FB Standard Wagon

[FbSTDwagon]

So I got the engine bottom end dummied up with out the RMS to see how the crank spins, which feels perfect.
Crank got reground to .040” oversize and it’s been balanced, spins nice and free. Very happy with how it feels.

Dummy fitted the pistons to the rods without the spiro locks so I can easily remove the pins incase any further mods need doing, which it does.

With the pistons in its clear that the con rod lengths are all different after being resized, one looks to be .015 longer then the shortest.

#4 piston is sitting proud of the block deck and the shortest seems to be at almost zero deck so the piston heights will need to be matched so the compression is even in the cylinders.

I’ll make a deck bridge tool for my dial indicator and get some accurate measurements before disassembling the bottom end.

I’ll then make a fly cutting tool for the mill, and I’ll also make a jig to hold the pistons so I can fly cut them individually to suit.

Only issue them is that the piston balance will be out so I’ll need to re balance the pistons afterwards.

[FbSTDwagon]

Traditionally piston weight is removed from the bottom of the piston inside the skirts, considering I’ll be fly cutting the top of the pistons the weight will be removed above the height of the gudgeon pin.

I am thinking to match the top weight of the pistons I may need to machine under the crown on the remaining pistons to match the weights so the top of the piston weights will be similar.

Do you think going to that degree is necessary or shall I just take the easy access option and die grind weight from the bottom.

Would a piston with a lighter crown than the other make any difference?
Or as long as the overall weight of the pistons is the same in the end will be all that matters and sufficient?

[Errol62]

I’d be looking at getting my hands on some shorter rods, not machining pistons, I dunno…


FB ute fixer upper, EK van on rotisserie

[ardiesse]

Drew,

Piston height, con-rod length and engine balance are normally the preserve of engine shops. Measure everything first.

I'd be inclined to measure the length of the conrods themselves (edge of big-end bore to edge of small-end bore would be easiest), to see if there's any variation in the conrods. A second check - piston crown height - would be useful too.

Six-cylinder engines are fairly easy to get into balance. The reciprocating masses need to be equal, and the rotating masses also. Your pistons are pure reciprocating masses, so where the mass is removed from is of secondary importance, as long as you don't weaken them. The conrods are part reciprocating, and part rotating mass. They should weigh the same, but also have the same weight distribution: equal big-end weight when suspended from the small-end bore, and vice-versa.

But I'm concerned about the diference in piston height at TDC. The last thing you want is for the piston crowns to bash into accumulated carbon in the combustion chambers.

Rob

[Blacky]

Are they all over place or is it just one that varies ?

[Harv]

Sounds like they were a bit gung-ho when they ground the big-end mating faces prior to closing... removed more meat from some faces than others.

Suggest measuring as Rob suggests. If they rest of the dimensions are constant, and the only issue is that some big-end mating faces have had more meat removed than others, then get them to reclose and rehone the long ones until they are all flush with the deck. Perhaps easier than machining then balancing the slugs.

Cheers,
Harv

[EK283]

If pistons are all the same height then it’s a vote for correct Conrods from me as well.

Greg

[Errol62]

Conrods will need rebalancing after resizing.

Sent from my SM-G781B using Tapatalk

[FbSTDwagon]

I’d be looking at getting my hands on some shorter rods, not machining pistons, I dunno…


FB ute fixer upper, EK van on rotisserie

Definitely an option mate which I will keep in mind

[FbSTDwagon]

From Robs reply…

Piston height, con-rod length and engine balance are normally the preserve of engine shops. Measure everything first.

* Exactly why I got Southcotts to do the con rod resizing mate, I thought they would match them all up to be equal lengths

I'd be inclined to measure the length of the conrods themselves (edge of big-end bore to edge of small-end bore would be easiest), to see if there's any variation in the conrods. A second check - piston crown height - would be useful too.

* I will double check the con rod lengths when I dismantle the bottom end mate, the piston compression heights should all be bang on being new out of the box but yes I’ll double check this out too.

But I'm concerned about the diference in piston height at TDC. The last thing you want is for the piston crowns to bash into accumulated carbon in the combustion chambers.

* Exactly what I’m doing this measure up Rob, having the pistons above deck is not a concern as long it has adequate clearance.
HSD advise the max height above deck they do is .015” with a .045” head gasket. Which leaves .030” compression squish.

I am using on of Harvs late EJ style head gaskets which measures .060” thick, I’ll guesstimate no more than 10% gasket squish which will leave the gasket at .054” compressed thickness.

So even if the piston were .020” above deck there will be heaps of clearance, but when I get this issue sorted the pistons will all close to zero deck.

Which then leaves the next issue… with a zero deck why would I use a .060” head gasket?
All I’d be do is robbing my self of some compression, so after I get everything measured I may get a new gasket made up at .040” thick… but I’ll wait and see my findings first.

Rob

[FbSTDwagon]

Are they all over place or is it just one that varies ?

Making up a deck bridge tool as we speak, will have the exact figures soon mate, but at this point there Is clearly 1 piston about .015” higher than deck and another piston that is on deck.
The rest vary in between those 2 extremes but will know exact heights hopefully tomorrow.

[FbSTDwagon]

Sounds like they were a bit gung-ho when they ground the big-end mating faces prior to closing... removed more meat from some faces than others.

Suggest measuring as Rob suggests. If they rest of the dimensions are constant, and the only issue is that some big-end mating faces have had more meat removed than others, then get them to reclose and rehone the long ones until they are all flush with the deck. Perhaps easier than machining then balancing the slugs.

Cheers,
Harv

Harv I agree, I think this mob at Southcotts have been treating me like an idiot.
Every time I go in there I feel like I’m a hassle for them.
Bloody hell I am a paying customer but it’s like they don’t want the work.
Yes I’ll get the rods out and go and give them a gee up for good measure, they have definitely ballsed it up.

I would have thought when resizing rods they would make them all the same length.

[ardiesse]

Drew,

Would it be better to start with another set of conrods? I have a spare set, but they're FX (drilled up the rod for small-end lubrication).

Rob

[FbSTDwagon]

Drew,

Would it be better to start with another set of conrods? I have a spare set, but they're FX (drilled up the rod for small-end lubrication).

Rob

Rob i have thrown alot of money at these rods already so I’ll leave that to a last resort.
Next time I’ll just buy new rods.

[Harv]

I've got a set of later rods (splash-fed little end) if you need them. I pressed the big end bolts out and sent them to one of the FE/FC guys as his bolts had issues... his slipped the threads before meeting the 30ftlbs. Agree though that it would hurt starting afresh after the effort you have put into yours.

Conrods will need rebalancing after resizing.

Went back and looked at the photos - looks like grind marks on both the big and little ends (balanced).

Cheers,
Harv