I now have to see if I am going to have a balancing issue ? The crank weighs about 78 pds, and I am assuming back in the day, it was ran with the heavier Lemans rods and the heavier TRW pistons, so if I go lighter on the rods & pistons, which will be easiest enough to do, how much grinding will the crank need ?
hard saying......you'll have to have the whole rotating mass spun up to see how that balance looks. maybe see if you can find an FE builders reference on a similar build...? I gotta think somebody has gone down a similar path
That's what I was thinking, some one has done it before, so I was looking for an idea of what I would be looking at. The cast cranks weigh about 65 pds, the forged steel cranks weigh about 75 pds, but mine with the extra counterweights weighs slightly more.
So I was thinking about if I would have to go heavier rods, like when a cast 390 crank has to have Mallory metal to offset the weight of lets say heavier Lemans rods.
I'm taking it to the balancing shop tomorrow, to see if I can get it spun for an idea. I do have a set of SK wide jrl rods that were cut down for a stock width jrl crank, that still weigh a ton, that I was going to use on a FT steel crank build to go in my 4x4, so I don't want to use them on this crank.
An in case people are wondering, I wanted the heavier crank, the car will be a daily driver for a while with a lot of freeway miles.
I stopped by the balancing shop today and talked to the guy. I had found earlier the C4AE 6303 G cranks out of the High Riser had a 2,303.5 gr. bobweight, and my crank is the C4AE 6303 G but my crank has the extra 2 counterweights off the center main, the balancing guy says the extra 2 weights won't effect the bobweights very much if any since their on the center main.
My dilemma is, if I go too light on the rods and pistons, he'll have to swiss cheese the crank weights to balance the assembly and if I go too heavy he'll have to add Mallory Metal. I took him one of the SK rods and a stock 390 C7AE-B rod, the 390 rod is too light, and the SK is too heavy.
So referencing the rotating weight of 650 gr of the SK rod and a guesstimate weight of 800 gr for a TRW piston & pin those would add 300 gr to the bobweight requiring Mallory metal. Options are finding a piston & pin weighing 500 gr to lose the 300 gr or find a rod & piston combo to loose the 300 or so weight.
So the trick is finding what I need off the shelf other wise I will have to go custom ($$$$).
Regular Lemans rods would probably be light enough and work, and I would possibly go that route if I found some new and cheap enough.
I haven't found much, but I did come across a NOS set of Lemans rods on Ebay, but bidding started out at $850, so I just passed on them. I will probably have to go a set of reasonably priced SCAT rods.
The biggest ticket item I am dealing with are the heads, I want aluminum with quick burn chambers and flow around 320cfm at .600" lift, pricing is around $3000 so I have to save a while for those.
So in order to get this car running for now I am still going to put the 390 together I picked up. I have picked up a few items to finish it, a new Isky cam an ee-391 grind, .560" valve lift and 250* dur @ .050"and a set of shell lifters, also a new Romac balancer so I can get the bottom end balanced.
Things have not moved along as I would of liked, money has been tight but have picked up a few minor items.
I had gotten it into the garage some time ago, but until recently had not done anything to it.
I got the headers off and that took a lot of work.
The heads I was very curious about so those came off, and found out some interesting things. The No.1 piston has a nice indentation from where it was hitting the head, so I know which rod bearing went, and cyl No.5 & No.6 were sucking water from the intake manifold, indicated by the rust on top of the pistons.