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Discussion Starter #1 (Edited)
In my other post I first planned on building a B7 but surprisingly I couldn't find a used one and instead bought a used A6 for 100 bucks.

It had been sitting for a while, had some rust on the cylinder walls, ugly looking bottom end and sludgy oil inside.

Since then the bottom end has been torn apart, cleaned and sent to the shop. I'm placing my order for the FJ Distributor's Hi Compression rebuild kit this week with 76mm PG6 pistons.

Starting with the bottom end:
It has been jet washed, resurfaced, bored to 76mm and honed. The PG6 pistons will be thrown in there with reconditioned A6 rods and ACL race bearings (ARP bolts) and the freshly micro polished crank.
The bottom end will be balanced.


Top end:
I have not put too much thought into how the head will be but this is what I'm thinking.
Skim some off the top, Port & Polish, Jet wash, resurface, Bisimoto valve train upgrade, Bisimoto Stage 2 cam and some kind of adjustable cam gear.

Misc:
Planning on an Edelbrock intake manifold, an intake, header (Bisimoto) and exhaust.
EX/SI transmission that I will mate to the engine.
 

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93 Legend L Coupe.
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FJT sells 76mm PM3s.

On stock everything, the PM3s will sit about .028" out of the hole. Using a .030" headgasket is a good bet.

As for the head, it is my recomendation to have the quench pads machined to the same depth across the whole head. There is some variability, and with this build, it is enough of a varation on most heads to lead to some icky results. Once you match the quench pad height across all four cylinders and open up the chamber bore to the side of your piston, plus some extra room to have space for the piston to rock (it will), you should mill the head so that the quench pads will come to under .040" from the piston. You will also probably need to open of the valve pockets some, especially if you go with oversize valves. Do NOT overdo this. Big valve pockets lower compression dramatically.

That will be a fun build. =)
 

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what head are you planning n using? If an a6/b7 head is used there really wont be any clearance issues but you can clay the motor to be sure. A GOOD valve job will be key to the head. Im pretty sure you can buy 75.5's from honda also, id have to check but im to lazy :p
 

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Discussion Starter #5
what head are you planning n using? If an a6/b7 head is used there really wont be any clearance issues but you can clay the motor to be sure. A GOOD valve job will be key to the head. Im pretty sure you can buy 75.5's from honda also, id have to check but im to lazy :p
planning on using the A6 head
buying form honda will be a bit expensive just for the pistons and i trust fjt's products and theyre cheaper so i plan on cantacting them about the 76mm pm3s
unfortunately because the web site wasnt clear to me i didnt realize they dont have 75.5 pm3s and i had my machine shop guy bore to 75.5 already but he said hell just re bore it to 76mm no charge

any risks going 76mm?
 

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Discussion Starter #6 (Edited)
FJT sells 76mm PM3s.

On stock everything, the PM3s will sit about .028" out of the hole. Using a .030" headgasket is a good bet.

As for the head, it is my recomendation to have the quench pads machined to the same depth across the whole head. There is some variability, and with this build, it is enough of a varation on most heads to lead to some icky results. Once you match the quench pad height across all four cylinders and open up the chamber bore to the side of your piston, plus some extra room to have space for the piston to rock (it will), you should mill the head so that the quench pads will come to under .040" from the piston. You will also probably need to open of the valve pockets some, especially if you go with oversize valves. Do NOT overdo this. Big valve pockets lower compression dramatically.

That will be a fun build. =)
god damn i have some researching to do
im kinda new to all this and while i know this is good info its all jumbled to me
:wacko:
is this all necessary?
im just looking for a fun DD
 

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Don't use the PM3s if you want a simple build. They require more checking to make sure they will work than other pistons, but you can build a powerful, fun to drive, very fuel efficient engine with them if you do put in the work.
 

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Discussion Starter #8
i see...what do you suggest?
i was also looking at the PG6s
 

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well the pm3's work well if you mill the quench pads down but PG6's are great also but may need the valve reliefs enlarged
 

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Could you explain mill the quench pads down?

Is that the area on the head outside the combustion chamber above or below the valves on opposite sides that is like a 1/4 circle? Not sure how to explain that, lol.

Would milling the head do the same thing or do you mill the quench pads down seperately?

edit* I am going to be putting a y7 head on my d15b2 block.
 

