Angle torque head bolt advice

sdlsaginaw

sdlsaginaw

Steven Lawson
I have new head bolts for the Uno turbo, but the long ones are shorter by the thickness of the washer. They also have heads with a washer-like base.

There are three options that I'd like to run by those that would know (Bernice?)

1) Use no washer. While the bolt heads have a washer-like base, I think it would still be a bad idea rotating steel against aluminum.

2) Use stock washers, not enough missing threads to worry about. This is hopefully the answer. :)

3) Find some thinner hardened washers. This would bring back maybe half the missing thread length. These style bolt heads probably don't *need* as thick of a washer.
 
I would advise against not using washers, the aluminum will get scored. So your bolts are short by what 4mm? I doubt that would be an issue but don't know enough to state for sure. You could find some hardened washers half the thickness to split the difference.

Chris
Oakland, Ca.
 
I say

Just back the stud out of the block enough to get the stock washer and a full nut full of threads. There are more threads in the block than on the nut, so just back the stud out enough to allow the nut to get full of threads. At least that's what I would do.
 
Option 4.

Mill a relief at each bolt location by 3 mm into the head. That way stock bolts can be used. The bolt hole boss should be solid all the way through to the head face and not bring any problems by doing so.


TonyK.

Grimsby Ontario Canada.
 
#1, Will result in serious galling of the aluminum area where the bolt seats. Do not do this.

#2, Stock washers, if these are the ones that are about 4mm thick, they have been known to crack. We had one fail like this resulting in a failed head gasket. Fiat later stopped using this thick washer (appears to be powered metal and hard) and began to use thinner hardened washers. I no longer use these on Fiat engines.
failedheadboltwasher1.jpg


#3, What I use now are hardened washers from ARP, or "grade 8" SAE hardened washers (3/8" for 10mm , 1/2" for 12mm), or "tooling washers" that are commonly used to set up machine tool fixtures. These are about 2-3mm thick, heat treated and work well under head bolt/stud-nuts.

http://arp-bolts.com/

http://www.wroughtwasher.com/washers-and-related-stampings/standard-washer/mil-carb-grade-8-washers/

http://www.carrlane.com/catalog/ind...006280B1713050245221E0107070F1A3C3B2853504554

*Note, I don't use any "torque to angle" or stretch bolts for the cylinder heads. The old fashioned way of high quality studs, hardened washers & nuts all torqued in proper sequence and to the proper final torque level with an accurate torque wrench work for me. This also mean a re-torque after some hours of running.

Bolts/washers/nuts are basically a spring and these springs need to set at the proper amount of tension at all times. Stretch or torque to angle bolts allow some margin or compliance to account for change in head gasket dimension and etc.. It makes production cars engines easier to deal with and more tolerant to production variations. In a performance or race engine, everything needs to be well controlled and documented.

Bernice


sdlsaginaw said:
I have new head bolts for the Uno turbo, but the long ones are shorter by the thickness of the washer. They also have heads with a washer-like base.

There are three options that I'd like to run by those that would know (Bernice?)

1) Use no washer. While the bolt heads have a washer-like base, I think it would still be a bad idea rotating steel against aluminum.

2) Use stock washers, not enough missing threads to worry about. This is hopefully the answer. :)

3) Find some thinner hardened washers. This would bring back maybe half the missing thread length. These style bolt heads probably don't *need* as thick of a washer.
Click to expand...
 
Bernice, I have a quick question for you...

On these head bolts Steve received, it apparently talks about having to soak them in oil for a specific amount of time, the also about allowing them to drip for a certain amount of time as well.

I know this does nothing to the bolt itself, is this intended for some other reason? Steve and I were trying to figure out why this would make any difference.

Thanks.

Eric
 
The oil process is all about friction when the bolt is threaded into the cast iron block and torqued. Any change in friction will alter the amount of clamping force for a given amount of torque applied.

Example, try pushing a 100 pound block of wood up an incline with the entire surface dragging on that surface, then put the block on ball bearing wheels. There will be a significant difference in the amount of force required to move that block up the incline a given distance.

This is also why different lubricants used on threads will produce a different clamp force for the same amount of torque applied to a threaded fastener. Or, why Fiat specified oil and allowing the excess to drip off before installation, torque to set, then the final torque to angle. Fiat engineered the entire joint taking into account elasticity of cylinder head, compression of the head gasket, complince of the bolt/nut/washer.. and produce the procedure in the factory service manual.

Any one of these factors change, the Fiat specified procedure no longer applies.

Proper joint design is very complex, but is often taken for granted and often works OK due to the amount of over-design for the typical joint. When more than a number of the original design factors and criteria have been violated or changed without a complete understanding of the orginal design intent, failures happen and the manufactire is often to blame for the failure.

Bernice

fastx19 said:
On these head bolts Steve received, it apparently talks about having to soak them in oil for a specific amount of time, the also about allowing them to drip for a certain amount of time as well.

I know this does nothing to the bolt itself, is this intended for some other reason? Steve and I were trying to figure out why this would make any difference.

Thanks.

Eric
Click to expand...
 
Thanks everybody!

Thank you for all the responses, I'm plugging away at this motor build with Erics help in his garage. :thumbsup:

Looking forward to the day I load a completed turbo motor in my truck and bring it back home for the install.
 
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