quote:Originally posted by Jérémie:
For the remaining engine I have stock rods with arp bolts, and the balancer seems 46 year old.
What can be the problem with the balancer ?
The stock 4v balancer is a "street" balancer intended to be used within it's 6,000 rpm limit.
If you change the cam for one with more lift and duration, valve springs, etc, and it is now capable of 7,000 or above regularly, then the stock balancer is insufficient.
The engine, 351c, is subject to developing engine harmonics (vibrations) above 6000 rpm.
You need a better balancer, but IMO, a balancer with the mass of the Boss 351/ho unit. It has to be heavy enough to dampen the vibrations.
Some will say that I am "full of it" you just need a good balance job on the reciprocating assembly. I disagree...on both accounts.
The Boss flywheel is cast iron and theoretically is fine for above 6000 rpm use.
Why it gets changed to steel is really as a safety concern.
I would tell you to get the Centerforce dual friction clutch, but an 11", not the pre-packaged direct Pantera 10-1/2" unit.
Be warned though that combination NEEDS to be seated. It initially slips like a son of a gun. Reason being is the flywheel is harder in steel, that side of the disc is the hard side and it takes longer for those two to come to some sort of an agreement.
What you will feel will be like you just hit a slick in the road, i.e., oil or the like and the wheels just jerked through it, but it wasn't the tires, it was the clutch just slipped. It's a very strange scenario.
I've used the Centerforce dual friction in several cars and they all did the same thing.
The rest of the Pantera reciprocating assembly with ARP rod bolts is pretty sturdy.
The only reason you would need to go to a forged steel crank would be to reduce the bearing inbedment into it's surface and thus reduce the amount of times you need to re-cut the crank journals.
Also, the Boss351 has got a slightly different balance spec then a 4v does. So the balancer and flywheel will be in slight inbalance when installed on a 4v assembly.
WHATEVER YOU DO, when you have the assembly balance, balance it as an assembly and give very specific instructions DO NOT TOUCH THE FLYWHEEL AND THE BALANCER.
You need to be able to change those in the future without having to worry about rebalancing the entire assembly.
A knowledgeable, experienced and conscientious professional should have no issues with that BUT I personally have had one engine, a very expensive 447 Ford screwed up by the balancer.
It loosened all the main caps within 20 minutes of running. Only a mis-balanced engine can do that.