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Engine Rebuild Part 2

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  #691  
Old 01-12-2018, 04:01 PM
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Originally Posted by mwm4.2tdi View Post
?? dont these run v8 pistons,size.
Hey mwm,
Welcome to the forums.

I saw your question here and and on my other post about the Holley 465. Your comments/questions are disjointed and hard to understand. A few moments to write out complete sentences really helps with communicating when all we have is text.


The 300 uses a different piston than the v8s. The 300, 302, and 351 all use a 4 inch bore, but the v8s use a different wrist pin diameter than most 300s (except the early ones), so they don't easily fit. I purchased early era connecting rods so I could use 351 pistons and raise my compression.
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  #692  
Old 01-12-2018, 04:30 PM
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Originally Posted by AbandonedBronco View Post


The 300 uses a different piston than the v8s. The 300, 302, and 351 all use a 4 inch bore, but the v8s use a different wrist pin diameter than most 300s (except the early ones), so they don't easily fit. I purchased early era connecting rods so I could use 351 pistons and raise my compression.
Just to add to your answer. If you run 351W pistons you also have to make sure you get ones without offset piston pins. The KB's I went with don't have the offset pins.

And to reply to his statement in your other thread. I would stay away from flat top pistons. A correct compression height flat top piston will raise the compression too much for pump gas. You'll want a dished piston. You just get your desired compression ratio by sizing the dish size to work with the rest of your engine combo.
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  #693  
Old 01-12-2018, 04:36 PM
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Agreed. Also, every flat top piston I looked into did one of two things. It either actually LOWERED compression (usually around 7:1), or it kept it around the same and decreased the squish distance since the top of the piston had to be lower. Either way, I saw no benefit.

And yeah, they need to be offset, as well has having the compression height checked and matched to the build.
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  #694  
Old 01-12-2018, 04:58 PM
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Originally Posted by AbandonedBronco View Post
Agreed. Also, every flat top piston I looked into did one of two things. It either actually LOWERED compression (usually around 7:1), or it kept it around the same and decreased the squish distance since the top of the piston had to be lower. Either way, I saw no benefit.

And yeah, they need to be offset, as well has having the compression height checked and matched to the build.
Yea that's why I said with the correct compression height. And if you go with those stock style flat tops you get very little quench.

I think you meant no offset or 0 offset.

Summit racing should just offer a kit that has everything you used in your build! They have the lame kit that was on the Powernation tv show. They need a kit for a real build!
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  #695  
Old 01-12-2018, 05:21 PM
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Heh, I missed you said "no offset". I used offset pins in mine.
I'd read good things about the benefits, such as reduced noise and less stress on the connecting rod (since it isn't pressed straight down on cylinder fire), with no real detriment. Why do you say to have none?
Just be sure they're installed the correct direction. Mine had little arrows that pointed them the right way.

I would have a blast putting together an off-the-shelf performance kit for the 300. Sales would probably be small though. I remember hearing that Powernation build was mostly just what was already available, and nothing fancy, something's needed.
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  #696  
Old 01-12-2018, 06:09 PM
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Originally Posted by AbandonedBronco View Post
Heh, I missed you said "no offset". I used offset pins in mine.
I'd read good things about the benefits, such as reduced noise and less stress on the connecting rod (since it isn't pressed straight down on cylinder fire), with no real detriment. Why do you say to have none?
Just be sure they're installed the correct direction. Mine had little arrows that pointed them the right way.

I would have a blast putting together an off-the-shelf performance kit for the 300. Sales would probably be small though. I remember hearing that Powernation build was mostly just what was already available, and nothing fancy, something's needed.
I don't see the benefit to the offset pin in a inline engine. To me it's just something else for someone to screw up during assembly( not all offset the same side ) . And to me it seems like offset pins would cause uneven cylinder wear. But that's probably just me being paranoid.


I was so excited to see what they would do with the 300. Then so disappointed when I saw how little they tried. It was basically a infomercial for the very basic bolt ons. It was just sad the most tech they showed was actually the repair to the broken block. Not to mention they used those stupid flat tops that sat a mile down in the cylinders. They didn't do any porting, larger valves or a decent sized cam.
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  #697  
Old 01-12-2018, 06:31 PM
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From everything I've read, piston offset has nothing to do with an inline vs. V configuration, but more to do with the angle of the connecting rod when the piston is at TDC and the stresses placed on it when the engine is firing. The concept would be the same on a single cylinder engine.

When the piston is at TDC, if the pin is centered, the connecting rod is straight up and down. Firing straight down on it produces a lot of load and stress on the connecting rod, which transfers to the bearings and can accelerate deformation. By offsetting the pin, the connecting rod is slightly tilted at TDC and pointed in the direction it's already going to go. This makes a smoother arc when it spins and takes a lot of stress off the whole system, including the cylinder walls. All good stuff.

Fortunately, whether they're in an inline or a V8, the offset is the same if the crank rotates the same direction (as it does on the Fords). So, even though I had v8 pistons, they all went in the same direction, and the arrow marker lined them all up. It was easy to quickly double check after they were installed.



I'd really love to see a show like that really dive into the 300 and show off what they can make it do. Like, do the research and really make something out of it. They kinda phoned it in on that one since it "wasn't a V8". A real bummer.
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  #698  
Old 01-12-2018, 07:31 PM
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Originally Posted by AbandonedBronco View Post
From everything I've read, piston offset has nothing to do with an inline vs. V configuration, but more to do with the angle of the connecting rod when the piston is at TDC and the stresses placed on it when the engine is firing. The concept would be the same on a single cylinder engine.

When the piston is at TDC, if the pin is centered, the connecting rod is straight up and down. Firing straight down on it produces a lot of load and stress on the connecting rod, which transfers to the bearings and can accelerate deformation. By offsetting the pin, the connecting rod is slightly tilted at TDC and pointed in the direction it's already going to go. This makes a smoother arc when it spins and takes a lot of stress off the whole system, including the cylinder walls. All good stuff.

Fortunately, whether they're in an inline or a V8, the offset is the same if the crank rotates the same direction (as it does on the Fords). So, even though I had v8 pistons, they all went in the same direction, and the arrow marker lined them all up. It was easy to quickly double check after they were installed.



I'd really love to see a show like that really dive into the 300 and show off what they can make it do. Like, do the research and really make something out of it. They kinda phoned it in on that one since it "wasn't a V8". A real bummer.

If that was the case and it wasn't different between the V's and inlines. Why did the V8's get offset pins but not the 300's? It seems like Ford spent a whole lot of time and money on making the 300 bulletproof. So why didn't they do that to the 300 pistons? I understand the basic theory behind it. What I can't see is how the offset pin wouldn't increase side load on one side of the piston. Now it may be such a small amount that it won't matter.

I would like to see a real world comparison on between two identical engines. The only difference between the two is offset vs. non offset. Then you'd be able to see if there is a difference in bearing or cylinder wear between the two. But on these engines that would be one long test!


I'd like to see a show like that too. Too bad the 300 isn't more main stream. But if that was the case we'd be able to buy a Edelbrock cylinder head for it. Like I believe the 4.0L jeep guys can.
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  #699  
Old 01-13-2018, 08:01 PM
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Well, they have a common 4.000 bore size like many V8s, but finding a suitable V8 off-the-shelf piston is not so easy taking into account dish / dome size, pin size, compression distance, etc.
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