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Old 07-27-2014, 09:50 PM   #1
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I'm assembling my spare engine bottom end.
Installed are :
Wossner 84.5mm 12:1
Scat rods
I've never dealt with these pistons before and they breach the deck.

The pistons breach the block deck by 0.013, my head gasket is 0.040 thick leaving 0.027 clearance.

Can any one give me info on whether or not this will cause P2V interference when using a factory head?

I've got a few solutions that would reduce compression but I was hoping some one might've been through this.

Thank you
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Old 07-27-2014, 09:59 PM   #2
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Which head?
I'm pretty sure there will be interference on any BP head, but most so on a vvt.
Interesting choice in pistons and comp ratio. Will this use pump gas or e85? Turbo or n/a?
I've just built a EJ255 subaru engine using these and overall they are not bad, though a bit more noisy than we hoped for (despite opting for 4032 alloy for this reason)
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Old 07-27-2014, 10:06 PM   #3
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Quote:
Originally Posted by 18psi View Post
Which head?
I'm pretty sure there will be interference on any BP head, but most so on a vvt.
Interesting choice in pistons and comp ratio. Will this use pump gas or e85? Turbo or n/a?
I've just built a EJ255 subaru engine using these and overall they are not bad, though a bit more noisy than we hoped for (despite opting for 4032 alloy for this reason)

The head is a 96 bp and it is N\A. I'll be using 100 sunoco.

The head has
Fidanza adj gears
super tech valve train
Web camshafts .352 lift, 225 duration, 205 @ .050.


I need to be able to move my power to mid range using cam gears

Should I get a cometic .051 head gasket to make up for the piston height?

I also have a stock head as an option
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Old 07-27-2014, 10:26 PM   #4
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I am unaware of any other BP running Wossner pistons. I think you will need to assemble and clay the engine.
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Old 07-27-2014, 10:52 PM   #5
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I am unaware of any other BP running Wossner pistons. I think you will need to assemble and clay the engine.
I believe sir you are correct. That is my next step. But the hydraulic lifters being collapsed may skew the results.

Outside of that method my only other option, I believe, is to remove lifter and keeper on one intake and one exhaust valve and manually measure clearance with a dial indicator.
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Old 07-28-2014, 01:50 AM   #6
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I've seen 12:1 Wossners before, but the custom cams mean you need to clay YOUR motor to find YOUR clearances.
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Old 07-28-2014, 09:39 AM   #7
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Quote:
Originally Posted by Savington View Post
I've seen 12:1 Wossners before, but the custom cams mean you need to clay YOUR motor to find YOUR clearances.
Will my hydraulic lifters being collapsed affect the results?

not necessarily collapsed, just not under pressure
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Old 07-28-2014, 10:41 AM   #8
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Quote:
Originally Posted by Savington View Post
I've seen 12:1 Wossners before, but the custom cams mean you need to clay YOUR motor to find YOUR clearances.
Any comment about finish vs SuperTechs, shape edges etc?
I also wonder if they are truly 12:1, since they list stock CR as 11:1 IIRC.
A dome volume of 7cc would not give 12:1 without decking some (or no valve reliefs).

With spending time and effort, custom pistons are probably the best way to get high CRs, not that expensive either.
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Old 08-04-2014, 11:24 AM   #9
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Clay modeled the head/piston clearance and p2v clearance. I will need a cosmetic mls 0.051 thickness to prevent piston (high side) contact with the head.
Attached Thumbnails
Wossner piston question-forumrunner_20140804_102319.png   Wossner piston question-forumrunner_20140804_102342.png  
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Old 08-04-2014, 12:08 PM   #10
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What will the resulting compression be?