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Discussion Starter #11
i think ill just be going p29 and re mill the head to get it sitting flush with the block
 

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The quench pads are the flat(ish) areas of the chamber that are "below" the intake and exhaust valves.

Milling the quench pads is not the same as milling the head, at least on most Ds. The A6 is a good example of this. The quench pads need to be milled to the same height. There is some variation in the casting. If you mill those areas below the valves flat, and to the same height all across the head, you can be assured that the combustion chambers will be more consistent (which should be checked by CC'ing the chambers after all the work is done). This leads to more consistent combustion and easier tuning. It will also allow an advanced builder (or one with enough balls) to run tigher tolerances between the head and piston.

WangLung-
I don't recomend P29s as they are terrible designs. They are not at all ideal in terms of developing consistent and good-burning combustion cycles. You are going to have to pull a lot of timing due to the large dome effectively splitting the chamber in two. This leads to detonation and the only cures for this kind of detonation are to pull timing and add fuel. You will make good power, but it won't be operating at the engine's full potential and it will also require 93 octane.
 

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Discussion Starter #13
as of now its pretty difficult for me to decide. i did read all that stuff about p29s but i dont feel like i have any choice but that, or wait.
i contacted fjdistributors today and they told me while they do have 76mm PM3s
its very popular in their local area so they are kinda hard to come by

he said he can double check tomorrow so i will be calling them up again
but i really hope they have those pm3s

if they infact do have 76mm PM3 pistons you suggested milling the quench pads but
what about the chamber bore thing and valve pocket thing?

Whats your take on PG6 pistons?
do you suggest the same head work to be done on it? and what about the block?

thanks so much for all the good info in here
 

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With any 76mm piston it is a good idea to match the bore to the head. This will allow you to unshroud the valves, and that is a VERY good thing.

If you are not going to mill the head to an unsually extreme amount (over 1mm), you will (probably) not have to worry about the valve reliefs. Rushi, a member here and on other forums is building an extreme D15 with 76mm pistons. He has a head milled over 2mm, and he had to greatly open up the valve reliefs. Worst comes to worse, if you use the PM3s, you may have to open them up a bit to clear the valves. This may also depend on whatever cam you decide to use.

The PG6s are a good choice, too. They will sit zero-decked or very close to it right off the bat. You won't have as many issues with valve clearance since they sit ~.70mm lower than the PM3s. However, they only come in factory sizes, so the largest you can go is 75.5mm. You MAY have issues with the edges of the valves and the slight domes of the pistons coming into contact, but this will depend on the cam, I think, and for most cams, I doubt this will be an issues. I personally do not know of anyone who is running them in an engine currently, but they are my almost favorite piston to use (only because they don't have much in the way of a dome, and some dome is good).

Don't get me wrong, the P29 is a tried and true piston, I just personally think the suck. I think that if people put just a little moer time and effort into thier builds, they would run better, be more powerful, easier to tune, and probably not require 93 octane and a severely hampered timing table just to live and run well. If you are willing to accept the fuel requirements and the time it will take to tune the engine with P29s, go for it! They are a great value for the money. If you like to tinker with things a bit more and want to go for something different and probably better, go for the PM3s or PG6s.
 

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Discussion Starter #15
well as of now i called him up again and for PM3s they only got 75mm
and for the pg6s they got 75 and 76mms
i guess later today i will be placing an order for those 76mm og6s

:D
 

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im going to be using pg6's in my build im currently wait ing on a used set i bought just to do some testing befor i buy new oversized ones just to make sure there is no major maching involved with using them in a z6 with crower stage 2 cam
 

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Discussion Starter #19

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http://www.aclperformance.com.au/us/prod_e_bearingsus.htm

Main bearing grooves occupy
only 3/4 of the circumference
thereby providing optimum
oil supply while increasing
the surface area for better
load-carrying capacity.

Increased crush and the elimination of
flash plating improve seating of bearings
in their housing for better thermal
transfer from bearings to rods and block.

Large chamfers are designed
and precision machined to allow
use of crankshafts with larger
fillets where applicable.

Tight, consistent wall tolerances
(+-0.004mm/ +-0.00015”) help
maintain accurate clearances.

Improved overlay and reduced
overlay thickness where applicable
increases fatigue strength.

Designed with a medium
degree of eccentricity.

Connecting rod bearings have hardened
steel backing which helps maintain their
crush under high load and temperature
conditions during operation.

Decide for yourself?
 
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