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Compression is around 10:1. +- a little depending on the exact measurment of the dish in a dished B21ft piston.
Currently the ignition consists of (eBay bargains, all of them!):
- Mallory dual point distributor body (mechanical only advance) ($65)
- Crane/Allison XR700 optical ignition ($70)
- Mallory Voltmaster coil ($25)
The problem I have is that the distributor doesn't seem to have a wide enough range of advance. Currently if I retard the timing a little I get better low end power but less top end power. If I advance it a little it will lose low end power and gain high end. So I end up with a bit of a compromise - typically I'm willing to settle for a little more low end bog in return for that high end rip. I've taken the distributor apart, cleaned the advance mechanism, and played around with the springs - but the end result is that I just can't get enough advance out of it.
So the plan is to mechanically lock out the distributor, set it to a fixed large advance setting (75 - 80 degrees) and use the optical sender in the distributor to instead signal the MS box. Then I can get a 'massaged' ignition signal out of one of the ports on the MS box which I can feed to my XR700 box. The MS box will know the fixed advance, and will calculate the proper delay from the distributor signal til the 'real' signal, based on the 8X8 (or 12X12, depending on code version) table of manifold pressure and RPM. That way I will have virtually free reign to craft a timing curve that suits my motor perfectly, not try to approximate it with overlapping spring ratios and weights. The MS box won't have all the sensors hooked up, just power and the 'tach' signal from the locked down distributor, and whatever else it *has* to have to function.
From there I'll gradually add the other sensors in that it will need to run the fuel system as well, and as a least step I'll add the DCOE style ITB's, injectors and do the replumbing of the fuel system - adding a F/I style regulator, high pressure pump, and return line.
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I'm JohnMc, and I approved this message.
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