View Full Version : Head bolts

Paul B
14-11-03, 01:33 PM
I know I have read somewhere that certain head bolts were omitted from later engines and that if heads are removed and replaced on earlier engines, these bolts should not be fully torqued up.

Can someone please advise which bolts are we talking about and what should the new torque be ?

I am using a 1976 SD1 and will fit composite head gaskets.

Thanks guys.

14-11-03, 03:27 PM
Composite head gaskets will lower your compression ratio, ( I think by 0.5) so if you've already got a lowish cr you might think about skimmng the head. RPI reckon that the 4 outer head bolts on the earlier engines with 14 bolts should be torqued to about 25ftlb. Cylinder head bolts should be torqued to 65 to 70 ftlbs, don't forget a smear of oil on the threads when torquing them down.


14-11-03, 05:44 PM
Paul, Russell is the man who knows about RV8's but the bolts that He recommends if you are using the composite gasket are the ones used on the new 4.6L Rovers. They are stretch bolts and you don't do them up to a specific torque, I used them on my engine when I rebuilt it and how you do them up is as follows. First torque them all up IN ORDER to about 15lbs then as per the other post Ignore the outer ones as they can contribute to a warped head, then once again IN ORDER ( per the Haynes manual) turn all the bolts 90 deg , and then after that another 90 deg. When I did this I have never been so scared in my life as about 40% of the bolts went slightly loose as I turned them the last bit, but I am told that this is quite normal as this is the bolts STRETCHING. I have now done over 6000 miles with no problems at all. I have spoken about this method to Russell and he confirmed that it is correct, and I have since spoken to people who have had exactly the same experience as me. But one thing to remember is as stated before you will loose some compression as the composite gasket is that much thicker. I think when I bought the bolts you only get 16 as the new engines don't have the third row of bolts and I just used some ordinary ones there and torqued them up to about 40 lbs.

Good luck Martin :tu :tu :tu :tu

Paul B
17-11-03, 12:50 PM
Thanks for the info guys but, I may be a little slow here, which bolts are classified as the outer 4 bolts ?

Do you mean the two forward and two rear outboard bolts on each head?

Any chance of a photo ?

What impact will lowering the compression ratio have on a standard engine ?

Thanks again for your help.

17-11-03, 01:35 PM
Outer as in outside the rocker covers, or outer as in the 4 furthest away from the centre of the engine on a logitudinal line, same 4 bolts. You will notice on a head gasket that the bolts that tighten up to 70ftlbs or 180deg whichever you use, are spaced in a square pattern around the cylinder bore. NOT the 4 for and aft of the engine, these are needed to torque down the head gasket.

Lowering the compression ratio will reduce the engine efficiency,(less power); on an older design using traditional controls, ie carb and dissy, as a rule of thumb, you should go no higher than 10:1. Aim for at least 9:1. My Rover engine will be 11:1 on EMS and EFI and I know of engines running higher than that.