I installed the gm 847 with all the "fixins", and after 500ish mile I started seeing oil pressure problems, I replaced the oil pump with a HV HP and that took care of it for a little while... as I slowly watched the pressure get worse and worse with a large drop everytime I took someone for a joy ride it came down to pulling the motor... to sum it up...
1500 miles later
1 spun rod bearing and one roasted and destroyed main.

now I'd just like to know how it happened, I would really like to have that motor back in there again and be able to spin it to the moon without worrys.

I was thinking a 355, simple yet makes some power in a LT1.

 

Old bearings, not enough oil pressure and too high rpms= bearings

 

When you rebuild it set the clearances RIGHT and not .0015 on the main's.Get a good pump and pan and a GOOD set of bearing's--not the cheapest.Part's ain't Part's.If you want it to stay togeather @7000RPM's you need good stuff and the proper clearances.You also need an electric water pump to take the load off of the front cam brg.

 

Curious, not to steal the thread, cause I just went through the same crap, Formula. 2 spun rod bearings and 1 main with a CC305. I bought a stock motor with roughly 90K and put in a GM847. I replaced all the gaskets and seals and put in a new oil pump with a GM whitespring. When first cranking it up, it has good oil pressure, roughly 60 psi. It stays high until a few WOT blasts, then drops to the first line on the gauge above the red. I'd guess 10 psi. It instantly goes back up to 60 with a tap of the gas tho, and is good whenever there is a load on it. What is your oil pressure at idle? It seems these cars always have low pressure at hot idle. I am using the Melling M155 pump with a stock pickup and pan. Any ideas? If this thing spins another bearing I'm gonna part it out. Too much money for not enough fun...

 

May I ask what a GM847 is ( I am new to camaros and chevy in general )

 

GM847 is GM's #847 camshaft. Relatively big.

 

There's that ugly "I replaced the cam and now my crank is wiped out" monster. I don't suppose any of you guys put new cam bearings in did you??????

 

You guys who had problems would have happened to have your blocks hot tanked did you?

When my block got hot tanked, it turns out the machine shop forgot to remove the plug under the rear main bearing cap (the one that looks like a ball that goes in the channel that feeds the oil filter, you have to pop out by going down through the oil pressure sending unit hole), and a BUNCH of metal shavings from the hot tank had settled there. (at least a shot glass full)

Did you guys pop that plug out and clean out your blocks real good?

-Dave C. '97 Z28

 

never been hot tanked, the motor was a gm crate 4 bolt main with 30,000 miles on it so I thought it would be ok.

I had a electric water pump.

sorry in a rush get back later.

 

Specifically, it comes from the part number.

p/n 12370847

In/Ex
duration
232/242

lift w/1.5 rockers
.539/.558

lift w/1.6 rockers
.575/.595

LSA
112

 

My oil pressure drops as well after a few WOT runs or a hot idle.

Cam similar to GM 847.

I'm doing a rebuild soon with new rings and bearings. Any recommendations on bearings?

 

Clevite

 

Just wondering, what needs to be done to run the GM 847 safely in these cars without oil or bearing problems? Is 6500 RPM's too high to spin the stock bearings? Also, can the bearings be changed with the motor in the car with the oil pan out?