1971 340 Build - Choosing piston rings dilemma

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70Hardtop

70Hardtop

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Hi all from Perth W.A., I have not posted a question for a while although I have spent many hours sifting through posts about 340 builds and pistons and rings and more...

I am collecting parts for the build of a 1971 340 - it's all machined up ready for assembly (although the cast 1.88" int. heads might yet get some port work). I have a set of new KB Hypers 107 (0.070 over) to suit the block's 30 over rebore. But now looking for rings. I want a step up from the OEM cast type rings but it's not a high budget race engine so the in-between I guess are moly rings. Need to be 5/64, 5/64 and 3/16 for the oil control rings

Many of you guys have decades of experience in Mopar engine building...so my question is: As with many other things in life, is it a case of "you get what you pay for" with rings? Or does the name have a lot to do with the price ... Hastings rings prices are all over the place - even for their Premium Moly range. How do Speedpro Moly rings for $85 compare in quality to Total Seal at $116 ? Speed Pro are Sealed Power which are a Federal Mogul company. Then there is Summit Racing, some of their ring sets are not cheap - are they all made in China? I looked at Mahle Original ring sets but for this size bore, their second ring is different to their top ring, Weird! (5/64 and 3/32). Perfect Circle are same as Mahle I think. Then there's Howards, Ross etc

Are these companies all making their own rings or do they all buy generic rings from a couple of manufacturers and put them in their own box with their own advertising?

Also is "Plasma Moly" and just "Moly" the same thing, or is Plasma Moly better?

Lots of questions (maybe too many for one post!?!), hoping for some guys who have knowledge and had experience with different brands of Moly ring sets for the common KB Hypereutectics.

Thanks.
 
70Hardtop said:
Hi all from Perth W.A., I have not posted a question for a while although I have spent many hours sifting through posts about 340 builds and pistons and rings and more...

I am collecting parts for the build of a 1971 340 - it's all machined up ready for assembly (although the cast 1.88" int. heads might yet get some port work). I have a set of new KB Hypers 107 (0.070 over) to suit the block's 30 over rebore. But now looking for rings. I want a step up from the OEM cast type rings but it's not a high budget race engine so the in-between I guess are moly rings. Need to be 5/64, 5/64 and 3/16 for the oil control rings

Many of you guys have decades of experience in Mopar engine building...so my question is: As with many other things in life, is it a case of "you get what you pay for" with rings? Or does the name have a lot to do with the price ... Hastings rings prices are all over the place - even for their Premium Moly range. How do Speedpro Moly rings for $85 compare in quality to Total Seal at $116 ? Speed Pro are Sealed Power which are a Federal Mogul company. Then there is Summit Racing, some of their ring sets are not cheap - are they all made in China? I looked at Mahle Original ring sets but for this size bore, their second ring is different to their top ring, Weird! (5/64 and 3/32). Perfect Circle are same as Mahle I think. Then there's Howards, Ross etc

Are these companies all making their own rings or do they all buy generic rings from a couple of manufacturers and put them in their own box with their own advertising?

Also is "Plasma Moly" and just "Moly" the same thing, or is Plasma Moly better?

Lots of questions (maybe too many for one post!?!), hoping for some guys who have knowledge and had experience with different brands of Moly ring sets for the common KB Hypereutectics.

Thanks.
Click to expand...


I like the mancini Racing engine "kits"... Kits A & B are basic lower end refresh with kit A has cast iron rings, and kit B has moly rings for $200 - $230 which includes main and rod bearings, rings, and a complete gasket kit...

Kits C & D come with main and rod bearings, rings, and a complete gasket kit, pistons, oil pump, hardware kit (freeze plugs)... Kit C has cast pistons, kit D has forged pistons... All kits are either Federal Mogul or Clevite parts, I like the Federal Mogul ones myself, but either one is good.

Here's the main engine kit page...

https://www.manciniracing.com/enrebkit.html


Here's the federal mogul kit B that I would recommend for you...

Sealed Power Engine Kit - "B"
 
krazykuda said:
I like the mancini Racing engine "kits"... Kits A & B are basic ....
Click to expand...

