Author Topic: 302 Replacement Pistons  (Read 13321 times)

Z28Project

  • Member
  • ***
  • Posts: 220
    • View Profile
302 Replacement Pistons
« on: July 25, 2016, 01:16:26 PM »
I'm looking at doing a 302 +.030 rebuild and going to buy a set of pistons.  There was a good thread on this a few years ago discussing the various pistons available, but it looks like piston choices have really narrowed in the last few years.  It looks like you can change rod lengths and use 350 pistons, which have more choices, but if I stay with a 5.7" rod, the choices I'm seeing are hypereutectic or the JE/SRP forged.

I don't really want to go hypereutectic, and I have no problem with the JE/SRP piston, I'm just wondering what others have done (if anybody has done any recent rebuilds), or if I'm missing something in my searches.

JE offers the pistons and rings along with some nice looking MLS head gaskets in various thicknesses (.027, .030, .039, .051").

One goal I have is to keep the compression UP!  11.0:1 at least. :)

I plan to run the stock 30-30 cam.

Thanks for any info/opinions.

John
John

69 Z/28 NOR 12B X33 H.O. 'Ex-Racer'

jdv69z

  • Hero Member
  • *****
  • Posts: 1275
  • 69 RS Z/28 52E
    • View Profile
Re: 302 Replacement Pistons
« Reply #1 on: July 25, 2016, 01:24:44 PM »
I thought to go to a 350, you have to change the crank, and the rods stay the same.
Jimmy V.

Z28Project

  • Member
  • ***
  • Posts: 220
    • View Profile
Re: 302 Replacement Pistons
« Reply #2 on: July 25, 2016, 02:31:54 PM »
That would give you a 350 CI engine.  In some of the posts I was reading they indicated you could change the rod length to compensate for the different wrist pin location of the 350 piston, use 350 pistons (more choices), and still end up at 302 CI.
John

69 Z/28 NOR 12B X33 H.O. 'Ex-Racer'

jdv69z

  • Hero Member
  • *****
  • Posts: 1275
  • 69 RS Z/28 52E
    • View Profile
Re: 302 Replacement Pistons
« Reply #3 on: July 25, 2016, 07:04:44 PM »
New one on me!   ;D
Jimmy V.

1968 Z28

  • Hero Member
  • *****
  • Posts: 562
    • View Profile
Re: 302 Replacement Pistons
« Reply #4 on: July 25, 2016, 08:18:58 PM »
If you are looking for an exact replacement piston, the JE #123567 is the exact 302 factory replacement.  It is not a SRP piston but is the NHRA approved replacement piston for the 302ci engine.  It will give you the stock compression ratio of 11.1 and it has the original size ring grooves.
Jerry G.

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

Z28Project

  • Member
  • ***
  • Posts: 220
    • View Profile
Re: 302 Replacement Pistons
« Reply #5 on: July 25, 2016, 09:49:41 PM »
Thanks!  Let me see what I can find out about those.

John
John

69 Z/28 NOR 12B X33 H.O. 'Ex-Racer'

1968 Z28

  • Hero Member
  • *****
  • Posts: 562
    • View Profile
Re: 302 Replacement Pistons
« Reply #6 on: July 25, 2016, 11:20:48 PM »
Here is a link to the JE web site......http://www.jepistons.com/Catalogs/Automotive/NHRA.aspx
Jerry G.

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

janobyte

  • Hero Member
  • *****
  • Posts: 1531
  • Before it was called Day 2 !
    • View Profile
Re: 302 Replacement Pistons
« Reply #7 on: July 26, 2016, 12:30:56 AM »
JE are good pistons. Maybe lighter then stock, a plus with theses engines. Stock are heavy. Rod failure secondary to " yanking" them back down during high revs. All in all stout rods, after stress relief, good forged cranks. 
68 Z/28  born with: 302, drive line, etc..

Z28Project

  • Member
  • ***
  • Posts: 220
    • View Profile
Re: 302 Replacement Pistons
« Reply #8 on: July 26, 2016, 01:07:56 AM »
Thanks for the link Jerry.  I was having trouble finding them on their site.  From your link I see I needed to click on NHRA.

Yes, everything I've read sounds like JE makes good stuff.  I think it will come down to either the 123567 or the JE/SRD 202890.

Thanks,  John
John

69 Z/28 NOR 12B X33 H.O. 'Ex-Racer'

X33RS

  • Hero Member
  • *****
  • Posts: 1092
    • View Profile
Re: 302 Replacement Pistons
« Reply #9 on: July 26, 2016, 03:21:09 AM »
I just finished my 302 build and used the JE pistons.  Excellent pistons.  I noticed the dome configuration slightly different as well as the quench area when compared to my NOS DZ pistons but nothing that affects much of anything.

My compression with the pistons .005 in the hole, .039 gasket and 62cc heads came in exactly 11:1  They are slightly lighter than the stock piston.

Z28Project

  • Member
  • ***
  • Posts: 220
    • View Profile
Re: 302 Replacement Pistons
« Reply #10 on: July 26, 2016, 01:07:37 PM »
Thanks for the info X33RS, especially the numbers!

Did you use the SRP series?
John

69 Z/28 NOR 12B X33 H.O. 'Ex-Racer'

X33RS

  • Hero Member
  • *****
  • Posts: 1092
    • View Profile
Re: 302 Replacement Pistons
« Reply #11 on: July 26, 2016, 07:45:15 PM »
Yup,  SRP series 202890 part number full floating with a 1/16 ring package and went with total seal rings.

Z28Project

  • Member
  • ***
  • Posts: 220
    • View Profile
Re: 302 Replacement Pistons
« Reply #12 on: July 26, 2016, 07:51:05 PM »
Great.  Exactly what I was looking at!

Thanks,  John
John

69 Z/28 NOR 12B X33 H.O. 'Ex-Racer'

asm69

  • Member
  • ***
  • Posts: 206
    • View Profile
Re: 302 Replacement Pistons
« Reply #13 on: July 27, 2016, 12:45:56 AM »
X33RS, why didn't you use pressed pins instead of full floating pins? I believe Jerry McNeish uses pressed pins for the safety issue.

X33RS

  • Hero Member
  • *****
  • Posts: 1092
    • View Profile
Re: 302 Replacement Pistons
« Reply #14 on: July 27, 2016, 02:53:41 AM »
There were a few reasons, one of which was to stay true to form.    I've used floating pistons in several builds without issues over the years so no real concern for me.

 

anything