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Supercharged "77 B Distributor Choice

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Supercharged "77 B Distributor Choice #1 Engine Supercharging Tuning This topic is about my 1977 MG MGB
ltcmgb Lonnie Cryan Oxford, NJ, USA Sign in to contact 1977 MG MGB	Topic Creator (OP) Apr 25, 2024 07:15 AM Joined 10 years ago 138 Posts

I am to the point of just about resolving the crankcase oil leaks. Now I thinking about a choice of an appropriate distributor for use with the Vmaxscart supercharger install. I'm not sure the current distributor is stock, but it came with the car 25 years ago. It is electronic with vacuum advance. What should I be looking at?

Lonnie

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Re: Supercharged "77 B Distributor Choice #2
inverse121 Chris K East Central, NY, USA Sign in to contact 1963 Austin-Healey Sprite 1976 MG Midget 1500	Apr 25, 2024 12:10 PM Top Contributor Joined 3 years ago 644 Posts

There are several options but for pure ease of use and peace of mind…

I’d recommend you contact @crankjournal and get his price on a programmable CSI distributor.
He’s a helpful forum member and a good human being. Don’t be surprised if you make a friend on the process.

https://www.mgexp.com/forum/vendor-market.68/csi-ignition-distributors-dealer-abingdon.4285320/

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about 1 week and 3 days later...

Re: Supercharged "77 B Distributor Choice #3
B-racer Jeff Schlemmer Shakopee, MN, USA Sign in to contact 1950 Willys Jeep Pickup "Ratrod" 1964 Land Rover Series IIA 1971 MG MGB	May 6, 2024 07:44 AM Top Contributor Joined 17 years ago 20,055 Posts

Your stock distributor has a horrible timing curve, even for a non-boosted engine. The key will be getting a good timing curve in a consistent distributor. By design the original Lucas 25D offers the best consistency by design - fewer points of friction which makes it more consistent through acceleration and deceleration than any other design. The biggest issue with "digital" distributors is that our engine bays aren't designed for low RFI like modern cars. Electrical noise in the engine bay (think Faraday cage) can damage a "programable" ignition signal.

jeff@advanceddistributors.com

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Re: Supercharged "77 B Distributor Choice #4
inverse121 Chris K East Central, NY, USA Sign in to contact 1963 Austin-Healey Sprite 1976 MG Midget 1500	May 6, 2024 10:33 AM Top Contributor Joined 3 years ago 644 Posts

In reply to # 4793540 by B-racer The biggest issue with "digital" distributors is that our engine bays aren't designed for low RFI like modern cars. Electrical noise in the engine bay (think Faraday cage) can damage a "programable" ignition signal.

Which items in our engine bay are going to interfere with and damage the signal?

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Re: Supercharged "77 B Distributor Choice #5
B-racer Jeff Schlemmer Shakopee, MN, USA Sign in to contact 1950 Willys Jeep Pickup "Ratrod" 1964 Land Rover Series IIA 1971 MG MGB	May 8, 2024 07:57 AM Top Contributor Joined 17 years ago 20,055 Posts

Alternator, coil, plug wires, anything 12V or higher can emit RFI. It gets reflected around in the steel engine bay and can affect your ignition the same way it can affect your AM/FM radio. When you're dealing with low voltage signals, high voltage (anything more than double) signals can cause interference. I've seen it many times where a Pertronix used on an engine dyno lost 10% power once it was installed in the engine bay with the bonnet closed (plus drivetrain losses.) Its the same type of issue you see all the time with home built EFI, where something as simple as non-shielded signal wires or grounds attached in various different places can cause drivability issues. Don't believe this is a real problem? Join a Holley Sniper forum on FB and read for a while. Even the simplest of setups can have massive issues.

jeff@advanceddistributors.com

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Re: Supercharged "77 B Distributor Choice #6
inverse121 Chris K East Central, NY, USA Sign in to contact 1963 Austin-Healey Sprite 1976 MG Midget 1500	May 8, 2024 08:40 PM Top Contributor Joined 3 years ago 644 Posts

I know RFI is real. Just wasn’t aware that the biggest issue with “digital” distributors was RFI and wanted to know which items were causing RFI problems for people with “digital” distributors.

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Re: Supercharged "77 B Distributor Choice #7
crankjournal Len Fanelli Yonkers, NY, USA Sign in to contact 1953 MG TD	May 10, 2024 07:40 AM Top Contributor Joined 18 years ago 1,410 Posts

First, Thank You Chris!
Second, As CSI distributors have more accurate advance curves ( 16 of them), than any mechanical advance distributor, many have up to 4 degrees more total advance.
Prices start @ $ 350
MGB $ 399 ( 4 types of Optomized MGA-MGB in stock)
MGT $ 430
A am the only CSI US dealer that purchases directly from CSI.
Len Fanelli
Abingdon Performance Ltd.
914 420 8699
laf48@aol.com

Edited 1 time(s). Last edit at 2024-05-10 07:47 AM by crankjournal.

Abingdon Performance Ltd. www.ttalk.info

MG XPAG Crane camshafts, roller lifter & flat lifter CSI ignition distributors, Roller rocker arms Swirl polished MG T valves, Positive stop Teflon valve stem seals. Safety Faster! Len Fanelli Abingdon Performance Ltd. laf48@aol.com 914 420 8699

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Re: Supercharged "77 B Distributor Choice #8
B-racer Jeff Schlemmer Shakopee, MN, USA Sign in to contact 1950 Willys Jeep Pickup "Ratrod" 1964 Land Rover Series IIA 1971 MG MGB	May 10, 2024 07:42 AM Top Contributor Joined 17 years ago 20,055 Posts

Chris, anything that produces RFI in the engine bay can be the source of troubles for any electronic distributor. Every situation is different, but usually its the arc that jumps from the rotor to the cap terminals inside the distributor, millimeters from the electronics package. Sometimes its plug wire noise, weak engine grounding that corrupts the distributor ground, or alternator noise.

jeff@advanceddistributors.com

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Re: Supercharged "77 B Distributor Choice #9
GeoffDuniam Geoff Duniam Wurdibuloc, Victoria, Australia Sign in to contact 1977 MG MGB	May 12, 2024 07:32 PM Joined 9 months ago 4 Posts

Hi Lonnie,

On the advice of Russ Holt, who runs a 76 or 77 MGB with a Moss blower and is active from time to time here, I'm running a 123 Tune+ Bluetooth distributor, a high-energy Bosche coil (a MEC 717) and a 6AL style CDI. It's been flawless so far and very easy to maintain. Ignition curves are easily modified and can be changed for testing on the fly.

I'm also fitting a new, larger crank pulley, and I acquired a supercharger-specific camshaft from Hans Pedersen, the local MG Supercharger Guru. The ignition system I put in is good for quite high levels of boost; it's a tested system.

HTH

Cheers

Geoff.

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