Piston options for 3.80 stroke crank and 5.85 rods

[19COBRA93]

I'm in need of pistons, so I'm looking for piston options for a 3.80 stroke crank with the 5.85 rods. Compression needs to be around 9.5:1, but bore size can either be standard, or .020. They're for my '05, so they'll need to be notched for the 3v heads.

I've been running custom diamonds, but they took 6 weeks to come in. So I'm hoping for a good quality piston that's on the shelf, or reasonably available.

I melted the ring lands on the whole left bank, and the other 4 don't look much better so I'm replacing them all. I still haven't found the cause, but right now I just need to find pistons. So I'm hoping some of you engine guru's know of a more readily available piston than the customs I have.

 

[BruceH]

I'm in need of pistons, so I'm looking for piston options for a 3.80 stroke crank with the 5.85 rods. Compression needs to be around 9.5:1, but bore size can either be standard, or .020. They're for my '05, so they'll need to be notched for the 3v heads.

I've been running custom diamonds, but they took 6 weeks to come in. So I'm hoping for a good quality piston that's on the shelf, or reasonably available.

I melted the ring lands on the whole left bank, and the other 4 don't look much better so I'm replacing them all. I still haven't found the cause, but right now I just need to find pistons. So I'm hoping some of you engine guru's know of a more readily available piston than the customs I have.

What compression height does that combo need? Those are the same rod and stroke used on the jdm and brenspeed kits. IIRC jdm quoted me $799 for the manley pistons they use when I was recently contemplating a stroker. It gives stock compression and I think it came with rings.

I know modmax keeps some but I think the compression height is 1.200. That's too much for your parts, right?

 

[Dread53]

If somebody does make these in .020 I'll be interested. When I put mine together I tried to get away with a little extra clearance in one cylinder and I've got the resulting piston slap.

 

[19COBRA93]

What compression height does that combo need? Those are the same rod and stroke used on the jdm and brenspeed kits. IIRC jdm quoted me $799 for the manley pistons they use when I was recently contemplating a stroker. It gives stock compression and I think it came with rings.

I know modmax keeps some but I think the compression height is 1.200. That's too much for your parts, right?

1.187 is the compression height on my current Diamonds. 1.200 is too much if I remember right.

 

[MexGT]

uhmmm i'd look for the possible reason, cause even with new pistons it should repeat?

 

[BruceH]

I'm looking at a set of pistons I have and wondering why you couldn't mill a dished piston to get the proper compression height? We are talking about less than .040". There would still be plenty of material on the top and the diamond piston I'm measuring would still have .24 from the top of the piston to the top ringland after milling.

I must be missing something here.

 

[lito]

I wouldn't do that, you will loose dish, loose crown and raise the compression ring.

Someone has to have a set of CP's or Manley's the Saleen rotating assembly that Brenspeed and JDM came with.

And I would sincerely look at what may had happened there.

 

[TexasBlownV8]

Im using cp 2618 pistons with a 3.8 crank; 9.4:1. stock bore.

 

[19COBRA93]

uhmmm i'd look for the possible reason, cause even with new pistons it should repeat?

I'm changing my whole setup, so everything will be gone through, and hopefully the cause will be found.

I'm looking at a set of pistons I have and wondering why you couldn't mill a dished piston to get the proper compression height? We are talking about less than .040". There would still be plenty of material on the top and the diamond piston I'm measuring would still have .24 from the top of the piston to the top ringland after milling.

I must be missing something here.

There's no reason I should have to buy a set of pistons and then have them machined. The cost alone would make it completely unreasonable.

I wouldn't do that, you will loose dish, loose crown and raise the compression ring.

Someone has to have a set of CP's or Manley's the Saleen rotating assembly that Brenspeed and JDM came with.

And I would sincerely look at what may had happened there.

I have a few theories as to the cause. Remember not long ago I mentioned to you my car threw 4 misfire codes for the whole left bank? This is the result of that. Or rather, that was the result of this. I'm having my injectors flowed, checking all gaskets, intake, etc, and I'm going over the engine harness with a fine tooth comb.

Im using cp 2618 pistons with a 3.8 crank; 9.4:1. stock bore.

Good to know. CP's aren't my favorite with this stroke. They shrink the ring lands to keep the piston pin from intercepting the oil rings. That's the problem with this stroke, you either get skinny ring lands, or it pushes the pin up into the oil rings.

With a good tune though the CP's should be more than fine, and I can work with 9.8:1 compression.