I'm using him for my 5.9 build. Personal recommendations carry a lot of weight with me, and Greg speaks highly of Rick's work.
The 360 build that has more turns than Willow Springs
- Thread starter Kern Dog
- Start date
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Here is a new consideration:
I'll need new pistons for this 360, likely going from the .020 to .030.
Tomorrow I'm helping the FABO member @RBConvert pull the MP 360/380 from his '68 Dart. If the teardown show the engine to have pistons that are .030 over, what are the chances of those pistons working in the 360? I know that the deck heights of the LA series is supposed to be .019" taller than the Magnum series. The use of these in an LA would probably be a difference of half a point. The crate engines were supposed to be just over 9.0 to 1. A thinner head gasket could make up for some of that difference in deck height.
1990 DODGE Cometic C5633-027 Cometic MLS Head Gaskets
1990 DODGE Mr. Gasket 1121G Mr. Gasket Head Gaskets | Summit Racing
It would be nice to save the money and just reuse the Magnum pistons. I'm not looking to set speed records with this engine. I had planned on keeping compression closer to 9 to one anyway. I didn't want to be obligated to using premium gas all the time.
Does anyone have some feedback to this idea?
I'll need new pistons for this 360, likely going from the .020 to .030.
Tomorrow I'm helping the FABO member @RBConvert pull the MP 360/380 from his '68 Dart. If the teardown show the engine to have pistons that are .030 over, what are the chances of those pistons working in the 360? I know that the deck heights of the LA series is supposed to be .019" taller than the Magnum series. The use of these in an LA would probably be a difference of half a point. The crate engines were supposed to be just over 9.0 to 1. A thinner head gasket could make up for some of that difference in deck height.
1990 DODGE Cometic C5633-027 Cometic MLS Head Gaskets
1990 DODGE Mr. Gasket 1121G Mr. Gasket Head Gaskets | Summit Racing
It would be nice to save the money and just reuse the Magnum pistons. I'm not looking to set speed records with this engine. I had planned on keeping compression closer to 9 to one anyway. I didn't want to be obligated to using premium gas all the time.
Does anyone have some feedback to this idea?
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Those are what was in this engine:
All the pistons look about the same. Some carbon but it cleans off with solvent and a Scotch Brite. I was hoping that I could reuse these but a few cylinders need to be bored just to clean up the rust pits. I may keep these for a future build of another engine.
I go back and forth with every big decision and piston choice is yet another one of those. If using those Magnum based pistons means compression drops to 8.5 to 1 or lower, I'd skip the idea of using them.
The piston deck oppo the stamped one shows detonation alley, that's what it looks like, & that's what's killing the gaskets. You're makin' the right call on the new piston choice, You can work the tune & avoid it, but You'll be able to make plenty of oats w/less squeeze/headaches.
Do you mean right here?
I didn't rub my fingers on that but you may be right if you think detonation was occurring there. I'm not sure though. The piston is upside down in this picture. Water sat in a few cylinders so that could be stains from that.
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I just went out to look at a few of the pistons. What I saw was discoloration but I can’t feel any pitting. I’m not dismissing the possibility of detonation damage, I’ll need to look closer. Water did sit in a few cylinders so at some point, aluminum stuff tends to change color and texture as a result. This engine had been sitting for 2-3 years (covered) in a region that gets light snow so I expected some cleanup would be part of the deal.
I’ll get a closer look tomorrow. Thank you.
I’ll get a closer look tomorrow. Thank you.
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May be cell-phone photo illusion, making it look that way, but........
mopowers
Well-Known Member
Is there a meaningful weight difference in the magnum pistons? That may be another consideration with respect to the balance.
Stock, the magnum pistons and pins are about 134 grams lighter than the LA's. The rings are lighter too. But with the aftermarket pistons installed, the weight difference is probably closer. It will be interesting to weigh them after tearing down the 5.9.
Otherwise, the magnum and LA pistons have the same general dimensions. The assembly will have to be re-balanced.
mopowers
Well-Known Member
Maybe consider a set of these: https://www.summitracing.com/parts/slp-h405cp30?srsltid=AfmBOoqHKuGfPWx4GBWh1urvrrEpY6lupP7a-JqmdO1nx40ClRW4W4L7
Relatively inexpensive (cheaper than a re-balance) and the weight should be "close enough" to not have to re-balance the assembly. Not sure where the compression ratio would land though.
Relatively inexpensive (cheaper than a re-balance) and the weight should be "close enough" to not have to re-balance the assembly. Not sure where the compression ratio would land though.
It is my nature to look at ways to spend as wisely as I can but sometimes that works against me. I may be better off just cracking open the wallet.
The last engine that I balanced cost me $350 to do it. If the Magnum 5.9 pistons weighed less and provided only around 8.5 compression, that would be a crappy way to go. I don't know how they'd balance that without adding weight which can get expensive. I'd have more money tied up while having compression lower than I'd want.
The Speed Pro dished pistons would get me around 9.0 to 1 and might weigh close enough to just install as is.
