3.8 OMC skipping at high speed

[greentahoe]

I have a 1984 OMC stringer 3.8, 185 hp 4bbl quadrajet. Last time out fishing it wouldn't idle on the way in. Back at home it started but skipped a lot. It was time for a tuenup anyway so I changed the points, condenser, rotor, dist. cap, plugs, plug wires, coil, and fixed a frayed wire to the + side of the coil. Now it starts well but it breaks up at high rpm's. I've checked with the stethescope for a vacuum leak but haven't been able to detect one. I haven't changed the fuel filter yet, but that's on my todo list. When I took out the plugs there was no water on them. There is some rust around the points mounting plate inside the distributor, and I haven't taken it out so I don't know what the advance springs look like underneath. I noticed when setting the points that there is a little side play on the distributor shaft, but since the engine was running very well before it began it's skipping problem I doubt that is the cause of the problem.<br />Could there be a problem with the mechanical advance mechanism causing this? <br />I also now have the tach jumping around whereas it has always been very steady.<br />Thanks for any help.

 

[Don S]

Re: 3.8 OMC skipping at high speed

Did you set the point dwell and reset the timing? Did you check the advance timing?<br />PS, you check for vacuum leaks with a vacuum gauge not a stethescope.

 

[greentahoe]

Re: 3.8 OMC skipping at high speed

I don't have a dwell meter so I've had to settle for setting the points as per spec. I did not make any changes to the timing via changing the distributor position. As for the stethescope, you can hear a lot of things through little tubes attached to your ears, a vacuum leak being only one of them. If I can't find anything else then I suppose I'll have to borrow a vacuum gauge and hook it up to the only vacuum port on my carb.<br />Thanks for the reply.

 

[greentahoe]

Re: 3.8 OMC skipping at high speed

Does anybody know how much sideplay is allowable on the distributor shaft? I've pretty much narrowed the problem down to point setting, but I have a small amount of side play in the shaft which affects the distance the points are open. I have the points set closer than spec and the engine runs better, but still misses at high rpms.<br />Thanks

 

[jeff13601]

Re: 3.8 OMC skipping at high speed

Im not compltely positive but mine does not have side to side play so that may be the problem. Try setting the points closer together and then farther apart and see if that changes anything

 

[greentahoe]

Re: 3.8 OMC skipping at high speed

I'm thinking that that is the source of the problem. I've tried numerous gap settings and it runs best when they're pretty close together, until the rpms hit around 3,000, then it breaks up. Without measuring the side play I'd guess that the shaft can run out up to about .008, maybe just a tad less. If it's doing that when the engine is running, then the point setting is constantly changing quite a bit.<br />Thanks

 

[greentahoe]

Re: 3.8 OMC skipping at high speed

By the way, does anybody know what a new distributor for the 3.8 costs and the best place to get one, just in case?<br />Thanks