GT750 Cylinder Head Bolt Torque Procedure

[water cooled]

Question:

When torqueing the 10mm and 8mm cylinder head bolts, the Service Manual is not crystal clear about the best method...only the order and range

Is it best to torque the 8 and 10mm bolts in order and all at the same time starting at 0 ft-lbs increasing in increments of say 3 ft-lbs until you reach 15 ft-lbs for all 19 bolts, then continue on with the 10mm bolts only until you reach 27 ft-lbs?

Then, heat cycle the engine, start back again at 75% and re-torque.

[Suzukidave]

Kevin , like you i havent read exactly how to do it so like you posted i did mine in stages and then heat cycled and retorqued . Did you talk to Richard as he had some thoughts about not useing more torque on the head bolts ?

[water cooled]

Dave,

I did...but John at Medina Motorsports also says the same thing. He is a big fan of ARP and uses them on all his high performance engines. He is the guy that machined my block and cylinder head. He advised not to over-torque (go beyond the OEM specification) and do everything possible to keep the incrementally increasing load (from torque) as consistent as possible across the head. A fellow racer in the UK explained the importance of heat cycling a freshly built engine. I think these two pieces might help... as you know, I am trying hard establish a reliable method or procedure for the copper head gasket before I change to the insert head design.

This is the first time I torqued the head with this procedure. In the past, I did all the 10mm bolts to full torque spec then went back and did the 8mm bolts to their spec. In hind site, that might not be the best way...I figured some of the racers and engine builders on Sundial could verify a proven method.

Thanks Dave.

[tz375]

Do it progressively as you suggested. part way up for all bolts then all the way for 8's and the same torque on the 10s, then the rest of the way for the 10s.

I was taught to oil the nuts/studs and never try to torque them dry because too much of the torque is used to overcome friction which can be different from one bolt to another. the other thing I was told was to take time and do it in stages. A little at a time - no big bites. So 3 stages should be enough.

[tz375]

BTW, the part number for ARP studs is

AM4.950-1LB according to Zac at ARP and sets of ten are available with nuts as kits # 151-5405 and 218-5402

I don't have any here to compare to stock studs, so i can't confirm whether there's enough thread on the upper end, but I think they should be OK.

[water cooled]

Thanks Richard,

Thats great on the ARP part number. Id like to persue that a little further.

Kevin