SOHC ZC Issues

 
Old 09-04-2017, 08:22 PM
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Default SOHC ZC Issues

So since day one with this "project" I've had issues, but have kept on going making repairs in the hopes of having a nice, reliable 1990 Civic Si. At this point I'm coming to the forums for some help as my searching through past threads has yielded many answers, but not enough for me to feel safe pulling any trigger. I bought the car with a POS b15b in it that had massive oiling issues along with many other 20+ year issues that I've been repairing. I pulled the motor apart to further diagnose and repair the issues, and as a result of the findings scrapped the motor to look for a stock D16A6 and get the car back to OE. A friend of mine found a 1990 Civic Si with a complete motor in a junkyard for sale and looking at the pictures and in person (to him) it looked like a good motor that just needed a little love. For $500 local it seemed like a good deal. Upon delivery of the engine we found it was a JDM ZC engine that appeared to come with VTEC at some point in time, but the two bolt port on the corner of the head was blocked off (I assumed it's use was for the VTEC solenoid). Not to concerned with this, I replaced all the seals, timing belt, water pump, yada yada and put the engine in. Upon start up the engine ran well, but Cylinder #3 would not fire at all. Tested compression, and found it to be nil. Tried the old transmission oil trick to attempt to diagnose as a head or ring issue and found the same results. Finally pulled the head and found that an exhaust valve had cracked leading to an obvious lack of compression. Piston and bore show no signs of damage or scoring.

This is where I'm stuck as I am in all honesty not a Honda guy but can find my way around most any car in particular. I would like to get a decent amount of power out of the engine without having to go crazy as I would like to do some auto-x with it and daily it on non-rainy days (no A/C makes the window fogging an issue and in the Southeast humidity is crazy high). I cannot for the life of me find the VTEC solenoid for the ZC head as it appears to be a two bolt design and everything I see when searching is three bolt. I've read that the SOHC VTEC ZC is closely related to the D16Z6 in the DelSol.

My question is this; should I salvage the ZC head despite not being able to find a VTEC solenoid or do I find a different head (VTEC or non-VTEC) that has the potential for more or the same and go from there? I currently do not have a VTEC ECU. From what I can tell I have a stock ECU with a Bullfrog Cam chip in it (came with the car) despite not having a cam in the car.

I appreciate any help and do apologize for the n00b questions but I'm running out of resources or just don't know where a proper one is.
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Old 09-04-2017, 08:43 PM
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Default Re: SOHC ZC Issues

you can't just add a vtec solenoid. the entire internal setup of the head has to be all vtec components as well, including the cam.
just buy a stock replacement valve and call it a day. if you want vtec, you'll need a vtec head and vtec ecu. and if you want to race autocross, be careful what you alter, because literally everything, even a simple cai, can and will bump you into a higher class.
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Old 09-04-2017, 08:53 PM
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Default Re: SOHC ZC Issues

Originally Posted by motoxxxman View Post
you can't just add a vtec solenoid. the entire internal setup of the head has to be all vtec components as well, including the cam.
just buy a stock replacement valve and call it a day. if you want vtec, you'll need a vtec head and vtec ecu. and if you want to race autocross, be careful what you alter, because literally everything, even a simple cai, can and will bump you into a higher class.
That's just the thing. The head is VTEC but the VTEC solenoid port has been blocked off. For reference looks like this.




As for Auto-x, I'm using the stock intake with a K&N drop in, and a 4-2-1 header with stock exhaust along with Tein coils and adjustable front and rear upper control arms. Everything else is stock bushings.
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Old 09-04-2017, 09:22 PM
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Default Re: SOHC ZC Issues

That actually looks like the mechanical oil pump port and you can see the oil pump lobe of the cam in your picture. I have that same non vtec 16 valve no LMA or third lob head to be scrapped in my garage.

That normally is found on the carburetor non vtec motors of Honda. A bit more prevalent over seas than north America but found here too on older civics.

You can see the oil pump attached to the ZC/D15B dual carb non vtec JDM motor here:
http://jdmengineland.com/index.php?m...image&pID=3190
http://jdmengineland.com/index.php?m...ckuveg474ja4h5
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Old 09-04-2017, 09:49 PM
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Default Re: SOHC ZC Issues

So then how should I go about verifying which engine I've got? I never thought it would be so difficult and at this point I really just want to get it running again without having to sink much more money into it.

Would I carbureted ZC still allow a a fuel injected intake manifold to be bolted up to it? That's really whats been throwing me for a loop is just how expansive and swappable the parts are in the older Hondas. It's not a bad thing, it's just more difficult to figure out what you have and where to go in my case.
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Old 09-05-2017, 12:37 PM
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Default Re: SOHC ZC Issues

So, I've been digging some more into what motor I actually have and from what I'm reading it would appear keeping the current head would work in my favor as the carb cam is slightly aggressive. What would be a safe amount to shave off the head to bump the compression a bit but not cause any clearance issues? I only ask as I haven't found a good answer besides ones for a D16A6 and D15B and am not certain either would cross in my case. I'll be pulling the valves soon to match them, as I currently have no idea what they'll cross to. Will keep updating.
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Old 09-07-2017, 08:06 AM
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Default Re: SOHC ZC Issues

Originally Posted by Zanbato View Post
So then how should I go about verifying which engine I've got? I never thought it would be so difficult and at this point I really just want to get it running again without having to sink much more money into it.

Would I carbureted ZC still allow a a fuel injected intake manifold to be bolted up to it? That's really whats been throwing me for a loop is just how expansive and swappable the parts are in the older Hondas. It's not a bad thing, it's just more difficult to figure out what you have and where to go in my case.
If the picture you posted is your motor, you have the regular SOHC ZC/D16A6/D15B2/D15B1 setup.

You're over thinking it. Just pretend you have a D16A6 as the only main difference is the camshaft which is slightly larger on your engine.

As motoxxxman already posted, if you are going to race in a class then the class is going to dictate what you can change. Otherwise the usual n/a "don't have much money to spend" route was to port the head yourself, get it milled as much as your fuel and tuning will allow (max is like ~.080"), get delta to regrind a 272, run a z6 or y8 intake manifold, header/exhaust, and then shoot for 130-150rwhp. Your ability to port, the compression, the camshaft, and ability to tune usually dictated to what end of the scale you were.
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Old 09-12-2017, 11:55 AM
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Default Re: SOHC ZC Issues

Originally Posted by Pro-SeriesFab View Post
If the picture you posted is your motor, you have the regular SOHC ZC/D16A6/D15B2/D15B1 setup.

You're over thinking it. Just pretend you have a D16A6 as the only main difference is the camshaft which is slightly larger on your engine.

As motoxxxman already posted, if you are going to race in a class then the class is going to dictate what you can change. Otherwise the usual n/a "don't have much money to spend" route was to port the head yourself, get it milled as much as your fuel and tuning will allow (max is like ~.080"), get delta to regrind a 272, run a z6 or y8 intake manifold, header/exhaust, and then shoot for 130-150rwhp. Your ability to port, the compression, the camshaft, and ability to tune usually dictated to what end of the scale you were.
Appreciate it. I have been overthinking this. Fortunately I already have a y8 manifold that came with the d15b that was blown. Thinking we'll probably mil .055, get the cam ground and get her tuned and see how she does.

Thanks for all the info.
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