A couple months ago my buddy blew up his Y-Block and we need to get the detonation down on the new motor were putting together, It's a 292 with a 4-71 blower, it has a Vertex mag and were sticking with that because the firewall is made for it, I'm wondering if there's any kind of control box to mount under the dash that will retard the ignition when needed.
I do not know about a box with a mag. If you can find or make a water injection set up, this will help with detonation. This is what I run on my blown slant six to control the detonation. I also have the va***m advance hooked to the manifold, so it backs the timing down as it makes boost. It will not let the dizzy advance. i run a 50/50 mix of water and methanol, and it works fine.
Even if the compression ratio is correct you will need to still retard at higher rpm's when boosting.
It's a devil post! Okay,got that out of my system.LOL To my knowledge there is no way to retard a Vertex except manually or using a solenoid that moves the mag at a preset RPM(need an,Autometer rev limiter for a mag, I think it's 15303 or 15306...that will let you trigger rpm activated stuff )Don't quote me on those #'s. Or you can use a signal generator driven off the tach drive (if your mag has one)to signal an RPM activated switch to pop a solenoid at a pre determined rpm. Or there is always the old "solenoid and ****on" manually operated by the pilot trick.The latter is the way the moden Nostalgia t/f guys were doin' it for a while I think. If on the other hand you use a modern OXC(external coil) type mag,MSD,Mallory etc, I'm sure there are boxes to do preset rpm stuff with those.I think even in multiple stages.Prolly pretty pricey though. I doubt they make a modern mag specifically for the Y block but isn't the Y-block distributor housing very similar in fitment to all the other Ford distributors up into the 80's or so? Or is it all alone? Good luck and Happy Retarding.
I'm ***uming the Vertex has a locked/solid drive plate with no advance mechanism. You might consider making a replacement drive with a centrifugal advance and then adjust the curve mechanically. I know that the earlier Mallorys came with either a centrifugal plate or a solid plate, depending on the application. Shouldn't be too hard to build.
The solenoid sounds interesting I will have to look into that since it does have a tach drive, the only other thing I was thinking of is setting up a manual cable to adjust while driving, similiar to the old Kong ignitions.
We had 8:1 in the motor and at one point were overdrivng the blower quite a bit, I'm no expert on this but was told that while on boost you need to take a ton of timing out it, at low rpm the motor was great once you spun it up it was pinging like mad.
My motor is 8:1, but at 10-15lbs of boost, it will detonate. When I installed the water injection, that solved that problem. My blower is 10% overdriven.
This is from BDS - -"Blowers love ignition advance. Especially initial advanced. For most blower applications, the initial timing should be set at 16-24 degrees initial advance with a total of 32-36 degrees advance, in all by 2500-2800 RPM. More advance can be run if there is not a detonation problem. Some vacuum advance systems will have as much as 45-50 degrees total advance under part throttle, cruise conditions." Look at summit racing - there is a advance adjustment box that has a knob you can put in the car that will allow you to advance or retard like 7 degrees. I don't know if it'll work with a magneto. But it will let you adjust the advance slightly with out moving the distributor.
running more than 10 psi boost with a gmc blower makes a lot of heat, which is probably why it was having problems. Sounds like water injection could be a solution, thanks REJ. I'm running less boost than that, I can get away with it having lots of cubic inches.
If timing on the fly is mandatory, you can wire in a second switch. You'll need to add a second set of contacts in the mag. It's not "easy" but I've done it using a set of TCM 10-382584 or 10-382585, depending on rotation, aircraft magneto contacts (on a tiny aluminum spacer to center the follower with cam lobes). Special tools time (I won't bore you with them now). You'll need to install the capacitor found inside the magneto on the outside. I did this with both capacitors as they are separate circuits for each set of points. This setup permits one set of contacts to MASK OFF the signal from the other set until they're exposed (using a switch). I did this with a 1952 military gmc 302, Bonneville engine, blown fuel, for a friend that wanted it done that way. It gives the operator TWO timing curves. One curve is dialed in for high rpm. Did it help the gmc? NO. It was a lot of work and did not help at all. I ended up removing the contacts eventually. We found that the best tune up on a ch***is dyno was with our medium compression, Lots of pounds of boost, and a properly calibrated, filtered and CLEAN Hilborn injection system (!). We managed roughly 750 horsepower. Ultimately, with the hotter coil installed, and a rare earth magnet, the old 6 cylinder Vertex performed like a modern ignition. Engine starts and runs amazingly well for what it is. Easy to over-prime and blow flames out the pipes now. Scary. I'm a professional magneto guy, so I'd imagine this sort of thing isn't for everyone. I don't recommend modifying your mag at home, but it can be done. I can send you a diagram if you're really intent on trying it. Any questions you might have about mags, I'm happy to help answer. I mostly focus on air racing, general aviation, oddball restorations and Bonneville stuff. Some sprints. 19 years in the business (just enough to get into a lot of trouble). Have fun! -Andy
This is good reading about vertex magneto. Vertex do have mechanical advance. http://www.fbekholden.com/forum/viewtopic.php?f=25&t=20727
Its amazing I have no recollection of this from 2006. Lol. The correct answer to this question would be to limit the advance to say 6 degrees with the magnetos mechanical advance. Then you get 12 total in. Blowers like a lot of intial. So set the initial close to 20 and you'd have close to 32 total. Works well this way.
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