TCCoA Forums banner

1 - 8 of 8 Posts

·
Registered
Joined
·
1,779 Posts
Discussion Starter #1
So I got a long block today for my F-150. I plan on installing a new oil pump, piston rings and honing the bores along with new head bolts and head gaskets. I want to check it out, rod and main bearings.

My question is can I reuse the old main and rod bolts to reassemble it?
Chris
 

·
Registered
Joined
·
7,758 Posts
I'm not 100% sure, but I think the only bolts on a 4.6L engine that are reusable are the side bolts. Every other bolt is a torque to yield bolt.

The way I determine if a bolt is reusable is if the final "spec" is a torque number, or a certain amount of degrees. If it is a torque number that it is reusable. If it is a torque number and then a certain number of degrees additional rotation (like torque to xx lbs, then turn 90 degrees), then it has to be replaced.

I talked about this in-depth with my machinist (who builds high end drag racing engines) and he said that was probably a pretty good method.

Just my .02 and hopefully other people that have built more modular engines that I, will chime in. :thumbsup:
 

·
Registered
Joined
·
1,522 Posts
Word direct from a Ford engineer that worked on both the Romeo and Windsor design teams is that the bolts are designed for 5 uses minimum. I reuse them once all the time now. Only bolts I have ever seen or heard of failing on a 4.6 are actually ARP.
 

·
Registered
Joined
·
7,758 Posts
Word direct from a Ford engineer that worked on both the Romeo and Windsor design teams is that the bolts are designed for 5 uses minimum. I reuse them once all the time now. Only bolts I have ever seen or heard of failing on a 4.6 are actually ARP.
Does that include the head bolts?
 

·
Registered
Joined
·
1,522 Posts
He stated all bolts on the 4.6 can be reused. If you read the factory manuals they say to replace every single one, mains, rods, heads, etc. I have taken a couple Ford reman engines apart and all the bolts were reused and painted with a white stripe. So Ford doesn't even give the same responses. If you are going to lose sleep over reusing bolts just get new ones IMHO. I have rebuilt a few now and don't worry about it anymore myself, but I understand the "used bolt" feeling as I used to have it myself.

IMHO - TTY is a bad phrase as if you tighten/stretch the bolt to where it yields (deforms) the bolt has already failed.

Edit - I haven't reused the headbolts myself yet as they come with the FRPP head changing kit which is the cheapest way to get the head gaskets at the moment.
 

·
Registered
Joined
·
7,758 Posts
Thanks for the clarification. And I'm with you... if the bolt stretches, it's on it's way to failing!! :thumbsup:
 

·
Super Moderator
Joined
·
10,583 Posts
if the bolt stretches, it's on it's way to failing!! :thumbsup:
That's not exactly correct...

In steel there's Tension, First yield, and Strain Hardening; the bolt gets much stronger, up close to the point it snaps.

http://en.wikipedia.org/wiki/Tensile_strength

When you torque a bolt, you are in the first region, Tension.

If you torque, plus rotation, you are stretching the bolt past first yield, where the bolt strength peaks, and decreases, before rising again. This is much stronger than the first value for the type of steel we're talking about.

Without going to the TTY process, the bolts would have to be Much larger, for the same force/strength.

The part why it's important is here:

After the yield point, steel and many other ductile metals will undergo a period of strain hardening, in which the stress increases again with increasing strain up to the ultimate strength. If the material is unloaded at this point, the stress-strain curve will be parallel to that portion of the curve between the origin and the yield point. If it is re-loaded it will follow the unloading curve up again to the ultimate strength, which has become the new yield strength.
Short version: If you Don't make it yield, it will probably snap.

How many times per second do these get stretched? :)
 

·
Registered
Joined
·
7,758 Posts
That's all good and dandy, but I have absolutely no use for a bolt that I can only use once. :D :thumbsup:
 
1 - 8 of 8 Posts
Top