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  #1 (permalink)  
Old 09-11-2006, 08:49 AM
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Default What pistons to use

I am having my brother rebiuld my thunderjet and was womdering what pistons to use. He told me Ross, also what Compression should I use for a daily driver? Ilooked up Ross and they had 10:1 for 600 bucks.
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Old 09-11-2006, 12:46 PM
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What kind of engine, 429, 460, 514, 521, 545? What heads 75cc, 95cc? What is your desired compression? Cast, forged or hyper?

There are a number of variables that contribute to compression, but you are best off finding out what shelf pistons are available and figuring what your compression choices are before deciding which way to go.
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Old 09-11-2006, 02:41 PM
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Ross and JE Pistons are both well thought of in racing and engine building circles. Take your specifications to them for a quote.
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Old 09-11-2006, 08:08 PM
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its a 68 429 c9ve block and heads, the heads are 72cc if im correct. I want to stil use pump gas. its for my wifes car that she will drive on weekends. I want good HP but not enough that it will scare her. So does this help.lol
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Old 09-11-2006, 10:05 PM
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Mahle ... all the time every time!
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Old 09-12-2006, 04:19 PM
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Quote:
Originally Posted by racedraper
its a 68 429 c9ve block and heads, the heads are 72cc if im correct. I want to stil use pump gas. its for my wifes car that she will drive on weekends. I want good HP but not enough that it will scare her. So does this help.lol
If you plan to retain the 429 rotating assembly, piston choices are going to be somewhat limited.

Given that this is for your wife's car and you don't need axle snapping power, I would suggest a flat top piston and changing to D3VE heads. This should give you approx 9:1 compression. Stock replacement pistons with a ~12cc dish will give you approx 10:1 with the 72cc heads you have. That would probably be okay with premium fuel, but it doesn't sound like you need to push the compression for your power goals.

Pair the 9:1 piston/heads with a dual pattern cam that has 204-214 @.050 intake duration and you should have a nice running engine that will still make more power than she needs.

I believe Summit Racing sells a rebuilt kit with the flat top TRW pistons and everything else you need except the cam and lifters for about $600.00. You might want to check that out.

429 Pistons I'm familiar with are as follows:

Kieth Black: KB368 (hyper w/flat top), 1161 (cast w/dish)
Clevitte 224-1869 (cast w/dish)
TRW: L2366F (forged)
JE: 3977 (forged)
CP PISTONS: F6-CP (forged)
ROSS: 78473 (forged)
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Last edited by CarsByCarl; 09-12-2006 at 04:26 PM..
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Old 09-17-2006, 12:31 PM
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well im getting Kieth black hyper soethig 909's but I cant use my stock rods cause they are pressed in pins. so Im in the market for floating ones if anyone has them.
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Old 09-17-2006, 03:06 PM
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I don't like hyper pistons, even though a LOT of modern cars run them. There expensive compared to other alternatives and generally 'strong enough'. I went forged myself...

Last edited by Excaliber; 09-17-2006 at 03:09 PM..
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Old 09-18-2006, 07:09 PM
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I found some for 400 bucks for them. can you tell me the differnces between them, pros and cons. thanks
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Old 09-19-2006, 01:12 AM
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Sorry, I'm not well versed in this subject to render a worthy opinion as to pros and cons. I'm just going on a 'gut' feeling from what I've gleaned here and there. For instance, at one point I was considering a 'blower' for my Excalibur. During that 'research' phase I heard from several sources that the hyper pistons I was running were not strong enough for boost, let alone a 'bottle'! Perhaps a mild boost, but care should be exercised or the pistons should be changed.

If there not strong enough for boost or a bottle, how would they stand up to a 'lean' condition or 'pre-ignition'? Not as good as forged I'm thinking, so 'get that motor right', right from the beginning!

I came across an article at some point addressing 'piston slap', complaints from NEW car owners on a warranty level. Turns out hyper pistons, commonly used in new cars, do tend to 'slap' more than other pistons. No big deal, not a warranty issue, but it 'bothered' me.

Manufacturers like them for various reasons, ease of installation and price I suspect are big reasons why. I guess the real question is: Are they strong enough for YOUR intended use? There certainly cheaper than forged, so when you consider 'cost benefit analysis' they might be a good call for you. LOTS of people like them for various reasons.

Last edited by Excaliber; 09-19-2006 at 01:16 AM..
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Old 09-19-2006, 02:08 AM
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Red face Hyper pistons.....

Hyper pistons are cast, the main difference between hyperuetectic pistons
and conventional cast pistons is the silicon content of the alloy. Hyperuetectic
alloys contain as much as 16% silicon. The higher silicon content alloys have
lower thermal expansion rates and as such can be installed with tighter clearances than pistons made with more conventional aluminum alloys. This
is why they have become popular in the car industry because emission control
becomes easier with "tight" fitting pistons. If there is a problem with "piston
slap" or rattle it is most likely due to the manufacturer fitting the pistons
with excessive clearances. Since they "grow" less with heat working into them,
they may not quiet down once the engine is warm because they can't fully compensate for the cold installed clearance. In application terms, hyper pistons can generally be used in applications where cast pistons are appropriate,
but they should never be considered as an alternative in an application that
calls for forged pistons. If your application calls for forged pistons, then that
is what you should use.
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Old 09-19-2006, 04:20 PM
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Quote:
Originally Posted by racedraper
well im getting Kieth black hyper soethig 909's but I cant use my stock rods cause they are pressed in pins. so Im in the market for floating ones if anyone has them.
You probably don't need to float the rods. The piston/pin clearance is the same in a press fit or float, the only difference is in the rod/pin clearance. Just press fit the pins in the rods as usual and leave the retaining clips out.

As for the strength of hyper pistons, you shouldn't have an issue. Ford uses them in the 460 crate engine with 545lb/ft and 550hp at 6250rpm. I use hyper pistons in my 514 Workhorse crate engine that makes 453hp and 581lb/ft and have no problems. If you follow the KB clearance and ring gap guidelines closely you should have no problems.

That being said, I think regular cast pistons would be fine for your application and a little less expensive too. I've personaly run them in 429's set up the way I outlined above for 50,000+ miles of street/strip style driving and never had a problem.
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Last edited by CarsByCarl; 09-19-2006 at 04:25 PM..
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Old 12-02-2006, 10:39 AM
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Je Makes A 10.5 Pistion Press Pin For Ur Apt, In 30,40,60,use Your Rods,and The C9 Head For 10.5 To 1 ,
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Old 12-02-2006, 04:08 PM
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Diamond makes a high quality piston, each one
cnc'd out of a single piece of forged aluminum.
While building our engine and weighing the pistons we had to make zero weight correction on 8 seperate pistons. We would literaly blow them off with compressed air and they weighed out identically. The builder I work with has since switched to diamond exclusively.
I paid $660 for 8 custom sized pistons, 11 to 1 compression including rings and wrist pins, the distributor had a wide variety of "standard" sizes as well.
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Old 12-07-2006, 08:41 PM
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Are you guys telling this guy he can get by on the stock rods? That's something I would never do in even a minor performace build with any 385 build. I agree with most of the stuff mentioned above with the added clevate that pressed pin pistons can be used in even high performance use to a certain point, floaters are way overrated. Stock 385 rods are a huge weakness in all 429/460 stock builds. Better to buy stock pistons and spend your money on a performance rod setup if you buzz the darn thing.
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