Several years ago I installed the MSD components from a SBC distributor into my Buick 455 HEI distributor. I have never really had any trouble... But now I wonder if I should replace the components with stock GM or something else after seeing the info below. "One thing to note with the MSD kit, it will come with the wrong ignition coil for a Buick. MSD does not make an HEI in-cap coil with the red/white wires needed for a Buick. They only supply the Red/Yellow kind that is correct for Chevy, Cadillac, and Olds Toronado. MSD is a first-rate company, I don't know why they've chosen to ignore the red/white ignition coil." this quote can be found at the following link. http://www.v8buick.com/showthread.php?t=89205&highlight=HEI Here is a link for you to study up on this and lots more about HEIs. Most of what I've written above is talked about on pages 10 and 11. (See link below) http://fiedlerh.home.att.net/HEI.pdf I checked and the MSD coil I have uses the red/yellow wires. Bert
Bert, The most important thing to realize is that coils are made to work hand in hand with certain modules, especially in the aftermarket. I really don't know the difference between the 2 GM HEI coils, but if you are running the MSD module, there is nothing to gain by switching coils. The MSD module is a nice piece, and made to work with the MSD coil. Are you having any ignition problems to speak of? http://www.jegs.com/webapp/wcs/stor...ategoryId=28009&searchItemId=318839&langId=-1 http://www.jegs.com/webapp/wcs/stor...eId=10001&categoryId=21037&searchItemId=70089
Dave Ray (Ignitionman) e-mailed me this info relating to this question. Larry, Hello, hope you are well. As far as the two different color feeds on HEI coils, the rumor from GM is that they were used with two different style windings magnetic pickups, one for right had rotation, the other for left hand rotation. Supposedly, polarity is the issue with them, BUT, this is not supported in real ilfe, as many dists use the same coil for different rotations. Now, a more likely scenario is that some GM systems used varying spark plug gaps, and needed different specs for same. Remember all those .080 plug gap Oldsmobiles that ate their coils left and right in the late 1970's? I figure that was the difference. Even with the supposedly "better" coils, GM needed to reduce the plug gaps back down to .060 to get the one type coil to live, and the other jsut plain died a quick death if it were overgapped. This premise seems to be supported by different manufacturers and just about everybody that has ever had a problem with a large cap HEI, just plop a coil into ot and drop the plug gap down to where it is supposed to be, .045 max. No need for a different set of coils, as long as the gap is correctly smaller. Modules don't have an effect on coils, but coils and plug gap sure does on the module's life. The wrong resistance coil or one with a layer shorting issue from overheating, and'or plug gap, say goodnite to the modules, no matter the color code. Anyway, take care, best regards, Dave Ray IgnitionMan DAVE's small-body HEI's 24 Buffalo Lane Yerington Nevada, 89447 (775) 463-1821 (775) 463-1809 (Fax only) www.davessmallbodyheis.com sparkman451@earthlink.net sparkman451@dslextreme.com
Kinda sorta having a problem... Thanks Larry and Dave Ray for the reply and the info. The only issue I have is just off idle, its seems like it has a flat spot. Hard to describe but it seems like it struggles between 1200RPM to around 1600RPM when you are starting off from a dead start using light throttle. It is not noticeable if you start off with very much throttle. Just at light throttle. I changed the carb. so I am pretty sure it is not the carb. It does the exact same thing with both carbs. It has been several years since I set the advance curve on the distributor I have been meaning to check it out but it has been kinda low on my to do list... Thanks for advice and info. Bert
Bert, Definitely look at your timing. I don't know anything about your engine combo, but most modified Buick engines like at least 12* initial timing. With an HEI, you usually need to have it recurved to run that much initial because there is alot of mechanical advance in most HEI's. If you aren't running enough initial timing for your engine, the throttle blades of the carb will be open too much to maintain a satisfactory idle speed. This can uncover too much of the transfer slot, which will give you a flat spot off idle. So you could have a combination of timing and carburetor causing your flat spot. Running more initial timing, allows the engine to idle with a smaller throttle opening, and the transfer slot works as intended. Try running your vacuum advance off manifold vacuum. This will increase your timing at idle, allowing you to close the throttle. If this eliminates your problem, your on the right track.
