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 Want piston weights comparable to stock for 400
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bullheimer
Tribal Scout

USA
5 Posts

Posted - 29 Jan 2017 :  5:30:53 PM  Show Profile  Reply with Quote
Hi can anybody give me a link to both stock, stock-replacement .030 over, and any after market cast OR forged pistons that are approximately the same weight as stock? i would like to junk my 8 brows some day so i can finish my build and replace them with anything else, while the crank remains in the short block on my stand without having to worry about balancing the rotating assembly. I have searched and found some info regarding this for the 455, but would like it for the 400. Any help appreciated. or- if you think simply the fact that i am at 30 over is going to mandate balancing, feel free to chime in on that to. this is for a relatively moderate mill with (at the present time) a 221.5/232.4 at .050 cam, 110 centerline cam installed. thanks. ps i have read i can dish heavier pistons to get my desired stock weight as an option. thoughts on that as well.

i would also like to know how i can subscribe to this thread. thanks again.

67 lemans roller, 400 cid short block

Blued and Painted
Chief PONTIAC

USA
3409 Posts

Posted - 29 Jan 2017 :  10:23:47 PM  Show Profile  Reply with Quote
I would get a balanced set of pistons and steel rods. Call butler and see what they suggest.
-- http://butlerperformance.com/i-24453555-rpm-5140-forged-i-beam-rod-6-625-2-250-pontiac-rj.html?ref=category:1234812


Bull Nose Formula/ 461/ Q-Jet/
TH400/ 3.08 8.5 / R44TS.
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Steve C.
Crazy Horse

1677 Posts

Posted - 31 Jan 2017 :  1:15:08 PM  Show Profile  Reply with Quote
Interesting tid bit. According to the old H-O Racing Specialties Specification book they state the factory pistons have a calibrated weight so that oversize pistons may be used without effecting engine balance.

Pontiac pistons listed in a old Federal Mogual Speed-Pro performance parts catalog... no weight listed. Probably by most considered replacement parts.

Edited by - Steve C. on 31 Jan 2017 1:57:24 PM
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Steve C.
Crazy Horse

1677 Posts

Posted - 31 Jan 2017 :  1:56:31 PM  Show Profile  Reply with Quote
Auto manufacturers used cast-aluminum pistons in production engines for many years. They are cheap to produce, and they operate quietly and consistently throughout an engine?s lifetime when properly designed. The piston that Pontiac developed during the late 1960s was an excellent piece. TRW copied its design to produce high performance aftermarket forgings.

TRW began offering a wide array of stock-replacement forgings for most Pontiac engines in stock displacement and popular overbore sizes. Several of the high-volume offerings remain available under Federal-Mogul?s Speed Pro line.

Pontiac's original cast piston had influence on the design of the TRW original stock replacement forging. Federal- Mogul purchased TRW in 1992 and began producing the pistons in June 2001, incorporating some modern technology in the process. The most apparent changes are in the skirt area.

Pictured here indicates the difference, and with it we can probably assume a obvious weight difference.

Source: http://www.pontiacdiy.com/pontiac-v-8-pistons-and-rings-performance-guide/

Amazing what you can find with Google !

Edited by - Steve C. on 31 Jan 2017 1:58:38 PM
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bullheimer
Tribal Scout

USA
5 Posts

Posted - 02 Feb 2017 :  02:23:09 AM  Show Profile  Reply with Quote
Wondering also about stock wrist pin wgts. i dont want to buy rods after reading jim hand's book. so you both think Speed Pro 030's over would work. How many valve reliefs and/or what were their CC's of a stock piston. Having all that relief area in an 8 brow would have to make it lighter wouldn't it. I believe i cc'd them at 14ccs. that is a hell of a good price for rods tho B&P. still out of my budget as pistons already are on threshold. great article Steve

67 lemans roller, 400 cid short block

Edited by - bullheimer on 02 Feb 2017 02:37:40 AM
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Steve C.
Crazy Horse

1677 Posts

Posted - 02 Feb 2017 :  07:17:47 AM  Show Profile  Reply with Quote
H-O stated factory pistons may be used without effecting engine balance. I doubt if your going to find a source for pistons that weigh the same as factory, thus I will presume you will have to re balance the assy. That said, I'm not a engine builder.


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bullheimer
Tribal Scout

USA
5 Posts

Posted - 08 Feb 2017 :  02:31:48 AM  Show Profile  Reply with Quote
yeah, i get that. me neither but trying to get factory spec at least, maybe somebody with a stocker can weigh one, or i will ask my machine shop if they can tell me. (w/o rings).

i can just get forged 30 overs by SpeedPro or whoever, actually, get them dished to the right weight and probably be in the ballpark of something that should be in the 9.5:1 c.r. range. i will have to go to a c.r. calculator and figure that out, then guestimate how much to remove from say the 2 or 4 relief pistons top and find somebody that does that kind of thing. but then i'm guessing if i had to pay a machine shop i might could just spend that extra expense on trying to find a closer match from the get go. i'll keep looking/asking around.

67 lemans roller, 400 cid short block
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bullheimer
Tribal Scout

USA
5 Posts

Posted - 09 Feb 2017 :  12:54:58 AM  Show Profile  Reply with Quote
i just read that speed pro and silvolite are both made offshore now. well crap, not using them then. CRAP!

67 lemans roller, 400 cid short block
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cortcomp
Coyote

USA
5338 Posts

Posted - 09 Feb 2017 :  09:49:17 AM  Show Profile  Visit cortcomp's Homepage  Reply with Quote
offshore doesn't necessarily mean poor quality. People in china are just as skilled at running a machine as someone here. The difference is, companies here don't always want to pay for that quality. China makes what it's paid to make, no more, no less. I've had american made garbage products pretty recently too.

SP/SL is a brand i still wouldn't hesitate to go with.
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bullheimer
Tribal Scout

USA
5 Posts

Posted - 27 Feb 2017 :  10:49:09 PM  Show Profile  Reply with Quote
Got a message from Falcon Racing, who sells a lot of parts on ebay, to the effect re: the speed pro/trw 4 relief pistons he sells, and it said "These weigh 'approximately' 575 grams each in standard size...........................I can't tell you what was in the o.e. application as far as weight. a link to the page on ebay with the pistons is here: http://www.ebay.com/itm/172055348862?ul_noapp=true

not sure if it's Kosher to post that here, but if not, mods, do your thang. i did some research on these new made in India slugs (SP) and it was not good news, that they are off by 20 grams from piston to piston, and sit down farther in the hole. cant remember specifically if the wrist pin locations varied from piston to piston, like the 8 relief piles i have in my short block right now, but just remember they are farther down that stockers, or, older made in the usa SPs. really bums me out since pistons are now out of reach for me. i guess that rather than buy more expensive pistons i'll have to remove my brand new cam that's too big for everything and order an 068, or maybe even just unload the whole thing.

67 lemans roller, 400 cid short block
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Pontimino
Tribal Scout

5 Posts

Posted - 15 Nov 2017 :  12:37:27 PM  Show Profile  Reply with Quote
I was surprised that my eagle rods and trw forged .030 pistons weighed about a half pound lighter than stock for my 326 build. That's 4 pounds less beating on the cylinder walls, facilitates quicker and higher revving, and will be easier on the bearings. Of course the crank had to be rebalanced for $140.
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tjs44
Cochise

USA
413 Posts

Posted - 15 Nov 2017 :  2:17:18 PM  Show Profile  Reply with Quote
My son does a lot of biz in China.They CHEAT!They will submit samples and then send subpar stuff.Tom
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