Bolted to Floor wrote:

You need to check out the area for real main seal. The early stuff was a 2 piece. My 85 had a one piece.

Yup, I know the early engines had a two-piece seal...the early bow-ties used rope... but anyway can the early crank be made to work?  I know the blocks are different due to the main seal issue and other stuff.

BB1

I believe the rear of crank requires machine work to remove some metal to work with the one piece seal.

Or, if its a stock build just find a used 5.0 crank.  They are super easy to find and cheap with everyone doing strokers now.  I wouldn't spend penny one on machine work, unless the '69 crank is forged for example and you think you need the insurance.  Though if it is forged I'm betting its worth a pretty penny, so selling it to fund the new crank for the 5.0 may ultimately be a better choice. 

Well, what got me to thinking is that the machinist I'm using keeps telling me that 5.0 cranks are flimsy and break often.  Hummm?  Well that's what's going in my new engine butt (TS&T), I happen to have a circa 69 302 out behind the shop.  I saved it from going to the scrap yard as a possible educational project for my grandson and I.  It's a "rebuilder special" that, according to a tag on the block, is punched .030 over and has a .030/.030 crank which wouldn't normally excite me much.
Since I still have a good 5.0 block from the Mustang Mess I just got to thinkin'...always gets me in trouble.

BB1
 

Last edited by Bullet Bob (11/09/2020 9:16 AM)

Thank you all for the info.  I may just steal the crank and rods from that old engine since I find myself with an extra good 5.0 block but no innards.

BB1
 

If you don't have a good rotating assemble, then buy new from some one. 

I would do a hard pass on a crank that's already been turned down .030 for the mains and rods. What advice did the machinist give on the 69 crank. For the rods, once you figure in the cost to resize both ends and add new bolts as a precaution, you should be at the price of a new set of rods. Who knows what kind of life they had. From the locked up FE motor I took out of my car back in the late 80's had 3 #8 rods in it. I know it didn't leave Ford like that

 

Bolted to Floor wrote:

If you don't have a good rotating assemble, then buy new from some one. 

I would do a hard pass on a crank that's already been turned down .030 for the mains and rods. What advice did the machinist give on the 69 crank. For the rods, once you figure in the cost to resize both ends and add new bolts as a precaution, you should be at the price of a new set of rods. Who knows what kind of life they had. From the locked up FE motor I took out of my car back in the late 80's had 3 #8 rods in it. I know it didn't leave Ford like that

 

 
This must have been a fun firing order? 😜

1-5-8-2-8-3-7-8

My buddy and I built that dirt track engine and used all Eagle rotating stuff. (non-forged) and it spun to 6500+ A LOT of times. Some things are good.....some things are bad....somethings are good & expensive. I think Eagle is good stuff.
You DO know.......a 5.0 with a set of 289 rods and "special" pistons  = a Boss 302. (rotating assembly)
"WE"......could advise you to do that with a healthy solid lifter roller cam and those AFR heads and step-off into Hi-Po hot rod land!!!  (A very expensive 'narrow' road I tinkz!)
Would love a ride in it at the next bash!!!
6sal6

red351 wrote:

As simple as I am, You hang 24.5oz. off each end of the crank, there will be some flex. How many times can it bend. Internal balance for for high rpm racing. 28 oz. is better than 50, but we all drive our cars as old men and ladies, don't we..........

I knew the guy who wrote the program Spin Balance, that most shops are using.  I talked to him extensively about balance and it really opened my eyes.  Creating a perfectly balanced engine is actually impossible due to the dynamics of the fact that the engine operates over such a large RPM range.  So you balance it to a target RPM range.  If the engine is going to spend most of its time at higher RPM you simply balance it accordingly. 

The idea that internal balance is better than external balance is true, but only where every last HP makes a difference as in racing.  That just has to do with the idea of where you would rather place the weight.  Obviously the closer to the crank centerline (impossible, that's why cranks have counterweights) the better, because it makes the engine accelerate better.  But these differences are in actuality extremely minor.  Plenty of successful racing engines use external balance, especially where internal balance is impossible or extremely expensive to achieve.

Bottom line, in a street engine its not worth spending anything beyond the typical $150 it costs to have the rotating assembly balanced in a SBF.  Trying to get to internal balance requires a lot of heavy metal, lengthening the balance job and adding another $250-$400 to the balance job (I'd rather spend that money on the heads or valvetrain to make a noticeable difference in power).  If you have a 50oz engine its fine.  If you have a 28oz engine its fine.  Interestingly, most strokers seem to use the 28 oz imbalance.