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300 RV Motor - Project Bulletproof

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  #31  
Old 12-11-2017, 06:14 PM
hansol04
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Hi guys,

Not too much going on with the engine this week. Ordered a few parts but stil waiting on a few others.

One question I was pondering was new pistons. I've been reading that the original cast iron pistons can sometimes be a problem when a guy starts increasing power. I don't know if this is true or not, but it has me wondering if I should be looking at forged pistons or something like that.

I read some comments on the "H519P" pistons - Does anyone here have any experience with these? Are they worth getting for a build like mine? Or will the stock pistons work fine?
 
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  #32  
Old 12-11-2017, 06:27 PM
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Glad you're build coming along. Been enjoying the pictures and updates.

On pistons, there's normally three types of material. Cast aluminum, hypereutectic, and forged.
The stock cast aluminum are generally the least expensive option.
Hypereutectic are aluminum with around 10 - 15% silicone added. This gives them a bit more strength.
Forged aluminum pistons are much stronger, but are also much more expensive.

I used hypereutectics on my build (which was a bit more radical than most builds), and they were around $230 for a set of 8. In comparison, forged are around $350 - $500 for a set of 8.

You don't really need forged unless you absolutely love knowing you have durability, or you're doing something like running NOS or a turbo, or the like. Otherwise, hypereutectic are plenty.

I had thought about going with the H519Ps in mine, but the CCs weren't low enough. I think they're around a 25cc. This only got me down to around 8.5:1 compression (I have a 300 head) with shaving the head and block. I eventually got different connecting rods and went with 19cc 351 v8 pistons, so I could get around 9.1:1. However, both are the same material and (roughly) strength.

There are some 19cc pistons for the 300 (stock), but they're cast aluminum only, which is why I avoided them. I don't recall the part number, but it's in my build thread somewhere.
 
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  #33  
Old 12-11-2017, 07:09 PM
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The hypereutectic pistons are both stronger material wise, and design wise, as they do not have internal steel struts cast into them.

If you use a forged piston the cylinder wall clearance needs to be greater, enough so that the engine is going to rattle until it warms up.
 
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  #34  
Old 12-11-2017, 07:41 PM
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The h519 piston should be fine. If your pictures are correct it should work out to about 9.0 compression. Looks like you got a 240 head which should be around 68 cc before any machining ( for flatness )
That piston is a hypereutectic casting with a 22 cc d shaped dish. with a stock block height it should set about .033 down in the hole. You don't want anymore than than that with today's pump gas.
 
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Old 12-12-2017, 08:52 AM
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Thanks for chiming in guys. Now I have another silly question:

If I get the H519 pistons (seeing as they are aluminium) will I then have to re-balance my crank shaft? I'm wondering if the aluminium pistons will weight less than my cast iron ones, everything else being equal?

(And yes, I could just weigh them and compare, but I don't currently have a H519 on hand at the moment...)

As always, thanks for all the info and help. There's certainly been a learning curve here.
 
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  #36  
Old 12-12-2017, 09:55 AM
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One really nice thing about an inline six is that you can change the weights of the rotating pieces and not affect the balance. Rods, pistons, etc - no need to rebalance.
 
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Old 12-12-2017, 11:48 AM
wallen7
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Your original pistons would be cast aluminum with a steel strut imbedded. The H519 will have similar look but a much improved design. A set will usually be within balance specs as they are a replacement for OEM pistons.
 
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Old 12-12-2017, 11:53 AM
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Well isn't that convenient. Guess I'm off to order some new pistons then.

Maybe if I'm lucky, I'll have all the pieces show up before Christmas and I can spend some time building over the holiday break.

Originally Posted by The Frenchtown Flyer View Post
One really nice thing about an inline six is that you can change the weights of the rotating pieces and not affect the balance. Rods, pistons, etc - no need to rebalance.
 
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  #39  
Old 12-19-2017, 05:39 AM
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Nice build mate, and thanks for the link to the manual - I got a trial sign-up and printed it off today. Woo!

I'm looking to do much what you are, except I'm removing a 351 Cleveland. Sure, its a great engine, but I don't really use the performance and I definitely could use better economy... plus I like inline sixes.

Have you considered a camshaft while you've got her apart? I'm looking to put a mild camshaft in my build, which along with the Chev rockers will see a decent street motor that has a bit of poke but still has something resembling economy.

Keep up the good stuff, the build looks great!

- boingk
 
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Old 01-09-2018, 11:34 AM
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Happy New Year to everyone. Yes, this build is still going, but Rock Auto has done their best to slow things down a bit.

All of these boxes showed up in early December:



So with everything having arrived, I figured I would be able to poke away on things over the Christmas break. But as I was organizing the parts I discovered that some "minor" pieces hadn't shipped: My main bearings and piston rings were missing, and the crank bearings were the wrong size. So that stopped everything dead.

Anyway the bearings and rings are now on their way, so hopefully this month I can finally start to assemble things.
 
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