What material to use for building a main girdle?

[Hemi Joel]

If there is one thing I have learned about this forum, it is that there are a lot of smart experienced metal guys here. So my question is, if a guy was going to build a full main girdle that incorporated five main caps and pan rails, what material would you select and why? Assuming you had access to the CNC machining center, what would be your process? Thanks, Joel

P.S. not for an FE, but for a Ford

[Joe-JDC]

1/2" steel plate is what I have on two of my block to mains' girdles.  Also, use steel plate in a SBF girdle that is mains tied together only.  Joe-JDC

[Royce]

Joel, are you thinking like a Donovan style girdle? 

[Hemi Joel]

Royce, yes, where the main caps and the rails are all one piece.

[Hemi Joel]

Like this. The block is cast iron. So would an aluminum girdle be good, or would still be better. What grade of aluminum or steel?

[WConley]

Joel -  For an iron block you don't want an aluminum girdle.  You need to match the block's stiffness. 

If you're machining it, go with billet steel.  Otherwise a good cast iron like CGI or nodular would do the trick.

[blykins]

You know, I know everyone here is dogging aluminum, but I will say that I have one bracket 347 in a car, built from a later 5.0 block.  It makes 540 hp here, guy launches at 5500, shifts at 7000.  Car runs 6.90's in the 1/8th.  It's been built for 10 years, had to refresh it 8 years into it because of a bad power valve that didn't get noticed.  It's got a DSS aluminum girdle, main caps and bearings looked perfect on freshen up, with a couple hundred passes on it. 

Either that block is a stout one or the aluminum actually helps with harmonics in that situation. 

I do know that the big block Chrysler guys always put aluminum main caps on their iron blocks for higher end engines. 

To the OP, if you do build one, try to make it with as least amount of parts as possible, as the block does have to be align honed with it on there.  If you have a ton of parts, spacers, jack screws, etc., etc., then it makes it harder to duplicate the housing bore with each time you remove/reinstall.

[Falcon67]

A 10 yr old 347 @ 540 - yea, that's a special one right there.     The "couple hundred passes" though - that's lame.  I can run easy 10~20 passes a race weekend, 16 race double weekends usually a year - that's over 200/yr.  So the 351C block I just broke has easy 600~750 rounds on it. 

[blykins]

A 10 yr old 347 @ 540 - yea, that's a special one right there.     The "couple hundred passes" though - that's lame.  I can run easy 10~20 passes a race weekend, 16 race double weekends usually a year - that's over 200/yr.  So the 351C block I just broke has easy 600~750 rounds on it.

Well, I certainly wasn't looking for anyone's approval on how many passes constitutes "lame" and "not lame".   The car sees street duty as well and doesn't get raced every weekend.   

[HarleyJack17]

Brent may be on to something with the harmonics.  Steel would be my first choice but aluminum would likely work and definitely "can" absorb vibration. You would be tying it in with the pan rail bolts etc. and if nice and tight that adds support to the material.

I would say on the machining side, as you may know, if you take a blank of aluminum and gut it, you may want your final pass to be to square/straighten up the flats. Aluminum tends to deform a good bit after a lot of material is taken away from the "centers". 

[WConley]

You know, I know everyone here is dogging aluminum, but I will say that I have one bracket 347 in a car, built from a later 5.0 block.  It makes 540 hp here, guy launches at 5500, shifts at 7000.  Car runs 6.90's in the 1/8th.  It's been built for 10 years, had to refresh it 8 years into it because of a bad power valve that didn't get noticed.  It's got a DSS aluminum girdle, main caps and bearings looked perfect on freshen up, with a couple hundred passes on it. 

Either that block is a stout one or the aluminum actually helps with harmonics in that situation. 

I do know that the big block Chrysler guys always put aluminum main caps on their iron blocks for higher end engines. 

To the OP, if you do build one, try to make it with as least amount of parts as possible, as the block does have to be align honed with it on there.  If you have a ton of parts, spacers, jack screws, etc., etc., then it makes it harder to duplicate the housing bore with each time you remove/reinstall.

For a relatively thin girdle plate that ties to the existing main caps, aluminum will work fine.  My recommendation was for an integral cap "bedplate" style structure.  With a massive piece like that, you can run into issues if the stiffness / thermal expansion do not match the block.  I've seen fretted fastener holes and worn mating surfaces on big load-bearing aluminum parts run against iron blocks.

[Hemi Joel]

What Joe is showing is what I would call a main stud girdle.  I need a full girdle that incorporates all 5 main caps into it.

[pbf777]

So my question is, if a guy was going to build a full main girdle that incorporated five main caps and pan rails, what material would you select and why? Assuming you had access to the CNC machining center, what would be your process?

     If the cylinder block is of a gray cast iron material, then a like material would be best for machinability and dimensional stability.  The use of what might perhaps be considered superior material in ductility and or strength even perhaps say a compact graphite iron casting if one is relying on the structure to carry a greater some of the cylinder blocks load responsibilities. If the block is of a white metal, then so should the girdle (crank bed-plate as you have pictured), whether of a casting or of billet, the same considerations as previously stated but for the iron.

     Also the cast iron does provide a superior vibration dampening value over rolled steel plate or even a more complex steel billet execution, though perhaps the aluminum alloy might be even better at this, the mixed metal assembly would still not be the best choice,..........I.M.O.

     I did some perhaps rather basic comparison testing of main-cap stud girdles of steel vs. aluminum units and have concluded for myself that the only benefit of the aluminum over the steel would be weight and ease of manufacture, but otherwise not recommended over the steel.  I am concerned that the steel "may" possibly induce a vibration harmonic, which with all over variables being equal "may" be better dampened by the aluminum but............... ; in the one piece "full main girdle" intention (the right way) as I envision such (what engine?), the more complex three dimensional creation, of greater mass, with the additional fixturing and out of plane will retard that effect solely on this, but.............     

     This would truly require a much more in depth study before I would "bet-the-farm"               on these comments but...... It's the best I can do from here.

     Scott.       

[Joe-JDC]

Joel, the mains have a washer and nut on each of them, and then the girdle is installed level with the main cap nuts, and another washer and nut is torqued in place.  Each of the oil pan studs has a self locking washer torqued down before installing the oil pan.  The reason for the rear main not having the longer studs and washer with nut is the oil pan would not fit over them.  Works great for upwards of 750 hp on a blown Y, and my 600 hp Y.  Joe-JDC

[Falcon67]

A 10 yr old 347 @ 540 - yea, that's a special one right there.     The "couple hundred passes" though - that's lame.  I can run easy 10~20 passes a race weekend, 16 race double weekends usually a year - that's over 200/yr.  So the 351C block I just broke has easy 600~750 rounds on it.

Well, I certainly wasn't looking for anyone's approval on how many passes constitutes "lame" and "not lame".   The car sees street duty as well and doesn't get raced every weekend.

Sorry if it came off like that, not the intention.

One of my acquaintances built a 347 that made about 500.  Lasted 4 passes.  Split right down the middle.  No details, other than it was a huge fail.