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Petronix distributor

Posted by fildog

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Petronix distributor #1
fildog Phil R NorCal, USA 1958 MG Magnette ZB	Posted: August 15, 2012 03:25PM Registered: 1 year ago Posts: 28

Recently, installed a Petronix Flame Thrower in a 1800cc, pos ground. Lined the distributor with the 1 plug, actually, 10 degrees BTDC. Car fires off but runs awfully rough. The vacuum advance is facing toward the firewall, doesn't seem to be right. Maybe somebody can steer me in the right direction, thanks.

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Re: Petronix distributor #2
fildog Phil R NorCal, USA 1958 MG Magnette ZB	Posted: August 15, 2012 05:06PM Registered: 1 year ago Posts: 28

To answer my own query, yes, I was 180 degrees out. No need to respond.

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Re: Petronix distributor #3
B-racer Jeff Schlemmer Minnesota, USA 1958 MG magnette 1971 MG MGB "POS" 1973 MG Midget MkII 2006 Dodge Charger "Daytona" 2008 Ford Super Duty	Posted: August 17, 2012 07:43AM Registered: 6 years ago Posts: 12,514

Its not physically possible to get the car to run 180-out. It'll just give you lots of cranking and a HUGE backfire. Try 10-14 BTDC at idle.

jeff@advanceddistributors.com

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Re: Petronix distributor #4
fildog Phil R NorCal, USA 1958 MG Magnette ZB	Posted: August 17, 2012 11:56AM Registered: 1 year ago Posts: 28

Thanks B Racer, I dialed the timing in at 12degrees BTDC. Now I need to sync the carbs. I think they are way too rich. Also, quite sluggish accelerator response is this because of new shaft bushings or out of sync? I do have a unsys device, but have never tried dialing in the carbs. They were recently rebuilt, so float and idle settings are okay. This car has a mild cam for higher speeds, do I need to change the needles? Appreciate any insights.

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Re: Petronix distributor #5
mjamgb michael anderson NORTHERN NEVADA, USA 1954 MG Magnette ZA 1967 MG MGB 1973 MG MGB 1974 MG Midget	Posted: August 21, 2012 02:38PM Registered: 4 years ago Posts: 6,395

Do a full tune-up and then start diagnosing particular issues. The shot gun approach always costs you time and money in the long run (but on occasion you hit it).

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Re: Petronix distributor #6
B-racer Jeff Schlemmer Minnesota, USA 1958 MG magnette 1971 MG MGB "POS" 1973 MG Midget MkII 2006 Dodge Charger "Daytona" 2008 Ford Super Duty	Posted: August 21, 2012 05:51PM Registered: 6 years ago Posts: 12,514

Carb rebuilders can't tune them on the bench for your engine - you DO need to adjust idle mixture, balancing, and tune at road speed to determine if you need different needles.

Set valve lash
tune ignition
adjust carbs
In this order!!!

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Re: Petronix distributor #7
riley1489 Bruce Hopgood Montreal, Quebec, Canada 1973 MG MGB	Posted: August 21, 2012 06:46PM Registered: 1 year ago Posts: 746

Be careful going down the 'change out needles' road it quickly can get expensive, metering needles are close to 12$ a pop.
Jeff is right on, smiling smiley

(was there any doubt) and suggestion of a rolling road is the ultimate way to go.

Bruce

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Re: Petronix distributor #8
fildog Phil R NorCal, USA 1958 MG Magnette ZB	Posted: August 22, 2012 12:00AM Registered: 1 year ago Posts: 28

Lashed valves, adjusted idle and got carbs close to sync. Won't do anymore till I get it on the road. Though it went around the block a couple of times, ( big day), still a little softness in brakes and clutch and one of the freeze plugs is weeping. Probably from when I had the timing too retarded. Should I replace freeze plugs with stainless or brass? It's taken about ten months to get it on all tires and running. Thanks for everone's insight and helpful suggestions.