Thanks for the reply and the links. However I don't need those things, I already have several gasket kits, TC seal, the bearings, The KB pistons, engine freeze plugs, TChain etc. It's just the rings and conrods I need now.
 
70Hardtop said:
Thanks for the reply and the links. However I don't need those things, I already have several gasket kits, TC seal, the bearings, The KB pistons, engine freeze plugs, TChain etc. It's just the rings and conrods I need now.
Click to expand...


I've had good results with speed pro/sealed power rings...

As far as con rods, I like to buy new bolts and have the stock ones reconditioned... Stock rods have oil squirt holes that oil the bore opposite to it... Some of the new aftermarket rods do not... I like squirt holes in my rods to help keep the bores oiled... If there is too much oil on the bore, the oil ring will take care of that... If you don't have enough oil on the bores, you do more wear and damage to the rings, pistons, and bores... I prefer to error on the side of too much oil vs not enough...
 
70Hardtop said:
Hi all from Perth W.A., I have not posted a question for a while although I have spent many hours sifting through posts about 340 builds and pistons and rings and more...

I am collecting parts for the build of a 1971 340 - it's all machined up ready for assembly (although the cast 1.88" int. heads might yet get some port work).
Click to expand...


A 71 340 should have 2.02" intake valves... That was the last year for the 2.02" valves...

72 & 73 the 340 got 1.88" intake valves
 
I think Mahle or Hastings bought up several ring companys.
I use both and seal power moly rings. For the few dollars more I run the molys.
I'm not talking about the old chrome bore your block out with each rpm type.
 
Sealed power single moly or Speed pro single moly plasma, either is a good choice. Be aware a different bore finish is required for moly rings than required for cast rings.
 
krazykuda said:
I've had good results with speed pro/sealed power rings... As far as con rods, I like to buy new bolts and have the stock ones reconditioned... Stock rods have oil squirt holes that oil the bore opposite to it... Some of the new aftermarket rods do not... I like squirt holes in my rods to help keep the bores oiled... If there is too much oil on the bore, the oil ring will take care of that... If you don't have enough oil on the bores, you do more wear and damage to the rings, pistons, and bores... I prefer to error on the side of too much oil vs not enough...
Click to expand...
.

Yes I agree with you there. I much prefer the OEM stuff made in America or Canada in the 70s to chinese made stuff in my cars. Even if it is strictly monitored by an American company. However there is no denying that there are many thousands of happy customers with SCAT rods in their engines and many turning high RPMs too. The oil hole is a very good point. However there is one main thing going against me using the original rods. Like an idiot, I think I sold them. I looked through my records and I sold some 340 rods, possibly from this engine, since I can't find them. I don't know what was going through my head, and only $50 too (Aust dollars), what a fool. This was back 10 years ago. I bought this engine back in 2009, complete engine, and it was a bargain at $1000 (about $650 US$) even though it was seized, but only one bore was responsible and the block cleaned up nice at 030. That leads me to the rods again... I have a set of low mile 273 rods I was considering (they are all bushed as you know) ... And before anyone laughs - I was getting new ARP bolts of course but also was going to get them cryo treated; there's a place in Sydney with a cryogenic facility and does a lot of drag racer's parts in there he says. Each cycle takes about 6 days for the full cycle: slow lowering, the retention and the ultra slow bringing back to room temperature. Which means that the rods will be as strong, or even stronger, than when they left the factory. Also this engine is only a mild engine, not more than 350-370HP I'd guess. However I would still be a bit reluctant to use 273 rods! Knowing that that's what they are.
 
krazykuda said:
A 71 340 should have 2.02" intake valves... That was the last year for the 2.02" valves...

72 & 73 the 340 got 1.88" intake valves
Click to expand...
Ok thanks, I was wondering about that. What a pity. As I said in the last reply, I got the engine for a bargain A$1000 (340 engines are very rare in Aust) and not sure of it's history but I do know this engine came out of a 71 340 Duster. Not sure why he sold it as he had a Duster in his garage. My 73 Rally Challenger has 1968 340 engine with the 2.02 X heads. So I'm happy with this smaller valve engine, I'm not sure when or where I'll be using it yet anyway.
 
