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#1
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ok,
350 gm mercruiser. I had a burnt valve. I took the head in to the machine shop and had it replaced. I put it back together, did the timing ect. It is running a lot better, but doesn't seem to have the full power. On the engine it says that the max rpm should be 4400 - 4800. Although I only seem to be getting 4200 at the most. Also it seems a little slugish out of the hole. I checked the compression on all clyinders and they are all very good. (160-170). I feel as though it might have something to do with the timing. I read in a book that the timing mark should hit in the same spot everytime. It's pretty close but seems to very about 2-3 degrees each time. Might this be the issue? Any thoughts on what the problem might be here? |
#2
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Cam setup timing?
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#3
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#5
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You know I was thinking about it. When I did the timing there were 2 marks
on the flywheel, the org. factory mark and was that was scratched in. It only seem to run ok when I used the scratched mark. But when I inserted the distrutor, I used the factory mark to align to Top Dead Center. The 2 marks are about a couple of inch's apart. Is this the problem? If so do I need to reinsert the distributor at TDC (with the scratch mark), or can I just move the timing a couple of inch's? "Gudmundur" wrote in message ... In article , says... ok, 350 gm mercruiser. I had a burnt valve. I took the head in to the machine shop and had it replaced. I put it back together, did the timing ect. It is running a lot better, but doesn't seem to have the full power. On the engine it says that the max rpm should be 4400 - 4800. Although I only seem to be getting 4200 at the most. Also it seems a little slugish out of the hole. I checked the compression on all clyinders and they are all very good. (160-170). I feel as though it might have something to do with the timing. I read in a book that the timing mark should hit in the same spot everytime. It's pretty close but seems to very about 2-3 degrees each time. Might this be the issue? Any thoughts on what the problem might be here? So, I am guessing it did run better back before the burnt valve, and gave you more power. If you had the head off, then you must have had to adjust the valve lash. Back off until you hear the tick-tick-tick, and then tighten slowly until the ticking stops, and adjust 1/4 to 1/2 turn more. Also, play with the ignition timing. It may be just a bit late, advance it a bit and 'road test it'. Listen for the ping of detonation, in case you advance to far. Also remember an over advanced motor will often not start when hot, it will actually kick backwards and try to rip the starter right off the engine. If you feel the engine doesn't make the power it used to, a bit of tweaking is in order. Hope the new head is the same as the old head. You did say you replaced the head? 67CC chamber vs. 73CC chamber? Port sizes differant? |
#6
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#7
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Gundmundur,
Thanks for the tips. I advanced the timing a couple of inch's this time (instead of just a few º). I played around with until until I got the best performance. It seems to be running really good right now. But I still have that ting ting ting. If I adjust the rocker arms witht he engine running, is oil going to go everywhere? "Gudmundur" wrote in message ... In article , says... You know I was thinking about it. When I did the timing there were 2 marks on the flywheel, the org. factory mark and was that was scratched in. It only seem to run ok when I used the scratched mark. But when I inserted the distrutor, I used the factory mark to align to Top Dead Center. The 2 marks are about a couple of inch's apart. Is this the problem? If so do I need to reinsert the distributor at TDC (with the scratch mark), or can I just move the timing a couple of inch's? I would leave the distributor alone for now, at least as far as pulling it out goes. If you can get the desired timing without the advance can hitting anything you will be o.k. I hope I am correct about your motor here, Turning the distributor counter-clockwise will advance the timing. I like a lot of advance, but you have to quit when you hear pinging under acceleration when the engine is hot, and you have cheap fuel in it. Also, I find with a lot of advance the engine is hard to crank over when it's hot. The spark occurs to early and almost stops the motor dead while cranking. If you have that much advance, back it off a bit. I time by ear and by feel, and not with a light. A light gets me in the ballpark only. Every engine seems to have a personality, and some like a ton of advance, others don't, and none seem to run at their peak using the factory setting. As for the 'ticking', I was refering to the click-click-click of a to loose rocker adjustment. I very very slowly adjust mine looser until they very lightly start clicking, then very slowly adjust tighter about 1/3 turn past where they stop ticking. Never more than 1/2 turn. Of course you do this one rocker at a time. If they are all clicking you can't tell what's going on. I made a very special valve cover with eight 3/4 inch holes punched directly above the rocker studs. I can adjust my valve train all day long, and never spill one drop of oil. Hope all of this helps. |
#8
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#9
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#10
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![]() "nate" wrote in message ... ok, 350 gm mercruiser. I had a burnt valve. I took the head in to the machine shop and had it replaced. I put it back together, did the timing ect. It is running a lot better, but doesn't seem to have the full power. On the engine it says that the max rpm should be 4400 - 4800. Although I only seem to be getting 4200 at the most. Also it seems a little slugish out of the hole. I checked the compression on all clyinders and they are all very good. (160-170). I feel as though it might have something to do with the timing. I read in a book that the timing mark should hit in the same spot everytime. It's pretty close but seems to very about 2-3 degrees each time. Might this be the issue? Any thoughts on what the problem might be here? You have had this running 44-4800 at some time? If it never ran that speed than you need a smaller pitch prop. If it did run at speed and all you changed was the head than timing may be an issue. Advance it 2 degrees at a time till you hear knock. See if that picks it up a bit. You did follow the timing instructions and remove/plug correct hoses or disconnect certain wires (you didn't mention the year so I don't know what kind of ignition you have) |