jmos4

Hi,

Ok while re-torqueing my head bolts, one snapped, I was using the factory manual which calls 80 ft lbs, yet when I looked online and in the Mondello reference book it says 85.

So which is it 80 or 85?

Also as I couldn't find a replacement (Sunday)I found a grade 8 7/16-14 x 4"long bolt should this work?

Monday I was ordering parts from Inline Tube and they listed head bolts but had a disclaimer stating 60 ft/lbs 80ft/lbs max. So is the manual wrong or is Inline Tubes disclaimer incorrect?

Regards,

MDchanic

What's the degree of precision of your torque wrench?

5% would be darned good for a consumer product.

The proper torque is 80 ft/lbs.

Why not just buy a head bolt from a member here?

- Eric

jmos4

Hi,

Well either both of my torque wrenches are way off or I am feeling way too strong. I've stretched 2 grade 8 bolts, when I google torque for a 7/16-14 thread it says grade 8 70 ft/lbs dry and 50 ft/lbs lubed.

I got 4 head bolts on order from Inline Tube as they are semi-local yet what do I need to torque these too? Their disclaimer says "torque spec 60 ft/lbs max torque 80 ft/lbs"

As I have been lucky so far as none of the head bolts have broke flush. I did get both heads on and torqued to 80 ft/lbs, all but 1 bolt that is giving me a issue. Do I torque it dry light oiled as breaking bolts is getting old not to mention I want to get the car back together before summer is over with.

Not sure if it makes any difference, but I am using Cometic .027 thick mls gaskets.

Regards,

olds 307 and 403

The factory bolts are supposed to be dipped in oil before torquing them to 80 ft/lbs. The only time I broke a head bolt was using non hardened washers, talk about non accurate torque.

Octania

I have never had one break at 80.
Deflecting beam TW's are accurate until they break
clicker type, not so much.


I would ck the TW you are using against a calibration machine, or a beam type, or dead weight such as a cable on a drum (bike cable around a socket). Of course then you have issues with how accurately is your weight and radius known...


I did break a main bolt once, because I tried to bring the 7/16 #1-4 ones to 120, the value for the 1/2" #5 cap. Ooops.


They good news, if that happens, they are not rusty, comes right out.

1970-W30

The method I used in the rebuild I'm just finishing up is to first make sure the head bolt holes are clean and clear to the bottom, then lightly oil the bolt with 10/30, not too much, you don't want to create a hydraulic lock caused by excess oil trapped in the hole. Then I also used a little assembly lube under the bolt head, torque em down in three steps ending at 80. I use a "click" type torque wrench and verified the results with my old deflecting beam torque wrench.

jmos4

Hi,

Well 1 reproduction head bolt broke, I tried another this time I placed a grade 8 washer under the head incase there was an issue with the mating surface. It still seemed iffy so I only got it to about 74 ft/lbs. I also ran out and got a beam type torque wrench and all the others were fine at 80 so not sure what was up with this one hole. I did slightly oil the bolt and washer, hopefully I don't have any more issues, fingers crossed.

Regards,