2200b engine through bolts

[Eric McCandless]

I am trying to determine whether my 2200B engine can be fitted with 7/16" through bolts as I am trying to minimise risk of through bolt failures. I have a factory built J170-C (Nov 2008) with engine s/n 22B-144 with 210 hours. I have read the service bulletins from Jabiru but still cannot determine which serial number range the 7/16" bolts were applicable to and whether they can be fitted to earlier engines. My engine has had AD JSB-013 with the 12 point nuts, so I assume that mine has the original 3/8" bolts (short thread) (my aircraft is not handy to be able to check). Should I consider fitting the longer 3/8" through bolts or can the 7/16" through bolts be installed on my engine? If 7/16" can be fitted, would this involve engine modifications to fit the larger bolts? Have there been any reported 7/16" through bolt failures? Any advice would be appreciated.

 

 

[slartibartfast]

Hi Eric.

 

Jabiru are your best resource for the definitive answer, but the new nuts can be fitted to the old bolts.

 

Come over to hangar 9 on the weekend and you can check Mark's (he should have the new nuts fitted to the old bolts by now) or mine (I fitted new nuts, bolts and studs). Fitting new nuts on old bolts leaves the nuts overhanging, which seems to be bad practice. It does leave more threads in contact than the current arrangement though, and the old nuts are crap. Loctite 620 is used to keep them there. Potentially.

 

I didn't need to modify anything to fit the new bolts. You have to remove the cylinders anyway. Removing the old studs was interesting though.

 

Edit: My new studs and bolts are the same diameter, just longer. As SP6 points out, there would be mods for the 7/16th bolts. I wasn't worried about the bolts, the problem seemed to me to revolve around the nuts (like most things wrong with society). I've had 3 of them fail.

 

 

[JabSP6]

Eric

 

If your motor did not have the heads on one side removed as part of the AD JSB- 013 then all that would have been done is the 12 point (ARP) nuts fitted to the standard 3/8" (Short thread) through bolts.

 

You can easily identify this when you look at the Nuts on the through bolts as there will be no thread protruding past the end of the Nut. In fact you will see a couple of threads of the Nut.

 

If the Heads were removed then it is possible that the 3/8" (Longer thread) through bolts were fitted and you can see this by a few threads protruding past the end of the 12 point nuts.

 

The only way you can upgrade to the 7/16" through bolts is to strip the entire motor and split the cases. The dowels that fit between the 2 cases are replaced with a thinner walled Dowel which then allows the Bigger threaded bolt to pass through the engine. You will also need to open up slightly the holes in the barrel to allow for the 7/16" thread.

 

If you have had the SB done and only have reasonably low hours on the motor i would not strip the motor just to replace these bolts.

 

If you are close to needing a full rebuild on your motor then it would be advantageous while the motor is apart to upgrade to the 7/16" bolts.

 

I believe that all motors coming out of the factory now have the 7/16" through bolts.

 

I have not heard of any 7/16" through bolts breaking.

 

Safe Flying

 

JabSP6

 

 

[Eric McCandless]

Thank you all for the advice. It has made it a lot clearer to me now. I also discovered another thread on this forum discussing some technical aspects which I found very enlightening. Thanks.

 

 

[Bruce Tuncks]

The service bulletin about changing to 12 point nuts did not apply to my engine (2200A sn 425) but I've acquired a set of 12 point nuts anyway. I'd like some advice from anyone who used the universal-drive socket method in ADVALSR071-2 ,for instance, did you have to remove the cylinder heads?

 

cheers, Bruce

 

 

[brilin_air]

Hi Bruce,

 

When I do the 12 point nuts I always remove the heads as it is not that big of a job and it is a good opportunity to look inside and check how things are travelling, it also does make the job of fitting the nuts easier on the bottom of the barrells.

 

Brian

 

 

[ianboag]

Edit: My new studs and bolts are the same diameter, just longer. As SP6 points out, there would be mods for the 7/16th bolts. I wasn't worried about the bolts, the problem seemed to me to revolve around the nuts (like most things wrong with society). I've had 3 of them fail.

Hmm. Our experience was that it was the bolts were crap (undersize threads) rather than the nuts. The threads pulled like a Christmas tree. Longer nuts was a bit of a band-aid fix.

 

We have gone the way of using 10mm bolts/nuts from ARP who make them for racing engines. Jab only went as far as (12-point) ARP nuts. Go figure.

 

OK here in NZ, but paperwork probably makes it a bit hard in Oz.