postion to a set of stock 28cc 4.6ltr heads and i shouldnt run into intake manifold dramas..

The comp gasket i have are from a land rover gasket set (pn sfp 2804 which replaces a stc 4082.

Can anybody tell me what thickness a comp gasket is after its been installed and torqued?

If worse comes to worst i'l just buy a spare gasket and torque it but if anybody could tell me that would be great!!

I've decided to use a Wolf 3d ecu i've got to run the engine that should give me a bit of headroom if i do get a bad batch of fuel as timing advance and retard is very easy from inside the car.

I also plan to run full closed loop on the car with a 4 wire oxygen sensor so i can have good cruise mixtures for decent fuel consumption and good wide ope AFR's for power...Im a little bit excited now and can wait to get the big green money pit back on the road....

cheers
Luke

Edit: forgot to mention the untorqued gasket is 86thou (2.14mm) at the fire ring im hoping a compressed gasket would be somewhere around 50thou?

The "Erhling"brand 4 bolt gaskets that I used compressed to 35 thou using non stretch bolts and normal torquing force 70 Ft Lbs?.

I took 50 thou off mine and ground some out of the chambers , as I said earlier.
Only problem is that I had to shim the rockers by 15 thou to get about 40thou preload. You can easily make the shims from shim stock, but do not forget to put a slot for the oil to get into the gear.

I think Peter R agrees with this as we had a long discussion back then.

I am also having a bit of a problem in splitting the end seals on the valley gasket . Shouldn't be a problem but maybe the valley gasket sits lower.
I slotted the bolt holes a bit and ground the lower port holes a bit ( of the valley gasket) to line everything up.
Of course it may be unrelated.
Regard sPhilip A

G`day Luke .

Philip and i have had many discussions about this over the years , often we`ve been left out in the cold , through i guess lack of interest or maybe it appers complicated .

The gaskets that were in my engine untill recently ( 3 or 4 yrs L/Rover gaskets ) were .....

10 bolt composite , on 1 side they have silicone lines ? around the coolant ports , on the same side the fire ring material extends to encompass the bolt holes .

On the other side there is just the gasket material with metal fire ring circles showing .

On lower edge ( exhast manifold direction ) there are 2 small holes , not central .

The gasket material with the 2 holes contained will foul on the dip stick tube .

If these are the same as you have ....

The used fire ring thickness is 1.5 mm +/- 0.04mm approx

There is only 1 small area i can measure the uncompressed gasket face it is ..... 1.9mm +/- ? ( not very reliable )

On paper the efficiency between 8:1 and 10:1 is not vast .

Between 6:1 and 8:1 it is .

In practice the difference between 8:1 and 9:1 is noticable ( approx )

What i mean is that as Philip has said if your using unleaded petrol there is little advantage going high .

My heads have more removed than the higher figures given in other posts but my engine runs LPG 99% of the time .

As RangingRover say`s a modification is needed to fit the inlet manifold .


For my interest would you mind telling me if your heads are HRC 2210 ?

Also would it be possible to give me a measurement or 2 from the heads before they are machined ?

If possible the machined surfaces mentioned earlier on each corner , could i have 1 short and 1 long , opposite each other ?

Not greatly important just handy .

Cheers

Peter

Sure mate i'l get those measurements off the heads when i goto the machine shop. Im not sure what part number they are but i will find out and report back!

I would suggest getting hold of a spare gasket to measure it - i got figures around 45 thou with the old gaskets I measured, but I have heard of figures either side of this. Realistically the difference 10 thou makes is quite negligible, as you will see if you start playing with calculations, it depends on how fussy you want to get with your target comp ratio, but as PeterR says, its probably not that big of a deal how exact you are. If you open out the ports in your heads a little, and same for the intake manifold, run decent injection (as you've decided with wolf), and slap on some extractors, the breathing and tune gains will ultimately give you considerably more power than .1 of compression here or there.

I will make this recommendation though, since you're obviously keen to do it properly - JAGUAR V12 RUBBER MOUNTS. On the engine and if you can fit it with your car (viscous?) on the gearbox as well. I snapped a 6 month old stock rover rubber mount clean in half on the weekend, as well as the two gearbox mounts (all in one go). Currently have a Jag V12 one under the left of my gearbox (the important side!), a rover item on the RH side of the box only because the jag one doesn't fit there, and Jag V12 mounts under the engine. They are about 30% bigger in diameter than the rover items, and I believe made of harder rubber. Probably doesn't matter so much if you aren't planning to go 4wding, and just drive around on the road, but they will break if you are giving it berries in low range - I know a few others who've done the same thing with big horsepower Rover motors.

