Lampropeltis

I posted this in the TPI forum but thought it was relevant here too. Before I pulled off the intake assembly on my GTA the car was running a little rough; it didn't quite sound like a good L98 with flowmasters should - muffled almost - and it obviously didn't have full power and would stall after a bit. So I pulled off all of the intake parts with the intent of maybe porting those or upgrading to higher flow parts. Once I pealed off the manifold I found some serious issues. I am posting a couple of short vids for ya'll to see - hope someone may know what may have caused this so I don't have to tear into it this far (at least until I swap out the heads/cam/and valve-train ) again right after making the mods want to. Thanks for any comments.

http://www.youtube.com/watch?v=At9xbk4WFq8

http://www.youtube.com/watch?v=w-rNH22JEQE

Guest

In that first vid, you're focusing entirely on the rear water passages, which dead end there. No flow. No ports in the intake manifold back there. No wonder that stop-leak stuff has accumulated there. Not a big deal, and not the cause of it running wrong.
Your power and sound issues are most likely ignition timing related. If your computer has been pulling timing due to overheating, then that would explain the power and sound.
I may edit this to add more, after I watch your second vid.
Edit: The heads have water ports at both ends so they can be used on either side.
Your second vid said no overheating, so the timing may be caused by carbon deposits in the chambers and on the pistons. I'd do some de-carbon-izing, the old way was to mist ATF into your engine while it ran. These days, I think they use something called Seafoam? It may hurt your cat, so investigate.
Also. I would check the temp gauge accuracy, and that the check engine light works as it should, to rule out overheating. If the computer was pulling timing, it should light the check engine light.
If the car is 74,000 miles, and has never been tuned up, then the timing would be off simply from accumulated timing chain stretch.
All this should have been checked before deciding to do speed mods.
Always check the timing before pulling the dizzy. If it's right, then use white-out to mark the clocking of the dizzy, and the rotor, before dis-assembly, to aid re-assembly.

Lampropeltis

Thanks ronnjonn. I had a neighbor who had experience with chevy 350's and he also surmised that the car sounded like it had some kind of ignition problem - he also suggested changing out the coil. I figured since I was going to have to get back there I would replace or port the intake parts anyway. Now as an "oops" I did NOT check the timing prior to pulling the dizzy - but I did mark it (both on the firewall and on the dizzy itself) plus I took a bunch of overhead pics prior to pulling it out. I have been careful with it. As for the check enging light - it was coming on occassionally prior to parking it. There is definitely alot of carbon build up in the ports of the manifold and some in the heads to (interesting bout the heads - I always figured they would be side specific - go figure) - I was thinking since I had the intake pulled off if there was a way to clean out the ports so I didn't have to run seafoam. Too I do not know where the sensor for the temp guage is located - but when I find it will a test with the ohmmeter work to see if its working properly? Thanks for the input

Lampropeltis

Let me ask you this ronnjonn - Could I get away with just purchasing a new aftermarket dizzy (msd I was thinking), checking the temp sensor, reassembling with some new intake parts and setting the timing??? Basically covering all of the ignition and intake bases - I am really trying to avoid putting it all back together to take it apart again to put on new pieces.

Guest

If your old dizzy isn't bad, then a replacement gains you nothing. Even an MSD. The primary consideration is if the shaft is still well-located by the bushings pressed into the housing, because those are difficult to service.
If yours is okay, then just clean up what you have, new cap and rotor, set the timing, and invest the MSD money into a mod you'll be able to feel when you drive.
Cleaning the carbon out of the intake manifold won't be any challenge. But doing the heads, on the engine, there's only the methods already covered, AFAIK.
Some engines do have heads that are side-specific. Like the Nissan VG30E and related.
As for the knock sensor, it's there to save your pistons. But if you're running premium, and still having it pull dynamic timing, even with the static timing where it should be, then you have problems in the chambers, and the most probable is carbon deposits. Fortunately, it's cheap and easy to remedy, if it doesn't hurt your catalytic converter.
Head gaskets are more work than replacing a cat, but probably cheaper.

Lampropeltis

ttt additional input welcome

Guest

Maybe not what you meant, but I'll add this: Since your intake is off, if you pull the heads, you have a chance for better valves, porting, and mill for compression.

Lampropeltis

Yeah I want to do that - problem is I am in a bit of a time crunch. So i figured I would just take care of intake performance for now and next year when I am settled into my new gig I would go back and get down to the heads and do that along with a cam change or something.