I was talking with an engine rebuilder this week. He explained that the early L24 motors had 8mm “stretch” rod bolts that MUST be replaced in a rebuild (if not going with new rods and 9mm bolts). Question: Is this the experience with any of you that have had an early L24 rebuilt? Or, can the stock bolts be safely re-used in a motor that will not see track, AX, or similar use?

Some additional info: The 8 mm bolts are NLA from Nissan, he has located a replacement. The catch is that the replacement has a slightly larger shoulder that is a tight slip fit in the rod. This eliminates any “float” in the rod cap to line up the bearing surface. He machines the rod and cap to have an exact fit for the bearings. Of course, all of this drives up the cost of the rebuild. This rebuilder admits to being an anal perfectionist; he has many years experience in building Datsun race engines.

Thanks for any help or advice.

Jim

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Jim Arnett
Richardson, Texas
HLS30-15320 12/1970 (original owner)
ZCON 2015 Gold Cup - Street Modified class

Just my two cents here, others have more experience ~ all the rebuilders I have spoken to have ALWAYS upgraded the bolts to at least 9mm for street use and 10mm for track use, but HEY ~ the original 8mm bolts lasted more than 100,000 miles of everyday driving on the original cars, so they aren't "bad".

Bob Sharp Racing discovered the very early crankshaft (first ones only) and the light rod bolts were not up to the stresses of all-out racing. They were improved and replaced. As usual with racing improvements, as soon as the street enthusiasts heard about this, they "had" to have these improvements on their engines. It sort of makes sense if you're in there anyway, to upgrade the lower end just in case you (or subsequent owners) want to romp on it more than occasionally. But it also makes sense to leave it alone if you're gonna keep the car and don't intend to beat it.

Look at it this way ~ if you DON'T upgrade them now, you 'might' get a chance to go back in there and replace them later!

I guess it would depend on your budget.

If you want a professional opinion, you could call Vinny Bedini's speed shop at 860.355.1829 and ask him. He has built more Z engines than anyone else I personally know. Tell him you're our member.

Z you at Nashville!

Jim, You might want to check out ARP,
http://www.arp-bolts.com/index.html,
I believe they make both 8, and 9mm rod bolts.
If it was me, being an anal machinist and all.... bigger is better! If you have to re-size the big end of the rods you have to remove the bolts, and once you disturb the bolts most of the time you have to re-size the rod anyway... The rod bolts should be a light press fit in the rod and a slip fit in the cap.

My two cents, you have done a ton of work to your car and it looks great!... Do not skimp on the fasteners holding the bottom end together you only want to do this once.

Hope this helps, Dave

Dave - you are right on the money! These are the bolts and process he talked about. We did not get into detail on what "re-sizing" entails, other than some machining is involved. Looks like the right way to get the job done.

Thanks.

Jim

_________________
Jim Arnett
Richardson, Texas
HLS30-15320 12/1970 (original owner)
ZCON 2015 Gold Cup - Street Modified class

Jim, glad I could help and it sounds like you have the right man for the job.

Dave