Okay i sacrifised a new land rover composite gasket for the greater good this afternoon

I measured the gasket as 2.2mm (97thou) at the fire ring. Once installed and torqued i measured it again as 1.86mm (77thou) so once compressed i have lost .16mm or sweet fa.

The head was also measured at the machine surfaces as requested by Peter and the exhaust side measured 63.64mm and 23.97mm and the intake side measured 63.62mm and 23.90mm.

So i've got a compressed gasket thickness of 77thou and a combustion chamber volume of 34cc. If i had any money left i'd be willing to bet the heads are going to need 77tho off them to make the compression that i want..

On a side note: I did some tests with bolts torques today and found the difference in actual bolt tension when using a preset torque vs an initial torque and using degress measurement is quite vast.

i oiled the bolts and washers and torqued the bolts to 20nm as described in the rover manual i have and then torqued them to 70 ftlbs. before they where torqued to 70ftlbs i marked the 90deg plus 90deg on the bolts. Less than half the bolts made it to the second 90deg marks! (a total of 180deg past the 20nm initial torque point) a couple where almost 45deg's before the final degree point!!

Goes to show how much thread binding and friction between the bolt head and washer and the washer and head affect final torque. I will defiantly be degreeing the bolts when i assemble the engine to ensure even tension on the bolts!

Luke

You have to take the thickness of the tin gasket off!

I should have remembered better. The 35 Thou is the net difference, Ie composite minus tin. I think the tin is about 18-21 thou but you can measure it.
Regards Philip A

G`day Luke , thanks for the figures , are they HRC 2210 ?

My interest again , will the 77 give you around 26 chambers ?

The bolt thing is very valid , i agree that degrees will give a more uniform pressure and it doesn`t really matter what the threads are doing .

You will also know that the pressure will be different using lubed and no lubed ordinary bolts .

One thing i`d mention is that the 2 types of bolts are made of different material as in an ordinary bolt streches after torquing but returns to close enough to the same length when released .

Torque to yield or strech bolts do the same after torquing but don`t return to their original length .

After the fact i did some fiddling with bolts and came up with a similar thing using ordinary bolts . While torquing i measured the degrees with the start point for Yeild bolts .

I have the degree difference written down here somewhere , i was surprised at what would be needed to achieve the same degrees as a yield bolt .

I think i concluded that some bolts would go as far as 90 ft lbs maybe more to reach the degrees .

The reason why it`s after the fact is because the head gaskets mentioned were replaced last month i think , maybe 2 .

It spat a cup full of coolant out the overflow 1 day when stopped .

Anyhow because i had a fair idea why ( gasket leak ) i looked further into it .

It was very hard to diagnose because the gasket was only in its very first stages of leaking but because i was fairly certain i pulled it apart ( it could have gone for months as it was ) Mostly because nothing kills these engines quicker than being overheated .

When i put them together i torque everything to specs .

When i pulled it apart the rocker bolts cracked ( that nice noise not as in broken ) , the valley bolts also cracked .

When i undid the head bolts they were firm but didn`t crack and i know as far as possible i tensioned them right .

This was the reason the gasket leaked , it did take 3/4 yrs and the comp ratio is above std .

What i want to make you aware of is that these gaskets i have and if the same as yours are 1.5 mm average or most consistantly after use .

If the bolts where loose from first fitting , i doubt it would have gone for the length of time it did .

I don`t have any answers but could it be that the gasket thickness decreased in use ?

Is you 1.86mm , my 1.5mm after running ? ( not really questions )

The last thing i`d like to mention concerning the head bolts is that one of the theorys for cracked blocks , which then allows the liner to move and the problem with coolant in these blocks is ......

The theory goes that because the torque to yeild bolts exert more pressure than ordinary type bolts .

They actually distort the alloy around the bolt holes and because of the amount of alloy around the liners , for a Red block somewhere around 2.8mm if the block is predisposed it will crack .

It`s a theory i don`t know if right or wrong , just having you aware .

If you feel it may be valid you could always torque/degree some bolts in your 3.9 block and judge if the final tension may be in excess .

The figures you have are the ones you`ll use , it may seem like it but i`m not trying to worry you or complicate things , though i can see it could be taken as such .

Cheers

Peter .

6.5 rangie wrote:lots of good info there!
mate of mine just had all his liners done on his 4.6 to flange liners, cost him $1300, worth it though

G`day Damien ,

If your able can you tell me exactly what your mate got for his $1300 .

Was that supply and fit the liners or was there more ?

Pressume he put rings and bearings in , were they from the same place .

Also could you tell me where he had it done ?

I`ve got a 4.0 that has had 1 liner fitted but it only did 30K and the 1 beside it has moved also , i bought it in this condition .

It`s from a 98 RR , which is 1 of the measured ones or the ones that use the paint code .

Cheers

Peter