Don Terrill’s Speed-Talk

I recently bought a 79 El Camino with a Buick V6. When it is up to temperature it runs fine, but on cold start, (it starts instantly), it runs on 4 cylinders until it gets warm. The compression test indicates all 3 right bank cylinders are down 30%. Plugs are squeaky clean. I heard the word of mouth wisdom that a bad valve will cause a cylinder to miss until it gets warm. Is this true? For sure I need to go through the engine, but inquiring minds want to know. Even in the poor running condition it produces all the power I need, but will these even fire V 6 engines get any kind of decent mileage? The light front end makes it a dream to drive.

Probably has a weak ignition system. Replace the coil and wires. That usually always helps.

It's all new. When I got it, the timing was so far advanced I couldn't see the timing mark. I suspect that is why the motor is sick. 100 psi cranking compression on 3 cylinders is pretty low.

Need a can of "compression".


Maybe too much timing broke the ring lands............as it does.

Pull the plugs, check for oil on the threads.

Is the 3.8 Buick a factory deal? I’ve seen them with the 3.8/229 V6 Chevy engine and they were horribly gutless. I had a ‘79 with a completely worn out 250 I6/TH350 that wouldn’t even spin a tire in wet grass lol

I always like the 3.8 Buick’s though. I briefly had a ‘77 Pontiac Ventura (Nova) with a 3.8 Buick/3 on the tree that actually ran really strong for what it was, and get 25mpg to boot.

I worked on a coworkers 3.8 Buick one time, an ‘82 regal iirc, that the timing chain let go on. I put a chain and gears in it, and yanked the heads to get half the valves replaced. 288k miles...bores so worn that you could easily see every hole was oval. She was a broke single mom, so against my possibly better judgment I patched it up and got it running. It had the same issue...sounded like it was hitting on only a few cylinders when cold, but still ran suprisingly good once warmed up. She drove that thing for several more years.

rfoll wrote: ↑Mon Jun 25, 2018 11:23 pmIt's all new. When I got it, the timing was so far advanced I couldn't see the timing mark.

Check the timing chain.

Pull a valve cover. Turn the crank a bit one way, then a bit the other. The rocker movement should follow crank rotation.

If there's a dead spot where the rockers don't move, the cam chain and/or tensioner are bad.

The compression test gave me 142, 152, 155 on cylinders 1,3,and 5 respectively. 2, 4, and 6 were 110, 100, and 115. On cold start, 2 and 4 are dead when you pull a plug wire. This thing has a rather perverse exhaust where the driver side head pipe runs under the motor and comes up into the passenger side exhaust manifold and then it all exits in one down pipe. In 1979, the 3.8 was standard on the California cars for emissions reasons. That could explain the perverse exhaust arrangement. Most people would say just drop a 350 in it, but then I would need to pull a TH 350 trans out of the pile and rebuild it. This car appears to only have 80,000 miles on it, and the transmission seems to be really good.

That sounds like that era of 260/307 olds exhaust, which I always thought was pretty weird.

A leak down test might be more revealing, especially with the engine dead cold. Odd that one bank is low, but sort of consistent. Was there any noticeable difference between the plugs on one bank vs the other?

I also agree the timing chain is worth checking. I don’t remember Buick ever using the nylon coated aluminum upper timing gear but if they did you can almost bet it is junk even with only 80k miles.

I saw a 403 Olds B body with that ex arrangement.

Anyway you look at this issue at least the heads must be pulled,so stop debating the issue and get it apart!

Vacuum leaks from anywhere can be the cause of a misfire like that.

Walter R. Malik wrote: ↑Tue Jun 26, 2018 6:32 pm Vacuum leaks from anywhere can be the cause of a misfire like that.

There doesn't appear to be any vacuum leakage form any hoses. Most of that stuff got removed when the egr and smog pump went away. I haven't checked the carb base gasket. I'm somewhat baffled the misfire will almost completely go away when it warms up, making me wonder about the old wives tale about it being an indicator of a bad valve. I am going to pull the motor, but it needs to go on the schedule of up coming events. The people I worked with for 30 years ask me if I got bored when I retired.

You gents have great knowledge of high perf
Builds but as an example suggesting pulling off a V/C to check For a loose timing set is ludicrous additionally
Suggesting r and r ing cylinder heads or the complete
Engine without diagnosing is possibly excessive.
What I would suggest is first hooking up a good vacuum gauge on a cold engine , loosen distributor hold down slightly,have a can of carb cleaner to hand set choke , release fast idle cam , start engine
note vacuum gauge , slightly open and close choke plate
And see if the vacuum gauge reads higher and the weak cylinders start firing . If no change carefully move distributor and note Change in vacuum if the Engine
Does not respond to even a small change in distributor
Position timing set is a schneid . Then report back Please
I’ve only built a dozen race cars but worked on a 1000
231 buicks !!
No disrespect intended just my opinion!
Dave B

At least 2 minutes, and outside air temp is in the high seventies. Basically completely up to operating temperature. I am pretty sure the problem is in the engine and nothing to do with external equipment. Compression test with the right bank of cylinders down 30% compared to the left bank tells that story. I suspect that all 3 top rings could be broken and the engine would not smoke excessively. I realize this is all academic, the engine needs an internal inspection. I am tossing around the idea of finding one of the 4.1 liter,(252), engines fro the early 80s to build. I have a set of .030 over Speed Pro pistons for that motor on the shelf. What I really don't know is what kind of fuel economy these engines are capable of. My 2 ton Impala with the same gearing and a Vortec 350 gets 19+ mpg. Is I wishful thinking to expect this car at 1000 lbs. less weight to get that kind of economy?

I pulled the engine and did a teardown yesterday. The engine had been rebuilt by a professional shop, it has the little telltale heat slugs on both the engine block and heads. The exhaust valves have been pounded deep into the seats, no margin left at all, about 0.220" wide seats. The block is .060 over, and the pistons sit .080 in the hole. Add a .040" head gasket and it starts looking like someone's nightmare. Its amazing how well it ran when up to temperature. The good news is the Turbo 350 transmission is a dual bolt pattern. I won't need to build a transmission to swap in my SBC engine of choice. Thanks to all who replied, Rick.