[NeighborsComplaint]

I just got my GTO back from an oil pan (Milodon) and pan gasket (BOP) swap. The shop had changed out my leaking Viton (Cadillac) seal for a Best seal and installed the pan with RTV and no gasket(!?!) The pan leaked like a sieve so this was a do over on their nickel. I furnished all new parts and gaskets and the car is now bone dry underneath.

I noticed that the engine popped a couple times on cold startup and idles very rough. It used to have a choppy fast idle and now it idles like I have a more radical cam than 234/242 duration @ .050. It sounds really wicked but I am also getting a surging and bucking right at 3,000 Rpm under steady to light throttle that I didn't have before. Above or below is fine and under heavy throttle it runs good.

Assuming the only variable is ignition timing, you think they just put too much advance in? I told them 12 degrees initial but I haven't checked and assumed they have way too much intial timing? No hot start issue but it never backfired before either. I had them disconnect the choke (broken Holley plastic counterweight caused the fast idle to set everytime I hit the gas) and I thought maybe that was the cause of the popping.

Check initial and total advance?

[shaker455]

Yes check your timing to start.

What oil are you using?

If you have vac advance disconnect it and notice if it's on a ported or full source.

[NeighborsComplaint]

Originally Posted by shaker455

Yes check your timing to start.

What oil are you using?

If you have vac advance disconnect it and notice if it's on a ported or full source.

Running 10w30.

[nkowi]

As I was reading I was also wondering; how could simply putting in some seals cause the problem noted in the post's title? Then you hint that there might be more to the story. So I gotta ask, just what work was this shop enlisted to perform? What do you know they did? What do they tell you they did?

[Erik_H]

Just a thought, I had a pan swap done a while back and I had similar issues of bucking, backfiring, etc. afterwards. As I have figured out since, I think what happened was that since they had to pull the engine nearly out of the car to do the pan, the distributor and ignition box wiring got jacked up. After correcting the loose wires and the timing all was well. Sometimes it is that simple, but yet I chased down so many things before I got it.

[NeighborsComplaint]

Originally Posted by nkowi

As I was reading I was also wondering; how could simply putting in some seals cause the problem noted in the post's title? Then you hint that there might be more to the story. So I gotta ask, just what work was this shop enlisted to perform? What do you know they did? What do they tell you they did?

They installed the new pan and pan gasket and removed the distributor for clearance when they pulled the motor out.

[shaker455]

Are you running a zinc additive to your 10/30?

[track73]

Did you check your spark plugs? I had a tick I could not get rid of and it surged also. After 2 hours of checking the valve lifter preload I noticed a spark plug wire that was disconnected. I hooked it back up and all was well. Maybe you cracked a plug installing the engine.

[SDGoat619]

Did they have to pull your dizzy to lift the motor up. If so it might be off by a tooth. Also on my 455 with ebrock 800cfm carb i have noticed that it runs 100 times smoother when the vac adv. is hooked up on the port on the right of pcv inlet. That helped a ton on mine.

[NeighborsComplaint]

Checked the timing. They had it set for 18 initial ... too much. Went back to 12 initial and 36 total. Runs better. No backfire, no surging.''Now I have ti tackle the exhaust fumes. I have exhaist leaks up the a**. They evidently reused the exhaust header gaskets and collector gaskets since they were not happy to pull the motor for gratis.