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Discussion Starter #1 (Edited)
Hey guys im new to this site and this is gunna be my first stab at a d series. i havnt resurched much about d series as this motor is gunna be for my dayly driver. i have a built ls/vtec turbo with a gt30r for my weekend fun so i dont expect this to be fast by any means. anyways i have a 95 cx eg hatch and the good old d15b7 burns about 2 liters of oil a week. i just picked up a d16z6 full swap but it needs a rebuid. my goal is to build a high comp single cam screamer that will beat a stock b16 on the mega cheap. from what i have read some people say that the p29s will give me over 13:1 cr and others say 12:1 so im a bit confused. i want the motor to be at roughly 12:1. I also have a d16a6 sitting in my basement not sure witch bottom end u guys will suggest. i was gunna throw a b series TB on it and port match the intake mani and do some port work to the head. its gunna have an intake on it and maybe an ebay header and no cat. im to cheap to buy a cam but i will tune it on crome... seeing how i have the d16z6 and a6 what combo with the p29 pistons will yeild me roughly 12:1 cr? what head gasket should i use and what should all the specs be? also i have the cx tranny in the car and the si one which one has beter gear ratios?thanks for any input guys
 

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94 civic, 90 talon
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check out zeal autowerks compression calculator and for the rest the search bar and google are your friend
Zeal will be your best friend. I wouldnt use p29's for any build. They are not the best design and the ring lands are terribly weak, but they will yield 12:1 compression, give or take a few for head gasket and other variables. Pg6's are a better design, they have a flat top and not domed liked the p29's which helps a lot with the actual combustion. The only down side, other then them just being a cast piston, is the mini valve reliefes. That shouldnt be a problem for you because you want to run the stock cam, which i would advise against doing. Another thing is, there are 2 different designs for the p29, the oem design which is 29mm compression heightm wich is slightly smaller then the npr? style with a 30mm ch. I forgot to mention that the pg6's will also be around 11.X:1 in a z6. I dunno about any compression numbers with the a6 head (use zealautoworks.com).

I would recommend you port the intake manifold and also match it to a 60mm tb, but use the stock size tb. You wont sacrifice mid range power and still gain some *umph* in the higher rpms. Making those steps help fight reversion, and should be made through out the head. Doing that and using the appropriate camshaft will benefit you the most. You can have 15:1 compression, but not make shit for power with out a proper intake manifold (carbs, itbs, etc.), camshaft, portwork, and of course header design.

I think a decent set up, that can be had on the cheap, would be use the a6, get a ''stage 2" cam shaft from whom ever (delta would be cheapest), do the port work, use pg6 pistons, modify the collector on your header, and tune. Should be a pretty peppy engine.

There could also be holes in my logic, so do the research your self and listen to whom ever corrects me, unless they are just being foolish!
 

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I have used the pg6 in a b7/z6 build and it is a very good running engine. I am currently running a z6 with pm6 pistons and it is also a great engine. My fav one though was the stock short block jdm d15b non vtec with a y8 head i ported and polished it was extremely fun. I never ran it at the track but being in a light crx it would have went 14s easy.
 

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There are two kinds of P29s on the market now: Stock ones and the NPR 30mm compression height units that are much, much, much, much better and the only type of P29 pistons I would ever run.
Is the only benefit from the npr p29's, larger valve reliefs and they sit at deck height? Do they have thicker ring lands and better quench pads? Wouldnt sitting closer to the deck give them even more? quench?

exp: Iirc correctly, p29s with a y8 head is a problem because the head needs pistons with a larger quench pad to produce less? quench. The p29s dont have a very large quench zone and leaves very little room in the cc to produce an efficient burn? Im just tring to get my facts straight...
 

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well it sure sounds reasonable if you look at the design of the head and piston. I could see it almost making 3 seperate "combustion spaces" with the design of the pistons, like the charge would get stuck behind the large dome on the piston. Then again, how much is too much, you'll have to wait for somebody with experience with the combo to give you some input as I'm just hypothesizing.

Nick
 

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93 Legend L Coupe.
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Is the only benefit from the npr p29's, larger valve reliefs and they sit at deck height? Do they have thicker ring lands and better quench pads? Wouldnt sitting closer to the deck give them even more? quench?

exp: Iirc correctly, p29s with a y8 head is a problem because the head needs pistons with a larger quench pad to produce less? quench. The p29s dont have a very large quench zone and leaves very little room in the cc to produce an efficient burn? Im just tring to get my facts straight...
well it sure sounds reasonable if you look at the design of the head and piston. I could see it almost making 3 seperate "combustion spaces" with the design of the pistons, like the charge would get stuck behind the large dome on the piston. Then again, how much is too much, you'll have to wait for somebody with experience with the combo to give you some input as I'm just hypothesizing.

Nick
Yes. Especially with the Y8 head, you would have low areas to the intake and exhaust side, and not much in the middle around where the spark plug is.

The NPR P29s solve this. If you look at how the top of the piston looks, you will see a large difference. The top of the dome is about the same height as the P29, but with the higher compression height, the dome is actually less intrusive, as the whole chamber is moved up farther. The dome has less volume. This is a much better situation for the SOHC heads. The overall combustion space is more compact and better able to burn.

I am wary of running ANYTHING with a dome in Y8s because of the very low quench pads. I think any dome is a bad thing. I still recommend PG6s for a Y8 UNLESS YOU KNOW FOR SURE you are going to be running a cam with very high lift AND long duration.
 

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98 Prelude turbo
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Having the best flow is going to be your best friend..( I know this isnt the best adviceif you never done this or know how to) i would get a dremel set, and port the head, Port match the intake manifold.. port your exhaust manifold/ headers if possible, Larger Valves would help, I would get a delta cam like $160.00 or something to gain alot of power, Anything that will make it flow as much as possible
 
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