The V8 Owners Forum -

Hi Reader,
I am about to bolt down my cylinder heads, the block has only got the 10-holes.
I am going to use new bolts ( not arp ).
The book I am reading states the sequence and 90Nm tight. Then a 90 degree turn and then a further 90 degree turn. This all correct?
The bolts threads will be copper eased and under the bolt shoulder, I will be careful to ensure no copper ease can get under the bolt due to hydraulic action.
Many thanks ..... Mike

Can't comment of the torque sequence but if it was me I wouldn't be using copper ease. Its meant for stopping hot things from getting sized and isn't a very good lubricant. Use either molly grease or even just plain engine oil.

I must be odd in still using 3M Scotch-Clad 776, as specified in the first Rover V-8 workshop manual when Rover was still Rover. It's like a clear varnish, and lubricates, seals and locks. From aerospace. Never had a problem with any thread seizing after using that stuff - even the water pump ones.

Hi all,
Many thanks regarding copper ease/slip ..... a no .. no.
What about that torque? 90Nm ( one book states 88 another 90Nm ) seems right then, what about the 90Nm then a further 90-degrees .... then yet another 90-degrees.
What I don`t want to do is strip the block thread.
Cheers ...Mike

I'm sure its not 90nm first. I think its 25nm then 90+90 degree's.

Perry

Hi Perry,
Many thanks ... I know you never go the the max torque to start with ( though neither manual I am reading states that is so ) I was just worried about that 90 + 90 when the correct torque is reached. I feel happier now ..... thanks.
Mike

Hi Mike,
My book says 20Nm for the first stage of tightening then 90 degrees + 90 degrees. Lightly oil the threads.

I assume your new bolts are the stretch type with built in washers.

If they have loose washers then you would torque them gradually in sequence up to 90Nm

Regards Denis

Hi Denis, many thanks ..... yes they do have the built-in washers.
I know about why the sequence, and the torque for each bolt.
The original problem was that 90Nm ( after a lesser torque ) and then a further 90 degree and then yet another 90 degree just seemed very tight for an alloy block and I was worried about stripping the block threads.
Though my info came from a Rover V8 engine overall manual, a publication by Rover tech communications that just states take it to 90 Nm, then a 90 degree and the yet another 90 degree - using a sequence of course.
The last engine I fitted a `head onto was a cast iron job - hence the post here.

Many thanks to you all, Mike

If you did the stretch bolts up to 90nm (66 ft/lbs) and then tried the 90 + 90 I reckon you would pull the bolts out of the block.


I've only used stretch bolts twice. And I didnt like the way you can feel them letting go on the second 90 degree's turn. I thought the thread was stripping.

But both those engine are still going ok after 4 years with no head gasket problems.

On my race engines I was having the heads of so many times a year it was worth buying the ARP stud kit.

Jason got his ARP setup when we bought a scrap RV8 that had ARP top and bottom. £70 for the whole engine with £180 worth of ARP bits fitted was a no brainer.

Whilst on this subject (and since I have an engine I am just about to screw together!), there is an aspect of this that does worry me.

1. Tighten the 10 bolts to 20Nm.
2. Angle tighten them (in sequence) by 90 degrees.

Now, only the first bolt will be tight. The other 9 will be loose because the head has clamped down a bit.

In the past, I have ignored this, and just angle tightened them by 90 degrees, maybe with the first 30 degrees being completely loose.

Is that right?, or should one ensure the bolts are 20Nm before angle tightening by 90 degrees? (this meaning that you retighten each bolt a bit before angle tightening it).

Chris.

The thing to remember is that if you start with 20 Nm on all the bolts and then you turn them all through 90 degrees and then again through another 90 degrees , they will all have the same force in them. They all will have stretched by the same amount, hence the same force in each bolt which is what you are trying to achieve.

This is why the later manufacturers went for a set number of degrees rotation of the bolts to tighten heads etc. This is more accurate than the torque method as the thread quality and friction can vary so much.

To answer your example. when you turn the second bolt through 90 degrees, the first bolt looses some load but they will all end up with the same force in the end as it all depends on the pitch of the thread.

Regards Denis

Hi all,
It seems I may have started a topic that is going places!
The manual I am reading from ( a Rover publication ) states the following ...

"Using sequence shown, tighten cylinder head bolts to:
Stage 1 - correct torque.
Stage 2 - 90 Degree
Stage 3 - Further 90 Degree"

( The correct torque being ( as stated ) 90Nm )

Today Sat. I put my later `heads on and done exactly what it states above and got as far as stage 2 and just about pulled my guts out doing it !!!!
IF yes IF I have to go to stage 3 I will need a pipe 3/4 inch diameter and about 3 foot long. ( looks like a building site visit )
Before I got to 90Nm I started at 25Nm, then 50Nm then 90Nm at each torque change I went through the sequence. My idea being to take the heads down slowly but surely but still in sequence.
Can anyone see anything wrong with the method I used?
Cheers Mike

Mike,
90 Nm is the final torque for normal bolts (non stretch type)
Any more than that and you will start to pull threads out of the block.

Your manual is incorrect if it suggests 90 Nm plus 2 x 90 degrees as well, as you would wreck the threads in the block.

If you have torqued stretch bolts by the old method, I'm not sure what force is in the bolts now.

They are designed to be used only once so I don't know the best route forward.

Anybody else got a suggestion?

Regards Denis

20nm then 90 then 90 on 10 bolt stretch.

90nm final torque if using non stretch bolts.