VX engine build/swap (in-progress) w/ pics - Page 3 - Fuelly Forums

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Old 12-08-2007, 02:05 PM   #21
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Originally Posted by jadziasman View Post
It's been really interesting to see a VX engine being torn down. Thanks for the view of its guts, 350.

Did you machine some metal off of the cylinder head to increase the compression ratio slightly like you wanted?
the head is still at the machine shop...it should be shaved down enough to reach around 10:1 CR


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Originally Posted by Danronian View Post
Looks like you're making some good progress.

Did you install new piston rings? Or are you sticking with the originals?
yeah - I got all new bearings, rings, gaskets...I figured if I'm taking it this far, I should just replace those too. (I know I could cut corners and do this cheaper, but since this is my first rebuild, I'm trying to be conservative.)
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Old 12-08-2007, 02:06 PM   #22
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Dont forget the adjustable cam sprocket youll need (or a custom offset cam key) to put the cam timing back where it's supposed to be.... Unless there is more FE to be gained by running retarded cam timing. I can't remember where I saw the chart for shaving the head vs how much it retards the timing....probably not applicable in this case because I'm sure it was for a DOHC head (b16 etc) not a VX head.
humm....I"ll have to search around about this...
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Old 12-08-2007, 02:35 PM   #23
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Have you thought about how increasing the CR will effect the way the cylinders fill with the stock VX cams? You may actually lower the FE with the increased CR. See the article on team-integra.net that explains static and dynamic CR and cam timing.

http://www.team-integra.net/sections...?ArticleID=472
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Old 12-08-2007, 06:15 PM   #24
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Have you thought about how increasing the CR will effect the way the cylinders fill with the stock VX cams? You may actually lower the FE with the increased CR. See the article on team-integra.net that explains static and dynamic CR and cam timing.

http://www.team-integra.net/sections...?ArticleID=472
I read the article...interesting stuff, but IMO the reason 'hot' cams loose power is due to too large of an overlap (intake valve staying open for too long and loosing cylinder pressure on the compression stroke (air/fuel in cylinder going back to intake)...do the VX cams have that kind of overlap?

And if they did, raising CR wouldn't effect the cylinder pressure looses b/c that occurs closer to BDC, where an increases CR wouldn't affect it, right?

*I could be totaly off...I have a general understanding of engines - but not nearly enough practicle.

thanks for the article!
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Old 12-08-2007, 07:07 PM   #25
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I'm not really sure what the effects would be. Would there be increased pumping losses from the increased CR that would offset the increased HP? I suppose the other concern would be increasing detonation when the car is in lean burn.

I'm not sure you will still be able to use 87 octane gas. My Integra GSR has a 10.1 CR. I'm supposed to use premium (in CA, this is 91). I usually use the medium, 89 octane and don't hear any pinging, but it will ping with 87. And the Integra doesn't have a lean burn.

I think it's cool you're trying this, I'm just trying to think of any possible down sides.
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Old 12-08-2007, 09:19 PM   #26
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The engine looks like in great condition, I'm wondering how much miles you will be able to put out of that rebuilt vx engine, cause when mine will be going out (in many years... I hope ), I'm already thinking of having it rebuilt (and putting a roll cage in the vx because its not to safe, and people dont drive safe so i'm no safe).

Good post I will follow the all progress, good pics too.
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Old 12-09-2007, 01:06 AM   #27
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I'm not really sure what the effects would be. Would there be increased pumping losses from the increased CR that would offset the increased HP? I suppose the other concern would be increasing detonation when the car is in lean burn.

I'm not sure you will still be able to use 87 octane gas. My Integra GSR has a 10.1 CR. I'm supposed to use premium (in CA, this is 91). I usually use the medium, 89 octane and don't hear any pinging, but it will ping with 87. And the Integra doesn't have a lean burn.

I think it's cool you're trying this, I'm just trying to think of any possible down sides.
I really appreciate all the comments...from my general understanding, a slightly higher CR should increase the efficeny of the engine (which leads to more peak power, but also better FE...you're using more of the energy stored in the gasoline). The main downside is the increased stress on the engine and possible pinging...but from reading on another honda forum, ppl have gone to 10.5:1 CR and were able to maintain 87 octane w/ the VX engine. Each engine is unique, so I spent several days searching and asking to find someone who's actually done a CR increase on this engine.

Also, from talking w/ my machine shop guy, he showed me where Honda puts the indicators for the maximum amount you can shave off on the head (they build in a certain amount knowing that ppl rebuild)...normally ppl would just get a thicker head gasket and maintain the same CR, but Honda has to have added some margin of safety for variations of fuel, degredation of engine components, weather,...so, in the end, I think/hope 10:1 is a good bump, but hopefully nothing too extreme that it'd cause problems.
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Old 12-09-2007, 08:26 AM   #28
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Yeah, most Honda heads can be shaved about 2 times just to make the flat after a blown headgasket, so I can't see that you would have a big problem at all. I had a lot shaved off my integra head to make it flat, and I had no problems with aligning the timing belt and getting the timing right....and a dohc head is always more of a pain to get the timing belt aligned.
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Old 12-10-2007, 06:52 AM   #29
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how much has it cost you so far??
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Old 12-10-2007, 05:45 PM   #30
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I'm sorry if I missed it. But did you hone the cylinder wall for the new rings?

Are you going to check the compression ratio before you button it back up?
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