MUMMERT offered the rods in 2018 and forward but no longer carries them. looking for anyone who might have 2 or a set they have in storage.
Dean Markuson 612 two45 9305  dmdb1969@gmail.com

 

I’m guessing that the crankshaft survived without any damage?  If so, that begs the question on exactly what happened to make the connecting rod fail.

Lorena, Texas (South of Waco)

Yes Inquiring minds want to know. So it will not happen to us. Cos

went to smaller blower pulley to increase boost for final round of eliminations. found the weakest point. will put the big pulley back on and leave it there!
rod bearing was flattened but still intact..

 

I think I would look for another brand of connecting rods for blower usage.   What is the exact length of those rods?  Rod journal?  Pin size?  Weight?   Piston weight?   I have been contemplating building a Y to use with my Pro Charger and intercooler, but that rod is giving me second thoughts.  Joe-JDC

JDC

Any idea what the blower pressure was with the pulley change?  Head gaskets are typically the safety fuse for excessive blower pressure, not the connecting rods.  For non-O-ringed heads or decks, I will typically try to limit blower pressure to 10 psi.  As a footnote, I had a blower engine on the dyno last week that blew a head gasket at 10.35 psi.  With the boost pressure reset to maximize at 9 psi, the replacement gasket is still holding up.  32° BTDC timing on that engine both before and after the head gasket change.

Lorena, Texas (South of Waco)

calculating the boost with 33 tooth pulley from the known boost with the 34 tooth pulley, comes out to 11 psi. i had the blow off valve set at just over 11 and also warning light set with a hobbs switch to just over 11.psi. no indication of them tripping. I am resigned to the fact it was a grain structure failure in the rod itself. examination of the rod indicates heating in the middle of the rod, that tells me it bent/ twisted before it broke.  looking to repair engine and limit boost pressure to about 9. Had run 3 seasons of hard racing as well as street driving.

 

Love the race truck! I've been running about 6lbs of boost on the street for years now with no problems.



Y's guys rule!
Looking for McCullouch VS57 brackets and parts. Also looking for 28 Chrysler series 72 parts. And early Hemi parts.

MoonShadow, 292 w/McCulloch, 28 Chrysler Roadster, 354 Hemi)
Manchester, New Hampshire