You may have nailed it? Bone stock 70GS455 with MSD HEI components and a K/N open element air cleaner. (I about forgot about the carb.) 800CFM Quadrajet I got from TA Performance several years ago. Seems like I set the initial at 10* trying to be conservative. I will get a light and check it soon and will reply with the results. Thanks for you help. Bert
While we're on this subject maybe someone can explain to me why the HEI and Ford Duraspark II have the large caps? I thought I read years ago that due to the higher spark energy, you needed larger gaps beween the posts to eliminate crossfiring. If thats true, how does dave's small body HEI eliminate crossfiring?
I think the GM cap size had more to do with housing the coil, then it had to do with crossfiring problems. Dave's HEI works exactly the same way a GM big cap HEI works. I've never heard of anyone having a problem. If the rotor was way out of phase, there might be some issues. Maybe with an MSD 7-10 series ignition, the big caps become more of a necessity. MSD makes a bigger cap that will fit the small body distributors. It also helps to drill a series of holes in the cap, to prevent ionization.
Manifold vacum? Larry, I was thinking about your suggestion about using manifold vacum for the advance. Where on the carb/manifold would be the best port to use? Thanks Bert
On a Q-jet, the passenger side port is usually manifold vacuum. You can tee into anywhere there is manifold vacuum though.
Very conservative! The timing was set on 4* BTDC. (way too conservative) I set it on 10* initial and checked the mechanical advance which was 11* for a total of 21*. I dont have a tach but my highly trained ear tells me the mechanical(centrifugal) advance is in somewhere between 1800 and 2200 RPM (stop laughing its not that funny). The vacum advance is hooked to manifold vacum now. I am going to read the Power Timing Sticky again and try and figure out how to determine the amount of vacum advance... Thanks for help and suggestions. The car is running just fine. Bert
Bert, How do you know you maxed out the mechanical timing. I can tell you that HEI distributors have alot more than 11* unless they have been modified. You need some very light springs so you can be sure the mechanical timing is ALL IN. Most of the stock springs on an HEI don't allow full mechanical advance untill upwards of 4000 RPM. If you want to do this right, buy the Crane adjustable vacuum advance kit. Use the 2 lightest springs to determine how much mechanical is really in the distributor. Then power time it for the desired total advance, and then see where your initial ends up. Do all of this with the vacuum disconnected. Then put in some stiff springs and hook the vacuum advance to a manifold source. See how much the timing increases at idle. (you need a dial back light) Subtract the timing with the vacuum cdisconnected from the timing with the hose connected, and that is how much is in the cannister.
Got me a dial back light! I will check the springs tommorrow and see which one it has. I know they have been changed to a lighter set than the factory springs... I have a dial back light (went and got it this morning). I have a Mr. Gasket spring/bushing kit around here somewhere also, I will go and dig it out of the attic and proceed tommorrow. Thanks Bert
You are correct! The initial timing was set to 10* with the medium springs. I have now installed the very light springs. With the engine revved up until all the mechanical advance kicks in I have to set the dial at 32* to get the mark back to 0*. Just trying to make sure I am on track before I proceed to check the amount of vacum advance. Thanks Bert
OK, so you have 22* of mechanical advance. That's excellent for an HEI. Now put the heaviest springs you have in, start the engine, connect the vacuum advance to manifold vacuum, and see where the timing advances too. Set the idle as low as possible without stalling to avoid the mechanical advance affecting your readings. This should give you a good idea how much advance is in the vacuum cannister.
Revised mechanical advance equals 25* I checked again and torqued it higher and the mechanical advance actually was at 25*(sorry). I then installed the heaviest springs and it appears that I have 14* of vacum advance. I am going to get one of the Crane adjustable kits(eventually) and lower the vacum advance. Meanwhile should I lower the initial timing? The car seems to run just fine with the timing adjusted as is. Cool here today, it may change during warmer weather. Thanks for the guidance and the patience. Bert
That's fine, but if you run light springs to get your advance in quick(below 2500 RPM), you'll want to limit your vacuum advance to 8-10*. It's easy, just make a plate like this.
