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-   -   Should I replace Rod bolts (http://forums.pelicanparts.com/911-engine-rebuilding-forum/565392-should-i-replace-rod-bolts.html)

cmcfaul 09-20-2010 05:46 AM

Should I replace Rod bolts
 
I am rebuilding my 73 E 2.4 but not splitting the case. It has been suggested that I replace the rod bolts.

Is replacing the rod bolts recommended?

Can it be done without splitting the case?

Thanks,

Chris
73 911 E

Flat6pac 09-20-2010 06:40 AM

Why, theyre still holding arent they?
Bruce

cmcfaul 09-20-2010 06:48 AM

That was my thinking as well. Unless I hear otherwise I am going to leave them alone. The enging was not over reved. I broke a piston ring I believe because of detination resulting from high compression and a distributor that is advancing way too quickly.

Chris

dhrcr911s 09-20-2010 07:16 AM

I had the bolts in hand after a small over-rev.. put the engine back together without doing the bolts... Now i have a new case..... Nuf said, i'd do them.. you never know:(

Steve@Rennsport 09-20-2010 07:34 AM

If the engine was detonating hard enough to break rings, you need to replace the rod bearings and that means new bolts.

Have them resized, as well.

Cupcar 09-20-2010 08:32 AM

Quote:

Originally Posted by dhrcr911s (Post 5571251)
I had the bolts in hand after a small over-rev.. put the engine back together without doing the bolts... Now i have a new case..... Nuf said, i'd do them.. you never know:(

Hmm..."bolts in hand", does that mean you re-used the rod bolts?

cmcfaul 09-20-2010 09:37 AM

Does replacing the rod bearings / bolts require the splitting of the case?

Steve@Rennsport 09-20-2010 09:39 AM

Quote:

Originally Posted by cmcfaul (Post 5571497)
Does replacing the rod bearings / bolts require the splitting of the case?

Nossir, but does require removing the pistons and cylinders.

cmcfaul 09-20-2010 09:45 AM

NP there, already have the pistons laying limply from the case. Took two of the pistions off already. One for replacement the other to be used as an example. There is no free play in any of the pistons, rods, etc. Everything moves as smooth as silk. Pins were nice and tight and came out with a few gentel taps. replace them anyway?

Chris

boyt911sc 09-20-2010 10:02 AM

Follow-up question........
 
Quote:

Originally Posted by Steve@Rennsport (Post 5571278)
If the engine was detonating hard enough to break rings, you need to replace the rod bearings and that means new bolts.

Have them resized, as well.


Steve,

I have a follow-up question regarding this subject. I'm starting to start my engine rebuild ('78 SC). I'm replacing the rod bolts and crank shaft bearings, do I need to have the case line bored and crankshaft resized? Could you elaborate your statement 'Have them resized, as well'. Thanks.

Tony

YTNUKLR 09-20-2010 10:37 AM

What he means is resize the big end of the rods (make them circular and the correct bore). Also install and ream new brass bushings to the correct sizes.

If your case and crank are standard size and within specifications you do not need to resize them.

johndaroza 09-13-2011 05:47 PM

question? big end of the rods (make them circular) Rods are not cirular in Porsches, untel loded, right? I,m asking because that is what I have learned in School for engine building

Flieger 09-13-2011 05:55 PM

I know when resizing old rods they need to be torqued to spec so I guess it follows logically that they come from the factory shaped such that they are circular only under load from the fasteners.

Eagledriver 09-13-2011 06:08 PM

While some modern engines may have big ends that are not round until high RPM, our aircooled engines don't have that. The big ends are perfectly round when the caps are torqued inplace. The rods are resized by shaving the mating surfaces and then machining the bore back to spec.

-Andy

Flieger 09-13-2011 06:10 PM

I think he meant loaded as in the bolts torqued, not rpm related.

Ken911 09-13-2011 06:50 PM

rod bolts are an easy thing and stock ones are also known to be weak


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