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Discussion Starter #1
Hi guys, I've got a customer that just bought a 97 240sx with a SR20DET swap. It doesn't look to pretty under the hood. My expertise is with Subaru's/Honda/Acura/Chevy etc... but I'm trying to help him out. Thanks for any advise in advance!

SR20DET redtop
62 ecu/from 91-93 180sx/s13 silvia 5-spd
"fabricated" wiring harness
stock USDM SOHC S13 MAF(my thought, maybe needs Z32 MAF)??
Apexi AFC

The car idles VERY rough and sometimes dies out. Only about 10-15in vacuum. Once above 2500RPM while accelerating in boost(stock turbo, although spiked to 16psi!!) the car pulls nicely but harsh pinging is heard. Most likely because it's pulling 16psi. I plan to adjust to stock wastegate psi...

I pulled the plugs and they are VERY black. My first thought was timing, so I checked the timing to make sure I'm at 15deg. I noticed the 6 marks on the pulley are supposed to be at 12oclock position about....but my marks were flashing about the 3oclock position. Keep in mind I'm hooked to the #1 coil(front of car). But I never disconnected the TPS. If I disconnect the TPS it dies out.
So, I then line up the second notch(TDC) from the left on the pulley, to the timing pin, and pull the valve cover and notice the cam timing marks are about 5 teeth off each(10oclock/12oclock guides on cams). So I pull the #1 plug and insert a long skinny screwdriver to measure the piston stroke. I rotated the engine until the piston was all the way up, looked at the timing marks on the pulley and they were at the 3 oclock position again, same as with the timing gun, but now the cams were aligned perfectly... So what I've come to find is the timing marks on the pulley are not right? Different pulley? Obviously the marks are about 90deg off...and it only goes on one way, it's key'd..

But just to make sure I adjusted the cams with the notch lined up on the crank at 12 oclock again. "the way it's supposed to be" and turned the engine over slowly by hand to find the valves most likely hitting the pistons, so now I know the marks aren't even close. So changed the cam timing back based on where #1 piston was at by the screwdriver, instead of the crank pulley marks. I also aligned the CAS properly over and over again. Still chugs and coughs, but runs decent above 2500 under load. Thinking about just winging the CAS marks and moving the CAS a couple teeth in each direction see what happens. Otherwise I'm kinda stumped....but I did have him order the Z32 MAF just because...

Don't know what I'm dealing with on these things. How can I check codes with this thing? Any help at all would be appreciated....Any obvious things I'm skipping over? Common problems? Different crank pulley/bent/wrong crank? Is that USDM MAF sensor compatible with JDM ecu? Bad CAS?

Thanks again!

Ian
:newbie:
 

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i'm an asshole
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sounds like a MAF problem. i was having a similar problem with mine and found out later on that a MAF wire had been completely cut. but by then it had already fucked up on me, so i won't be able to tell if that was the problem or not until i put it back together. you can use a SOHC KA MAFS, you just need to wire it up. the good thing about it is you don't have to get it tuned, but you will need to for the Z32 MAFS.
 

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Discussion Starter #3
Thanks Nismo240!

There is a SOHC MAF in the car now. He ordered the Z32 yesterday, and it's got the Apexi AFC so I can tune for the new MAF.

This morning I did a quick compression test and it's about 125psi across the board. I've looked up the specs, calls for 156psi standard, 128psi minimum, 14psi differential max... So I'm pretty dam low, although it's basically even across all cylinders.
So I removed the valve cover again to check out the cams, come time find out they are HKS cams, and both cams look VERY worn. Looking at the cams I can tell the lobes are wearing away pretty bad due to the tall lip found on each side of each lobe. My last experience with what I've found was due to the cams being to big for the stock valvetrain causing the springs to bottom out trashing the cam lobes...
I can see the "fork" that pushes down on the valve and there is NO play at all, I'm thinking maybe could be holding the valves slightly open causing my low/equal compression. I'm not too familiar with these valvetrains, or how to adjust the lifter/forks? Everything is kind of covered up by the oil squirter tubes.

Again, this customer JUST bought the car days ago, knowing it ran like crap. The seller supposively just put the SR swap in, sent out the harness to get fabricated to work and the 62 ecu also. Wiring looks like a 4 year old did it. So at this point it could be anything, or multiple things! Dam, I told him not to buy this thing, then all of the sudden it shows up on a tow truck at my shop 2 days later... I've found multiple problems and repairs that must be done, but I can't say for sure if those would fix or even help the main problem. It's a cluster fuc*. I'm half tempted to just start from scratch, NEW harness, NEW ecu, cams, etc... and go from there. Do it right, or don't do it
 

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i'm an asshole
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i'm thinking since it has aftermarket cams, and with it having low compression, they are at least the "step 2" hks cams. those require aftermarket valve springs, so it would make sense that the bigger lobes are holding the valves slightly open. so you have a pretty good idea of what it might be, thanks for letting use know that.
 

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Sup Mod keeping the peace
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Here's some info on setting up SR20 cam timing:


SR20DET Camshaft Installation Procedure

1. Set crank to top dead center (TDC)…2nd mark from the left on the pulley. With the #1 cam lobes facing away from each other.
2. Remove tensioner.
3. Look at the front of the exhaust cam. You will see that there is a pin that locks the cam to the gear. You will also see a dot stamped into the cam gear at approximately 1 O’clock. This dot is used to mark tooth #1.
4. Starting from exhaust cam tooth #1 count (clockwise) the number of teeth until the top surface of the head. The head should be between 8 and 9 teeth.
5. Adjust cam position as necessary.
6. Find the DOT on intake cam. Once again this is tooth #1. Count COUNTER-clockwise to the top of the head. You should find that the top of the head should be between 4½ and 5½ teeth. Adjust as necessary.
7. Count the number of chain pins between the 2 dots across the top. You should count 20 pins.
8. Install tensioner. Rotate engine 2 full turns and slowly bring it back to TDC ( #1 lobes out)
9. Re-inspect cam position as listed above. Repeat if necessary.

 

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Discussion Starter #6 (Edited)
Rogoman, I have done my research on the timing marks over and over again, AND I found a post you left someone else on here with that timing procedure, thats exactly what I did. By the way, it's the most detailed procedure I've found in the last 3 days, thank you for that! I've got ALLDATA and MITCHELL ON DEMAND, your description/procedure blew them away along with various others I've found on the net...

I've got a Hummer H2 I'm putting heads, headers, cold air intake, and cat back exhaust I'm finishing up tomorrow/today (1am now), along with a nice tune with HPTuners. After that I'm gonna have a the customer come down and take a look at what I've found and see how far he wants to go with it.

I will keep you posted as to what I find, incase it helps anyone else...

Thanks again guys for your info!!!!!

Ian
NorthWest Performance
 
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