340 PISTONS: Between a rock and a hard place

[Captainkirk]

OK; here's the deal:
Due to corrosion/pitting and a CR too high for pump gas, I'm being forced to re-think my position on the old TRW L-2322 forged pistons I was using. I would like to replace them with the TRW/Sealed Power L2316F forged flat-top, but here's the kicker: they only come in +.020, +.030, +.040 and +.060. My block is ready and prepped for 4.04. This leaves me several choices:
a) Bore my standard-bore block .020 over (not a good choice IMHO)
b) Install standard bore Keith Black hypereutectics (also not a good choice compared to forged)
c) Dip and prep my spare 340 block (which needs an overbore) and have it bored .020 over (more cash outlay for the hot tank, cam bearings and freeze plugs)

The ideal scenario would be to find a set of forged pistons that would fit a standard 4.04 bore but I haven't been able to locate any.

So, 2 questions for you builders out there in Mopar land...
1) Is there a decent standard forged piston out there for a reasonable price, and:
2) If not, which option would you choose, and why?

 

[fishy68]

Why do you feel boring your block isn't a good choice? IMO boring it will more than likely straighten out the cylinder walls promoting better ring seal

 

[RustyRatRod]

Run the domed pistons and quit bein a crybaby. lol

 

[Captainkirk]

Why do you feel boring your block isn't a good choice? IMO boring it will more than likely straighten out the cylinder walls promoting better ring seal

Mainly because you can't put metal back once you've removed it. Boring a standard block .020 over is the equivalent of about 80K of useful life. But I hear you on the straight bore issue. Really hadn't thought of that.

 

[72golddustermike]

got some new std L2316 pistons I will sale

 

[Captainkirk]

Run the domed pistons and quit bein a crybaby. lol

Honestly, Rusty...I would if, I could get around the CR issues. Tony cc'd the head again, the chamber volume is 67cc's which would put that piston at right around 12.5:1 as it sits (Criminy...no wonder it was such a little screamer!) Shaving the domes and/or cc'ing the heads a bunch more would likely cost half the price of a set of forged Sealed Powers or more. Plus, it would ruin those heads for any future use other than with domed pistons.

 

[72golddustermike]

they are TRW L2316 forged STD. Rings Included

 

[InItSwingIt]

IMHO...if you can kustify the expence to yourself in any way....2 is always better than one...wait untill you find pistons to do exactly what you want...or pick which will take the most and push out to as big abore as you can...cubez iz cubez...in the end, do what makes YOU happy...

 

[EL5DEMON340]

Your standard bore block is already prepped? are the bores straight ? no taper?

 

[Marcohotrod]

a-exactly what do the cylinders of the prepped block measure? most old blocks could use a bore + hone, and now it could be done with a honeing deck plate=better than factory. b-a K.B. hypereutectic is stronger and lighter than stock, and fine unless u are running big blower or nitrous. c-the L2316F was available in standard and is the equal weight as stock at 720 grams. the L2322F was lighter at 662 grams-was your engine rebalanced to match the L2322F pistons? d-how many miles do u plan on getting out of this block? go +.020 for 80,000 miles, and +.030 for another 80,000, and +.040 for 80,000 and +.060 for 80,000=320,000 miles

 

[RustyRatRod]

Honestly, Rusty...I would if, I could get around the CR issues. Tony cc'd the head again, the chamber volume is 67cc's which would put that piston at right around 12.5:1 as it sits (Criminy...no wonder it was such a little screamer!) Shaving the domes and/or cc'ing the heads a bunch more would likely cost half the price of a set of forged Sealed Powers or more. Plus, it would ruin those heads for any future use other than with domed pistons.

Then send um to me. I've always wanted to build a LOOSE high compression 340.

 

[RustyRatRod]

Your standard bore block is already prepped? are the bores straight ? no taper?

It's possible. My Ford 400 block cleaned up good with .0002" taper on the worst cylinder.

Forged pistons require more clearance.....especially the older ones. They swell up pretty good when they get hot. He might have good bores. Mine turned out fine.

 

[Captainkirk]

a-exactly what do the cylinders of the prepped block measure? most old blocks could use a bore + hone, and now it could be done with a honeing deck plate=better than factory.

True. I don't actually know the actual bore of the prepped block other than "standard". I guess I would need to mic it to see for sure.

b-a K.B. hypereutectic is stronger and lighter than stock, and fine unless u are running big blower or nitrous.

Yes, but arguably not as good as forged. There are still some sketchy report out there about KB's shattering...most but not all attributed to improper ring gap...but still a concern to me.

c-the L2316F was available in standard and is the equal weight as stock at 720 grams. the L2322F was lighter at 662 grams-was your engine rebalanced to match the L2322F pistons?

