Ok, first off, I know this idea may seem a little extreme, but...

Ever since my motor swap, when I put a stock '79 Z28 350 (about 20,000 kms on it, and in great shape) into my '83 Z28, this engine has always run a little rough and always had a cold starting/running problem. It is a little shakey when idling, but not violently shakey and I am 99% sure that its just worn out, 20 year old motor mounts. But this engine has NEVER liked to start if its been sitting overnight or longer. If i try to start it in the morning, regardless of the weather, i always had to hold the RPMs to about 1500-2000 untill it was a little warm, or else it would just stall. The idle speed is set at 750rpm, so I know its not because of too low idle speed. When warm it does run at 750 rpm and won't stall. It got an oil change about 300kms ago, and the oil in before that change was only about 1200kms old (the oil put in after the swap).

I also checked the plugs about 2 weeks ago, and they all look good.. all a tan-ish color.

Now... I read in a Mopar magazine of a Hemi car that seemed to have all of the same running/starting problems that my 350 has. As it turns out, the cam was installed a little too far advanced on the Hemi. The cam advance was backed off a bit, and all was well afterward.

Could I possibly have the same problem? This is really the only thing I haven't checked yet...

 

I doubt that has anything to do with it. Your choke probably needs adjustment.

I had a 79 Z28. I also had a 78 Z28. Both of them rolled cam lobes. The 79 I paid good money for in about 81 or 82, seems like I gave $6000 at a dealer for it. It came to me with a rolled lobe; I replaced the cam, it rolled the same lobe within 3000 miles (The Lifter Bore Problem that so many 70s blocks have). The 78 I bought in about 86 or 87 to use as a work beater, it was a trashed-out POS so I only gave $1600 or so for it, it had a rolled cam lobe at the time; I fixed a bunch of stupid stuff it had wrong with it and sold it to a guy I knew for $2000 along with a cam I had bought but had improperly installed so I wasn't getting the full benefit (it was laying in the back seat), he swapped it to where it belongs, said it rolled that cam's same lobe within a month.....

Take a look at your valve lift. See if all of them move about the same amount.

 

Oh yea, almost forgot...

It does have a small exhaust leak on the drivers side manifold (I can hear it).

It also has a bit of an erratic idle sometimes too, when the engine temp is just over the bottom line (40* on the canadian cars like mine), but this is not very often.

 

Ok... so you are saying I may have a wiped out cam lobe?

 

Well, maybe; it's something to check, anyway.

 

I really hope thats not what it is.. but I'll check anyway. No harm in that, right? heh.

I really hope that isn't it though.. never swapped a cam before. Gotta learn sometime though

 

May just be a vacuum leak. Push the choke partially closed and see if the eng speeds up and smooths out.

 

Good idea... i'll try that tonight. Thanks ZZ

 

double posting

 

Is this a Rochester 4bbl? The reason I ask is to throw a stupid observation in here---we had a Buick with the 4.1 4bbl option---best running 6cyl I ever had. Sometime during the car's middle age it started running "shaky" as you described, and lost its punch. A mechanic friend at the time sprayed around the carb with carb cleaner, we noticed a marked improvement in the idle.

Apparently the Rochester 4bbls of that era (mid-80's) were noted for developing internal vacuum leaks due to premature wear of the metal parts. The only solution was a brand-new carb, which at the time were $350-400. Mech said a rebuilt carb would do the same thing, only sooner.

We never replaced the carb, gave the car to the kids and forgot about it.

Just a thought.

 

I agree with that, I have same problem, I replaced the pcv valve, that helped the ideling a lot, but it starts very very very hard in the morning, or any time if not ran for a while. Replace the carb, rochesters **seem** to always go out , you will also get much better performance.

 

Yea.. its the L69's Rochester CC carb. It was rebuilt only a few months ago by my uncle, who is a professional mechanic. It ran MUCH better after he did that, but your suggestions are somethin to look into

 

Well, today I adjusted the choke a little, swapped in a new PCV valve, and put in a new cap, rotor and plug wires. Starts much easier and runs smoother now

Thanks for your help guys