Here are the results from Simon Erlands analysis of my Honda engine from Spa if anyones interested
I also have a load of pics that came with the report - i will try to upload them later
Honda engine failiure - preliminary report
Description of failiure:-
No 3 rod broken under the L/E with severe damage to the underside of piston, valve impact damage to the piston crown,and chamber no 3.One inlet valve broken
B/E rod housing and both bolts broken, some damage to no3 crank pin and cheeks.
Crankcase punctured either side of no3 pin, and debris damage to B/E housing and cheeks of 1,2 and 4 pins.
Bearings exhibit loss of material from both fatigue and debris damage on all B/E and mains shells.
Much speculation has suggested that the cause of failiure was a broken conrod bolt. Experience with such failiures or B/E journal failiures is that the crank pin suffers considerable damage as the remains of the rod are held in the cylinder and the crank impacts against the remains of the rod’s usually broken ends until the rod is knocked out of the crankcase.
Therefore breakage unber the little end is a secondary failiure. In this case the damage is overwhelmingly to the piston and cylinder bore and the crank pin is relatively clean.This suggests the rod was repeatedly thrown against the piston before it was ejected. Further the rod is broken just under the little end, which is the common rod failiure mode.
Further analysis to advance this theory can only come from crack testing the remaining three intact rods, if they all , or in part show some cracking under the little end this will lend weight to the theory that the failiure was due to rod failiure at it’s weakest point, under the little end. until such analysis is complete, and with similar analysis of the Brands Honda failiure, this theory can only be considered the most likely failiure given the evidence available.
Without question the fuelling and mapping of the engine played no part in this failiure, since all pistons and head chambers are clean and without any signs of det damage.
Third party experience :-
Conversations with Guy at CPL,and Richard at TTS reveal that they both have seen occasional piston and rod failiures in new K20s.Both have seen several pistons have the gudgeon pin pulled out-an inertial load failiure, which means a n/a engine is more susceptible to this failiure than a SC engine, and both have seen occasional rod failiures - apparently even a new Ariel Atom on its very first outing broke a rod under the little end.
Consequently both Guy and Richard are of the opinion that while a standard engine is reliable for road use, replacing rods,pistons and bracing the top of the bores is essential for any track work in a n/a or SC car.
Richard quotes ï¿½4000 for replacing rods pistons and the bore brace.
Very considerable damage was apparent to the bearings from both metal losses due to fatigue failiure and debris damage.Clearly this engine was suffering low oil pressure before the failiure though this would not have contributed to the failiure.
I am of the firm opinion that the oiling on this engine is poor and marginal for road use - inadequate for track use, however the damage points to oil starvation possibly due to oil way contamination froma previous Honda failiure ? This may also account for the debris damage, since the filter should have collected debris from the broken rod.If the oil ways have been correctly plumbed, it may be that the filter became clogged from the previous failiure and opened the valve - this would explain both the fatigue failiure and debris damage, but remains speculation without the filter to cut open.
The crack testing of the rods will give substantial new evidence to demonstrate a failiure mode and necessary modification to engines to avoid a repeat failiure, but analysis of the complete Brands failiure intact and with oil filters will give a much more complete understanding of the issues involved, though the provisional finding must be that the stock engine is prone to occasional failiure, even when new and that pistons,rods,valves and block brace are minimum modifications to make this engine track worthy.