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  #1  
Old 08-14-2002, 09:31 PM
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Default hypereutectic piston options on 360

Hi guys I want to get 9.5 compression on my 360 with hypereutectic pistons to avoid detonation on 93 octane gas. I've found Federal Mogul pistons which should do 9:1 on my 65 cc heads and KB silvolites which are 10.5 and over. I have found nothing in between. I want hypereutectic because I want to get about 400HP and want to leave room for a small amount of nitro if I want to go that way later. Are there other hypereutectic options out there?

Thanks in advance!
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Old 08-14-2002, 09:49 PM
Doug Wilson Doug Wilson is offline
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Get the 9:1 pistons and deck the block or shave the heads to get the CR that you want. However... if you intend to use nitrous sometime down the road, I'd get forged pistons, just for the extra safety factor, even though they cost a couple of hundred dollars more. The top ring groove in the hypereutectics is prone to collapse under heavy loads, even without nitrous.

There was a pretty good thread on this a couple of weeks ago, with the leading opinion by cuda66273. If you use the search function, I'm sure you can find it.
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Old 08-14-2002, 10:12 PM
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Firelord....Doug is right on with his suggestion about the forged pistons. Ross is a good choice or now Diamond. They are more expensive, but there is something to be said for doing it right the first time. I have excellent luck with the KB hypertutectic (sp)
pistons for general street strip use. There are now 4 different 360 pistons and the CR is dependent upon you head cc size. Doug is right about the top ring, but if you follow the KB ring gap chart this is minimized greatly. will sound like a lot, but Follow the formula. run .030 to .032 on the 360's. If you use a nitrous system, use a wet one. Fuel will cool the pistons tops and prevent detonation. I have one 360 that has made over 200 nitrous passes with KB 190's and a 150 shot. (wet) It is still together.......but it will not live as long as a forged Ross piston.
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Old 08-14-2002, 10:19 PM
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Thanks guys! I'm just a bit confused because I checked a post by professor overdrive in the summit web page. He's saying hypereutectic will do with nitrous as long as you take 2 degrees off timing for every 50 hp of nitro. Also, I like the stability of the piston. I hear forged will definetely increase oil consumption at startup. Can you guys enlighten me on this?

Also, the KB I was reffering to was the mildest one, the 107.
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  #5  
Old 08-14-2002, 10:37 PM
Doug Wilson Doug Wilson is offline
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A well built engine with proper clearances will use more oil with a forged piston than with a hyper.. However, you are probably looking at maybe 1 quart per 600 to 1000 miles. No biggie.

Remember, if you eat a piston, Summit will just tell you "too bad". and you'll be buying the new slugs. They really don't have much to lose. Try looking at SRP forged pistons - they are part of JE. Don't use FM/TRW forged slugs.
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Old 08-15-2002, 08:43 AM
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Firelord....you are getting good advise. Knowledgeable people out there. The reason for the basic increase in oil consumption is the piston to wall clearance on the forged piston, as the hyper pistons can and do run tight sidewall clearance, some as tight as .002. Forged pistons will use .008-.010 (some less, some more) Some of the early street hemis had as much as .014 from the factory. The piston does not rock, and is consistent in size after the heat of combustion. The SLP mentioned by Doug is an excellent choice and is produced by JE. The timing correction is correct and I forgot to mention it. You can retard even more down the track in high gear if you have the controller.
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Old 08-15-2002, 09:21 AM
Dr. Righteous Dr. Righteous is offline
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Default Federal Mongul has a HUGE valve relief

I always used KB hypernutectic when I build an engine but I was on a budget when I built my 360. I bought a Summit kit that used Federal Mongul hypernutectics. The specs promised 8.8:1 comp with stock heads. That is exactly what I was after. The pistons has a HUGE valve relief down the middle of the pistons. Not just the eyebrows like most. Well my static CR turned out to be around 8:1 instead of 8.8:1. I suggest the KBs.
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Old 08-15-2002, 12:29 PM
Dr. Righteous Dr. Righteous is offline
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Default Heard of the top ring land failures.......

Hey Doug,
The KB instructions that come with the pistions are very explicit about using the correct ring gap for your application. They even have picture of what happens if you don't.
(Interesting that a manufacture would include pictures of their own product failures).
Also their website has a wealth of information on Hypernutectic pistions. Very interesting reading. The KBs will be the only pistons I will buy from now on because I am very disappointed with the Federal Monguls.
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Old 08-15-2002, 01:15 PM
451Mopar 451Mopar is offline
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What cylinder heads are you using? You said they are 64cc, but are they open or closed chamber?
I used the Keith Black KB232 "Quench" dome D-Cup (dished pistons) with stock type open chamber heads, and the compression ratio after all the machining to set-up the proper "quench" was about 9.5:1
The keith Black pistons can handle small amounts of Nitrous, but they are not really designed for it because the top piston ring sits really high on the piston (sees more combustion heat), so for nitrous useage you have to run extra large top piston ring gaps.