Yes. It will need to be re-balanced to run L2316s if I install them

d-how many miles do u plan on getting out of this block? go +.020 for 80,000 miles, and +.030 for another 80,000, and +.040 for 80,000 and +.060 for 80,000=320,000 miles

Yeah...LOL! Thought about it after I wrote it. I'll probably be lucky to ever get 10K on this thing if I ever finish it.

 

[Captainkirk]

a-exactly what do the cylinders of the prepped block measure? most old blocks could use a bore + hone, and now it could be done with a honeing deck plate=better than factory. b-a K.B. hypereutectic is stronger and lighter than stock, and fine unless u are running big blower or nitrous. c-the L2316F was available in standard and is the equal weight as stock at 720 grams. the L2322F was lighter at 662 grams-was your engine rebalanced to match the L2322F pistons? d-how many miles do u plan on getting out of this block? go +.020 for 80,000 miles, and +.030 for another 80,000, and +.040 for 80,000 and +.060 for 80,000=320,000 miles

Your standard bore block is already prepped? are the bores straight ? no taper?

Yes, been prepped and ready to build for 8 years now...LOL! The bores were given a clean bill of health at last prep by this same engine machine shop to run with STD pistons...but I don't have his actual figures from back then.
Time to drag out the mics, tee-gauges and the bore gauge.

 

[Marcohotrod]

so I would use the KBs at standard bore with standard rings gapped per KB instructions, which is more than average pistons, and probably where some who do not read instructions go wrong. and the KBs are probably very close in weight to the 662 gram units so rebalancing is not needed. years ago I rebuilt on old superstock 340 that had been rebalanced with L2322f 30 pistons, I was street and strip so was lowering compression with L2316f 30. Should I rebalance? called the old 340 guru Ed Hamburger, he said if the piston weights are within 10% no problem. did not rebalance, still runs great, thanks Ed.

 

[EL5DEMON340]

Ok the main thing for power is to have a straight bore, so ring gaps stay constant. I have three standard 340 blocks that look fine with no ridge. I hope I'm luck enough to be able to leave one standard with a hone job and run it!

 

[Captainkirk]

Ok the main thing for power is to have a straight bore, so ring gaps stay constant. I have three standard 340 blocks that look fine with no ridge. I hope I'm luck enough to be able to leave one standard with a hone job and run it!

....however, as was mentioned earlier, stock blocks were not bored using torque plates. Although I never had any trouble when running the 2232's. Didn't burn any oil at all.

 

[RustyRatRod]

Ok the main thing for power is to have a straight bore, so ring gaps stay constant. I have three standard 340 blocks that look fine with no ridge. I hope I'm luck enough to be able to leave one standard with a hone job and run it!

You probably can. Forged pistons require a bit more clearance anyway. I have run .010" piston to wall clearance before because that's what I HAD. The bores were straight, but big. One of the strongest running stock bore and stroke street motors I ever had and it didn't smoke and had good compression, because I file fit the rings. It did have some piston slap when cold. Sounded like a diesel but all that dropped out when it warmed up.

My motto is as long as they ain't got enough clearance to swap holes, run um. LOL

 

[perfacar]

hi, is the piston a hollow or solid dome?? either way both can be cut down. I cut a 2322 piston to stock pin height, according to TRW or speedpro, the dome can be safely removed.
which makes it a flat top style. there is a lot of meat left. also, don't worry about balancing it. it'll run just fine.

 

[340sFastback]

I would go .020" over and run the KB hypers. That way you can be sure bores are straight for maximum ring seal.

 

[oldkimmer]

........I have taken the domes off a few sets of pistons and not re-balanced because of cash shortages and they seemed fine, but the proper way is a rebalance........I just use an old farmer friend to mill the pistons ...how accurate he was is debateable...kim.....

 

[replicaracer43]

I would go .020" over and run the KB hypers. That way you can be sure bores are straight for maximum ring seal.

This is the best option, but option number 2 would be mill those domes off and reuse your old pistons in your old bores.

 

[MRL Performance]

Call Racetec and have them make you a set.

 

[Captainkirk]

I would go .020" over and run the KB hypers. That way you can be sure bores are straight for maximum ring seal.

If I was gonna bore it .020 over, why would I want to run the KBs when I can get forged SP's for around the same $$?

 

[Captainkirk]

Call Racetec and have them make you a set.

Never heard of Racetec. What sort of pricing/time delays are expected? Do they have a website?