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73-87 Chevy _ GMC Trucks => Performance => Topic started by: square81 on June 18, 2014, 08:12:40 pm
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Hey guys just wondering if anyone has used an adjustable advance and lock out kit from crane cams with their HEI ignition. The reason I'm asking is. It's getting pinging under light load and sometimes cruising. Most of what I've read says its getting WAY to much advance all the time and this is not good. This kit is suppose to lock out some vacuum advance and then let you adjust it as well through the vacuum pot with a allen wrench.
Engine info if needed. 355ci with vortec heads. Flat top pistons. Not sure on compression ratio around 9:0:1. Edelbrock intake, 600cfm carb. Not sure on camshaft but pretty mild. Dual exhaust with headers. Timing @ 8 degrees running mid grade fuel. Any feedback would be great. Thanks
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Is it a stock HEI?
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Yeah stock except for an Accel high output coil.
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I have used one on several HEI's...might not have been Crane's, but many are the same. They work well. What I suggest you do is to get a dial back timing light or the correct balancer tape so you can figure where your at & from there, where you can be before you notice ping. You could do it without really know the "number"...if it pings on this notch, move it back one & repeat however it's best to know where the mechanical is/can be & go from there.
Many HEI's have too much vacuum advance so if you get the distributor to have the "correct" mechanical advance...you quite often end up with what your finding, especially in a heavier vehicle like a truck.
I would try to get around 34* in mechanical & work with the advance limit stop (the odd shaped tooth thing) in the kit to hold the total to what ever you can get away with...may be as much as 40*-42*or so...which is really only 6*-8* of vacuum. What you may very well have is 30*-32* & 14* added & it pings. You could improve all around drivability by spending a little time here. My Two Cents, Lorne
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To follow up on what HAULIN IT said, I have found some good write ups on other boards about the toothed cam thingy he was speaking of.
Do a google search about HEI ignition timing. Lots of good stuff written out there about it and what effects the changes make.
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Awsome thanks guys. I have been reading quite a bit about the HEI stuff. There is so much. I have had this motor in the truck for about 6 years. But now I'm finally getting around to fine tuning it and making it more of a daily driver. By what you guys have told me and what I have read. It's just trial and error until it's right. Also I have seen a lot about the B20 and B26 vacuum canisters. Their using these instead of the lock out kit. Apparently these canisters work by only pulling a certain amount of vacuum to keep the timing right. Don't know which would be better. Thanks for the input.