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Discussion Starter #1
So I got a nice d16z6 (it says d16z9 on it, but it's basically the same). The motor is in pieces, so I'm gonna get a full rebuild set.

I have been thinking about getting 75mm p29 pistons to get a 12:1 CR. A friend of mine has done that before and said it worked pretty well. He used all stock parts and only changed the pistons to p29 ones.

My question is if it would really work and make a reliable motor? Using all stock parts (including rods) and just throwing p29 high comp pistons. 12:1 sounds too much to me to call it a reliable motor.

I'm not planning about braking records of n/a motors, I just have the chance to rebuild the motor, so I want to get a bit more out of it by getting those high comp pistons.

I would really appreciate your opinions about it, thank you.
 

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BATSLOMAN GIVES NO FUCKS.
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are you sure the bores are straight and still stock specs? you don't build the pistons around the engine.
 

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P29 high dome pistons are a great way to gain compression, but generally WAY too much for the stock ecu, unless EVERYTHING else is running PERFECT and you have high octane fuel to help AFTER adjusting ignition timing.


Much easier to go with PG6 pistons. Google for "zeals compression calculator"


PG6 pistons are a great middleground to add compression, and its generally as simple as running 91-93 octane fuel, and adjusting the distributor a bit to dial in some timing.


You really SHOULD try and make your own DET can (copper piping bolted to block, rubber hose to a stethescope)
 

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Just used the Zeals comp calc, seems PG6 pistons brings a Z6 up to 11.67 compression.

Combine it with a 88-95 d15/d16 nonvtec headgasket, and you will bring it down to approx 11.3:1 compression due to the 88-95 nonvtec blocks using a thicker headgasket
 

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Discussion Starter #5 (Edited)
Just used the Zeals comp calc, seems PG6 pistons brings a Z6 up to 11.67 compression.

Combine it with a 88-95 d15/d16 nonvtec headgasket, and you will bring it down to approx 11.3:1 compression due to the 88-95 nonvtec blocks using a thicker headgasket
Thanks for the advice. Never thought about PG6 pistons and a d16a6 head gasket, but it looks like it's a good CR for my setup (all stock internals but the pistons and pump gas).

are you sure the bores are straight and still stock specs? you don't build the pistons around the engine.
The bores are straight. This engine is in a very good condition. I got it from a friend where it was sitting in the garage, waiting for a the right car to get into.
 

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Unless you check the bores, you wont know. Piston rings expand enough to cover up ovalized bores and even bores worn out at the top, where under light load or idle, engine doesnt smoke at all, but under load and higher rpm, the rings cannot act fast enought o expand, and cause oil burning and loss of compression temporarily as the rings sturggle to expand fast outwards.

Basically he is saying, if you are going to bother changing pistons and rings, have a shop check the block out for best results.


No engine is perfect with a lot of miles!

Basically "while you are in there" approach.
 

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Discussion Starter #7
I got the engine in pieces, that's how I know how the whole bore looks like :D. The block is completely naked.
 

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What did the measurements come out to be?

Im always curious how different blocks "age" over the years.
 

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PSSSHHH.... Dudes..

This engine has been around for 30 !!!!!!!!!!!!!!!! years, and y'all don't know the recipe yet..?

SMH..
 

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Stop using those Junk calcs, they dont do shit. Use your brain and be reasonable.

Cast piston? Rebore with minimal P2W, ~0.001.
Ring gap 75% max spec

Mill the block until the piston stick out the top ~0.005
Use a Y8 0.027 HG

P29s are dumb. Do some hooker math on a napkin with the forces pressing down on a 45 degree face..
Where does the force vector point..? Perpendicular to desired thrust vector.
Use flat, or slightly cupped pistons. Get your compression by milling the head, make sure the valves clear. Adjust with Cam gear.

You're one of The Chosen People? What's your Octane rating over there? That matters
What cam you plan running? Density Altitude?

ARP rod bolts, rebore the big ends!!

Exhaust valve guides need replaced at LEAST. Get a 3 angle valve job. Mill head and deck. Do what matters. Port your oil pump, and oil filter housing by yourself with a dremel BEFORE machine work, or clean very thoroughly.


And then I am here with my jaw on the floor at Matt suggesting you tune it by moving the dizzy.. ...

I'll see myself out..
 

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P29 pistons are dumb? Look at most factory K series pistons, especially RSX Type S, and TSX. Honda would like a word with you.

The D's already have a 3 angle valve job factory. Much like everyone else.

I certainly did not say "tune it" with the distributor. You can remove some timing advance to compensate for the lack of a tuning solution. You know, so it doesnt detonate and blow up?

No need to be a dickbag.

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adirsabag, still wondering how you checked the bores.
 

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Discussion Starter #12
137052


After light honing at home, it appears that there are some noticable scratches. I'm thinking about doing a 75.5mm over bore.

Aftera lotof thinking, I really thought about just rebuilding the engine, and having something like 10.5:1, to make it a more daily driver.

Any thought about 75.5 pistons that would help me to get there?
 

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Then you need to get some sort of tuning solution with the P29s for best engine life. It is impossible for someone to prevent themselves from doing a few full throttle rips on a fresh build.

75.5mm bore is fine. I recommend taking the block to a shop, and having them inspect it for cracks. Not every scratch is ONLY a scratch. Who knows what 20-30 years of operation, has done to it for sure.
 

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Discussion Starter #16
Then you need to get some sort of tuning solution with the P29s for best engine life. It is impossible for someone to prevent themselves from doing a few full throttle rips on a fresh build.

75.5mm bore is fine. I recommend taking the block to a shop, and having them inspect it for cracks. Not every scratch is ONLY a scratch. Who knows what 20-30 years of operation, has done to it for sure.
I wil definitely get a tune for that.
I will take the block to a shop and inspect it before we over bore it.

Thank you for your help guys, I will updat when this build starts to get together.
 

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I think you will really enjoy the P29 build once its tuned up.

Be sure to search on here for what others have used for headers and intake manifolds. The P29 builds can be very picky on what makes peak power, and what is in the usable midrange. Your driving preference and how lightweight you end up making the car should help you determine if you want it very peaky, or you want a fat midrange.

It is very easy to get to and beyond 135-140whp. It is a challenge, but very possible, to touch 160whp. Of course, that is the path of people who fabricate parts, port and polish the head, and have mutliple camshafts to test out, along with an adjustable cam gear to figure out peak numbers.
 
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