Tore down engine, back together, runs like crap, HELP
Thread Starter
Racer
Joined: Oct 2000
Posts: 383
Likes: 0
From: Moss Point Ms.
Tore down engine, back together, runs like crap, HELP
This engine was just built about a year ago,,, it's a 383 with mostly TPIS parts,, see sig line for spec's. Anyway, was driving on hiway went to pass car and knocking started,,, tore down motor, only problem found was broken stud in head that hold's rocker arm and lifter for that cylinder broken. Replaced lifter, stud in head, put in shorter pushrods so more thread in nut , put motor back together, put in car, now run's like it's running real rich, smoke coming out exhaust, gas fumes will burn your eyes standing next to car, but no codes and O2 sensor says o.k..
Here's what all we've done to try to correct the problem. Changed plugs (3 times), changed o2 sensor, engine temp switch, Maf sensor, checked plug wires, firing order, chked for sticking injectors, swapped computer, chked fuel pressure.
Engine won't rev past about 3500 RPM's, it just bog's down. I hooked Diacom software up to it and everything seems o.k.. Everyone I've talked to is out of ideas of what to check next.
I would appreciate any suggestions. :mad
[Modified by ham, 11:38 AM 6/4/2003]
Here's what all we've done to try to correct the problem. Changed plugs (3 times), changed o2 sensor, engine temp switch, Maf sensor, checked plug wires, firing order, chked for sticking injectors, swapped computer, chked fuel pressure.
Engine won't rev past about 3500 RPM's, it just bog's down. I hooked Diacom software up to it and everything seems o.k.. Everyone I've talked to is out of ideas of what to check next.
I would appreciate any suggestions. :mad
[Modified by ham, 11:38 AM 6/4/2003]
Drifting
Joined: Dec 2002
Posts: 1,861
Likes: 4
From: Houston TX
Re: Tore down engine, back together, runs like crap, HELP (ham)
When you say you tore down the motor, did you tear it down all the way and check everything, or did you stop when you found the rocker stud problem?
Thread Starter
Racer
Joined: Oct 2000
Posts: 383
Likes: 0
From: Moss Point Ms.
Re: Tore down engine, back together, runs like crap, HELP (ham)
If you can't see my sig line for the engine spec's, then you don't have "show sig's" turned on in your profile, here's how to do it. http://forums.corvetteforum.com/zero...ounce&id=38#57
Thread Starter
Racer
Joined: Oct 2000
Posts: 383
Likes: 0
From: Moss Point Ms.
Re: Tore down engine, back together, runs like crap, HELP (CorvetteZ51Racer)
Engine was torn ALL THE WAY down, cylinders honed, new bearings, new rings,,,, everything checked ( supposedly).
If interested, I can put some video's on my web page showing exhaust and you can hear how bad it's running....
[Modified by ham, 11:53 AM 6/4/2003]
If interested, I can put some video's on my web page showing exhaust and you can hear how bad it's running....
[Modified by ham, 11:53 AM 6/4/2003]
Pro
Joined: Oct 2001
Posts: 682
Likes: 23
From: loxahatchee fla
Re: Tore down engine, back together, runs like crap, HELP (VetNutJim)
we need WAY more info but not being there to test things it sounds like the cam index timing is off the correct setting , (CAM IS NOT DEGREED IN CORRECTLY)
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Re: Tore down engine, back together, runs like crap, HELP (grumpyvette)
:withstupid:
Eactly what I was thinking. It either sounds like a cam out of time, not degreed right, the firing order off, valve not opening all the way, ie valve train problems.
What cam is in the car? Was it degreed. Pull the valve covers off while its idling, it going to be messy, to see if you can see any acting weird for example moving as much as the others/loose lash.....you really have to with the simple things then work towards the more complex.
Just a stupid question....your TB is opening all the way isn't it? I don't know why your car wouldn't go past 3k rpms :confused:
[Modified by ski_dwn_it, 2:55 PM 6/4/2003]
Eactly what I was thinking. It either sounds like a cam out of time, not degreed right, the firing order off, valve not opening all the way, ie valve train problems.
What cam is in the car? Was it degreed. Pull the valve covers off while its idling, it going to be messy, to see if you can see any acting weird for example moving as much as the others/loose lash.....you really have to with the simple things then work towards the more complex.
Just a stupid question....your TB is opening all the way isn't it? I don't know why your car wouldn't go past 3k rpms :confused:
[Modified by ski_dwn_it, 2:55 PM 6/4/2003]
Le Mans Master
Joined: Oct 1999
Posts: 9,713
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From: Sachse Texas
Cruise-In I Veteran
Cruise-In II Veteran
Re: Tore down engine, back together, runs like crap, HELP (ski_dwn_it)
Check plug wire routing as well. Could have a crossed plug causing similar symptoms.
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Instructor
Joined: May 2003
Posts: 180
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From: Indiana
Re: Tore down engine, back together, runs like crap, HELP (Vette92)
Rocker arm geometry is critical to proper valvetrain performance. This may not be the root cause of your engine problem but you said you went with a shorter pushrod to get more rocker stud above the rocker arms. It doesn't take much of a change in pushrod length to severely throw this geometry off. I've never run a motor with improper rocker geometry but this should be checked. Do you have roller tipped rockers or standard stamped steel? If your unsure how to check rocker arm geometery let me know, I can point you in the right direction.
Other than that I would agree about the incorrect cam timing idea.
Good luck, hope you get this sorted out soon.
Al
Other than that I would agree about the incorrect cam timing idea.
Good luck, hope you get this sorted out soon.
Al
Racer
Joined: Feb 2001
Posts: 276
Likes: 0
From: Springboro OH
Re: Tore down engine, back together, runs like crap, HELP (ham)
I agree with the pushrod theory, if they are to short you valves will not open properly and you will not get enough air in or out. Take a valve cover off and set up a dial indicator, turn the motor by hand and see how much the valves are moving, my guess is not enough. With non-solid lifters unless this will not be perfect but you should get a rough estimate.