I have used forged pistons in many of my rebuilds and have not had only oil consumption problems, but the forged pistons may have some piston slap noise because of the extra piston to cylinder wall clearance. I'm also glad the pistons are forged because last week I got some crap gas, and when I got on it, the engine started pinging! This is the first time I ever had pinging with this engine, so I'm pretty sure it is the gas I had just put in it.
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  #10  
Old 08-15-2002, 06:55 PM
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Default Side note;

Hyper-u-tectics are fragile due to the addition of ...ooooo crap, brain frezzzze...silicone? I hate when this happens!
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  #11  
Old 08-15-2002, 06:58 PM
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From 451 mopar

Quote:
Try keith Black - silvolite's web page
http://www.moparchat.com/forums/show...threadid=57269
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Old 08-16-2002, 02:58 PM
Dr. Righteous Dr. Righteous is offline
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Default Fragile??

The hypernutectic alloy has a higher silicon content than 'cheaper' alloys. This special alloy has advantages over regular cheap pistons. they are very tough pistons and much lighter than forged pistons. Read up on them on the KB website.

www.kb-silvolite.com
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  #13  
Old 08-16-2002, 03:21 PM
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451 mopar- I have 974 heads- but I'm not sure if I will use them for the rebuild. They are open chamber. They should cost me about the same to rebuild as buying the prepped ones from aero racing. Spec says it is 65cc.

Should I just forget the nitro? Is 400 Hp enough for a street machine?

BTW, thanks all for the good advice. I'll look at the SRP and KB 107's
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  #14  
Old 08-16-2002, 03:39 PM
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rumblefish360 rumblefish360 is offline
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400 hp makes for a nice street machine. What you miss in HP, you should make up with suspention tweaks. The quicker you plant the power and get going, the beter off you'll be.
I have seen very powerful cars lose a race just due to the fact they can't get a grip[ on the pavement. They lose to a car that's (easy to see), less powerful.
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Old 08-17-2002, 11:05 AM
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Rumblefilsh,

Did you mean brittle instead of fragile? Brittle being fracturing not deforming; whereas, fragile would indicate poor strength?

Anyone want to list any reccomended pistons for a 318? I'm about to have mine rebuilt. Only got a 192K miles out of it.
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  #16  
Old 08-17-2002, 11:31 AM
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Splitting hairs????

OK If forced to answer...without opening a dictonary.

Fragile and brittle can fall into the same cat.

The answer would be brittle. But calling the piston ethier is not giving credit to the piston.

A piston for you? Depends on driving and or intended use. Not to mention the wallet.
Nothing wrong with cast, Hyper u's are better.
Hyper-U's pistons are stonger than cast, weaker than fordged.
Hyper-U's can take more abuse than cast, less than fordged.
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Old 08-17-2002, 03:57 PM
Doug Wilson Doug Wilson is offline
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DusterBill - you should really start a new thread for your inquirey. It'll make it easier for you to find in the future, and it won't mis-direct this thread.

I would NEVER misdirect a thread, would I????????
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Old 08-18-2002, 11:23 AM
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Cuda66273...just shakes his head......

Hey!....if you think that a $18.00 piston will outlast and out perform a $800.00 set of Arias light weight high silicone forged pistons then go for it...but....if they were that good why isn't everyone using them?...

THEY ARE strictly a budget piston and if your serious you'll chuck the catalog and loose Smummits phone number, they'll always tell you exactly what your wallet wants to hear.

Ross Pistons has a secondary line...Probe, excellent and about $100 cheaper than a Ross

JE as mentioned has the SRP line

Diamond makes a good slug and there's lot's of other GOOD choices......Hyperuthectic just isn't one of them, no matter what their advertising say's.

My choice is Arias....good deliver, excellent quality and reasonably priced for the quality you get.

Good, Fast or Cheap pick any two.....

Sorry Guy's but sometimes I just need to vent a little, I've just seen to much carnage from cheap parts......Chinese copy's....and the infamous "I'll make you a smokin' deal" which is usually just that ...a trail of smoke....
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Old 08-18-2002, 10:41 PM
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cuda66273 speaks the truth.
Cast or hyper-U, I wouldn't takem to high in the HP range.
If there fordged, sky's the limit.
Buy quality, get quality, live a long life.
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