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Blue cap dizzy

Hi All

Just looking through some old posts about distributers and found comments explaining that when fitting one to an older 308 you'll need to fit a relay to give dizzy full charge. I looked on the Monaro and has never had one fitted. Recently i was speaking to a dyno guy about booking in the car and I explained that it seems to run out of breath at around 4800 revs. He explained that it should easily be able to rev a lot higher and the likelihood was that the blue dizzy would be an issue as some need the coil in the box on the side of the dizzy replaced. Depending on what serial number is stamped on the coil would determine if it needs replacing. Im thinking Ill wait and let him sort that out. However in the mean time I was wondering if anyone has an opinion on this and what effect no relay on the dizzy power supply would have. He also told me there was not much point lashing out and buying an expensive aftermarket ignition.

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Comments

"Just looking through some old posts about distributers and found comments explaining that when fitting one to an older 308 you'll need to fit a relay to give dizzy full charge."

Fitting a Relay is the easiest way of getting Maximum Voltage to the Coil. You can direct Wire it to the Ignition Switch as well.

"I looked on the Monaro and has never had one fitted."

OK. You will have to make some Wiring Changes to get HEI working.

"Recently i was speaking to a dyno guy about booking in the car and I explained that it seems to run out of breath at around 4800 revs."

Your current Ignition can be one cause of the Trouble. One Test is to try to make Redline RPM in Neutral. If you can, then the Trouble is the Ignition's Frequency Response has been exceeded because the Spark can deliver without Load but not under Load. HEI has a known reputation for this in very high Rev V8's, simply because there are so many Cylinders to Fire every Second, but this may not be your Problem.

A Loaded Engine needs more Spark Energy than an unloaded Engine.

"He explained that it should easily be able to rev a lot higher and the likelihood was that the blue dizzy would be an issue as some need the coil in the box on the side of the dizzy replaced. "

I agree that your Current Ignition may be the Trouble, but as above do the no Load Test first.

The item on the Side of the Dizzy is an Electronic Module. This *must* match the Coil. The Module's Job is to manage the Coil's Dwell which varies with RPM and Voltage which is why you need to run the Maximum System Voltage the Car has.

"Depending on what serial number is stamped on the coil would determine if it needs replacing."

All Bosch HEI Ignitions use the same Coil and Ignition Module. They are all interchangeable. The latest versions of both can prove beneficial because the Technology has improved (C-Core Transformer Type Coil for instance).

"Im thinking Ill wait and let him sort that out. However in the mean time I was wondering if anyone has an opinion on this and what effect no relay on the dizzy power supply would have."

These Ignitions *must* be powered from the System Voltage (whatever is stamped on the Alternator, typically 14.2 V).
Wiring a Relay to the Starter Tap will get you this Voltage quickly and easily.

"He also told me there was not much point lashing out and buying an expensive aftermarket ignition."

The Bosch HEI System is extremely good, excellent Spark and very long lasting. You will have to spend a lot of Money on specialised Ignitions to beat it.

My advice is to go Bosch first, then test your max Dyno RPM. You can always use the Bosch Dissy as a Trigger for expensive Ignitions.

Closing Plug Gaps compromises the Ignition's job - applying the Activation Energy to the Combustion Process.
If you need to close Plug Gaps, then the Coil's Frequency Response has been exceeded and you should investigate CDI or DFI. The Chemical Reaction will be compromised by weaker Spark - the very thing that makes HEI produce white Centre Electrodes.

Note that in a 308, fitting the Bosch HEI involves fitting the Distributor in backwards ... http://holdenpaedia....

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T

My Shed

Holdenpaedia, they're the brakes Mate.

Wow. Very concise and helpful advice. Your knowledge is humbling. Ill give this free rev test a go. I may have been using the wrong terminology with this coil in the dizzy reference. But think you got where im coming from.

Thanks

Aaron

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If the conversion was done before you bought it, it's possible the ballast resistor was bypassed to give the 12 volts required. Quick test is to check with a multimeter at the coil, if it reads around 12 volts all is good and you won't need to put in the relay. if it reads around 9 volts, the conversion was only half done and the best way is IMO with the relay as T said

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Money can't buy you happiness, but it can buy car parts, and that makes me happy :)

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