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Re: Petronix distributor #9
enigmas Vince Stok Melbourne, Australia	Posted: August 22, 2012 03:34AM Registered: 3 years ago Posts: 395

If you can easily get to the 'freeze' (welsh) plugs replace them with brass as the material is softer and will better seal in the block. Also if the welsh plugs are still in good order and there is slight weeping a product called 'Chemi-weld' (in OZ) is excellent and will have no affect on engine cooling. I have used it for the past 20 years and always on a new engine build to seal any porosities. One of my vehicles (alloy engine block) also had a small weep on a welsh plug that I replaced.(Just follow the instructions, then drain after a week and choose a suitable inhibitor for the coolant)

If you have flat spots on acceleration try a few different viscosities of oil in the dash pot (brass or plastic plunger at top of the carb) Start with ATF (automatic trans fluid) then through a range of heavier engine oils. The thicker oil slows the needle lifting hence creating a richer mixture when the throttle is 'floored' on hard acceleration. Without oil in the dashpot the engine will go suddenly lean.

The best method to check initial timing is to use a vacuum gauge and aim for the highest reading at idle. This will produce the best off idle acceleration. Fuels are quite different today then they were when the car was first manufactured so original timing marks are in my view more a point to start from than to use gospel.

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Re: Petronix distributor #10
B-racer Jeff Schlemmer Minnesota, USA 1958 MG magnette 1971 MG MGB "POS" 1973 MG Midget MkII 2006 Dodge Charger "Daytona" 2008 Ford Super Duty	Posted: August 22, 2012 02:46PM Registered: 6 years ago Posts: 12,514

I use the factory steel frost plugs (the kind you have to dimple with a hammer) and a good dab of JB Weld around the perimeter when installing them. Its about the only epoxy that isn't affected adversely by heat in the long haul. All other epoxies tend to fall out, loosen up, delaminate.

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Re: Petronix distributor #11
riley1489 Bruce Hopgood Montreal, Quebec, Canada 1973 MG MGB	Posted: August 22, 2012 08:09PM Registered: 1 year ago Posts: 746

Off topic but;
Factory steel frost/core plugs have worked fine for me. What we sometimes miss out is cleaning the perimeter of the opening in the block. If the core plug has been leaking there is a pretty good chance that some rust/corossion has deposited itself in the 'square corner' of the opening. I used a dremel with a rasp/burr type bit to clean out mine prior to re installing the plug. A couple of seasons on and no leaks.

Bruce

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Re: Petronix distributor #12
mjamgb michael anderson NORTHERN NEVADA, USA 1954 MG Magnette ZA 1967 MG MGB 1973 MG MGB 1974 MG Midget	Posted: August 23, 2012 01:30PM Registered: 4 years ago Posts: 6,395

Stock "dimple to seal" plugs and a healthy dose of Gas-ga-cinch. Messy when you whack 'em but no leaks for me!

Double ditto on cleaning up the hole so you have no loose corrosion products (rust bits).

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Re: Petronix distributor #13
fildog Phil R NorCal, USA 1958 MG Magnette ZB	Posted: August 23, 2012 11:57PM Registered: 1 year ago Posts: 28

Are the sizes 1 5/8 and 1 5/16th? How about those rubber expansion plugs, usually made in India? Also, will Ultra Grey silicone work instead of the JB Weld?

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Re: Petronix distributor #14
enigmas Vince Stok Melbourne, Australia	Posted: August 24, 2012 12:55AM Registered: 3 years ago Posts: 395

Phil, fitting the 'plugs' is quite a straight forward task and easy to accomplish. DON'T use rubber expansion plugs! They are an interference fit and you fit them straight on not at an angle. Don't use a silicone sealant but preferably a smear of gasket sealant (paste type) around the circumference of the plug. This is all that is required. If weeping occurs (and its very unlikely) use the 'Chemi-weld' product I refered to. There's no need to make a mountain out of a mole hill with this task.

(As an aside I really wouldn't touch the inside sealing surfaces with a dremel unless there is really obvious damage...they can be purchased in OZ for about $2.50 ea so price is not an issue)

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Re: Petronix distributor #15
B-racer Jeff Schlemmer Minnesota, USA 1958 MG magnette 1971 MG MGB "POS" 1973 MG Midget MkII 2006 Dodge Charger "Daytona" 2008 Ford Super Duty	Posted: August 29, 2012 03:00PM Registered: 6 years ago Posts: 12,514

Chemi-Weld and JB Weld are essentially the same product. Both are the best solution. Silicon is for gaskets around anti-freeze.

jeff@advanceddistributors.com

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Advanced Distributors Lucas distributor repair, restoration and parts supplier.

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