Author Topic: 302 engine build piston recomendations  (Read 7505 times)

zman1969

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302 engine build piston recomendations
« on: September 11, 2012, 06:02:21 PM »
Hello guys I am looking for recomendations for pistons for my 302 +.030 build - I have searched, I spoke to Jerry M (he recomended J/E pistons but I cant see $1200$ for a set of race pistons for a driver) I know they say TRW or Speed pro have wrong ring grooves 1/16" vs 3/32" but is there anything wrong with them? plans for my car is for cruise nights and some trips in my car no drag racing (not official anyway  ;)  )  what have Y'all used on yours and pros/cons? and whats the stock dome height .250? I want to be at 11:1 no decking done to DZ block
Thanks
Rich

69 RS/Z DZ302 Daytona bumble bee
69 T/A clone LS6/6sp
69 Nova SS 396

1968 Z28

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Re: 302 engine build piston recomendations
« Reply #1 on: September 11, 2012, 07:35:17 PM »
Well the skinny rings were designed for light weight and less drag for racing.....not long life on the street, like the stock ones.

If you don't mind using a hypereutectic piston instead of a forged piston here are a couple of vendors....

     http://www.rickscamaros.com/camaro-piston-set-302ci-11-1-0-030-over-high-performance-1967-1969.html

     http://secure.classichq.com/302-PISTON-SET-8-30-OVER-P44C8.aspx

I have been advised that you should keep your RPM down to around 6000 with these pistons....just to be on the safe side.  Just the difference in strength between the forged and hypereutectic construction.

And another thing...I'm not positive about the weight of the pistons, do they match the stock piston weights.  If you plan on re-balancing the rotating assembly, then the weight wouldn't matter.  If you are concerned about weight, might give the vendors a call or maybe someone on the forum might know for sure.
Jerry G.

Z28-1968-07C-Norwood
Ermine White, Red Std. Interior
2nd. Owner, 38,000 miles

zman1969

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Re: 302 engine build piston recomendations
« Reply #2 on: September 11, 2012, 07:51:12 PM »
I have looked at the Hypereutectics and they are also avail, thru summit for about 40$ cheaper. I am wanting to stay forged as OE and I dont think the ring thickness will matter it wont get alot of miles on it

z28z11

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Re: 302 engine build piston recomendations
« Reply #3 on: September 12, 2012, 02:17:19 AM »
First design 302 pistons used the narrow ring, '67 up to very early '68, when it was changed to the wider ring groove/second design piston. I'm pretty sure as I have the .030 over early '68 design in my '68 Z engine on the stand (hand filed the rings myself) - like yours, it won't see that many miles, so I decided to use them. They look different (see Jerry's book if you haven't already) but I like 'em. Second design 302 pistons used the wider ring, obviously, plus floating pins instead of press fits. I was fortunate enough to buy a NOS '68-9 set from GM right after they were discoed - wish I could have bought a bunch of them.
Biggest difference between the hypereutectics and the forged piston is piston growth - the cast pistons don't expand near as much as the forged ones under use, and are more stable/seal better in the bore, and don't require as near as large of a bore (read as skirt clearance), therefore less blowby. On the other hand, as was mentioned, I don't trust them at the higher rpm ranges (piston manufacturers would probably not want to hear that from anyone !)
The third set of 302 pistons I have is a set of forged Manley 12.5:1's - I actually ran them on the street in the 302 for nearly 30K miles - of course, I was putting 100+ octane leaded Union 76 gas in the tank at the time - '73-'75. The look exactly like the std. GM 302 pistons, except taller dome, and were floaters themselves. Made a liar out of my machinist - he said I'd pound the mains out of it within 10K miles - bearings still look brand new - plus you could have probably run kerosene in it and it wouldn't have complained.
Just some opinions -
1968 Z28 M21/U17 BRG/W
1969 Z28 X77/M20/VE3 LeMans/W
1969 L78 X66/N66 Cortez/BVT
1969 Z11 L48/M35/C60/C06

zman1969

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Re: 302 engine build piston recomendations
« Reply #4 on: September 12, 2012, 12:52:44 PM »
anyone have thoughts on the speed pro pistons available now with the coated skirts? they show 11.8:1 w 64cc heads I assume i would need to mill them down to get 11:1

tmodel66

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Re: 302 engine build piston recomendations
« Reply #5 on: September 12, 2012, 04:08:52 PM »
Speed Pro has been around a long time and I've used them in dirt track cars. These cars as you know hit 6 to 7 grand on the straights.  I've never had a problem with them.
Daniel  
'69 SS 350/4 speed  Fathom Green--POP

