GT40s.com - View Single Post - 302 failure

Andy Green · 02-28-08, 03:57 AM

Hi Julian,
I’d mainly concur was has previously been said.
If you fit a dash warning light, connect it to a pressure switch that trips about 20 psi. Normal switches are around 7-8psi and if it comes on during surge conditions, it will be too late. Also use a high intensity LED (Maplin do a nice 25mm cluster LED) which aren’t intrusive when mounted on the dash, but when illuminated you won’t miss it.

Normal oil pressure gauges aren’t accurate enough to pick up any minor dips in oil pressure caused by oil surge. My friend’s race engine had a period of running the big-end bearings, however he had a Pi dash-logger fitted and we were able to look at the oil pressure prior to the failure. The pressure had been dropping momentarily (less than 0.5 sec) and under the mechanical high loads, it was enough for the hydro-dynamic oil film to collapse and metal-metal contact to be made. One this happens, the bearing fails in a matter of seconds. We ended up curing the problem with wider bearings and a dry sump system.

You may have the best oil pan available, but it’s no good if you have oil hang-up in the valley & cylinder head. I’m no expert on these engines, perhaps someone else can add to this part.

You will need a complete engine strip & rebuild to ensure that there is no bearing swarf in any of the oil galleries.

Regards
Andy

02-28-08, 03:57 AM	#14 (permalink)
Andy Green saxoncross A Tenth Join Date: Mar 2007 Location: Norfolk, UK GT40: Tornado Posts: 100 Rep Power: 3	Re: 302 failure - any opinions??? Hi Julian, I’d mainly concur was has previously been said. If you fit a dash warning light, connect it to a pressure switch that trips about 20 psi. Normal switches are around 7-8psi and if it comes on during surge conditions, it will be too late. Also use a high intensity LED (Maplin do a nice 25mm cluster LED) which aren’t intrusive when mounted on the dash, but when illuminated you won’t miss it. Normal oil pressure gauges aren’t accurate enough to pick up any minor dips in oil pressure caused by oil surge. My friend’s race engine had a period of running the big-end bearings, however he had a Pi dash-logger fitted and we were able to look at the oil pressure prior to the failure. The pressure had been dropping momentarily (less than 0.5 sec) and under the mechanical high loads, it was enough for the hydro-dynamic oil film to collapse and metal-metal contact to be made. One this happens, the bearing fails in a matter of seconds. We ended up curing the problem with wider bearings and a dry sump system. You may have the best oil pan available, but it’s no good if you have oil hang-up in the valley & cylinder head. I’m no expert on these engines, perhaps someone else can add to this part. You will need a complete engine strip & rebuild to ensure that there is no bearing swarf in any of the oil galleries. Regards Andy