Has anyone figured out the DOHC pistons

[sd_iconoclast]

Is it possible that the pistons you are describing are from Silvolite/Keith Black rather than from Sealed Power? The reason I wonder is because, as I recall, the link that used to exist was to silvolite's website.
As much as I agree with you that the Sealed Power guy might not have been very on the ball, thier catalog does list .040 domes for both pistons. Secondly, Sealed Power lists the greater compression height (1.464) for their "late" piston.
I would still really like to see the pics though.

[SappySE107]

http://60degreev6.com/backup%20html/DOHC%20perf%20pistons.htm

Guess i need to put that back on the site soon.

[BowtieKid79]

The page I was looking at was for Silvolite. They only list one piston which is factory spec:

http://www.beckracing.com/slvpg24.htm

I have sealed power (the late model style with the dome). When i talked to the sealed power rep here in CO, he told me that only the late model actually has a .040 dome since the factory 96/96s have it. I don?t know why they list the early one as having a dome also. In the case that they both have a dome, then i guess the late model style will have a little more compression since the comp height is .006" more (hardly worth mentioning really). But i know for a fact the dome doesn?t cover the whole top (which means that it would be a really poor design to use with the early heads since the CC is so much bigger around). FYI the list price for the late piston is $51.18 each and the ring set is $140.58. I didn?t notice ANY difference between the stock 92 (9.5:1 5 spd pistons) and the domed style. If there is any compression difference, it?s not anything you will notice. I am going to try to attach a pic of the late model (H684CP) piston now. Notice the dome is only in the center of the piston (makes the valve reliefs look bigger/deeper, but they are not)

[sd_iconoclast]

Thanks for the pic BowtieKid. That helps alot. I now have another mystery. I have measured my pistons (which came out of a '92 Lumina Z34 Automatic) and I calculate their compression distance to be 1.47675". This is greater than any of the pistons listed by Silvolite or Sealed Power. Check my measurements:
Top of piston to top of wrist pin hole: 1.024" (H)
Wrist pin hole diameter .9055" (D)
Compression distance = H + D/2 = 1.47675"
Are we doomed to lose compression no matter what aftermarket piston we choose, or have I made a mistake?

[sd_iconoclast]

By the way, the pistons I am measuring appear to be identical to those shown in the "picture gallery" having part number 10130958 cast into them.
The best price I have found on pistons is from Summit. The have the Sealed Power H684CP pistons for 25.99 each. Also, Sealed Power says that the pistons ARE available individiually despite what the retailers say.

[Anonymous]

Are we doomed to lose compression no matter what aftermarket piston we choose, or have I made a mistake?

I do not know what brand or what specs my pistons are, I just know that the shop that did the long block assembled it with new .030 over forged aluminum pistons, and when testing the motor, the guy said I am running at 9.75:1 C/R, but that is also with a head decking.

[BowtieKid79]

Are we doomed to lose compression no matter what aftermarket piston we choose, or have I made a mistake?

I do not know what brand or what specs my pistons are, I just know that the shop that did the long block assembled it with new .030 over forged aluminum pistons, and when testing the motor, the guy said I am running at 9.75:1 C/R, but that is also with a head decking.

Get a manufacturer and part number or that info is worthless. You can bump it up to that decking the heads about 20 thou. so they are probably stock specs.

Summit does have the best price on the pistons... but good luck getting them anytime soon. I ordered mine from summit and waited 3 weeks and they hadnt been shipped yet. So i canceled my order and got them direct from federal mogul. Checker and Advanced also said they could get them, but the wait was also about a month. I got them 3 days afer i ordered them from FM.

Your calculations seem to be correct. I dont know why it is not closer to spec.

[sd_iconoclast]

A little more info:
I called Sealed Power's tech line again to ask why my stock pistons have a compression height of 1.478" and their replacement (Part #H813CP) has a compression height of 1.458". The tech guy said that they had redesigned the piston with dome but assured me that it would give stock compression. I also asked (again, see my previous call to SP tech above) which of the two pistons they offer gives the higher compression. He first said that H813CP would give higher compression, then he seemed to suggest that they would give the same compression ration, but he could not explain how he arrived at that. A little further into the conversation, it became clear that he did not even understand how to calculate compression ratio. In my mind this confirms that Sealed Power's tech guys have no clue. I suspect the only way to find out is to CC these things.
It is really a shame that Sealed Powers Tech support guys are so combative and seem to know so little. I remember calling TRWs tech support (like ten years ago) with similar piston questions and the guy I talked to was extremely helpful and knowledgable.