TooManyReels

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Re: 302 engine build piston recomendations
« Reply #6 on: September 12, 2012, 09:55:34 PM »

Copy this into your browser...This is a set of used of .030 JE piston for sell...

http://www.ebay.com/itm/DZ-302-PISTONS-/290772270972?pt=Motors_Car_Truck_Parts_Accessories&hash=item43b360bf7c&vxp=mtr

Eddie
Eddie
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z28z11

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Re: 302 engine build piston recomendations
« Reply #7 on: September 13, 2012, 12:07:19 AM »
I agree with tmodel - Speed Pro makes good stuff, research point-of-origin for where they come out of, and I believe they purchased/merged the TRW Automotive Group parts division when TRW got out from under it. Still, if you can find a set of used +.030 L2210's, I would buy them if it was me - still hard to beat good 'ole TRW pistons.
Good luck - hope you find a worthy set.

Regards,
Steve

dutch

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Re: 302 engine build piston recomendations
« Reply #8 on: September 13, 2012, 01:06:44 AM »
My 302 was rebuilt years back with TRW's - actual ID is L2210AF (in the .030" oversize) and they use the narrow ring set. They can be milled down a considerable amount (if I recall up to .250") to vary the compression to suit various needs and situations and TRW reccomended .005" - .007" of bore clearance depending upon application.
When I last had the 302 in my car it was running between .007" & .008" and cold it still had no piston slap although it did smoke a bit at 6000 rpm and up - but not at all badly considering those tollerances with that type of set up..

Randy

zman1969

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Re: 302 engine build piston recomendations
« Reply #9 on: September 13, 2012, 02:19:41 AM »

Copy this into your browser...This is a set of used of .030 JE piston for sell...

http://www.ebay.com/itm/DZ-302-PISTONS-/290772270972?pt=Motors_Car_Truck_Parts_Accessories&hash=item43b360bf7c&vxp=mtr

Eddie
OK what can we tell about these pistons JE appears to be a good brand and idea what compression these may be or the specs on them?? price seems reasonable
Speed pro is all i have found and they are discontinued I would figure that these would be fine but need a little milling down to 11:1 they are listed at 11.8:1 any machinist know how much needs to be milled down? I believe they are at about .400 - so down to .250?

TooManyReels

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Re: 302 engine build piston recomendations
« Reply #10 on: September 13, 2012, 09:14:52 PM »
These are listed on e-bay : Just search DZ 302 and select newly listed items..   New TRW 67 thru 69 302 pistons. L2210AF .030.  I'm not sure who make Seal Pro. Pistons. though...

TMR,,

69Z28-RS

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Re: 302 engine build piston recomendations
« Reply #11 on: September 14, 2012, 04:58:40 AM »
Sealed Pro used to be made by TRW..  but that was long ago..?
Gary W / 09C 69Z28-RS, 72 B 720 cowl console rosewood tint
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zman1969

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Re: 302 engine build piston recomendations
« Reply #12 on: September 14, 2012, 11:07:19 PM »
Sealed Pro used to be made by TRW..  but that was long ago..?
sealed power or speed pro?

acelr8

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Re: 302 engine build piston recomendations
« Reply #13 on: September 15, 2012, 03:36:28 AM »
Sealed power, Speed pro and TRW are all morphed into the same CO, Federal Mogul.Speed Pro is the performance line of Sealed Power.Me personally use Diamonds. 1/16 ring package with no issues and are significantly lighter than the originals.About $800 a set.Jeff

69Z28-RS

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Re: 302 engine build piston recomendations
« Reply #14 on: September 15, 2012, 05:13:22 AM »
I think two of us screwed up 'speed pro' and sealed power... :)