This is for a dyno reclass PTE car right?
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Old 08-04-2014, 05:59 PM   #11
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Approx 11.5 to 1.
The PTE reclass is 140hp @2425lbs.
My actual numbers will be 135hp @2450
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Old 08-04-2014, 07:49 PM   #12
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Isn't 12:1 pistons with a thick head gasket a little over the top for 135whp? I think a '99 motor with flat top intake manifold, some mild cams and I/H/E would get you to 140whp with plenty of area under the curve..
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Old 08-04-2014, 08:39 PM   #13
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Quote:
Originally Posted by Efini~FC3S View Post
Isn't 12:1 pistons with a thick head gasket a little over the top for 135whp? I think a '99 motor with flat top intake manifold, some mild cams and I/H/E would get you to 140whp with plenty of area under the curve..
A '99 with I/H/E is a great HPDE setup. A purpose-built PTE motor looks more like this:



I'll give you a hint: '99s with I/H/E don't produce 136wtq during the break-in period. OP is on the right track for a very competitive PT car.

Last edited by Savington; 08-04-2014 at 08:49 PM.
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Old 08-04-2014, 09:22 PM   #14
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My AFR is going to be around 11.5 to 12 which will kill a little HP but make motor last longer. My old build with 11 to 1 wiseco pistons at 13.8 afr produced 158hp 132tq, but reclass made my weight 2585lbs. And that weight, sir, is unacceptable. So i dropped weight and hp.

my main reason for this choice in engine components is to gain as much TQ as possible. Naturally aspirated reclass doesn't regulate TQ only HP.
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Old 08-04-2014, 11:29 PM   #15
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Quote:
Originally Posted by Savington View Post
A '99 with I/H/E is a great HPDE setup. A purpose-built PTE motor looks more like this:
.
Yea but he'll be racing on the east coast against a bunch of poopy PTE cars and drivers. Does he really need an all out "purpose built" PTE motor?
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Old 08-04-2014, 11:44 PM   #16
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Quote:
Originally Posted by Efini~FC3S View Post

Yea but he'll be racing on the east coast against a bunch of poopy PTE cars and drivers. Does he really need an all out "purpose built" PTE motor?
If I could find a Jackson racing supercharger then no, I would have a bone stock 1.8 pushing 5psi and make 145tq 130hp. Which is what my east coast competitors run.

Since I'm more likely see to pigs fly than find a Jackson supercharger, I made a choice. Go full N/A, detune and have a gnarly engine with a long life ahead of it... Assuming of course the tuner doesn't lean out the Afr and melt down the forged aluminum pistons. It took 4 seasons but that's how it happened.
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Old 08-05-2014, 12:02 AM   #17
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We run our NA grand-am motors at 13.5:1 on stock cast pistons and have never melted a piston. Are you sure it was fueling that was your issue? Obviously I'm comparing apples to oranges a bit but 11.5 afr on an N/A motor seems overly rich. I'm no expert in PTE motors though.

I do remember a certain yellow Miata running in PTD(?) with a low boost supercharger and doing pretty well.

Aren't you worried about EGT's tuning a 160hp back to 135?

Last edited by Efini~FC3S; 08-05-2014 at 12:03 AM. Reason: Punctuation son
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Old 08-05-2014, 12:10 AM   #18
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Quote:
Originally Posted by Efini~FC3S View Post
Yea but he'll be racing on the east coast against a bunch of poopy PTE cars and drivers. Does he really need an all out "purpose built" PTE motor?
If he wants to beat the aforementioned M45-powered car, then possibly/probably.
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Old 08-05-2014, 12:20 AM   #19
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If I run anything higher than 13afr my coolant temps avg 210. 11 to 13 afr it's at a nice 170 on a hot day. I like to leave at least 20 for a few laps with dirty air.

Egt do get out of control. I've broken 2 headers at the collector since this engine went in. But that's 2 in 4 seasons. I don't fret it because exhaust valves are unharmed.

PTE cars/motors in my opinion are fickle bitches. The point indexing path or reclass path allow so many different ways of producing a competitive car without having to spend 50k. Not to say I wouldn't if I could.
In my eyes, PTE cars are not the slowest nor the fastest.. They're just right for having fun while still getting the thrill
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Old 08-05-2014, 06:22 PM   #20
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Quote:
Originally Posted by Efini~FC3S View Post

Yea but he'll be racing on the east coast against a bunch of poopy PTE cars and drivers. Does he really need an all out "purpose built" PTE motor?


Out of curiosity, what makes you say east coast has such bad PTE cars and drivers?

As you may have assumed, I am one of the said drivers
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