70Hardtop said:
.

Yes I agree with you there. I much prefer the OEM stuff made in America or Canada in the 70s to chinese made stuff in my cars. Even if it is strictly monitored by an American company. However there is no denying that there are many thousands of happy customers with SCAT rods in their engines and many turning high RPMs too. The oil hole is a very good point. However there is one main thing going against me using the original rods. Like an idiot, I think I sold them. I looked through my records and I sold some 340 rods, possibly from this engine, since I can't find them. I don't know what was going through my head, and only $50 too (Aust dollars), what a fool. This was back 10 years ago. I bought this engine back in 2009, complete engine, and it was a bargain at $1000 (about $650 US$) even though it was seized, but only one bore was responsible and the block cleaned up nice at 030. That leads me to the rods again... I have a set of low mile 273 rods I was considering (they are all bushed as you know) ... And before anyone laughs - I was getting new ARP bolts of course but also was going to get them cryo treated; there's a place in Sydney with a cryogenic facility and does a lot of drag racer's parts in there he says. Each cycle takes about 6 days for the full cycle: slow lowering, the retention and the ultra slow bringing back to room temperature. Which means that the rods will be as strong, or even stronger, than when they left the factory. Also this engine is only a mild engine, not more than 350-370HP I'd guess. However I would still be a bit reluctant to use 273 rods! Knowing that that's what they are.
Click to expand...


273 rods are lighter than the 340 rods and you may have to get it balanced to compensate for the weight difference...

You can keep an eye on the mechanical for sale forum on here to see when a set of 340 rods are posted...
 
70Hardtop said:
Ok thanks, I was wondering about that. What a pity. As I said in the last reply, I got the engine for a bargain A$1000 (340 engines are very rare in Aust) and not sure of it's history but I do know this engine came out of a 71 340 Duster. Not sure why he sold it as he had a Duster in his garage. My 73 Rally Challenger has 1968 340 engine with the 2.02 X heads. So I'm happy with this smaller valve engine, I'm not sure when or where I'll be using it yet anyway.
Click to expand...


You can always have the intake valves opened up to 2.02" from the 1.88"... Most head guys can do that easy...
 
Jadaharabi said:
I think Mahle or Hastings bought up several ring companys.
I use both and seal power moly rings. For the few dollars more I run the molys.
I'm not talking about the old chrome bore your block out with each rpm type.
Click to expand...

The rings I get will definitely be moly but what I was wondering was what is the difference between a Hastings Moly set for $95 and a Ross racing Moly set or JP Pistons ring set for $300 ? And what is the difference between Plasma Moly and just Moly - is it all just voodoo naming, because we all know how companies tart up their products with various names and claims when often they are the pretty much the same as their competition.
 
krazykuda said:
273 rods are lighter than the 340 rods and you may have to get it balanced to compensate for the weight difference...

You can keep an eye on the mechanical for sale forum on here to see when a set of 340 rods are posted...
Click to expand...

Yes I had considered the need for a balance - but wouldn't I have to do that anyway with the lighter SCAT or Eagle brand rods? The OEM 340 rods are on the heavy side. The classified ads on this forum is a good idea. But I need to get this engine done sooner rather than later and also with the shipping cost plus the cost of getting them redone (crack tested, resized, honed and new bolts) they will be more costly than a new set, even though I would prefer OEM rods in it.
 
krazykuda said:
You can always have the intake valves opened up to 2.02" from the 1.88"... Most head guys can do that easy...
Click to expand...
Yeah that's true... I will ask my machine shop what that will cost. I have got the new stainless exh valves but not inlet valves yet. But then need to really open up the ports on the heads don't I? My next stop on this forum was looking at the Sticky Porting How-To posts.
 
raymond said:
Sealed power single moly or Speed pro single moly plasma, either is a good choice. Be aware a different bore finish is required for moly rings than required for cast rings.
Click to expand...
Ta for that, didn't realise about the bore hone - I'll ask the machine shop about that as they did this engine bore work. What is the difference anyway?