The last engine that I balanced cost me $350 to do it. If the Magnum 5.9 pistons weighed less and provided only around 8.5 compression, that would be a crappy way to go. I don't know how they'd balance that without adding weight which can get expensive. I'd have more money tied up while having compression lower than I'd want.
The Speed Pro dished pistons would get me around 9.0 to 1 and might weigh close enough to just install as is.
skep419
5.9 Magnum 4 speed afficionado
Could just start with a different engine and leave the bottom end alone.......
I could. A junkyard engine may be okay but I already have this ‘90 360 here. There is no urgency to this. The Darts are hobby cars, not daily transportation. I’ll probably go ahead with the new pistons.
skep419
5.9 Magnum 4 speed afficionado
The reason I'm always pushing the junkyard/stock long block is I had nothing but problems with my "built" engine. There's just a lot more to go wrong when you have to bore the block, balance the rotating assembly and rely on new aftermarket parts. Best of luck on whatever direction you choose!
Keepers for an LA360. Wish they were .030. I would gladly take them off of your hands since you need .030.
Those speed pro pistons were out of the MP crate engine? Had it been apart since bought from MP or is that what MP put into them?
The MP engine was 9:1 with those in it? I thought magnums were 9:1 with the stock dished pistons?
Some of what you're asking i asked about using some not very used Speed pros out of an LA into a magnum not long ago. Different number on the ones I was asking about though
The MP engine was 9:1 with those in it? I thought magnums were 9:1 with the stock dished pistons?
Some of what you're asking i asked about using some not very used Speed pros out of an LA into a magnum not long ago. Different number on the ones I was asking about though
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Me and Rich will be pulling out the MP crate engine that has been in his 68 Dart for many, many years. It is still together and in the car.
Every picture that I have shown is the 1990 360 that I bought from another friend a few months back. We are building engines here in the shop at about the same time. We almost traded engines to help speed up the process for him.
Every picture that I have shown is the 1990 360 that I bought from another friend a few months back. We are building engines here in the shop at about the same time. We almost traded engines to help speed up the process for him.
The machinist bored the engine to .028 over to see if the rust pits in the cylinders would clean up. They are still there in 2 cylinders so this will go .040 over.
I'm okay with that.
Now, onto piston selection. That is another thing to deal with.
I don't want to deal with a compression ratio so high that I am obligated to use Premium fuel all the time. Most of the cars out back sit for weeks, sometimes months and with the way that our California gas goes bad so quickly, I don't want the car to run like crap until I burn all the crappy gas out. Keep in mind, we only have 91 octane premium here.
The Speed Pro pistons that were in the engine were flat tops with 5 cc valve reliefs. The compression height was 1.660". Assuming the deck clearance was .010, this put me at over 10.5 to 1 with these #308 iron heads. I do not want to be that high with an iron head.
Speed Pro also has pistons with an 18 cc dish that drop the compression ratio by about 1.3 points. This will put the CR around 9.2 if the deck clearance is around .010.
The thing with that is, the popular Keith Black 107 piston has a compression height of 1.675. That extra .015 will make a difference in the compression ratio. This makes me wonder where the Speed Pro and the KB pistons actually DO end up at TDC.
I can only assume that you'd have to mock up a piston & rod in a block with the crank in place to actually know what to expect for deck clearance.
I'm okay with that.
Now, onto piston selection. That is another thing to deal with.
I don't want to deal with a compression ratio so high that I am obligated to use Premium fuel all the time. Most of the cars out back sit for weeks, sometimes months and with the way that our California gas goes bad so quickly, I don't want the car to run like crap until I burn all the crappy gas out. Keep in mind, we only have 91 octane premium here.
The Speed Pro pistons that were in the engine were flat tops with 5 cc valve reliefs. The compression height was 1.660". Assuming the deck clearance was .010, this put me at over 10.5 to 1 with these #308 iron heads. I do not want to be that high with an iron head.
Speed Pro also has pistons with an 18 cc dish that drop the compression ratio by about 1.3 points. This will put the CR around 9.2 if the deck clearance is around .010.
The thing with that is, the popular Keith Black 107 piston has a compression height of 1.675. That extra .015 will make a difference in the compression ratio. This makes me wonder where the Speed Pro and the KB pistons actually DO end up at TDC.
I can only assume that you'd have to mock up a piston & rod in a block with the crank in place to actually know what to expect for deck clearance.
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Nice thing about the 116-CP is that many here have used (not me) them and balancing was not required. Very close to factory weight. Perhaps a thicker head gasket?
I have some fel pro SB marine head gaskets I was thinking about using in my build. I got them off of eBay for what I thought was a decent price. As it turns out I punched the number on rock Auto and if it weren't for their shipping I'd have been cheaper to get them there, but they didn't come up by year make model lookup.
Damn another AD just completely blocked this window twice while I was creating it.
Damn another AD just completely blocked this window twice while I was creating it.
I have to check with Summit to see about their return policy on pistons. I'd like my machinist to do a mock up to see where they land at TDC to know where the compression ratio will be.
If I were using aluminum heads, I'd feel more comfortable with running a CR in the mid 10s.
