74_5.0L_Z Posted December 29, 2005 Share Posted December 29, 2005 What type of distributor/ignition do you have? I have had similar problems to yours when using an old optically fired ignition. The problem was caused when the rotor tip was not properly aligned with the contacts in the distributor cap. At idle it would run fine, then as the engine was placed under a load (and the distributor advanced) the engine would run terribly. You can get into this scenario with crank fired ignitions and other types of ignition that use a distribitor. The way to diagnose this is to rotate the engine by hand with the key ON (ignition energized but not the starter), the distributor cap off, and find where the ignition fires. Mark that point on the distributor housing, and verify that the center of the desired cylinder's electrode on the cap is properly aligned with the leading edge of the rotor tip. If the trailing edge of the rotor is at (or slightly past) the edge of the electrode, then you will have problems when then distributor advances. On small diameter caps, the advancing distributor can cause the distributor to fire the wrong cylinder. Have you checked your timing at 3500 rpms? Is it stable? Quote Link to comment Share on other sites More sharing options...
80LS1T Posted December 29, 2005 Share Posted December 29, 2005 Another thing you could do is take it to a shop to have it looked at. The guys that fix cars on a daily basis usually can figure these things out pretty quick. Just an idea if you get too frusterated with it. A few bucks at a good shop is money well spent if you ask me... Guy Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted December 29, 2005 Author Share Posted December 29, 2005 74_5.0L - I have an HEI, new cap, new rotor, checked to make sure the mechanical advance was working (or at least not binding). When revved it seems to advance and hold pretty steadily. 80LT1 - I'm actually seriously considering that. The key, though, is finding a shop that will look at it for me that has somebody that knows what they're doing when it comes to performance engines. I even asked a couple of the Chevy dealerships and there just aren't that many guys around that are willing to work on a high performance V8. Now...there IS a place here called Chuck's Speed Shop that I was referred to, but, they're not answering the phone...so, they might have taken the week off for Christmas/New Year's break. Quote Link to comment Share on other sites More sharing options...
80LS1T Posted December 29, 2005 Share Posted December 29, 2005 I dont think it really matters that is a high performance SBC. What you have going on is a drivablity concern that could happen to any engine. I know if you brought it to our shop we would treat it like any other carbed V8 engine, start with the basics and go from there. Then if it gets into a tuning issue or wrong head/cam combo then turn to a speed shop or call the head/cam manufacture for info. Im just glad I have some very knowledgable friends in the auto repair business so that when Im going through problems like your having I can ask around. Its often something simple that your just over looking. Once you figure it out you say "man how did I miss that?" Some times it just takes a different set of eyes and ears to figure out these issues. Guy Quote Link to comment Share on other sites More sharing options...
Guest tony78_280z Posted December 29, 2005 Share Posted December 29, 2005 Restab the dizzy. Pull it out, find TDC and restab it. I bet you are a tooth or two off. Quote Link to comment Share on other sites More sharing options...
jbk240z Posted December 29, 2005 Share Posted December 29, 2005 I'm sure this is probably a stupid question, but did you replace the timing chain/gears or pushrods? Are you sure the cam gears were installed "dot to dot" at TDC? I'm not trying to qiestion your work on the Z, I'm just trying to help. If I were a betting man, I would say it is valve train related. Maybe a broken rocker arm? It could be a binding valve, altough I doubt it with those new Dart heads. Anyway, good luck. Quote Link to comment Share on other sites More sharing options...
jt1 Posted December 29, 2005 Share Posted December 29, 2005 A couple of more thoughts- Since advancing the timing helps, any possibility the TDC mark on the damper is off, maybe the ring has spun? This seems unlikely since the problems began with the cam change, but it's something to check. New cam + 1.6 rockers- Piston to valve clearance OK? Any chance of a bent valve? jt Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted December 30, 2005 Author Share Posted December 30, 2005 Well, I found at least one problem... One of the replacement wires I used is arcing against the header again. I guess I'm just going to have to spend more money on some better wires and definitely get some spark plug boot protectors. The problem is that the boots are literally touching the headers, so, any arcing that occurs is very very difficult to detect, simply because you can't see a spark jump...turning off the light and moving the wires around helped me find it, though. Even though the boot doesn't appear burnt, there is still current jumping "through" it. Now...whether or not this is the ONLY problem I have has yet to be seen...but, it does explain why it occurs more whilst under a load. I'll update you guys when I can get some different wires in there. Quote Link to comment Share on other sites More sharing options...
getZ Posted December 30, 2005 Share Posted December 30, 2005 There are shorter plugs if that will help. The accel U-grooves look about a half inch short (at least in the ad I was looking at) Quote Link to comment Share on other sites More sharing options...
80LS1T Posted December 30, 2005 Share Posted December 30, 2005 If the length is the problem buy a set of wires that you can make into any length that you need. Thats what I did to solve my wire to header clearance issues. I bought my kit from Thunder Racing. Its the "Taylor Spiro-Pro Spark Plug Wires (Universal Cut-to-Fit)" Guy Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted December 30, 2005 Author Share Posted December 30, 2005 The length isn't the problem...the problem is that the Dart aluminum heads I have place the plug right in a spot that the boot physically touches the headers I have...I've seen those shorter ACCEL plugs, but, I'm not 100% they're going to be short enough to actually prevent the plug boot from touching the header. I think I'll just have to finding the smallest diameter plug boot I can find and go with them in addition to wrapping the plug boot with a heat protector... Quote Link to comment Share on other sites More sharing options...
peej410 Posted December 30, 2005 Share Posted December 30, 2005 theres always those ceramic plug boots... why not go onto one of the camaro forums and ask people with those heads what they use? Quote Link to comment Share on other sites More sharing options...
getZ Posted December 30, 2005 Share Posted December 30, 2005 I'm going to look at my dart heads to see what it is like. I havn't put any wires on yet. Quote Link to comment Share on other sites More sharing options...
fastzcars Posted December 30, 2005 Share Posted December 30, 2005 The problemwith ceramic boots is that they are very think, and if the header is in close proximity of the spark plug they won't fit. I have the same issue with my hedman tighttube/ AFR head combo. I bought a package of MSD boot ends that they sell separately. And checked my boot ends every couple of weeks. I did use a ballpeen hammer on my headers to get just a few milimeters of extra clearence. It seems to reduce the frequency of me having to change the boot ends so often. Quote Link to comment Share on other sites More sharing options...
getZ Posted December 31, 2005 Share Posted December 31, 2005 I took a look at my setup last night. Dart Heads, patriot block huggers and moroso blue max 8.0 mm wires. All outside cylinders will either have to go outwards or I need those accel plugs to route the wires towards the inside. Cylinders 3 and 6 come within a half mm of the headers. Nothing of mines touches but 3 and 6 will need a little header dinging. Quote Link to comment Share on other sites More sharing options...
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