My 93 SC 3800 Bonneville got a gulp of air in a lifter. I clacked for a week or two and I ignored it. Now the car is missing on one cylinder. It feels like an electrical miss as it is very sharp. It shakes bad when at low rpm in overdrive.

A mechanic friend took the valve cover off and saw that the pushrod was out of place.
He put in another pushrod but it does not move up and down as the engine is turned over.

I believe it is a roller cam engine, but not sure yet. Someone suggested that the cam is sectional and one lobe may not be turning. Could it be that the lobe is wore off??

Any suggestions would be greatly appreciated.

Also, if I have to replace the camshaft, is there a certain spec or model that would increase the performance some?

Thank you in advance for your help.

That is a really uncommon problem. But you can get in there to inspect the cam and replace a lifter pretty easily. Just remove the supercharger and the intake manifold below it. Should cost you less than $75 in new gaskets and coolant to put it back together.

If the cam needs to be replaced, the engine will have to come out.

I can't get the cam out through the wheel well?? I thought I saw a picture where one could...

Do you have a cam spec that you would recommend for a little more power??

I would like to take the blower drive off to rebuild it anyhow, so I will probably take the whole top off. My drive pins are wore and it is rattling at an idle.

Thanks for the info.

Your drive pins are not worn. Your coupler is.

The cam is not sectional, and nobody makes an off-the-shelf cam for it other than Crow in Australia.

Yes, the cam will come out the wheelwell. You'll have to remove the torque axis mount, support the motor from underneath, remove the harmonic balancer, water pump, timing chain cover, timing chain, sprockets, then Cam (after the top end). Lower the motor and slide the cam out the wheelwell.

Any thoughts on why a new push rod appears to short and does not move up and down when turned over??

Like I mentioned earlier, I had a lifter that could not seem to get rid of some air, or so it seemed. The problem all started when I got air in the lifter for sure. I ran it for about 50 miles that way. I am wondering if it beat the roller of the bottom and ruined the cam?

Thanks for the help.

It'* not going to be good.

The lifter would have to be shorter to do that. So the roller would have to be gone. If that happens, the cam lobe has to be trashed. I suppose it'* possible for the lifter to completely collapse and let the pushrod drop down, but either way it doesn't matter. You have to tear the top end off anyway.

Well, shut my mouth!

...He did put in a Series I pushrod, right? Series II pushrods are shorter.

Our hydraulic roller lifters are pretty good, even when they collapse, they don't make much noise. On my pulled motor (was grinding something), several were collapsed or had otherwise siezed the pushrod seat. But one was doing something different. At some point, the roller either siezed or got somethng stuck in it. I've pulled a few strands of copper out of it after playing with it. The roller is messed up all the way around almost and the cam lobe looked similar.

Well, got the intake off. Lifter will only come out part way. Looks like lobe is completely gone.

Can someone suggest a cam to replace it with, or is the stock cam the best bang for the buck.

The engine supposedly has 15000 km on it since a major rebuild... Maybe I was spammed.

Thanks to all for the info so far.