If I were using aluminum heads, I'd feel more comfortable with running a CR in the mid 10s.
Today I did speak with a rep from Summit.
It seems like there should be an easier way to do this but whatever it is, I don't know of it.
My dilemma? I'm trying to aim for a compression ratio between 9.0 and 9.5 to 1 since I have iron heads, use California gas and don't want to be stuck using premium gas all the time. This engine will go in this car:
I may do the body and paint on it someday, I might not.
Currently, it has a strong running stock bore 360 that runs fine on 87 octane gas. I'm pulling the engine to use in another car. This roller 360 will be more powerful but I don't want to go bonkers with it.
Aiming for a specific and narrow compression ratio isn't easy. The # 308 heads are rumored to have combustion chambers between 65 and 72 ccs.
I didn't measure the deck clearance of the old pistons...
....But they have a published compression height of 1.660". I thought of using replacements of the same brand, just at .040 since the rusty bores will need another .020 to clean up the pitted areas.
My machinist thinks that to get an accurate deck height number, he has to mock up a piston and rod in cylinders 1-2 and 7-8. He also does this to see if the decks are square. To mock up, the piston pin gets pressed into a rod.
I thought that there is a way to mathematically determine what the deck clearance is by adding up the rod length, stroke and compression height but that only works IF the decks are stock and UNcut. This engine was rebuilt before so who knows how much was surfaced from the decks.
The Summit rep thought that a return on a set of pistons are likely a NO if any of them were pressed into a rod and mocked up.
I understand that but it still leaves me in a spot.
Again, there are variables in play so it is hard to pin down where the compression will end up when the combustion chambers could be between 65 and 72 ccs. The deck clearance could be between .010 and .020. There are some fixed numbers...bore, stroke, then these Speed Pro pistons have 5 cc valve relief pockets.
I used the Summit Racing compression calculator using a range of combustion chamber sizes, deck clearances and two head gasket thicknesses.
I calculated between 10.32 and 9.09 to 1.
The high number is over a point above what I'd want. The lowest number assumes a 72 cc chamber, pistons .020 below deck and a .051 head gasket.
It seems like there should be an easier way to do this but whatever it is, I don't know of it.
My dilemma? I'm trying to aim for a compression ratio between 9.0 and 9.5 to 1 since I have iron heads, use California gas and don't want to be stuck using premium gas all the time. This engine will go in this car:
I may do the body and paint on it someday, I might not.
Currently, it has a strong running stock bore 360 that runs fine on 87 octane gas. I'm pulling the engine to use in another car. This roller 360 will be more powerful but I don't want to go bonkers with it.
Aiming for a specific and narrow compression ratio isn't easy. The # 308 heads are rumored to have combustion chambers between 65 and 72 ccs.
I didn't measure the deck clearance of the old pistons...
....But they have a published compression height of 1.660". I thought of using replacements of the same brand, just at .040 since the rusty bores will need another .020 to clean up the pitted areas.
My machinist thinks that to get an accurate deck height number, he has to mock up a piston and rod in cylinders 1-2 and 7-8. He also does this to see if the decks are square. To mock up, the piston pin gets pressed into a rod.
I thought that there is a way to mathematically determine what the deck clearance is by adding up the rod length, stroke and compression height but that only works IF the decks are stock and UNcut. This engine was rebuilt before so who knows how much was surfaced from the decks.
The Summit rep thought that a return on a set of pistons are likely a NO if any of them were pressed into a rod and mocked up.
I understand that but it still leaves me in a spot.
Again, there are variables in play so it is hard to pin down where the compression will end up when the combustion chambers could be between 65 and 72 ccs. The deck clearance could be between .010 and .020. There are some fixed numbers...bore, stroke, then these Speed Pro pistons have 5 cc valve relief pockets.
I used the Summit Racing compression calculator using a range of combustion chamber sizes, deck clearances and two head gasket thicknesses.
I calculated between 10.32 and 9.09 to 1.
The high number is over a point above what I'd want. The lowest number assumes a 72 cc chamber, pistons .020 below deck and a .051 head gasket.
I've read about the Keith Black dished pistons....
DODGE KB KB232.040 KB Performance Pistons | Summit Racing
These have a .015 taller compression height than the pistons I took out, but they also have an 18 cc dish. Doing the math before, this 18 cc dish makes a 1.3 point difference in compression. If the KB 107s delivered 10.5 to 1, these 232s would be 9.2....not too bad, huh?
Maybe it wouldn't be so terrible to err on the side of caution. I can get head gaskets between .027 to .75 to get the compression in the range I want.
DODGE KB KB232.040 KB Performance Pistons | Summit Racing
These have a .015 taller compression height than the pistons I took out, but they also have an 18 cc dish. Doing the math before, this 18 cc dish makes a 1.3 point difference in compression. If the KB 107s delivered 10.5 to 1, these 232s would be 9.2....not too bad, huh?
Maybe it wouldn't be so terrible to err on the side of caution. I can get head gaskets between .027 to .75 to get the compression in the range I want.
Before Rick gets too far on the heads, have him install the valves in one of the combustion chambers and you take the head home to measure the volume.
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