Sealed Power and Speed Pro are the same company (even their logo is virtually identical), just marketing products under different labels, like laundry detergent manufacturers do... They come under the massive Federal Mogul umbrella which have been around since before the First World War I think. And Fed Mog in turn are owned by Tenneco. So it would be interesting to get all the piston rings manufacturers and go up the chain and see just who owns who. Might be interesting.
 
I've got to ask a dumb question about the pistons? Will the KB107's that are designed to work with the 3.58 stroke of the 360 motor not come way too far out of the hole using the 340 crank, which as 3.31 stroke? I know this has nothing to do with the rings that the OP is asking about, and maybe I missed something. Just worried about the OP getting an unwelcome surprise after assembly! :eek:
 
Well spotted JD, I did not even realise this, I just checked and yes they are a 360 piston. Thanks for picking that up, :thumbsup: I must have ordered the wrong ones years ago, or else Summit sent me the wrong ones. But I'm surprised that they are so well priced, as surely there wouldn't be many people boring out a 360 to +0.070 ? So I thought they would be more expensive due to limited demand.

Anyway that's a frustration as now I have to fork out another $450 for pistons and try to sell these but don't like my chances on many people wanting this large bore size. Anyone know what a stock 360 block can be comfortably bored to? I suppose it depends on the year and casting thickness.
 
70Hardtop said:
Well spotted JD, I did not even realise this, I just checked and yes they are a 360 piston. Thanks for picking that up, :thumbsup: I must have ordered the wrong ones years ago, or else Summit sent me the wrong ones. But I'm surprised that they are so well priced, as surely there wouldn't be many people boring out a 360 to +0.070 ? So I thought they would be more expensive due to limited demand.

Anyway that's a frustration as now I have to fork out another $450 for pistons and try to sell these but don't like my chances on many people wanting this large bore size. Anyone know what a stock 360 block can be comfortably bored to? I suppose it depends on the year and casting thickness.
Click to expand...

Get a 3.58 stroke crank with a 340 main bearing size and stroke that 340 out.
 
Glad to help, even though I'm sure you're disappointed to have to hunt more pistons. KB243's are what I have bought for a future 340 build. You could do like @Jadaharabi suggested and get another crank. If you can find one in your area, you can get a 360 LA crank, and have the mains turned down to 318/340 size....have it balanced and use it to make your 340 a 372ish CI motor. I asked my machinist about doing this with a 360 crank in a 318, and he said sure, no problem. He said he would also turn the counterweights down to make it internal balance. He built a 360 a while back for a 4WD truck, and did the balance like that so the guy didn't have to buy a new flywheel. I watched it make 380 HP on the dyno, so I wouldn't be afraid of doing it. Just for kicks, and to maybe show the difference....take one of your KB 107's and one of your stock 340 pistons, and slide them onto a wrist pin side by side, and take a pic to show the difference in pin to crown height of the 2 pistons. It would be interesting to see the difference. Sorry you have to get new pistons or fool with the crank, but I'm glad it was caught now instead of later.
 
My block is a 76 360. I was hesitant to go .060 over with it because I had read that the later blocks were not as thick as the older ones. But my machinist told it was plenty thick enough. So I went with it. I guess time will tell. If the walls blow out ill let yall know haha.
 
Jadaharabi said:
Get a 3.58 stroke crank with a 340 main bearing size and stroke that 340 out.
Click to expand...
Yeah that was an option going through my head when I was thinking about it. But I want to keep it as a 340 with it's freshly machined forged crank. 340's over here are pretty rare and it's worth more and more accepted in it's original form. We have heaps of 318s and 360s so I would most likely follow that course with one of those engines, but not a 340.
 
dartfreak75 said:
My block is a 76 360. I was hesitant to go .060 over with it because I had read that the later blocks were not as thick as the older ones. But my machinist told it was plenty thick enough. So I went with it. I guess time will tell. If the walls blow out ill let yall know haha.
Click to expand...
Interesting... that was about the limit I was thinking of too. 360 engines are very popular here so it will be interesting to see if they sell or not. But compared to the US market for Mopar engine stuff, our market (supply and demand) is tiny.
 
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