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02-14-2011, 02:45 AM #11
- Join Date
- Feb 2011
Thank you. I'll post a new thread tomorrow. I'm going to try to get the valves adjusted tomorrow and i'll post an update as soon as i can. Thanks for all your help.
02-14-2011, 02:51 AM #12
You're welcome. Keep your fingers crossed that it's the valve adj. & the compression will come back up.
Just a side bar... is this a good compression guage that you're using? Is it new? Have you used it on other engines, & if so did they also read around 90 PSI? If yes, then it might be a good idea to borrow another guage from a friend & try it if the V.A. doesn't bring the comp. back up.1988 Chevy C-3500 2wd (no pic)
350 c.i. 5.7 L Stock Block, 4 Bolt Mains
L-31 Vortec Heads, Edelbrock Cam & Intake,
Holley 650, Flowtech Headers, Magnaflow exh.
Jet Trans 700R4, B&M Ratchet, 4:10 gears,
3" susp. lift kit "shadetree"
No rev limiter, No speed limiter lol
02-15-2011, 12:10 AM #13
- Join Date
- Feb 2011
I borrowed another compression tester from my in-law and here is what I got when
I checked compression on all cylinders.
Cyl 2 6 7 and 8 all had 130psi compression
cyl 1 3 4 had 120 psi compression
cyl 5 had 125 psi compression.
I do not have AC Delco plugs and wires. Can anyone tell me why these vortec's are said to like only ac delco plugs/wires? I am thinking about buying a new set tomorrow but I just bought these others a couple of months ago and cant get my money back. Is it just a plug issue or is it both plugs and wires?
I adjusted all the valves before I did the compression test by running the engine until it was warmed up with the valve covers off. Then I loosened each valve until it started clacking and then I tightened it until it just barely stopped making noise. Then I took it 1/2 turn more. It still ran rough though just barely, which is why I did the compression test again.
I cleared all codes (p0300 random misfire) with a code reader and saw no further codes, but I think I would have to road test it for 15 minutes before I started getting codes again. Even though it seemed like it was running rough.
I also did the compression test when the motor was warm but not HOT.
Any other thoughts other than replacing the plugs and wires. None of the plugs seemed to have any odd discoloration - they were all tannish grey not black.
Edit: I also noticed when I readjusted the valves on bank 1 drivers side cylinders 1 3 5 & 7 that they were all pretty tight. It took 2 to 3 loosening turns before they started clacking. bank 2 was ok as i had adjusted them before.
Thanks in advance.
---------- Post added at 11:10 PM ---------- Previous post was at 10:42 PM ----------
I also looked for a "Light show" before I did anything tonight and there were no sparks showing up in the dark anywhere in the engine compartment.
Last edited by jonejam2; 02-14-2011 at 11:45 PM. Reason: Correction
02-15-2011, 01:49 PM #14
I don't think the plug wires are the issue I think most people have said the vortecs just have to have the AC plugs. Most wires are compatable no matter the brand. I have no idea why they would run better on ACs cuz it doesn't make sense, but many posters have said putting ACs in their engines have fixed their running problems even though their other plugs were brand new.
Did you figure out why your valves were so tight? Have you run this engine enough that the valves could be seating deeper & making them tighter? A fresh valve job will allow the valves to seat deeper, but I didn't think you had much running time on this engine yet.
02-15-2011, 04:06 PM #15
- Join Date
- Feb 2011
I think the valves were tightened to much when we put the rockers/push rods in. We took them to zero lash and then another half turn. I'm wondering if our zero lash was too much. I managed to get about 200 miles on this from test driving to/from my town to the parts store to use their code reader. I finally bought myself a code reader so I'll be able to check it myself.
Someone else said to check the coolant temp sensor and the idle control valve as well. Once I put the new plugs in and test drive it and if I have the problem still I'll be checking those (if i can find them) and look for a vacuum leak again. I may take it in to a shop to check for a vacuum leak unless you can walk me through how to do it myself. Ive heard people use baby powder and stuff like that, but I don't really know how to go about it at this point.
I will update more tonight. Thanks for all your help!
02-15-2011, 06:05 PM #16
You're welcome JJ. Your zero lash was fine for the preliminary adjustment & even with 1/2 or even 3/4 turn it would have been fine. I think what happend is that you didn't go through the fireing order when you did your prelim. adjustment & so not all of your lifters were on the base circle of the cam. Did you adjust all the rockers with the engine crankshaft in one place? At any rate, no worries since your compression has come back up.
Don't take it to a shop to check for a vacuum leak. You can buy a vacuum guage for 1/4 of what a shop will charge you, & then you will always have it for future use. Buy an analog vacuum guage (not a digital one, cuz if you have vac problems it will be changing so fast you won't be able to read the variations) Get an analog guage with a needle & a dial. Hook it up anywhere you have constant manifold vacuum. In a perfect world your engine should have 19-21 inches & the needle should be steady, but with new rings that may not be seated yet, it may be lower than that.
I've been watching your other thread & Murdod is one of the best on these vortec EFIs so his suggestion of the IAC & the temp sensor are spot on if the AC plugs doesn't fix it & there is no vacuum leak.
02-15-2011, 07:53 PM #17
- Join Date
- Jan 2011
- Lake Conroe Tx.
You mentioned a roller cam. You don't have solid lifters? These are adjusted with a feeler gage
02-15-2011, 08:30 PM #18
That's a good question Conroe cuz they make both solid & hydraulic roller lifters lol.
Whadda ya got JJ?
02-15-2011, 09:26 PM #19
- Join Date
- Feb 2011
I think what happened with the rocker arms is that I had my top dead center wrong or something. When we adjusted them we went through each one in firing order but then again, my friend is the one who walked me through it and I wasn't all that sure what was going on.
I have hydraulic lifters according to the shop. I don't really understand all the differences but that is what I was told.
After replacing the plugs with ac delco the suburban ran smooth. I took it for a long test drive (before it would take about 15 minutes to cause the problem) and it ran smooth the whole time. No hesitation and it seems to be running strong. I think that the valve adjustment and the plug replacement may have solved the problem.
I think I will buy a vacuum gauge anyways just to have it on hand.
I will update over the next few days to confirm the problem is solved - I HOPE AN PRAY IT IS.
Thank you for all your help. I couldn't have asked for better help!
---------- Post added at 08:26 PM ---------- Previous post was at 07:48 PM ----------
I am going to start a new thread. As I was going up a slight hill the suburban RPM's rose and CEL came on with code 1850 = Trans component slipping. Otherwise it is running smooth. The wife told me it has done this in the past but I have never seen it.
I will leave this thread for the idle/smooth running issue.
02-15-2011, 09:28 PM #20
You're welcome JJ. I'm glad that fixed it. Also glad the shop said hydraulics cuz they do make both. As long as they're hyd. then your valve adjust procedure is correct. & definitely consider the vacuum guage somewhere down the road cuz it's a great diagnosis tool. There are about 12 eng problems you can find with them.
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