mmasse

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I am rebuilding my 993 engine. I am still waiting for the parts to come back from the machinist, and in the meantime I am reading as much as I can about the engine assembly process.

I have one question regarding the rod bolts. Following advice on several posts I decided to replace the stock rod bolts with ARP ones. In reading the assembly instructions for these bolts, I found out that the recommended method for installation is to torque them until a specific stretch of the bolt is achieved. Now, this is not possible in my case, given that I am doing a top end rebuild only and the cranck is still in the case, so i don't think I will be able to fit the measuring tool in there.

So, there is an alternative method mentioned on the instrcutions which is basically a torque specification. But, what concerns me a bit is that it recommends to torque the bolt to the specific value, then take the nut out and torque them again in order to secure proper sitting of the bolt head agains the rod. Now, my understanding was that these are strectch bolts and that once you torque them one time you can not re-torque them. am I wrong?

Please provide your advice on this.

Thanks
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Steve Weiner-Rennsport Systems

Factory rod bolts ARE indeed stretch bolts and as such, are one-use-only items.

ARP bolts, OTOH, are reusable IF they are still within specification for stretch so you'll be OK here as long as you follow the procedures. You are correct, one cannot fit the ARP stretch gauge in an assembled short block so this must be done with the rods before installation.

With the rod clamped up in a vice (using soft jaws), follow the ARP procedure and burnish the bolt threads by running the nuts up & down the threads after lubing them with the provided tube from ARP. Using the stretch gauge, pull the nuts slowly up to the specified value while observing the amount of torque it takes to hit the number. Do this twice to get an accurate torque value and be sure to measure the big end ID to determine bearing crush unless the machinist has already machined the caps for you.

Install the rods with bearings (oiling the bearings with assembly lube) on each journal, noting the measured torque spec to achieve desired stretch and pull them up to that spec. Its usually around 45-55 lbs-ft.

Done.

mmasse

Thanks Steve. Can I ask you to clarify what did you mean here? How do I measure bearing crush...and what is it??, sorry this is my first rebuild

Thanks again

Steve Weiner-Rennsport Systems

The term "bearing crush" refers to the fitment between bearings and journals. If they are too tight, the bearing shells deform and the journal will no have sufficient space for the oil film. If they are too loose, you lose oil pressure and the bearings can spin.

Its the job of the engine builder & machinist to coordinate these procedures by measuring the rod journals and giving that data to the machinist so he can properly resize the big ends of the rods during reconditioning. Further, he needs to have the bearings on hand to possibly modify them to fit.

mmasse

Thanks Steve. I will get in touch with the machine shop and see if they are considering this!!

One more question. I am relacing the rod bearings for new ones. should I expect any issues with this.? As mentioned before I am not taking the full engine apart therefore I will not be able to measures the crank. Is it still possible to measure the bearing crush appropriately?

Thanks