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Banned
1991 Honda Civic EX
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1 Posts
Discussion Starter #1
I recently purchased a '91 Civic EX and was told the car steadily misfired on cylinder one. Well I quickly realized that the engine smokes when it gets into the higher RPM range. I also noticed that cylinder one had no compression while idling but seemed to gain a slight bit while I was on the throttle. Everything I've seen has said that this is most likely the piston rings. If it is, I'm just going to replace all the pistons with brand new ones. I'd like to know if it would be better to go with the P29 ZC pistons or to go with GX pistons on LS connecting rods. I'd like to do the gx pistons if possible, but I'm having a hard time finding them. Any links and help would be greatly appreciated.
 

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BATSLOMAN GIVES NO FUCKS.
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4,054 Posts
why replace them? new rings, maybe a hone and good to go. while youre there, a tune up wouldn't hurt
 

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5,879 Posts
Put your wallet away.

Find out why its lost compression in that cylinder.
do both a dry and wet compression test.

both should be with ignition and fuel disabled via unplugging shit, or pulling fuses.

full throttle open position, crank for 5-10 seconds I would imagine. whatever it takes to peak out and level the numbers.

Have the battery hooked to a charger or running vehicle for best results if your current battery is old, that way you do not introduce a tired battery to the last few cylinders.

if the cylinder head is responsible for the oil consumption and loss of compression, fuck getting new rings or pistons. a shit cylinder head will not care if your block is in perfect health


EDIT I also cant imagine how the hell you can tell compression is gone at idle, but "picks up" with rpms. Sounds more like its waiting on fuel pressure, as vacuum decreases with more throttle, the regulator is allowing higher pressure, and perhaps pushing past a dirty fuel injector, which might be sticking occasionally and feeding more fuel than necessary, creating smoke.


Color of smoke, smell of smoke, is there buildup on muffler tip?
 

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Banned
1991 Honda Civic EX
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1 Posts
Discussion Starter #4
You'll have to forgive me. I'm brand new to Hondas, this is my real "first" car. Before I had a BMW 740i that was really just meant to be an $800 experiment to see if it would actually last more than 6 months(which it did not I might add). I know it's not a head gasket because the smoke is a bluish grey color. The grey is because of it not burning off the fuel in cylinder one of course. And the blue is it burning oil. It clearly smells of oil and begins to blow smoke when I go above roughly 4000 to 4500 RPMs. Also, I did the compression test today and there was zero compression at all. I'm going to tear the engine down soon and replace the pistons and rings with 76mm P29 pistons. I could use the extra compression for any power I can get to make it up the hills out here. I've also got a 91 Accord throttle body I'm going to install after I finish boring and polishing it. I need to get as much power from this engine as possible without ruining the reliability of it. What size head gasket should be run when I install the P29 pistons?
 

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BATSLOMAN GIVES NO FUCKS.
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4,054 Posts
why would you go straight to 76mm?
 

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Banned
1991 Honda Civic EX
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1 Posts
Discussion Starter #6
Well I was told it would help increase compression. What would you suggest? 75mm P29 pistons or possibly 75.5mm?
 

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BATSLOMAN GIVES NO FUCKS.
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4,054 Posts
75.5 will the head milled.
 

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Premium Member
2005 Legacy GT
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1,754 Posts
Jumping to a 1mm overbore right off the bat is probably not the best plan. As long as you are tearing it down check the cylinders. If they're still round you can likely just hone, rering, and be on your way. Overboring is a fix for when there's too much wear in the cylinder to get a good seal on the stock size piston rings. If they're still in good shape, and will have P2W clearance within OEM spec. Hone, rings and go. Otherwise bore it over as little as possible (0.5mm) to get the seal, because once you go to the max overbore ... well you're SOL if you need to do it again.
 

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Banned
1991 Honda Civic EX
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1 Posts
Discussion Starter #9
Alrighty thank you guys. Like I said I'm brand new to this. I appreciate the help with everything. I've been waiting on an exhaust(eBay) now that I ordered on Monday and I'm ready for it to get here so I can replace the entire rusty stock exhaust. If I'm looking to increase performance, what are some cheaper things I can do? I'd like to stay as simple as possible with mostly bolt one but I'd be willing to replace a cam or something like that, especially while I'm already inside the engine.
 

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Premium Member
2005 Legacy GT
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1,754 Posts
Anything you do beyond basic bolt ons (I/H/E) will need a tune to really wake them up. Yeah you could do a cam, but to really take advantage of the changes in lift/duration your timing and fuel maps really should to be adjusted to compensate. Same with bumping the compression up a bit (I'm not sure how much is considered okay on stock fuel/timing).

The biggest bang for your buck is going to be your suspension, since this doesn't take a whole lot of extra support. Refresh the old bushings, get a decent strut/spring combo, or a good set of coilovers (the difference between cheap coilovers and quality ones is magical ... don't cheap out). These kinds of upgrades can make even the most underpowered car a lot of fun to drive.

Also look into transmission upgrade options, these can also be expensive, but again do not require tuning. Shorter gears and an LSD can go a long way towards increasing the fun factor.
 

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Prelude, Integra DB9
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366 Posts
Although it sounds like you have to fix the engine anyway, don't lose sight of the fact that it costs nothing to strip weight out the car. If you're not bothered about passengers and sound-deadening etc, there are significant gains to be had.
 

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Banned
1991 Honda Civic EX
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1 Posts
Discussion Starter #13
So I have a body who's taking auto body at the local college. He asked his engines class teacher about working on the car there. The teacher said he'd be glad to have one of the classes work on it. They can give me a quote on parts or I can order my own. I'm going to order my own. What should I order that could make a difference in it that they could install while tearing down the engine?
 

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BATSLOMAN GIVES NO FUCKS.
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4,054 Posts
don't order anything until they tear it down. when you know for sure if you need a bore/hone then you can order. when you know the specs, then you can order the rings, bearings, seals and gaskets.
 

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DIY Guru
96 Ranger-stock
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637 Posts
Ohhh I remember my days back in Vo-tech

I learned alot at the expense of other peoples money!

Spinner, I wish you the best of luck with your endeavor at the school, and hope the one that works on your car is the hot shot of the class and a bit of a narcissist
 
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