Problem with my Ford 302

fbonaudi · #1 (**permalink**) 04-16-2007, 05:35 AM

Hi all you there,

I own a Cobra Replica with a Ford 302 engine. In 2006 I made a complete rebuild of my engine going to my first undersize. A few miles after I suddenly lost oil pressure. Checking the engine my rods where damaged again (Clevite 77 Tri-Metal). I'm rebuilding my engine again but here in Argentina this is not a common engine, in fact I have to buy everything in the US, I could not get here even the gasket engine kit. Our mechanics are not specialized in V8s. I'm going now to the second undersize (.20). Could some one inform me the spacing between the crankshaft and the rods. I hope you can understand what I need, I'm a spanish speaking person and I'm not probably using the correct words. Thank you anyway. Best regards. Fernando.

blykins · #2 (**permalink**) 04-16-2007, 08:49 AM

I would try to get about .002"-.0025" on the rod bearing clearances.

What caused you to lose oil pressure? Did the oil pump drive shaft break?

fbonaudi · #3 (**permalink**) 04-16-2007, 01:57 PM

Hi, first of all thank you for your fast response. I think the engine loose oil pressure because the damage in the rod bearings. The oil pump was tested and it's ok. The engine was running at about 5200 RPM and suddenly loose performance. When I check the oil pressure, it was under the normal pressure I used to see when I was accelerating. At idle, the pressure went to cero. I stopped the engine and called a truck to take it to my mechanic. When we took the oil pan out a lot of metal was found mixed with the oil, the main and rod bearings were seriously damaged. The shop were the engine was machined gave me the theory of what could have happened, the oil was so hot that it lose viscosity and the oil film between the crankshaft and the rod bearing disappeared. The water temperature never passed 210 F, I know the oil temperature is higher but not so much. For me, it's imposible that the oil could degrade in such way. I really don't know what happened, the fact is that I have to rebuild it again. Regards. Fernando.

WildBill3 · #4 (**permalink**) 04-16-2007, 02:45 PM

when we set up an engine we dont use plasticgauge we torque the new bearings in a resized rod and mike the inside diameter in an x patern and also mike the rod jurnals and mains to establish a true reading to get our clearences.normaly on perfomace engines we break them in on a straight 30w weight motor oil and then after a short time of running take the oil out and put in a 50w motor oil, ithink 50w wont break down as easly

fbonaudi · #5 (**permalink**) 04-16-2007, 07:35 PM

Thank a lot for your advice. I'll do it that way.

69boss429 · #6 (**permalink**) 04-17-2007, 04:32 AM

And don't reuse that oil pump,the price of a new one is cheap insurance.

DAVID GAGNARD · #7 (**permalink**) 04-17-2007, 10:45 AM

I think your problem lies somewhere in the clearances of the main/rod bearings, I'd double check the crank journals and clearances with the rebuild.........
Sounds like you spun a rod bearing,5200 rpms is not very high and should not have caused this, stock 5.0 Mustang GT motors had a 6200 rpm limiter in them from the factory!!!!!!!!!!!!..........definetly go with a new oil pump with the rebuild.....

I serouisly doubt your oil lost it's viscosity and caused this.....I normally run oil temps of 230 to 250 degrees in my 331 cu in race motor for 20 minute races, running usually from 3500 to 7000 rpms, motor has been in the car for a little over a year now and has at least 18 races/track days on it.........
The last race a few weeks ago, I was running a lot harder than normal and staying in 3rd gear more than normal and ran it up to 7000 rpms at least three times each of the 12 laps we ran, my oil temp went to 260 degrees and stayed there the whole race, oil pressure was about 45 psi, after a cool down lap things came back to normal............

David

fbonaudi · #8 (**permalink**) 04-17-2007, 01:15 PM

Thanks David for the information. I will look for a new one.

WildBill3 · #9 (**permalink**) 04-24-2007, 04:47 PM

hey Fernando what did your shop find???

CHANMADD · #10 (**permalink**) 04-24-2007, 04:59 PM

I think you were asking about the side clearance for the rods,between the crank.That should be 0.020 and the bearing clearance as discussed should be 0.002. Make sure that you take the engine completely apart and have the block hot-tanked(CLEANED) ALL the oil galleys MUST be properly cleaned and you will also have to remove the cam bearings and replace them to do this right.As said buy a NEW oil pump

CHANMADD · #11 (**permalink**) 04-24-2007, 05:00 PM

Also Fernando, if you have an oil cooler you will need to replace it and the lines from the motor.