bigpaulo

Locked dizzies are most suited to alcohol or race-oriented engines like Slydog's with big cams that bleed off lots of low-rpm compression. It just so happens that this allows low-rpm timing to be advanced to the point that it matches (roughly) the high-rpm requirement, so the timing is simply locked at this figure for the whole rpm range and the engine is reasonably happy with that.
 
On anything resembling a daily driver, many more variations must be factored in, like part-throttle response and fuel economy (vac advance), ease of cranking (base timing), and higher-rpm performance (mechanical). All of these parameters are catered for in a factory setup but as you chase more power using cams and compression, etc you find that the factory tune is inadequate.
 
We're not saying all this so you'll reach into your pocket and fork out for a whiz-bang setup that you don't really need. We all have personally seen definite advantages using the various systems we keep harping on about. I like my MSD not because I want to justify to myself that spending 450-odd bucks was worth it, but because I know I can tune that fucker exactly how my engine wants it. It starts and idles like it has no right to, barely needs any choke and I can actually jet the carby down for a bit leaner cruise. The flow-on effect of having a kick-arse ignition is not realised until you actually use one.

Ok easy one that...
 
Your stock dizzy advances the spark timing in relation to both rpm and vacuum. As you modify your engine, the timing requirements change drastically. You could either "recurve" your dizzy to suit (trial and error) or use a programmable ignition unit like those you mentioned. It's still trial and error but the difference is instead of pulling your dizzy apart for every little change you want to make, you can tailor the curves exactly to what your engine wants at the click of a mouse.
 
The ignition unit cannot predict when the spark will happen, so in order to get the spark timed correctly, it retards it back from the maximum you set the timing at.
 
Say the absolute most timing your engine will need is 45 deg. You would set the locked dizzy at that and the computer will hold back the spark to the preset value you've put in. This is why the MSD program only ever mentions "retard" and not "advance" because that's all the computer is doing. The graphs on the MSD program show this too, with a maximum of 30 deg total able to be adjusted. The reason why only 30 is allowed is not because the computer has such a small range of adjustment, but because your distributor cap has only so much distance between terminals. Any more timing variation would cause problems like cross firing between cylinders and spark degradation from having to jump such a large gap between rotor and terminal.
 
So my example is 45 total, and you program your dizzy at a particular point to knock it back by 15 degrees. That makes it 30. Another point might need less again (say when cranking) so you take it back a full 30 deg, that would then be at 15. Are you catching my drift?
 
What I did was go to the MSD site and download the software for free. It's their way of marketing it in a way but it got me familiar with it before buying the product. See what you think.

Paul, I was looking for pretty much the same as you not so long ago. I broke a major rule of modification: make a list and don't change it. If you change your focus you will pay ALOT more, doesn't mean you will be worst off but you will pay more.
Some cheap extra insurance is these bolt on non adjustable roller rockers which are perfect for a hydraulic cam which you are looking at. They come with a lifetime warranty and are a very nice bit of gear, I had a set until I broke the above underlined rule. Part number SCP-1069BL but you have to order direct from USA as it's for an american V6 but will fit a crossflow, $205US from summit racing.
When I started looking for info on crossflows I had owned several high performance cars but never had undertaken a major rebuild project before. Since talking to people on this forum I have ported this cylinder head which is the same as yours

and I am now working on deburring a cylinder block and modifying oil galleries. People here are more than willing to help, I would have never been in the position I am in today if it were not for this forum. I now own a solid roller cam crossflow that made 347 flywheel horse power and ran 11.5 in a cortina with a previous forum member. Another forum member found a cylinder head for me that cost $200 to buy(it flowed 330HP (209cfm) when I purchased it) I have spent a further $600 on porting the head (the machine shop and machinest was recommended by a forum member) and will flow 230-240cfm. I have had to rebuild this solid roller cam engine(this is the cost for breaking the above rule) but it will end up being an engine from my dreams.
The most important thing I have learnt from the many years of false starts on projects I have had is be honest with how you are going to use the car and be honest on your budget. These 2 things will be the biggest deciding factors on building your car.
Mate best of luck building your car and never be afraid to ask questions.

Thats because it has some lift.And yes I would like to see it have 10.1 minimum... 

The cross flow head is a pretty good unit and has a bit of headroom to work with before it becomes a limitation. Certainly for your application, it's pretty much spot-on without too much modification. Maybe a tidy up of the bowls and short-turn and that's it.
 
Sounds like you need a towing cam or one above that, say a 208/208 @ 0.050" but with no more than 0.500" lift to keep your stock valve train. Stock crossies run out of flow above 0.450" lift anyway. If you're after a really good deal, go with Precision International for all your bits. They sell a cam called "Dynotec" and are very cheap. When compared to a Crow I bought, it looked identical, they even use the same blanks!
 
Compression should be below 9.5 with a mild cam like that. Just a light skim off the head and deck will get you there, depending on what comp you're starting with.
 
You may benefit from a couple of tricks that the V8 crowd like to use, like dividing the barrels between cylinder groups to get better low-end response. In your case, you'd simply put a divider between the two halves of the throat in the manifold, separating 1-2-3 from 4-5-6 evenly. You could fab one out of sheet ally and epoxy it in or get it welded. This in effect turns your setup into two single barrel carbs. Your idle will be sweeter and torque should improve. Also you could put a 2-hole spacer under the carby to straighten out the flow from the barrels into the manifold.
 
The 350 is a well-sized carby for this application. However some old Holden boys at work talk of the old Stromberg WW-2 found on 253s and some 302 Fords and how they felt this was a better carby all round. I used one briefly on my Corty and it went well but went to LPG not long after. Good luck finding one now though.
 
You didn't say what manifold you had, but I'm assuming that it's something like a Redline. These aren't that good for fuel distribution but could be helped along with a but of tickling on the tight corners both on 1 and 6 and into the plenum from the carby. If you really want to get into it, find a single point EA manifold and graft it into the cross-flow port flanges. These are nicely shaped and would make a nice street manifold.
 
Go with 6-2-1 extractors for more space and better torque. 6-3-1s sound nicer though.
 
Yes Slydog is very correct in everything he mentioned, including my love of MSD programmable. It really wakes up any pre-efi engine and in conjunction with a GM map sensor, eliminates all mechanically variable timing, plus has other features like switched retard (say you come across shit fuel) and rev limit, plus a whole lot of other stuff. There are folks on here who know how to make the TFI dizzy talk to them so there's a wealth of info for you.
 
Sorry for crapping on, it's a bit much to take in but we're all sharing whatever knowledge we can. Have fun!

I will no doubt have many more questions to ask, please be patient while im learning!